By: Mary H. Dyer, Credentialed Garden Writer
Victoria blight in oats, which occurs only in Victoria-typeoats, is a fungal disease that at one time caused significant crop damage. Thehistory of Victoria blight of oats began in the early 1940s when a cultivarknown as Victoria was introduced from Argentina to the United States. Theplants, used for breeding purposes as a source of crown rust resistance, wereinitially released in Iowa.
The plants grew so well that, within five years, nearly allof oatsplanted in Iowa and half planted in North America were the Victoria strain.Although the plants were rust resistant, they were highly susceptible toVictoria blight in oats. The disease soon reached epidemic proportions. As aresult, many oat cultivars that have proven to be resistant to crown rust aresusceptible to Victoria blight of oats.
Let’s learn about the signs and symptoms of oats withVictoria blight.
Victoria blight of oats kills seedlings shortly after theyemerge. Older plants are stunted with shriveled kernels. Oat leaves developorange or brownish streaks on the edges along with brown, gray-centered spotsthat eventually turn reddish-brown.
Oats with Victoria blight often develop root rot withblackening at the leaf nodes.
Victoria blight in oats is a complex disease that it toxiconly to oats with a certain genetic makeup. Other species aren’t affected. Thedisease has largely been controlled by development of varietal resistance.
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Guest Author: Andrew Kniss, Associate Professor, Weed Biology & Ecology University of Wyoming | Follow him on Twitter: @WyoWeeds
This is an older essay that previously appeared on Control Freaks, but it’s an evergreen topic so we thought it deserved another look. It appears here by permission of the author.
Pollan was referring to a Grist article by Nathanael Johnson, which was a response to Amy Harmon’s excellent piece in the New York Times. Both of their articles are worth reading (as is some of the controversy around one of Michael Pollan’s other recent tweets on the issue), but I’d like to stick with Pollan’s criticism of monoculture. Michael Pollan has been blaming monoculture for the problems of modern agriculture for quite some time.
“I still feel that the great evil of American agriculture is monoculture.” – Michael Pollan
Pollan may be the most recognizable, but he is certainly not the only one to blame monoculture for many of the problems of modern agriculture. This is a pretty common refrain from the anti-GMO camp, and also from many folks who are just not big fans of conventional agriculture. There are even some who claim to be allergic to monocultures. So is monoculture evil as Pollan says? Well, it may depend on what you mean by monoculture.
Keith Armstrong, John de Ruiter and Howard Bezar
Oats are a multi-purpose crop in New Zealand and Australia, for grain, feed, fodder and straw. Oat forages comprise the largest component of the supplementary cereal forage markets. Dualpurpose cultivars are widely used in Australia for grazing. New Zealand has moved toward cultivars bred for forage. Oat fodder production is mainly in the southern agricultural regions of both countries, but grazing areas are expanding in subtropical Queensland and the temperate North Island of New Zealand, where Crown rust infestation is still the major limiting factor. Oats are mainly used on-farm in New Zealand, but an increasing proportion is traded on the cereal green feed market. In Australia, there has been a rapid increase in the export of cereal hay, around 75 percent of which is derived from oats. In New Zealand, traditional breeding and selection is being used to generate new fodder cultivars with desirable characters, such as disease resistance, improved cool season growth and improved quality animal response testing is ongoing. Most plant breeding programmes in Australia develop cultivars suitable for both grain and fodder uses, although, in Queensland, private and public oat breeding focuses almost entirely on oat forage cultivars for grazing. Oat production is likely to concentrate where oats have a natural advantage over other crops, notably in waterlogged environments, and where tolerance of frost and acid soils is needed. In Australia and New Zealand, there is an aging population of plant breeders and little succession planning by organizations. It is essential that investment be made in training new plant breeders, ensuring that new entrants have the necessary breadth of knowledge to succeed, and the resources with which to work.
Oats are a multipurpose crop in New Zealand and Australia, and are used for grain for milling, feed grains, grazing forages (or fodder), straw for bedding, hay, haylage, silage, chaff and green manure. Oat forages comprise the largest component of the supplementary cereal forage markets and play an important role in achieving animal production targets, compensating for high stocking rates, and supplementing forage supply for pastoral production systems. Dual-purpose oat cultivars are widely used in Australia for grazing. Forage is grazed before stem elongation, allowing the crop to recover and produce grain for harvest. Specialist cultivars for hay production are being developed to meet export quality specifications for Australias growing oaten hay export trade to Southeast Asia.
In recent years, the New Zealand oat industry has moved away from the use of dual-purpose cultivars toward specialist oat cultivars bred for forage use. This move is driven by an expanding dairy industry, intensification of livestock grazing lands and improved commodity prices for livestock products.
Oat fodder production occurs mainly in the southern agricultural regions of both New Zealand and Australia, but grazing areas are expanding in subtropical Queensland and the temperate North Island of New Zealand, where crown rust infestation is still the major limiting factor in production.
Hay is the major oaten product in Australia. In 1998/99, 1.35 million tonnes of oaten hay were produced, Western Australia and South Australia being the major producers. Cereal hays are used on-farm as fodder reserves, and traded within the Australian animal feed industry, and for export to Asian markets. In 1999, nearly 300 000 t of oaten hay were exported (Stubbs, 2000).
Oats forages are mainly used for onfarm grazing in New Zealand, but an increasing proportion is traded on the cereal green feed market. Hay and chaff continue to be produced for horses and other livestock, but are less significant as a total percentage of the oaten fodder production system. In New Zealand, oats for grazing are expanding, but total production is very small compared with Australia. There have been no recorded exports of oaten forage products from New Zealand since the early 1900s, when a substantial tonnage of oat chaff was exported to Australia.
Crown rust, Puccinia coronata , is the major foliar disease limiting production of forage and oat grain in many of the oat growing regions of the world. Crown rust has the potential to survive between cropping seasons on wild oats or volunteer oat plants, providing a continual supply of inoculum for rust outbreaks each year.
New Zealand comprises a land area of about 27 million hectares. About twothirds of the country is inhabited by people, and less than half is in established pasture. New Zealand agriculture relies heavily on grassland pastures, based around ryegrass and white clover, to provide the feed base for its livestock industry. Native tussock grasses predominate in the less productive areas of the "high country".
Production in New Zealand farming systems must satisfy two distinct sets of seasonal requirements. Cattle, including dairy cows, sheep and deer, are the predominant livestock and their feed requirements vary seasonally with the reproductive cycle, lactation and number of stock on the farms. In contrast, perennial pasture and annual crop production follow seasonal regimes that closely parallel weather and climate patterns. Pasture growth varies much more from season to season than do animal feed requirements, creating a demand for on-farm stored supplementary feed, usually in the form of hay and silage. Hay and silage have the disadvantage that their nutritional value is much less than that of the original pasture.
Pasture-derived hay and silage are more predominant on North Island farms than on South Island, ones where more fodder crops for supplementary feed are used. South Island farms have predominantly mixed livestock-grain cropping systems compared with the all-grass farming in the North Island.
The traditional seasonal and management regimes for fodder production and feeding have been challenged in recent years by the increasing demand for higher quality supplementary feeds, an expanding population of dairy cows in both islands, and for fodder supplements to be supplied outside traditional supplementary seasonal feeding timeframes. Forage brassicas and cereals (of which oat and maize crops predominate) are the major arable forage crops used for animal forage supplements in New Zealand.
Australia comprises a land area of about 770 million hectares, of which 551 million hectares are taken up by farms. About 3 percent of the farm land is used for crops and about 6 percent for sown pasture. The remainder is largely semi-arid grazing land that supports few animals. Improved and unimproved grazing lands, together with hay and other fodder crops, are the basis of the livestock industries. In recent years there has been a rapid increase in the export of cereal hay, of which around 75 percent is derived from oats (Stubbs, 2000).
Total annual fodder production is estimated to be between 4 and 6 million tonnes of hay and up to two million tonnes of silage. Most fodder produced, particularly silage, is fed on the farm in the season following production, or stored as a drought reserve (Stubbs, 2000). The domestic trading market for fodder is mostly pasture and lucerne hay, as well as hay products that are processed as chaff and pellets for the dairy and horse industries, beef feed lots, sheep and beef graziers, stock feed manufacturers and urban markets for use as horticulture and garden mulches. A four-fold increase in cereal hay exports occurred between the 1990 and 1999 seasons, the bulk coming from Western and South Australia. A significant proportion of the export increase was to Japan (Stubbs, 2000).
According to Claridge (1972), the rise and fall of oat growing in New Zealand is a reflection of changes in the horse population. This may also be true for Australia. As the total cropping area increased towards the end of the nineteenth century, greater quantities of grain and chaff were required to feed horses employed in cultivation and transport. For much of this period, the total area of oats grown in New Zealand exceeded the wheat area. In 1900-01, 178 000 ha of wheat and 182 000 ha of oats were grown in New Zealand (Statistics New Zealand, 1983). In Australia, the 1901 wheat crop accounted for 2 million hectares, and oats 187 000 ha (Pollard, 2001).
From around the late nineteenth century to the beginning of the First World War, considerable quantities of oat grain and chaff were exported to Australia. During this period, grain exports to Australia exceeded 1 million bushels per year and in 1901 exceeded 10 million bushels (Claridge, 1972). No records are available for chaff exports.
The initial declines in the area of oat crops grown in New Zealand and export of oat grain and chaff to Australia were associated with the decline in demand from Australia and the displacement of horses by tractors and other forms of motive power for transport in both countries. During the 25-year period to the late 1950s, the population of draught horses in New Zealand declined from 175 000 to less than 29 000, resulting in a decline in the demand for chaff (Claridge, 1972).
JOHN DE RUITER
Dairy cows grazing oats in Canterbury, New Zealand
Until 1950, most of the oat crop was used for chaff for animal feed. Substantial volumes were exported to Australia. Since then, green feed crops for grazing, of which oats was a major component, have become the major feed use (Wright, 1983). In the 1978-79 season, 30 000 ha of oats were grown in New Zealand for grain harvesting, mostly in the South Island regions of Canterbury, Otago and Southland. Over half of the grain produced was milled in either Gore or Dunedin, with the rest used for seed and animal feed (Wright, 1983).
According to Statistics New Zealand (1983), in the 1981-82 season 26 500 ha of fodder oats were grown in New Zealand, mostly in Canterbury (Figure 10.1). Statistics New Zealands 1996 and 2002 records for areas sown to grain and arable crops list oats at around 10 000 ha for each of these surveys, suggesting that the oat area may have stabilized.
The statistics give little indication of the multiplicity of fodder uses of oats for green feeding and grain consumed within the farm. An unknown area continues to be sown and used for animal consumption within individual farms, for which no production records are available. Approximate areas of oat production are shown in Figure 10.2.
Locations of oat production in New Zealand
In recent years, the intensification of land use, made possible through the expansion of irrigation systems and increased fertilizer use, has created new demands for tradable fodder products that can help achieve animal production targets and supplement forage supply from traditional pastoral production systems. These developments, together with the increased stocking rates on dairy farms, have created an increase in demand for cereals for supplementary grazing and silage.
According to de Ruiter et al. (2000), cereals provide a high energy supplement in autumn and winter and can provide a high-fibre feed source from spring sown crops. Oats can contribute to lactating cattle nutrition as a grazed forage, silage or grain. They have the advantage of high yield potential from autumn sowings, and in the North Island complement maize in a double cropping silage system. Their flexibility allows different sowing and harvesting options, depending on current feed supply. Their disadvantages include a lack of cultivars developed specifically for multiple grazing in cooler regions.
Access to cereals for grazing has given farmers greater flexibility to condition dry cattle and to supplement feed for lactating animals. Early autumn sowing of short-season cereal cultivars for grazing by lactating or pregnant cows is common, particularly where high winter growth rates of animals are required. If crops are sown in early March, when soil temperatures are higher, early herbage growth will capitalize on good nitrogen mineralization rates during early crop establishment. Research by de Ruiter et al. (2000) showed that a single cut harvest in early August produced 4.7 t DM ha -1 in 148 days from a March sowing in a warm autumn-early winter.
Potentially significant losses can occur through trampling and ground pugging (formation of consolidated mud due to animal traffic), when stock graze in wet conditions. However, according to de Ruiter (2000, unpubl. data), single-graze autumn green feed is a significantly cheaper option than feeding hay. Where midwinter or spring grazing is required, later maturing oat or long-season cultivars are the best options as they can survive frosts, produce higher dry matter than pasture and provide reasonably high quality feed in winter. Two or even three grazings are possible, depending on regional climates, reducing the wastage from animal treading, and providing more dry matter than a single-graze system.
There may be potential to improve winter production quality using mixes with grasses or legumes. Little research has been done to validate the potential of mixtures for producing the required dry matter quantity and quality for late winter and early spring grazing (de Ruiter et al. , 2002).
Developing and introducing improved oat cultivars suitable for multiple grazing in cooler climates would enable herbage quality to remain high for the duration of the grazing period, with potential for a silage crop in late November to early December, if grazing ceased in September. The triticale cultivar, Doubletake, recently released jointly by Crop and Food Research (CFR) and Agricom NZ Ltd, provides for the type of multipurpose cereal forage use that farmers have been seeking from cereal oat foragesearly grazing, multigrazing and silage production from a single sown crop.
Unlike triticales, oats have the advantage of very fast biomass production from late autumn sowing to first graze, in cooler temperatures. The breeding programme in New Zealand has been developing oat cultivars with greater capability for multigrazing situations, and silage production, whilst maintaining their early biomass production characteristics. The release of cv. Stampede was a step in this direction. It is a green feed oat suitable for one-off hard grazing in winter or multiple light grazing in autumn and winter in the North Island. It has high potential for biomass production, good frost resistance, good crown rust resistance when first released, and quick growth from autumn sowings (de Ruiter, unpubl. data).
Unfortunately, Stampede is now rust susceptible and is being replaced by other high performing cultivars that have more durable resistance to crown rust, equally high potential for biomass production and rapid autumn growth.
In New Zealand, new forage cereal cultivars will continue to be developed to provide feed for animals at times of seasonal pasture shortages. Management strategies will be updated regularly to optimize nutritive quality and growth characteristics. The widely differing genetic potential of a range of crops, including alternative oat species, have been evaluated for their patterns of productivity and for changes in herbage quality in relation to stage of growth and environmental conditions during growth.
An autumn-sown cv. Stampede oat crop in the North Island of New Zealand in 2001.
Pugging can be a problem for all grazing crops during winter in high rainfall regions
New Zealand researchers are also planning animal response experiments to examine the benefits of alternative production methods. Programmes of work are under way on improving the use of forage cereals, maintaining stock health, optimizing dairy production through selection of appropriate germplasm for supplementary feeding and by managing stock to minimize treading damage to soil structure (Figure 10.3).
In addition, research is aimed at optimizing cropping and pasture rotations to enhance the sustainability of production systems. Cultivars produced for specific feed use, such as cut-and-carry, e.g. hay and silage or grazing systems, will be supported by management guidelines and decision support systems. This information will support growers and enhance the adoption of new technology and uptake of new cultivars (Hogg et al. , 2002).
New cultivar information packages will include quality and yield characteristics for specific production requirements such as autumn, winter, summer and spring grazing, and hay and silage use. The outcome of these programmes will be more reliable and sustained milk and meat production by overcoming seasonal feed and production supply problems. As a result, dairy cows will maintain the lactation peak for longer in spring and productivity will be enhanced in summer. Factors that influence the suitability of oat forage for stock feeding include sowing date, seed rate, soil preparation (including fertilizer management), grazing or cutting manage- ment and grazing or harvesting time.
New Zealand and Australian oats are facultative types and most could be classified as short to mid-season maturing cultivars. However, with typical sowing of oats in autumn or early winter, development patterns are not dissimilar from long season types that require vernalization for floral initiation. Typically, crops are sown at 100 kg ha -1 and at rates of up to 150 kg ha -1 if direct drilled or broadcast.
A commonly grown New Zealand grazing oat, cv. Stampede, produces significant biomass before floral initiation when sown between late February (late summer) and early April (early autumn). The crop may require a period of vernalization, but this has not been quantified. Sowing dates for grain production of Stampede typically range from 1 April to 1 September. Flowering occurs over a short period, from 4 November to 2 December (de Ruiter et al. , 2000). The mechanism controlling flowering in this cultivar, and others used in the NZ market, are unknown, although there appears to be a dependence on increasing photoperiod or a critical day length for flower initiation. It is not known whether the crop will progress through to flowering when sown in early February. If flowering does occur, the chance of producing viable grain is much reduced in more southern areas because of frost damage.
Stampede has the capacity to produce a large leaf area and support higher aboveground biomass than selections with smaller leaves. However, oats generally have thick stems that may reduce their digestibility and palatability for stock. The crop should be used before the onset of stem elongation and before the rapid decline in feeding value that is directly related to the change in leaf to stem ratio with maturation. Light grazing by sheep is recommended at the first node stage, but good stock management is critical to minimize and reduce wastage and to allow re-growth. A single bite at the 2-3 node stage or later is the best grazing management option with cattle.
In small plot evaluation trials, singlecut harvests of cv. Stampede grown at Lincoln, Canterbury, on 1 July (1999) and 4 July (2000) from sowing in early March were 6.4 and 5.0 t ha -1 , respectively (Table 10.1). Yield of Stampede in the first year was higher than Hokonui (a very late maturing short, thin straw semi-dwarf forage cultivar used for grazing or silage) but comparable with Hokonui in the second year (Figure 10.4). Production rates in response to thermal time accumulation from plant emergence were 558 and 466 kg DM ha -1 100°C days-1 in the respective 1999 and 2000 growing seasons. The difference in productivity between years may be related to differing solar radiation. For example, during the equivalent period from 20 March to 1 July, an additional accumulated daily radiation of 51 MJ/m2 was recorded in 1999 compared with 2000. The difference in radiation interception would account for an additional 1 t ha -1 biomass production, assuming a typical growth efficiency of 2 g/MJ. The cultivar Hokonui produced similar biomass in response to thermal time in both years (438 v. 448 kg DM ha -1 100 °C days-1, respectively).
The yields shown in Table 10.1 were achieved under good growth and management situations. Temperatures were significantly warmer than the long-term mean in both years. The levels of biomass represent the upper range, given that in a grazing situation significant losses may occur from wastage and trampling.
Biomass production for CROA50 (cv. Stampede) and cv. Hokonui in trials at Lincoln, New Zealand, in successive years. Standard Errors of Difference (SED) (5%) given are for harvest × cultivar interaction (A) or cultivar comparisons within harvest date level (B).
Sowing dates were 4 March and 10 March, respectively.
Comparison of biomass produced by cvs Stampede and Hokonui in successive years in Canterbury, New Zealand. Harvest dates for the respective years were 1 July and 4 July for crops sown on 4 March (1999) and 10 March (2000). Emergence was on 18 March and 20 March, respectively.
Note: LSD = Least Significant Difference.
In this experiment, no adjustment was made for residual biomass after grazing. The level of wastage can be minimized by only allowing stock to graze when the soil moisture is significantly below field capacity, or harvesting herbage in a cutand- carry operation.
In situations where lactating or pregnant cows are being grazed, early autumn sowing of short-season cereals is a suitable option. Crops sown early in autumn showed good early growth in warmer soils and utilized the nitrogen mineralized during the establishment phase. Experimental blocks (2-15 ha) of cv. Stampede were sown alongside established cultivars on growers properties in the lower North Island of New Zealand in 1999 and 2000. Biomass production was measured on plots cut to 2 cm above ground.
Biomass ranged from 3.6 and 7.9 t DM ha -1 (Table 10.2). Samples for biomass yield were all taken before 1 July, and yields for cv. Stampede were up to 35 percent greater than the paddock reference cultivar (Table 10.2). Sowing dates were all within a relatively narrow period (13 March - 4 April). Crops were sown at rates of 95 and 110 kg ha -1 , with a range of fertilizers (e.g. 120 kg ha -1 of "Crop15", or 300 kg ha -1 super + 30 kg ha -1 urea). Establishment of Stampede was invariably better than the reference cultivar, with better early vigour.
Trials conducted at Crop and Food Research have provided information on the changes in nutritive value of herbage during plant development. This information was used to determine the optimum time for harvest using quality of herbage as the prime variable for harvest decisions.
For autumn-sown small plot evaluation (sown 4 March 1999), samples were taken for quality at three-week intervals. Comparative data for quality of cvs Stampede and Hokonui are shown in Figure 10.5. There were no significant differences between the cultivars within harvest date for any of the quality variables tested. However, the effect of harvest time was strongly significant (P -1 ) is also a good general indicator of the value of the herbage for maintaining stock condition or for meat and milk production. ME declined significantly when crops were in the stem elongation phase. Protein also fell to less than 15 percent during this phase, and continued to decline during reproductive development.
Dry matter biomass production for experimental blocks of cv. Stampede sown alongside standard cultivars in the New Zealand North Island districts of Manawatu, Rangitikei and Wairarapa in autumn 1999 and 2000
Yield relative to paddock cultivar (%)
Key: Control paddock cultivars were a = Awapuni, b = Caravelle, c = Makuru/Awapuni, d = Hokonui, e = Omihi, f = Awapuni, g = Finlay.
Changes in protein, total carbohydrate (CHO), metabolizable energy (ME) and organic matter digestibility (OMD) of autumn sown CROA50 (cv. Stampede) and cv. Hokonui in 1999 (sown 4 March). Vertical bars are Standard Errors of Difference (SED) (5%) for harvest × cultivar interaction (A) and cultivar comparisons within harvest date level (B).
In New Zealand, forage cultivar breeding and evaluation by Crop and Food Research is continuing. Research into the potential use of oat cultivars for enhanced dairy production has addressed the issue of pasture feed deficits during dry periods. Traditional breeding and selection is being used to generate new cultivars with desirable characters, such as disease resistance, improved cool season growth and improved quality.
Management strategies will be updated regularly to optimize nutritive quality and growth characteristics. Widely differing genetic potential of a range of crops, including a number of oat species, will be examined for their patterns of productivity and for changes in herbage quality in relation to growth conditions.
Animal response experiments in collaboration with Lincoln University are also planned to examine the benefits of altered production methods to improve the use of forage cereals, placing greater emphasis on maintaining stock health by providing high quality herbage optimizing dairy production through sound soil management and the use of appropriate cropping and pasture rotations to enhance the sustainability of production systems.
Areas of oat production in Australia
Cultivars produced for specific feeds, such as cut-and-carry, e.g. hay and silage, or grazing systems, will be supported by management guidelines and decision support systems for new growers contemplating the use of new crops or cultivars.
Programmes will also provide new cultivars with prescription quality and yield characteristics for specific production requirements, such as autumn, winter, summer and spring grazing, hay and silage use, and improved disease resistance. The outcome of these programmes will be more reliable and sustained milk and meat production by overcoming seasonal feed and production supply problems, and reliable seasonal supply for dairy cows to maintain the lactation peak for longer in the spring and enhance productivity in summer.
Oats in Australia have traditionally been grown in moist temperate regions. However, improved cultivars and management practices have enabled oats to be grown over a wider range of soil and climatic conditions (Figure 10.6).
Fodder oat crops in Australia are sown in autumn and either grazed, or grazed and harvested for grain after the removal of livestock, baled or cut for chaff. The fodder industry trading market has domestic and export sectors, both of which are growing in size. Domestic fodder use is highest in all areas during the winter months, but can extend from autumn to early spring and summer, depending on seasonal conditions, animal reproductive cycles and farm stocking rates.
Buyers and on-farm users are becoming increasingly conscious of fodder quality. Dairy farmers in Australia and New Zealand are conscious of cost-effective feeding and many buy on the basis of metabolizable energy (ME) content, protein (CP) and dry matter digestibility (DMD). Objective analysis and subjective appearance of fodder are loosely related but their reliability as indicators of feed value can vary considerably (Stubbs, 2000). Palatability and digestibility are important price factors, particularly for the Australian export market, but are difficult to analyse accurately. In addition to objective measurements, appearance, smell, feel and the level of impurities, such as weed seeds, may influence "grades" and therefore pricing.
A range of hay types are traded according to end use. They include grass or cereal hay and straw for dry cows, and lucerne and various legume+cereal hay mixes for lactating cows and young cattle. Lower quality hay and silage are often used for cattle maintenance feeds.
Feed lots are big users of traded feed grains, which are supplemented by roughage in the form of silage, hay and straw, sometimes at the lower-quality end of the supply range. About half the total feed lot activity is in Queensland, a third in New South Wales and the rest distributed between Victoria, South and Western Australia. Feed lots usually have extensive storage facilities for grain and fodder for year-round supply, and are located close to both grain and fodder producing areas.
Dairy farms, because of their relatively high stocking rates and the need to maintain lactating animal condition and production, are the biggest single buyers, but not the largest users, of conserved forage. The location of this market segment closely matches the main dairying regions in Australia, Victoria, New South Wales and Queensland. Seventy-five percent of conserved cereal is derived from oats (Stubbs, 2000).
The horse industry is also an important part of the domestic trading market. The racing industry and owners of horses used for recreational purposes buy fodder. This market segment is distributed around the urban centres, particularly Sydney and Melbourne, and major provincial and state capital cities.
Graziers running sheep and cattle on large properties aim for self sufficiency in fodder. The climate intervenes from time to time, resulting in either occasional large localized demands for purchased fodder or, less often, surplus fodder for the trading market. The interaction of climate, feed requirements and livestock numbers affects domestic fodder demand and supply, and therefore prices. When fodder must be purchased, there is little opportunity for graziers to discriminate on type and quality (Stubbs, 2000).
In Queensland, oats are grown as the main winter forage crop due to the states warmer climate hence farmers are able to produce good quality feed when most pastures are dormant. Farmers rely on oats for grazing in the dairy, sheep and beef industries from late autumn to early summer. Only 10 percent of the crop is harvested for grain, primarily to provide seed for sowing (Platz and Rodgers, 1998).
Multigrazed oat cultivars selected for use in Queensland grow rapidly and tiller well and, with careful grazing management, can be maintained in a vegetative state over a long period. Consequently, nutrient requirements, especially for nitrogen fertilizer, are higher for grazed oats than those required for grain crops.
Crown rust is the major constraint on forage oats production in Queensland because the appearance and spread of the disease coincides with when the crop is needed for grazing. Managing the timeframes for crop grazing is one of the tools Queensland growers use to slow the spread of crown rust in the absence of cultivars with long-term durable resistance (Song, 2002).
Other major diseases affecting oats in Australia are stem rust, barley yellow dwarf virus (BYDV) and Septoria avenae blotch. There are crown and stem rust races that can attack all known resistance genes available to plant breeders (Zwer and Hoppo, 2002). Cereal cyst nematode (CCN) has been identified as a problem in some areas in South Australia, and recently in Western Australia.
New South Wales (NSW) is generally the largest oat producing state in Australia. Most crops are consumed by stock on the farm. Consequently, few crops are milled or exported to other states. The area of oats fluctuates widely with the profitability of the livestock industry.
Dual-purpose oats are sown in early autumn and grazed through to early winter, when reduced temperatures limit pasture growth. In late winter-early spring, as temperatures rise and alternative pastures become available for feeding, livestock are removed from the oat crop, which is then allowed to develop for grain production and harvest.
According to the Australian Bureau of Statistics, 354 000 ha of oats were sown in NSW in 1998, but this area decreased substantially in the following two years, rising again to 260 000 ha in 2001. In 1996, 50 percent of the oat crop was sown using dual-purpose cultivars, and this proportion of the total crop was likely to increase (McLean et al. , 2000).
In South Australia, Victoria and Western Australia, 97 000, 122 000 and 111 000 ha of oats were sown for hay, grazing and silage respectively. This growing local and export hay industry increasingly relies on improved and specialized cultivars to maintain and improve the ability of growers to meet quality specifications for export hay.
Oaten hay for internal trading, onfarm uses and for export are the major end uses for oat crops grown in these states. According to McLean et al. (2000), production of oats for export hay is likely to increase. Though riskier than grain production, greater financial returns can be achieved from hay production.
In Queensland, over 200 000 ha of oats are grown annually as the main winter forage crop, due to its ability to produce good quality feed when most pastures are dormant. Farmers rely on oat forage crops to produce feed for livestock fattening and finishing from early winter to spring. In this situation, average liveweight gains of 1 kg head -1 day -1 can be achieved (Song, 2002).
Both Australia and New Zealand rely heavily on North American germplasm from oat improvement programmes. Oat germplasm from Canada and USA is well suited for fodder production, particularly for winter production. Selected parents for crossing or genotypes selected for release generally produce vigorous early growth (Oates, 2000).
Most plant breeding programmes in Australia develop cultivars suitable for both grain and fodder uses, whereas in Queensland, private and public oat breeding focuses almost entirely on oat forage cultivars for grazing.
Registration of cereal cultivars, and hence the ability of cultivar owners, or their licensed agents, to collect royalties from seed sales, came later in Australia than in New Zealand. The introduction of Plant Breeders Rights (PBR) stimulated greater private sector involvement in forage oat cultivar development and releases, particularly in Queensland.
The selection of cultivars below is not a complete list of forage cultivars used in Australia, but illustrates the importance of the international linkages involved in oat crop improvement programmes.
Oat cultivars were brought to New
Zealand and Australia by early settlers for porridge and feeding livestock. Cultivars were used for fodder and grain production (Wright, 1983). It was not unusual for an autumn-sown oat crop to provide winter grazing for livestock and then be left to regenerate to produce a grain crop for milling or animal feed. Only in recent years have oat cultivars been developed and released for specialty uses. Before that, certification of oat seed for purity was not standard practice. Consequently, cultivar integrity was easily lost and cultivars often became misnamed.
A popular early oat cultivar in New Zealand was the English-bred Gartons Abundance. It was bred by Messrs Gartons and released in New Zealand in 1892. It was the first successful oat developed by hybridization and was the standard milling oat cultivar in New Zealand for many years.
Gartons Abundance was a rust-resistant cultivar widely used for livestock fodder, representing 58 percent of the New Zealand fodder market in the early 1930s (Hadfield and Calder, 1934). By 1934, it had become susceptible to crown rust and was replaced by cv. Algerian, which had improved rust resistance. Algerian is believed to have arrived in New Zealand from Algeria via Australia in the early 1900s.
In areas of the North Island where oats were badly affected by crown rust, Algerian was widely used as green feed for grazing, chaff, hay, silage and grain production (Claridge, 1972). In Canterbury, Algeria was autumn sown for early winter grazing, followed by a grain harvest for animal feed.
Oat selection and breeding
Observations made by merchants also revealed that Algerian was a mixed cultivar of distinct types. A reselection, College Algeria, was distributed by Canterbury Agriculture College, but this cultivar also became mixed and misnamed (Claridge, 1972).
The cultivar Ruakura originated from a rust-resistant single plant selected from the cultivar Argentina in New Zealand in 1908 at the Ruakura Farm of Instruction. It proved to have better resistance to rust than Algerian.
Overseas introductions contributed significantly to the portfolio of cultivars used for oat production in New Zealand and Australia, and toward the establishment of oat breeding programmes in both countries.
An oat breeding and selection programme was established at the Department of Scientific and Industrial Research (DSIR, NZ) in 1938. It was suspended during the Second World War, but resurrected in 1952 by G.M. Wright, who commenced a formal pedigree breeding and backcrossing programme for New Zealand.
Commercially important general purpose cultivars bred by DSIR include Oware (1963), Mapua (1965), Amuri (1967), Makuru (1970), Taiko (1971), Omihi (1977) and Ohau (1980). Cv. Caravelle was released in 1980 by a private company.
Cultivar releases were based on improved resistance to neck break and lodging (Makuru and Mapua), crown rust resistance (Amuri, Hattrick, Omahi and Ohau), improved grain and forage yield (Makuru), and tolerance to BYDV (Omihi and Ohau).
From the 1990s, oat cultivar breeding objectives focused on the development of cultivars for specialty end uses, such as milling, feed or forage. Otama was developed as a special purpose forage cultivar and released by the New Zealand Institute for Crop and Food Research Limited (CFR) in 1994. It had good resistance to BYDV, produced high yields of green feed, but did not compete well with Makuru for green feed uses outside Canterbury.
Otama was also crown rust susceptible, although at the early stages of rust infestation it appeared to suffer less from rust than Makuru, giving Otama a slightly longer grazing window before succumbing to crown rust (Keith Armstrong, pers. comm.).
Otama is also grown in the USA, in the Northern Pacific states, where crown rust appears to be less of an issue. There it is known as cv. Charisma.
Cv. Hokonui was released by CFR in 1997 for green feed, hay and silage. Hokonui is a very late maturing, semidwarf, forage oat cultivar with excellent straw strength. It is marketed throughout the South Island, but is also grown in the North Island, where it is moderately susceptible to crown rust.
Cv. Stampede was selected and released for use throughout New Zealand by CFR in 2000 as a rust-resistant green feed oat. It was selected by CFR in New Zealand from a cross developed by Agriculture and Agri-Food Canada in Winnipeg, Canada.
In yield trials, Stampede significantly out-yielded all cultivars in the South Island. In the North Island, its yields are similar in volume to cv. Hattrick, and, together, these two cultivars make up most of the traded oat forage seed in the North Island.
Cv. Vasse is a tall semi-dwarf late maturing hay oat cultivar that was jointly developed and released in 1997 by Agriculture Western Australia, Grains Research and Development Corporation (GRDC), and The Grain Pool of Western Australia. Vasse is susceptible to crown and stem rust, CCN and stem nematode. Vasse has high hay yields in very high rainfall, longseason environments. It has thin straw and produces high quality hay with good digestibility, metabolizable energy and crude protein.
Cv. Glider was released in 1998 jointly by the South Australian Research and Development Institute (SARDI) and Texas A&M University, USA, as a late maturing hay cultivar. Glider has good foliar disease resistance and tolerance to stem nematode, but is susceptible to CCN. Glider is adapted to high rainfall areas where CCN is not present.
Cv. Eurabbie is a dual-purpose oat released by Agriculture NSW for grazing and feed grain production. It is suited to higher rainfall hay production areas where CCN is not present. It is moderately susceptible to crown and stem rust.
Cv. Enterprise was selected by CFR in New Zealand from a cross developed by the Canadian Department of Agriculture and released by Heritage Seeds in NSW in 1992.
Cv. Heritage Lordship is a forage cultivar selected by CFR in New Zealand from a cross developed by Agriculture and Agri-food Canada, Winnipeg, and released by Heritage Seeds in NSW in 2000.
Cv. Culgoa II is a forage type released by the Queensland Department of Primary Industries (QDPI) in 1991. It was reselected from Culgoa, an introduction from Texas A&M University, USA.
Cv. Cleanleaf is a tall, late forage type that was released by Pacific Seeds in 1991, from a cross developed by the Crop and Weed Sciences Department of North Dakota State University, USA.
Cv. Riel is a tall, spring forage cultivar selected and released by QDPI in 1991 from a cross developed by the Canadian Department of Agriculture.
Cv. Nobby is a tall forage oat cultivar with a prostrate growth habit released by QDPI in 1992 from a cross developed by Texas A&M University, USA.
Cv. Condamine is a spring forage oat released by Pacific Seeds, from a cross developed in Brazil.
Cv. Graza 50 is a tall spring oat released by Pioneer Hi-Bred in 1993, from a cross developed by North Dakota State University, USA.
Cv. Graza 70 is a tall spring oat released by Pioneer Hi-Bred in 1993, from a cross developed by the Canadian Department of Agriculture.
Cv. Barcoo is a short-season, spring oat with a prostrate growth habit that was selected and released by Pacific Seeds, Queensland, in 1995, from a cross developed by Texas A&M University, USA.
Cv. Moola is a tall hay and forage oat with CCN resistance released by QDPI in 1996, from a cross developed by Agriculture and Agri-Food Canada. Moola is widely adapted as a hay cultivar in most of the hay producing regions.
Cv. Graza 68 is a grazing cultivar released by Pioneer Hi-Bred in 1997, from a cross developed by Agriculture and Agri-Food Canada, Winnipeg. At the time of release, Graza 68 was recommended as being adapted to most areas of Australia, and particularly those where high incidences of crown and stem rust are encountered.
Cv. Gwydir is a semi-prostrate prolific tillering cultivar selected from the University of Queenslands pedigree breeding programme. It was released by Pacific Seeds in 1997. It is a late maturing, early vigour, grazing cultivar. At the time of release, it was resistant to crown and stem rust.
Cv. Warrego is a late maturing, grazing cultivar that was selected and released by Pacific Seeds, Queensland, in 1997, from a cross developed by the NDSU Research Foundation, North Dakota, USA. At the time of release, it was resistant to crown and stem rust.
Cv. Nugene is a tall grazing cultivar selected and released by QDPI in 1999, from a cross developed by NDSU Research Foundation, North Dakota, USA.
Cv. Taipan is a grazing cultivar selected and released by Pacific Seeds in 2001, from a cross developed by NDSU Research Foundation, North Dakota, USA.
Miscellaneous cultivars released in Australia before the introduction of plant variety protection
Cv. Swan was released in 1967. It has widespread adaptation as a hay oat, with good digestibility, but lower protein than other hay cultivars.
Cv. Saia is a diploid oat thought to have been introduced from Brazil. It is widely used as a hay oat. It has very thin straw, and better protein but poorer digestibility than cv. Swan.
Cv. Esk, released in 1975, has limited application as a hay oat for longer-season environments.
Cv. Winjardie was released in 1985 as a hay and grain oat. It has thin straw, with similar digestibility to cv. Swan, but higher protein.
Cv. Kalgan was released in 1988 for hay or feed grain. Its thick straw makes it unsuitable for export markets, but it has similar digestibility to cv. Swan, with high protein.
Cv. Hay was released in 1988 for hay production and has a consistently high yield, but its thick straw may make it unsuitable for export markets
Oat breeding programmes are based at Christchurch, New Zealand Toowoomba, Queensland Temora, NSW Adelaide, South Australia and Perth, Western Australia. The barley breeding programme in Tasmania also undertakes some oat improvement.
The Australian programmes exist within government departments of agriculture, while the New Zealand programme is within a government-owned research company, the New Zealand Institute for Crop and Food Research Limited (CFR) (Figure 10.7).
Crop and Food Research Ltd, New Zealand, cereal seed production plots
In Australia, private industry involvement in oat breeding and selection is limited to Heritage Seeds, Pacific Seeds and Pioneer Hi-bred. There is no known private oat breeding currently undertaken in New Zealand.
Efforts in oat breeding are limited by industry size. There is one full-time oat plant breeder at CFR, Lincoln, close to Christchurch. The programme focuses on forage, milling and novel food grains.
The programme has been very successful, with approximately 95 percent of oat production for forage, feed and milling oats in New Zealand based on CFR cultivars. Cultivar releases have been made in Australia and the USA.
The programme focuses on crown rust (Figure 10.8) and BYDV in all regions, and stem rust and Septoria avenae blotch to a lesser extent.
Stem rust, Puccinia graminis , is a potential future threat to oat grain crops and resistance is being added to new populations. Though it is not yet a problem in commercial crops, stem rust is appearing more frequently within the breeding nurseries. Germplasm derives mainly from North America, and segregating populations are developed using both pedigree and bulk breeding methods.
Rust tolerance (left) versus rust susceptibility (right). An autumn-sown oat grazing crop in the North Island of New Zealand in the winter of 2001
Genotypes are selected for evaluation and potential commercialization by collaborating companies in New Zealand, Australia, USA and the UK.
The small novel oat grain cultivar breeding component is closely aligned to CFRs food science programmes. The focus is on alternative processing systems and new food uses for the oat crop. The forage programme is developing oat cultivars specifically suited for more frequent winter grazings to meet the changing and expanding demands of an increasingly sophisticated livestock industry.
The University of Queensland is mainly involved in screening lines from other sources for their suitability for forage production, mainly in Queensland. The oat breeding programmes are developing cultivars that combine crown rust resistance and improved forage yield and quality. As well as producing cultivars suitable for grazing, cultivars suitable for hay production are being selected.
Cultivars for grain production are not a priority as only limited grain production occurs in Queensland. The major focus of the programmes is to develop cultivars with more durable forms of resistance to crown rust, and the approach chosen by QDPI is to "pyramid" resistance genes. Molecular markers are being used to select lines with multiple resistance genes, and these are then advanced for assessment of forage yield.
National Cereal Rust Control Programme (NCRCP)
The NCRCP is managed by the University of Sydney and is based at Camden. The major crop of interest is wheat, but limited resources are available to oat breeders. Each year, the NCRCP conducts a survey of races of crown and stem rusts prevalent in Australia, receiving samples of rust on oats and wild oats from collectors across the country, as well as from New Zealand. Results of the survey are published each year, guiding breeders in their decisions about the use of rust resistance genes.
The NCRCP also provides a screening service to breeding programmes. Glasshouse and field screening for both crown and stem rusts are conducted each year, with results - and in some cases resistant selections - being returned to the originating breeding programme. This service is of particular value to the Perthbased programmes as rust epidemics for screening are not reliable in Western Australia (McLean et al. , 2000).
The NCRCP programme is also investigating alternatives to single-gene resistance to the rusts, and screens related wild species for new sources of resistance.
The NSW oat breeding programme at Temora has concentrated mainly on dualpurpose oats for grazing and grain, with less emphasis on grain oats. While NSW is regularly the largest oat producing state in Australia, only a small quantity of the crop is either milled or exported from this state, the crop being largely used on-farm. This has resulted in very poor oat grain prices in NSW. Thus, in the absence of grower contracts to produce milling oats, farmers in NSW consider oats uncompetitive with other, higher value crops such as canola or wheat, unless oat crops can be used to provide grazing to livestock throughout autumn and winter.
Major disease problems are crown and stem rusts and BYDV. The NSW programme now focuses on dual-purpose oats and is placing increased emphasis on selecting for winter growth habit, disease resistance and grain quality parameters that are important in animal production. This will include metabolizable energy and digestibility if resources are available.
The South Australian programme is the largest oat breeding project in Australia and set to become Australias major oat breeding centre. It is based in Adelaide at an integrated university and state agriculture department facility. Interactions exist with scientists trained in a broad range of disciplines who are located at the Waite Precinct. Funding for the programme comes from state government, the Grain Research and Development Council (GRDC), the Rural Industries Research and Development Corporation (RIRDC) and private companies.
The programme is developing improved husked and naked grain oat cultivars with enhanced milling and feed quality, improved disease resistance and increased yield potential for the diverse agro-ecological zones in southeast Australia. The programme is also developing improved hay oat cultivars, with grower and industry support from Victoria and, more recently, Western Australia
A growing export hay industry from South Australia and Victoria relies on improved hay cultivars. Hay is also an important fodder reserve. These new cultivars should be of high quality so that first grade hay can be reliably produced, and economic losses due to down grading avoided.
For both grain and hay cultivars, the South Australian programme aims to improve resistance to crown and stem rusts, CCN, stem nematode, root lesion nematode, BYDV and bacterial blight. These diseases are seen as major factors limiting yield and quality for both grain and hay production. Both resistance and tolerance to nematode diseases are also required. Routine screening programmes are in place for the nematode diseases. Breeding lines are evaluated with specific pathotypes for resistance to crown and stem rusts and BYDV, in cooperation with the University of Sydneys NCRCP. The South Australian oat breeding group also takes advantage of regular natural epidemics in field trials to assess breeding lines.
Quality characters are important in the development of hay cultivars. Traits such as digestibility, palatability, stem diameter, hay colour, neutral detergent fibre (NDF), water soluble carbohydrate, and shear energy are among the quality characters assessed for the most advanced breeding lines (Zwer and Hoppo, 2002).
The South Australian programme is involved in cooperative programmes to improve the efficiency of the oat crop using the maize doubled-haploid methodology, and the development of molecular markers for CCN resistance and tolerance, stem nematode tolerance and quality characters.
Research is also underway in South Australia to improve the efficiency of oat haploid production. The doubledhaploid technology will be used to develop mapping populations and to create homozygous lines for selected elite crosses. This technology is expected to reduce the time needed for oat cultivar development.
A major benefit of developing and using molecular markers is the ability to "pyramid" disease resistance genes. The other technology to be explored is the use of transformation as a means of introducing effective stem rust resistance into oats.
The food industry requires cultivars with better milling yield, higher protein and b-glucan content, with low oil content. The feed industry is looking for higher-oil-content cultivars. Improved hay quality is essential for the growth of the export hay market. Identification of characters that improve palatability or preference is a particular priority for hay quality improvement.
Both Agriculture Western Australia (a state department) and GRDC, previously a major funding partner, recently reviewed and restructured the Western Australian oat breeding programme. Milling quality was the key focus of the Western Australia programme, but, more recently, researchers have improved and widened their quality testing methodology, and improved their understanding of what makes a good milling quality oat. Reliable near-infrared (NIR) calibrations have been developed for whole grain groat percent, moisture, protein and oil content. Quality is also an important consideration when developing hay cultivars, so work has focused on stem thickness, protein content, digestibility and metabolizable energy.
The programme has been very successful, with 95 percent of oats in the southwestern region being bred by Agriculture Western Australia. In the future, work on feed oat cultivars will be decreased and resources redirected to the development of cultivars suitable for the export hay industry.
There are major environment, soil type and disease pressure differences between the western and southern regions of Australia, creating the need for effective regional testing programmes to service these diverse regions. Western Australias focus is on export rather than domestic markets, due to its small population and lack of extensive domestic manufacturing. As a result, Western Australia is a significant exporter of both grain oats and oaten hay. This focus is reflected in industry partnerships, major partners being Agracorp, Australias largest grain oat exporter, and Quaker Oats Australia, which has a food export focus.
Diseases considered important in Western Australia include stem and leaf rusts, BYDV and Septoria avenae blotch, with bacterial blight of more minor importance. Disease resistance has not been a strong point of the breeding programme, though this has changed with the increased frequency of epidemics of diseases such as leaf rust. A nursery is set up each year to screen lines for resistance to Septoria avenae blotch.
The Western Australian programme team has worked closely with an oat agronomist and growers to provide growers with production packages for new oat cultivars, and to improve grower awareness and adoption of agronomic practices to improve both yield and quality of milling and fodder oats.
Oat production is likely to be more concentrated in areas where oats have a natural advantage over other crop species. Oats have advantages in waterlogged environments and are tolerant of frost and acid soils, particularly where aluminium toxicity occurs. Oats also fill an important role in forage production due to their ability to continue to grow in cold conditions.
Production of oats for export hay in Southern Australia is likely to increase. Though more risky than grain production, greater returns can be achieved from hay production, and new markets are still being developed. Markets have also been developed for second-grade hay, and this has reduced some of the risks associated with hay production. With the development of herbicide-resistant weed species, hay also offers a useful non-selective strategy for weed control, with the crop and weeds being cut before seed set.
Oats are an important break crop to control CCN and Take-all diseases in South Australian and Victorian rotations, particularly in low rainfall areas, where there are few feasible rotation crops.
In the northeastern parts of Australia and the North Island of New Zealand, oat production is limited by the lack of sources of effective resistance to crown rusts (and stem rust in Australia) due to the rapid evolution of virulence by the pathogens. New approaches to develop more stable and durable forms of resistance are essential, given the rapid breakdown of single-gene resistances.
Oats can contribute to animal nutrition as a grazed forage, silage, hay and chaff. They have the advantage of early biomass yields in autumn sowings and are used to complement maize in a double-cropping silage system in the North Island of New Zealand. Oats are a flexible crop that allows different harvesting options, depending on current feed supply. The disadvantages include a lack of cultivars developed specifically for intensive multiple grazing situations in cooler regions.
Oats, like other cereal crops and brassicas used in intensive production systems, can cause nitrate poisoning in cattle (Clark, Thom and Roche, 2000). Plants that contain from 1.0 to 1.5 percent potassium nitrate on a dry matter basis may cause acute toxicity in ruminants. Generally, unless other factors are involved that predispose animals to toxicity, stock may consume fodder crops without ill effect. Ruminants can tolerate high levels of nitrate if intake is spread over the whole day. Therefore, for feed high in nitrate, gradual introduction is recommended.
Governments in Australia and New Zealand are reducing their investment in plant breeding programmes for all crops. As a result, there are likely to be closer Australian and New Zealand industry alliances, with the creation of new joint ventures involving research institutes and stakeholders in both countries. Given the small size of the oat industry in New Zealand and Australia relative to wheat and barley, and its lower potential for royalty income, reducing public investment in genetic improvement will increase the urgency for application of enabling technologies such as molecular markers, double haploids and transformation. It will also increase commitment to pursue shared goals through national and international collaboration.
Increased interactions with industry and end users in the future will (from the New Zealand experience over many years) provide more clearly defined quality and commercial goals. The future success of breeding programmes is dependent on retaining access to international germplasm pools. Germplasm exchange between breeding programmes and the operation of international commercial shuttle nursery programmes between the Northern and Southern Hemispheres enables breeders to evaluate breeding populations in contrasting environments and to rapidly advance breeding plant populations, as a means of speeding up the process of releasing cultivars.
Characterizing and documenting germplasm, including plant breeders collections, for all the important food and forage crops of the world will continue to require some government and international agency funding, both for maintenance and for higher-risk research activities. This is of current concern in New Zealand, where state funding systems are becoming less supportive of the genetic improvement of plant material upon which the pastoral and food industries are based.
Increased regulatory border controls surrounding the movement of crop seeds for research and commercial activities into New Zealand and Australia are also beginning to restrict some research activities, and are adding substantial costs through additional quarantine compliance requirements. The benefit, however, is the improved security against introduced pests and diseases that such controls provide for our agricultural and horticultural industries.
An essential requirement for future successful breeding programmes is plant breeders. In Australia and New Zealand, there is an aging population of plant breeders and little succession planning by organizations. It is essential that investment be made in training new plant breeders, ensuring new entrants have the necessary breadth of knowledge to succeed.
Growing potatoes (Solanum tuberosum) in the same spot every year makes your spuds vulnerable to a host of problems, including diseases and insects that overwinter in the soil. In addition, potatoes and other members of the Solanaceae family, including tomatoes, peppers and eggplant, all use a significant amount of nitrogen in the soil. You'll save on the cost of fertilizers -- as well as save on pest and disease sprays -- if you practice crop rotation. Almost any vegetable other than fellow Solanaceae crops are suitable for following potatoes, but some are especially valuable for both succeeding and preceding potatoes.
Harvest potatoes in late fall or before frost occurs in your area.
Remove all potato vine foliage, along with stray tuber pieces, from the garden bed. Potatoes are especially prone to fungal disease and beetles, so raking up and destroying extra vegetation is important for preventing diseases and pest eggs from overwintering in the soil.
Lay a 4-inch layer of compost on top of the former potato bed in early spring.
Work the compost layer into the top 6 inches of soil. Remove stones and other debris you encounter as you are tilling the compost into the soil.
Set up individual stakes, bean tepees or other vertical support systems if you are growing vining legumes, such as peas (Pisum sativum) or beans (Phaseolus vulgaris).
Plant a legume crop according to the planting times of the specific crop. Peas, for example, are a cool weather crop typically planted in March in Mediterranean climates, while beans generally go into the ground in May. Legumes help replenish the nitrogen that the previous year's potatoes drew from the soil.
Water your legume seeds after planting, and provide about 1 inch of water each week during the growing season.
Remove all legume vegetation at the end of the growing season.
Plant a new crop to follow legumes. A spring crop like peas can be followed in early summer with a warm-weather crop. Green or dried beans, on the other hand, take the entire growing season, so you won't be planting a new crop until the following spring. Heavy nitrogen feeders such as turnips (Brassica rapa rapa), broccoli and kale (both Brassica oleracea spp.) thrive in beds proceeded with legumes.
Wait one to two additional years before planting potatoes or other members of the Solanaceae family in the same garden bed. Fungal diseases can lurk in the soil for three or four years. Rodale's "Ultimate Encyclopedia of Organic Gardening" suggests growing corn (Zea mays), oats (Avena sativa) or wheat (Triticum spp.) in the plot prior to growing potatoes again.
Ellen Douglas has written on food, gardening, education and the arts since 1992. Douglas has worked as a staff reporter for the Lakeville Journal newspaper group. Previously, she served as a communication specialist in the nonprofit field. She received her Bachelor of Arts from the University of Connecticut.