Chapter VIII - FODDER OATS IN CHINA

Shu Wang

SUMMARY

Oats have been cultivated in China since prehistoric times, and the country is a centre of oat diversity. Currently, oats rank tenth among cereals in terms of production, and oats are an important fodder crop in the nation, grown in eighteen provinces and regions in China. Although there are several wild and cultivated Avena species, the two major two types are hexaploid hulled and naked oats (Avena sativa L.). China is one of the major oat-producing countries in the world, with an annual harvested area of 350 000 ha, yielding 465 000 t, an average yield of 1.33 t ha^-1. With the development of China’s agriculture and livestock husbandry, oats are becoming a promising fodder crop in the areas where climate is favourable, especially in the remote, cooler mountain areas.

Background

Oats have been grown in China for approximately 2100 years, according to Shi Ji [Historical Records], a book by Si Matsian (145-87 BC). Few details are known about the origin of Chinese oats, especially on their migration to central and eastern Asia. Bretschneider (1881) stated that naked oats resulted from the mutation of hulled oats, and that hexaploid naked oats originated in China. Meanwhile, he identified this naked oat as Avena nuda. Stanton (1923) considered Central or Eastern Asia as their origin. Vavilov (1926) regarded China as their centre of origin.

Although wild species of oats can be found in some areas, compared with other oat-producing countries, the predominant form of Chinese oats has been the hexaploid naked type of Avena sativa (Yang and Sun, 1989). The name Avena nuda is sometimes used in local agricultural literature when discussing naked oats - but it is the naked form of A. sativa that is grown. This crop was cultivated as a staple cereal by the Chinese three decades ago and is still grown as food. Oat straw is of considerable value for roughage, bedding and for poultry litter, and the grain is an important feed for poultry and swine. Hulled types of Avena sativa, mostly introduced from western countries since the 1970s, are now becoming an important fodder as hay, silage and grazing for livestock in the cooler areas, where the thermal regime limits grain crops such as maize and soybean. The area sown to hulled oats was reported by Hu and Zhang (2003) to be 155 700 ha, in contrast with 118 700 ha of naked oats.

Production

Oat production in China since 1961 is shown in Table 8.1. Yield per unit area has increased greatly since 1974 with the release of high-yielding cultivars and the extension of improved cultivation methods. The total yield remained stable in the 1990s, but yield in 2003 was the lowest in 40 years, due to reduced area sown and the yield per unit area.

TABLE 8.1
Oat production in China since 1961

Source: FAOSTAT.

TABLE 8.2
Ratio of areas and tonnages of cereals in China in 2003 compared with 1991

Note: * cultivation was negligible before 1991.
Source: FAOSTAT

The area decreased sharply in 1974 and trend was still for decrease in 2002. During the last 40 years, the combination of maize and soybean, supplemented with minerals and vitamins, has become the standard diet for monogastric stock. The efficient production of both maize and soybean in China makes them ideally suited for efficient animal production. Maize has also been used successfully and efficiently to produce fodder. The increase in maize production has been largely responsible for the reduction in area devoted to oats.

Maize showed a big gain in area and an obvious increase in tonnage after 1960, with 23.52 million hectares grown in 2003 (Table 8.2). In some areas such as Qinghai and Tibet, where grain maize can not be grown with certainty, or where it is too expensive to import, barley and wheat are grown and used as an energy source by feed formulators. In China, many plant breeding and cultivation efforts have been made in the past half century to raise the productive capacity of wheat, usually with success, which has led to wheat overproduction. For a long time, the price of wheat was even lower than that of maize; therefore, some researchers began to study the feeding value of wheat grain (Wang and Zhao, 2001).

Wheat is not as well suited as maize for animal feed, especially for non-ruminants, because it contains less metabolizable energy. However, these cereals are grown extensively in cooler areas and used by feed manufacturers, especially when cheap. Their general availability during seasons of surplus production, or when poor weather conditions result in an oversupply of low-grade grains, has depressed the market for feed oats and led to a further reduction in oat area. Besides the influences of maize, soybean and wheat, the area increase in triticale is another factor, further reducing the area sown to fodder oats. The production of triticale has grown rapidly since 1991, and its area was 310 000 ha in 2003. Its cultivation did not start until 1975 in China, when 476 ha were planted (Table 8.2).

Nutritive value

In spite of the competition, oats are still grown in parts of China, although less than previously, and the grain, straw and forage still play useful roles in feeding domestic animals. Oats have a long and satisfactory history as food and feedstuff. Both protein content and quality, as measured by amino acid composition, are well recognized and of particular importance when feeding non-ruminants. Zheng, Han and Yu (2002) compared two new naked oat cultivars, Naked Oat 323 and Naked Oat 82, with maize grain for four nutritional components in the summer growing area of Inner Mongolia. Table 8.3 shows the general composition of two naked oats in comparison with the maize used in animal feed.

TABLE 8.3
Comparison of composition of grain between naked oats and maize

Source: Zheng et al., 2002.

TABLE 8.4
Oat consumption in China, 1960-1991 (‘000 t)

Source: Welch, 1995.

A study was also conducted on feeding dairy cows with whole-crop oats harvested at heading stage, or a bit earlier, in contrast with silage maize. Because of oats’ higher nutritive value compared with maize silage, each dairy cow could produce an additional 2.13 kg milk per day more, resulting in each dairy cow giving an annual extra return of US$ 225.36. In this area, growing naked oats is cheaper than handling silage maize, and therefore oats are an optimal crop, with dual use as cereal and forage. Breeders have tried to improve the amino acid composition of maize, barley and wheat proteins to increase their biological value, but oat protein is already quite rich in lysine because of its high globulin content. The lipid content of grain is largely unsaturated fatty acids, which, when fed, can alter the fatty acid composition of animal fat.

Economic importance

In China, since the 1960s, the proportion of oats used for feed has increased rapidly; it was double in 1990-91 compared with 1960-64 (Table 8.4). Generally, more than half of all oats are used as feed and another 40 percent for food and industrial use, with about 6.4 percent as seed. Oats used to be valuable feed for horses and mules; now the whole crop or the straw are mainly used as hay or silage for ruminants, while, the grain or groat are used for pigs and chickens. Grain yields vary from 2.4 to 3.8 t ha^-1 in the better environments, but less at higher altitudes (over 3000 m). Green yields range from 10 to 30 t ha^-1 and hay from 3 to 6 t ha^-1 in Qinghai and Gansu provinces (Shi, Li and Li, 1999; Xu, 2003). Recently, the oat grain harvest was valued at US$ 61.92 million, equivalent to an average price of US$ 133.17 t-1; straw was valued at US$ 16.88 million, or an average of US$ 24.21 t-1; hay was valued at US$ 2.59 million, or an average of US$ 48.43 t-1 (Yang, Yang and Liu, 1998).

PROF. HAN JIANGUO, CHINA AGRICULTURAL UNIVERSITY
Figure 8.1
Oats in Basang Region, Hebei Province

Distribution

As a coarse grain, oats only take up 4.6 percent of total cereal areas distributed in 18 provinces and regions. However oats are mainly grown in ten areas: Inner Mongolia, Hebei, Gansu, Shanxi, Shaanxi, Yunnan, Sichuan, Ningxia, Guizhou and Qinghai. Of the total sown area, Inner Mongolia has 36.8 percent; Hebei, 20.7 percent (Figure 8.1); Gansu, 18.0 percent; and Shanxi, 14.7 percent. Oats are also sparsely distributed in other provinces, such as Heilongjiang, Jilin, Tibet (Figures 8.2a and 8.2b) and Xinjiang.

The concentration of oats in these four regions is firstly due to climate, as oats can produce higher yields than other crops. Secondly, animal husbandry is so developed that oats are an important feed resource. Because oats have extremely wide environmental adaptability they can be sown from mid-April to mid- or late June so as to alleviate stress damage occurring in early spring. In China, spring oats occupy more than 90 percent of the oat-sown area and produce 95 percent of the total production. The rest is weak winter oats. According to ecological conditions and farming system, as well as topography, China can be divided into two main oat distribution areas and four subareas (Yang and Sun, 1989).

Northern spring oat area

Northern early oat subarea

This subarea comprises the Tumote prairie of Inner Mongolia Autonomous Region and Datong and Yiding basins of Shanxi province. Altitudes range from 800 to 1 000 m. The annual precipitation is 300 to 400 mm, and fluctuates widely between years and months. Irrigation is used in some places, providing crop yields that are much higher than without irrigation. The annual mean temperature is 4 to 6°C, with a maximum temperature of 35°C in June and July. Hot, dry weather during heading and ripening frequently lowers yields, so early-maturing varieties are grown in some sections. Hailstorms may cause damage locally. Diseases related to warm and wet weather often affect oat yields and quality. Sowing starts from early April and harvest is in mid- or late July; cultivars are characterized by early maturity, drought and cold resistance in this subarea.

S.G. REYNOLDS
Figure 8.2a
Oat trials at Damxung on the high plateau at 4 300 m, Tibet Autonomous Region, China

S.G. REYNOLDS
Figure 8.2b
Oat trials at Damxung on the high plateau at 4 300 m, Tibet Autonomous Region, China

Northern middle and late oat subarea

The northern middle and late oat subarea includes the central and western parts of Xinjiang Uygur Autonomous Region, Helan Mountain and Liupan Mountain of Gansu, mountainous areas along the Yellow River valley in Qinghai, northern parts of Shaanxi province, southern parts of Ningxia Hui Autonomous Region, Yin Mountain of Inner Mongolia, the northwestern plateau, Taihang and Lüliang Mountains of Shanxi, northern parts of Hebei, Yan Mountain of Beijing and southern Xing’an Ranges of Heilongjiang. Because of the mountainous character of this area, agriculture is confined to the river valleys, bench-lands and plateaux. This sub-zone has 80 percent of all the oat area in China; oats are grown at elevations between 500 and 1 700 m. Rainfall is very important in influencing production. The annual mean precipitation is 300 to 450 mm, with 70 percent falling during June, July and August. Because rainfall is relatively low in most sections, irrigation is used extensively where sufficient water is available. Temperature is also a very important factor. The annual mean temperature is 2.5 to 6°C. Soil type and fertility vary greatly. In many areas, oats are an important crop. In general, oat yields per unit area are higher in the irrigated sections than in most other parts of China. The quality of the oats is also excellent.

Southern winter oat area

Southwestern mountain late oat subarea

The southwestern mountain late oat subarea contains Big and Small Liang Mountains of Yunnan, Guizhou and Sichuan provinces, northern parts of Sichuan and Gaoligong Mountain of Yunnan. In many sections of this subarea, where little maize is produced, oats are one of the most important concentrate feeds for livestock. Oats are grown at elevations between 2 000 and 3 000 m. The annual mean temperature is 5°C. Mild winters throughout this zone permit the growing of autumn-sown oats. The annual precipitation is relatively high in most sections and averages 1 000 mm. The main yield-limiting factor is lack of sunlight throughout the growing season. The growth period covers 220-240 days as oats are sown in mid- or late October and harvested in late June or early July. The oat cultivars sown in this sub-zone are characterized by cold and drought resistance, but are susceptible to lodging.

Southwestern prairie late oat subarea

This subarea compromises the flat prairies of Big and Small Liang Mountains in Yunnan, Guizhou and Sichuan provinces. Climatic conditions are the same as the mountain late oat subarea. Owing to the relatively high rainfall, advanced irrigation facilities and high soil fertility, this subarea is well known for high yields of oats. The growth period is 200 to 220 days. Naked oat cultivars with large kernels are sown widely.

Place of fodder oats in rotations and farming systems

In China, oats are grown primarily to complete rotations and to meet feed requirements of animals on-farm and grain for human food. However, as cropping systems vary greatly in different sections of China, the place of oats in rotations also varies greatly. According to ecological conditions, rotations can be divided into autumn-harvested oat zones and summer-harvested oat zones.

Autumn-harvested oat area

Because of the climate, the main crops sown in this area are spring wheat, oats, potatoes, sesame, rape and pulses; it can be further divided into dryland and humid sections.

Dryland section

Rainfed farming prevails in autumnharvested areas with light soil fertility. Alternative crops in the farming system are extremely important to make the most advantage of soil to produce much more biomass and economic yield. In most sections where wheat and oats are the main crops, rotations often used include the following: pea-oat-potato + pea-wheat-sesame or rape; potato + pea- wheat-oat-sesame or rape; and potato- sesame or rape-pea-wheat or oat. In these rotations, cereals are the main crops and cash crops are minor ones. The ratio of the main to cash crops are 2: 1 or 4: 1.

In some drier areas, an alternative crop and fallow system is largely followed. The tillage methods used keep the soil rough and maintain crop residues on the surface to prevent wind erosion and water runoff. Oats must be sown early in spring for good yields. Thus, they are usually sown on fallow of the dry lands or follow an inter-tilled crop that leaves the soil in condition to be prepared quickly for spring sowing. In sections having more farmland and sparse population, a system with rotating green manure is followed, together with the fallow system. Rotations used in these sections are: green manure crop (e.g. lucerne (Medicago sativa))-wheat-oats-sesame or rape; or green manure crop-oats or wheat-potato- sesame or rape.

Humid section

In this section, oats are considered a main crop and take up 70 percent of the sown area. A decade ago, continuous cultivation of oats might be extended to four or seven years because of lack of labour, limited mechanization and lack of knowledge of rotations, thus limiting oat productivity. In recent years, wheat, broad bean and other crops are planted together with oats. Two common rotations for this section are: wheat-broad bean-oats; and broad bean-oats-wheat-potato + sesame + rape. In some areas of subtropical Guizhou, oats can be sown in paddy fields once rice is harvested and can be cut several times in winter and early spring for use as green feed (Luo, Mo and Long, 2000).

Summer-harvested oat area

Unlike the autumn-harvested oat area, ample heat and rainfall permit this area to grow heat-favoured crops such as maize, sorghum, millet and sugar beet. Because maize, sorghum and sugar beet are fertility-exhausting crops, in contrast with fertility-saving crops such as wheat and oats, the alternate cultivation of crops of each type probably gives the greatest return for the least expenditure of labour of any in this area. In some sections. oats produce more when grown after maize than after any other crop. Sugar beet may also follow oats in a four-year rotation of maize, oats, beet and wheat. Anyway, because a preceding crop has less influence on oats than on wheat or barley, most rotations are arranged to meet the special requirements of other crops and oats usually occupy the least favoured phase. The adaptability of oats allows it to work well in almost any rotation.

PROF. HAN JIANGUO, CHINA AGRICULTURAL UNIVERSITY
Figure 8.3
Oats and wild pea (vetch) mixture, Hebei Province, China

In recent years, it has been reported that oats are often used us a companion crop for maize, pea and vetch. Wu and Ge (1999) reported that in Lingtai irrigated area of Gansu, bare land in maize fields lasts 80 days before maize begins to grow fast, so oats intersown with maize can yield 46 861 kg ha^-1 of green feed in mid- June and the maize yield is not affected. Han et al. (1999) and Ma, Han and Mao (2001) studied the optimal harvest time in both monoculture and mixture of oats and pea in the northwestern parts of Hebei (Figure 8.3).

Results indicated that the late milk and early dough stage of oats and the podfilled stage of pea in the mixture were the best harvest time based on the highest crude protein (CP), good dry matter (DM) yield, lower acid detergent fibre (ADF) and lower neutral detergent fibre (NDF) contents. Some reports stated that in order to get high forage and high protein yield, the best ratio of oats to legumes such as vetch or pea is 5: 5 or 6: 4 in the mixture system used in mountain areas of Qinghai, Gansu and Hebei provinces (Han, Che and Zhou, 1992; De and Xu, 1998; Han and Ma, 1998; Ma, Han and Li, 1999; Bao and Zhang, 2002).

Catch cropping of oats mixed with vetch after the first summer harvesting crop have been reported by Sun, Lu and Ma (2003) in the highland region of Gansu, where wheat is a main crop. After the wheat is harvested, some light and heat resources can be used wisely to plant fodder oats and legume forage, which can produce 27 262 to 31 702 kg green forage ha^-1. However irrigation is needed to guarantee a harvest of high-yielding forage.

Use of oats

Oats for hay and grazing

A considerable area of oats is cut for hay in north China, especially in northwestern areas, where oats produce heavy hay yields used as emergency or supplementary hay for winter and early spring. In unfavourable seasons, or when prices drop, oats sown for grain are often cut for hay. When grown especially for hay, oats are frequently sown in mixture with field peas or common vetch. Oats at the milk or early dough stage make excellent hay. When cut at this stage and properly cured, oats make very palatable and highly nutritious hay that is relished by all classes of livestock. The addition of peas or vetch usually increases the yield of hay and improves its nutritive quality (Han et al., 1999; Ma et al., 1999; Kou et al., 2003).

Cultural methods for growing oat hay are similar to those described for grain production. When sown mixed with peas, a common proportion is 75 kg of oats and 75 kg of peas per hectare. For the oats+vetch mixture, the proportion is 75-90 kg of oats and 50-75 kg of common vetch per hectare (Han et al., 1999; Ma et al., 1999).

Hay from oats alone or from oats grown in combination with other crop is made similarly to other hay. The cultivars of oats commonly grown for grain in most sections are most satisfactory for hay. In sections where both short-straw early and the taller-straw mid-season cultivars are grown, the taller cultivars are preferable, because of the heavier yield of forage.

Because of the nature of their root system, oats will not stand much continuous grazing, and care must be taken to avoid overgrazing and excessive trampling. For grazing, oats may be sown at different times in summer if such feed is required throughout the season, since oats may be grazed four to five weeks after seeding. For grazing, the seed rate should be slightly heavier than for grain production. Cultivar choice is very important in that certain cultivars are better able than others to produce abundant leaves and tillers, and consequently to provide greater yields of forage. Some cultivars have the ability to recover more quickly than others after having been grazed. Rust-resistant cultivars are preferable in wet and warm areas during summer.

Oats for silage

Oats, sown in mixture with legumes such as vetch, are used extensively for silage. Frequently this is more profitable than when the oats are harvested for grain. Duo et al. (2002) tested the content of lactobacillus in oat wrapped silage and oats+vetch mixture wrapped silage. The results showed that the content of lactobacillus in the two wrapped silages was similar in winter, but increased at different rates in spring. The content of lactobacillus increased more in the oats wrapped silage than in oats+vetch mixture wrapped silage mostly because of much higher water content in vetch. Oat silage is an excellent feed for cattle, especially dairy cows. A special advantage of oat silage is that it is available much earlier in the season than is maize or sorghum silage, and thus provides supplementary feed in the late summer months, when pasture is often in short supply.

The most favourable stage for cutting oats for silage is when the kernels are in the soft dough stage and most of the leaves are still on the stalk. Cutting oats for silage gets the crop off the field about two weeks earlier than when cut for grain. Traditionally, the guidelines for making oat silage include wilting to 60-65 percent moisture, short chopping and consolidation in the silo (Sun, Wei and Zhang, 2003). In recent years, a new package technique has become widely used in Qinghai province (Xue et al., 2000), involving cutting oats for silage, then making them into small piles, and each pile is then made into an individual package using a grass wrapper. Each package, weighing about 40 kg, is wrapped in IPEX plastic film and stacked. The quality of the packaged oat silage is superior to oat hay, ranging from fair to good.

Use of straw

Oat straw has a high fibre content, which is extensively lignified, so it is poorly digested by monogastrics and its use is restricted to ruminant diets. Oat straw is, however, softer and more acceptable to herbivores than other straws and appears to be of good nutritive value. In China, most oat straw is from naked oats after threshing.

It has been long known that the digestibility of highly lignified materials may be improved by physical and chemical treatment. Treatment of straw with aqueous ammonia has been used for a long time in pastoral areas of China and has been proven to increase the crude protein content, intake and digestibility when fed to ruminants (Han and Ma, 1998). The solubility of NH3 in water is strictly dependent on the temperature. At normal pressure, 1 kg ammonia solution can hold 285 g at 30ºC and 342 g at 20ºC. Solutions containing 25-35 percent ammonia are common. The solution, sufficient to give 3.0-3.5 percent NH3 in the straw, is injected into stacks through a tube mounted in a metal pipe. To ensure proper distribution, the ammonia may be injected at several points of a stack. In cold areas, if the temperature is low, treated straw is stored in a greenhouse for a recommended six to eight weeks. If curing is done early, when the temperature is high, two to three weeks may be sufficient.

Feeding of oats

Oats for cattle

In China, oats are fed mostly in the form of hay, straw, green chop and silage. Luo, Mo and Long (2000) found that cattle fed on a mixture of oats and legumes could gain weight by 261 g day^-1 more than those fed on rice straw. In northwestern areas, farmers often use oat as an emergency feed when perennial forages have failed because of winterkilling. Most oat cultivars have been bred for dual-purpose use as forage and grain. Oat straw is often used as bedding and feed for overwintering beef cattle. Oats have been an important feed for dairy cattle over the years, but the amounts of grain used have decreased sharply as maize silage, grain maize and barley have gained predominance. Zheng et al. (2002) found that oats increased milk production in dairy cows compared with maize silage, so oat haylage is still used extensively in some areas. Oat-based diets increased the portions of unsaturated fatty acids in milk fat that are reported to be beneficial in human diets.

Oats for poultry

Oats have been well known for a long time as a good poultry feed, especially on the farm, but a major constraint is the hull, which is low in digestibility and contains little available energy and protein. When oats are used in balanced diets, the grain is ground before use, thus increasing the cost. However, evidence shows that naked oat cultivars give good results as a feed for broilers and laying hens.

Oats for yak and sheep

In recent years, due to the adjustment of production structure, some areas of Qinghai and Gansu provinces changed from raising horses and mules to raising cattle, sheep and yak. Before mid- November, when slaughter begins, the natural pasture becomes withered. Lei (1999) reported that feeding 3 kg of freshly cut oats daily to yak for 35 days could increase weight by 12.9 percent and commercial meat grade by 16.0 percent. Dong et al. (1998) studied the ratio of digestion of several forages in yak rumen, using the nylon bag method, and found the best hay was oats. The ratios of DM and NDF were 54.1 percent and 39.5 percent, respectively. Other researchers studied the weight-increasing effect of pure oat hay, oats+vetch mixed hay and wheat straw in sheep: oats+vetch mixed hay provided a gain of more than US$ 4.17 per head, and pure oat hay could provide a gain of more than US$ 2.34 per head compared with wheat straw (Wang, Zhou and Wang, 2002).

Naked oats

Naked oats, so called because the kernels thresh free of the hulls, are recorded as having been grown and used as food in China 2 100 years ago; they are grown by farmers who find it advantageous to grow oats that can be fed to young stock and poultry without being ground, and can also be used as porridge or other food for humans. The recognition in recent years of their medical value may encourage farmers to grow more naked oats. Interest in naked oat is growing, and feeding experiments substantiate their excellent feeding value both as a source of energy, which is similar to maize, and as a source of high-quality protein, which is similar to soybean for poultry and pigs. Lysine supplementation may be required, but it can be easily included in the vitamin and mineral premixes. The groat also supplies unsaturated fatty acids that apparently contribute to the production of higher quality eggs, milk and meat products.

The successful breeding and utilization of naked oat will have a profound effect on the rearing of both ruminant and non-ruminant animals. Removal of the hulls genetically, so that the grain is as free-threshing as wheat, is probably the last major step in the domestication of oat. The benefits will probably be first realized on-farm, but, later, naked oat will be accepted more by the food industry and diet formulators and become a grain of commerce, especially in cool regions where maize and soybean cannot be grown successfully because of low temperatures. This will provide farmers with a cash crop they can use in rotations and will provide many regions of China with an opportunity to become more self-sufficient in feed grains.

Normally, the best cultivars of naked oats yield slightly less than the better hulled cultivars, even when allowance is made for lack of hull. The lack of high yielding, well adapted, disease-resistant cultivars, together with a tendency to shatter when ripe and the danger of heating in storage, undoubtedly limit the increase of naked oats in China. This is possibly why a decade ago naked oats were predominant in China, but now the areas of naked and hulled oats are almost equal. Fortunately, oat breeders are making efforts to incorporate desirable genes from hulled oats into naked ones. A series of naked-type oats have been produced after hybridization between naked and hulled oats (Sun, Lu and Söndahl, 1991).

Diseases of oats and their control

Diseases of the oat crop in China cause annual losses of millions of dollars. Some of these diseases may be avoided completely, or considerably reduced by seed treatment, good soil management, proper crop rotation, or by growing resistant varieties. Most diseases depend on a particular set of environmental conditions for suitable development. In some regions, certain diseases rarely appear, partly because of isolation from sources of infection or because of an unfavourable environment. Of the many diseases that attack oats, the smuts, rusts and Barley Yellow Dwarf Virus (BYDV) are the most common and cause the greatest damage. Stem rust is much more serious than leaf rust, especially in northern China.

Main diseases of fodder oats in China

Smuts

Both loose smut, caused by Ustilago avenae, and covered smut, caused by Ustilago kolleri, are seedborne and seed is the only source of inoculum. Loose smut is more prevalent in humid regions and covered smut in drier regions. After seed is sown, mycelia grow into and infect young oat shoots. By heading time, kernels and hulls are completely replaced by chlamydospores, which are released into the air and disseminated by wind to healthy heads before harvest. Smut occurs prevalently in the north and northwest of China and has been one of the most destructive oat diseases. In the 1950s, infection by oat smut reached as much as 46 to 90 percent in some fields in Hebei, Shanxi, Inner Mongolia and Gansu provinces. The annual loss due to smut in China could be 7 to 10 percent. Both smuts may be controlled by seed treatment and the use of resistant cultivars.

Fungicides such as triazole, dithiocarbamate and maneb have proved to be very effective for controlling oat smut. They have no ill effect on seed germination if used correctly. Precautions should be taken against inhaling these fungicides. There is less danger when they are used in liquid or wet forms. Seed treatment five to seven days prior to seeding has better results.

In 1982, 479 naked oats and 611 hulled oats lines were inoculated with smut. There were only one highly resistant and three resistant cultivars in the naked group; in contrast, there were 148 highly resistant and 256 resistant cultivars in the hulled group. Through cross-breeding of naked and hulled oats, a series of naked smut-resistant cultivars were developed, such as Huabei 2, Neiyan 5, Bayan 4, Bayan 5 and Bayan 6.

Despite the use of resistant cultivars and chemical measures to reduce disease levels, smut still occurs in some areas. Comprehensive measures available to prevent smut include seed selection, rogueing out of infected plants after heading and avoiding continuous cropping.

Stem rust

Stem rust attacks the stem in particular, but in severe epidemics it may be found on the leaves and glumes, which results in loss of quality of oat straw for hay or for grazing. The pustules are reddish brown, oblong and usually begin to appear on the plants before heading. In contrast to crown rust, the pustules of stem rust are darker in colour and cause a distinct rupturing of the plant epidermis. The pustules are filled with spores, which are rapidly scattered by the wind to infect nearby plants or those in more distant fields. Air currents carry spores a great distance.

During humid weather, which is very favourable for rust development, the first infections spread rapidly and may result in a destructive rust epidemic. Cool, dry weather hinders the spread of the disease. The red rust stage is followed by the black stage as the crop matures. The black colour is due to the black overwintering spores formed in the same pustules. Black spores which have overwintered on stubble, etc., germinate in the spring and are only able to infect the leaves of the common barberry (Berberis vulgaris L.), the alternate host of stem rust. Spores from small cup-like bodies formed on the undersurface of the barberry leaves are, in turn, able, to infect susceptible oat plants in the early summer. Stem rust occurs greatly in Inner Mongolia in mid- and late July, when the temperature is around 18 to 21°C. In the southwest of China, such as Yunnan, Guizhou and Sichuan provinces, where autumn-sown oats are grown, very little stem rust is found because when stem rust occurs in the north and northwest, autumn-sown oats have been harvested.

The best way to control stem rust is the use of resistant cultivars, such as Bayan 4, Bayan 5, Neiyan 5 and Yongqing 473. In the northwestern region, where barberry is absent, early planting may effectively avoid and reduce infection from urediniospores blowing from other areas. Triazole-type foliar fungicide to control stem rust is available, but may not be economic. If rain occurs within one hour of application, reapplication may be necessary. Avoid spraying in a dead calm or when winds are gusty.

Crown rust

Found in the 1940s in the southwest of China, crown rust (Puccinia coronata) has proved to be worse than stem rust. It usually occurs in late March in the plains region, and infection time becomes later with increasing altitude. Crown rust at first forms small bright orangeyellow pustules, which are found almost entirely on the leaf blades and sheaths. Later-formed pustules are larger. They are long and irregular in shape. There is no conspicuous rupturing of the plant surface at the border of the pustules, in contrast with stem rust. The pustules of the black spore stage are covered by a thin layer of epidermis and hence are less noticeable than those of stem rust. The over-wintering black spores germinate in spring and cause elevated orange-yellow lesions to form on the leaves of the buckthorn (Rhamnus spp.), the alternate host of crown rust. The spores are then carried by the wind from buckthorn to infect young oat plants. Secondary infection, from earlier infected oats, is responsible for the main losses. Crown rust may lower both yield and quality of grain or hay, and bad infection can cause lodging in some fields. The effective way to control this disease is developing resistant cultivars. Proper application of triazole-type foliar fungicide can control oat crown rust.

Barley Yellow Dwarf Virus (BYDV)

BYDV, also called oat red leaf, was first recorded in 1951. In past decades, BYDV was occasionally prevalent in some areas, and caused great yield losses in some years. It is an aphid-borne disease caused by a group of virus strains that can infect most genera and species of grasses. Aphid transmission is the only mechanism of disease spread. There are two common aphids, Schizaphis graminum Rondani and Macrosiphum avenae Fab., known to be vectors in China. Virus strains are numerous and some are specialized in their relationships with the vectors. Virus strains that overwinter on winter cereals or perennial grasses constitute almost all of the virus inocula responsible for yellow dwarf outbreaks on oats in China. In the north, epidemics are caused by the first migrations of alate aphids in mid- or late May. Observations indicate that infestation caused by several aphid species were much more serious than by one aphid species. Occasionally, epidemics develop gradually within a field from an initially low aphid infestation, with wingless aphids as the main vector. Symptoms of the disease take two or more weeks to become visible. The most effective control of yellow dwarf is to grow tolerant cultivars. The Chinese Academy of Agricultural Science evaluated numerous hulled and naked oat landraces and found that Yong 492, Baxuan 1, Baxuan 2, Jinyan 8 and 738- 66-1 were resistant to BYDV. In Shanxi province, early seeding may increase damage to some extent because the crop can suffer twice from infection challenge (Guo et al., 1998). Insecticides to kill the vector aphids are available as a means of controlling BYDV, but are not economic.

Other problems

Lodging

Lodging is often responsible for great losses in oats; this is obvious in the areas where moisture is abundant, where storms commonly occur or where the soil is rich in nitrogen or deficient in minerals. Lodging usually lowers the yield and quality of grain and straw, and makes harvesting difficult.

The damage caused by lodging depends largely on the stage of growth at which the crop goes down. When a green crop lodges, the plants usually bend over at ground level. During heavy storms, considerable pressure is exerted on the stems and particularly at the point of anchorage to the ground. Cultivars that are not too tall and have thick lower stems, combined with large and branching anchor roots giving maximum support, are the ones that do not lodge readily. Lodging prior to maturity is commonest in crops on very fertile soils having higher levels of nitrogen. Where moisture is the limiting factor in crop production, the effect of previous crops on lodging is less noticeable. It is well known that phosphate fertilizers are important for good plant development and tend to hasten maturity, thereby lessening the damage from lodging caused by late summer storms.

High seed rates increase lodging because the plants are more spindly as a result of competition (Chen, Li and Shi, 2000). Early sowing has tended to produce crops with stronger straw. This may be the result of a more suitable growing season, which leads to better plant development. Early-sown crops also have a greater chance of escaping heavy storms.

Another type of lodging may occur as the grain approaches maturity, when the straw gradually loses its flexibility and become brittle. At this stage, breaks occur higher up in stem. Early in 1982, the Chinese Academy of Agricultural Science evaluated parts of naked and hulled oats, both cultivated in China and introduced, at filling stage, milk stage and dough stage. Thirty-six cultivars did not lodge at milk stage, and most of the lodging cultivars were early naked oats from Shanxi, with a plant height exceeding 100 cm. Only two naked oat cultivars kept standing at the dough stage: Yong 492, a naked oat derived from an introduction from France; and "Iron stem and large grain", a cultivar developed in Hebei province. The Inner Mongolian Academy of Agricultural Science evaluated hulled oats and found cultivars from Qinghai, Xinjiang and Gansu provinces, together with some introduced from Australia, Canada, Denmark, France, Japan and USA, that were resistant to lodging. Lodging resistance was found to be associated with internal stem structure and size, and with anchor root development. Such finding can be directly applied to the development of cultivars that will stand up under conditions of high fertility and abundant moisture, and at the same time meet the requirements for high yield and good quality.

Drought

For maximum development, oats require plenty of moisture throughout the growing period. Some areas of China suffer from too little moisture and a high degree of evaporation, which tend to increase the hazards of growing this crop. In these areas, drought may occur at various times during the growing season, with attendant danger of crop failure. Insufficient moisture in early growth stages tend to produce weakened plants with sparse tillering. The effect of drought in the latter part of the growing season is reduced filling and yield. Early seeding and the use of early-maturing cultivars often enables the crop to escape drought damage during the later stages of growth. In China, efforts are being made to evaluate the drought tolerance of cultivars in different areas, and to incorporate drought resistance from foreign sources and landraces into better oat cultivars (Xin, Dong and Song, 1996).

Frost

Frost damage, in either the spring or autumn, is a hazard for oat production in some areas. This is particularly important where the frost-free growing period is short, as in Qinghai. Usually oats are more able to make a better recovery from spring frost injury than are other cereals. Early autumn frost damage is particularly detrimental when the crop is intended for grain production. When oats are grown for grain, early maturing cultivars are favourable. If oats cannot be harvested for grain because of a limiting thermal regime, vegetative fast-growing cultivars should be used, such as fodder oat cultivar Qinghai 444 (Shi et al., 1999).

TABLE 8.5
Major oat cultivars grown in the period 1960 to 1989 in China

Oat breeding and germplasm enhancement

History of key oat cultivars

Although naked oats originated in China, no research institute engaged in oat breeding until 1949. Chinese oat breeding began in the 1950s, when some research institutes in oat growing areas in the north started to collect and evaluate local landraces. In the 1960s, the situation improved and the Chinese Academy of Agricultural Science organized specific agencies to collect, conserve and evaluate domestic and foreign hulled and naked oat germplasm.

TABLE 8.6
Major oat cultivars grown in the 1990s in China

Since the early 1970s, oat breeding institutions have focused on hybridization between naked and hulled oats, aiming to overcome the weaknesses of Chinese naked oats, such as weak stem and low grain weight. By 1989, the oat breeding programmes in provincial institutes had released a series of cultivars, including Sanfensan, Huabei 1, Huabei 2, Tongxihao, Yanhonghao, Jinyanhao, Baxuanhao, Wuyanhao, 73- 7, Yong 492 and Yong 578, all of which were naked oats (Yang and Sun, 1989) (Table 8.5).

Between 1990 and the present, new oat cultivars have been developed more rapidly than before. With strong support from the central government and cooperation between institutions, a number of new oat cultivars with high yield potential and multiresistance were developed and quickly released in the corresponding oat cultivation areas (Table 8.6).

Current breeding and research

Oat genetic resources

A large collection of Chinese and foreign germplasm, with almost 3000 accessions, recently set up by the Chinese Academy of Agricultural Science and Hebei Academy of Agricultural Science (Ma and Tian, 1998), is stored in the Germplasm Institute of Chinese Academy of Agricultural Science, Inner Mongolian Academy of Agricultural Science, and other institutes. This collection included 1 972 Chinese and 1 005 foreign accessions. Table 8.7 indicates the number, type and sources of this collection. Accessions have been further characterized for agronomic and quality characteristics. Seed stocks for breeding are furnished upon request. Enhanced germplasm is added to the stocks for future use. Most of the germplasm has been released or registered.

TABLE 8.7
Accessions of oat germplasm in China as of 1997

Source: Ma and Tian, 1998

Introduction and reselection

Early oat breeders assembled cultivars from throughout the world and grew them in field tests to identify those that were best adapted. Fu, Liu and Liu (1999) reviewed the application of introduced oat cultivars to new naked oat cultivar breeding. Two widely grown cultivars introduced into China were cv BnP 1988 from USSR in 1960, and cv. Nuprime from France in 1971. Many of the introductions were mixtures of homozygous genotypes, so oat breeders practiced "pure line" or "individual plant selection" to isolate the highest-yielding and best-adapted genotypes from the mixtures. Pure line selection is essentially the increasing and testing of the progeny from selected single plants. This method is still a basic technique for oat improvement. However, various methods are used to increase variability prior to selection.

Hybridization and wide crosses

Oat hybridization in China began in the early 1970s. To date, most oat cultivars have been developed through hybridization. Modern oat breeders rely almost entirely on hybridization, followed by selection, for the development of improved cultivars. The high-yielding naked oat Neiyan 5 is a successful example of a cultivar obtained through the crossing of hulled oat cv. Yong 380 and naked oat cv. Huabei 2 (Sun, Chang and Li, 1991). The technique of selection after hybridization between hexaploid naked and hexaploid hulled oats was reported by Gu, Li and Wang (1997). The results indicated that hybrid progeny between hulled and naked Avena sativa showed mixed inheritance. Selection focused on parental selection, pollination method, continuous single-plant grain selection, and biomass and harvest index.

Some researchers tried to use wide crosses between hexaploid naked oat and the wild tetraploid species Avena magna to increase genetic variability in the breeding material. Primary attention was paid to finding new sources of high feeding quality and resistance to diseases, pests and abiotic stresses. Fu, Li and Sun (1995) successfully incorporated high-protein genes from Avena magna into hexaploid naked oats. The protein content of several progenies reached 18-20 percent. Observations on fertilization and early embryo development in the intergeneric cross indicated that pollen germination of Avena sativa appeared to be normal on the stigma of Avena magna and the pollen tubes grew into the style and entered the embryo sacs (Zhao, Liu and Yang, 2001).

Tissue culture

In recent decades, there have been several reports of plant regeneration and potentially useful genetic variation derived from tissue culture of oats, and the use of such variation in a breeding programme has been reported (Fan and Cui, 1995). The use of tissue culture variation deserves serious consideration by oat breeders and hopefully such variation can be used to develop improved cultivars of oats.

Culture from somatic tissues

Li et al. (1991) studied the relationship between endogenous hormones of immature inflorescences of naked oats and somatic embryogenesis. They found that, along with the development and differentiation of the shoot tip, the requirement for indole acetic acid (IAA) for its growth and differentiation increased. In the undifferentiated and embryogenic calli the ratios of IAA to CTK were 1.8: 1 and 5.1: 1, respectively. The optimization of concentration of 2,4-D could increase callus induction. Fan and Cui (1996a) reported a technique of callus induction and plant regeneration with young panicles of naked oat on N6 medium.

The optimal length of the material was 1- 2 cm, which could increase the frequency of induction (74.7 percent). Cui and Fan (1996; 1998) also reported the successful culture of embryogenetic calli and plant regeneration from mature embryo on N6 medium. A suspension system was also established. Yang et al. (1998) reported obtaining hybridized plants from the cross of tetraploid Avena magna and hexaploid naked oats, using immature embryos on MS medium.

Culture from gametophytic tissues

Sun, Lu and Söndahl (1991) reported the production of haploid plants through anther culture in naked oat using MS callus medium. They found that MS medium with 4 percent sucrose, 1 percent activated charcoal and no exogenous auxin supplement gave the highest initiation frequencies (14.7 percent) of anther callus among media tested. The cell suspension cultures were established from pollen friable calli in liquid medium. The suspension cells were cytologically stable over one year. The successful application of this technique in oat production led to the development of Huazao 2, Huazhong 21 and Huawan 6, which were the first cultivars produced by this technique in China. They are all naked and have been released in north China (Yang, 2001).

Hybrid oat development

Since its discovery in China in 1994, CA [China Avena sativa] male sterility has been increasingly used in oat breeding programmes. Fan and Cui (1996b) reported that this male sterility was found in a hulled parent. Cui et al. (1999) looked at the genetic identification of this malesterile oat and found that the sterility was steady and that it belongs to the pollenless type, with 100 percent sterility. Fertility of F1 hybrids was restored in six combinations, and, when self-crossing, ¾ fertile plants and ¼ sterile plants segregated in the F2. When F1 progenies were crossed with the sterile plant, a 1: 1 sterile: fertile segregation was obtained. Based on these observations, the sterility is controlled by recessive nuclear genes. As it was the first oat sterility found in China, it was named the "CA male-sterile oat".

Themes and subjects requiring research or extension

Oats are chiefly a crop in northern areas of China. These areas have the cool, moist climate to which oats are best adapted. In recent years, the hulled oat area for fodder increased sharply compared with naked oats for grain. One of the explanations is that hulled oat introductions played or are still playing a very important role in these pastoral areas (Shi et al., 1999). In Qinghai, cultivation of hulled oats in Quan Wozi (the winter pen on a family farm) has had an especially great effect on the development of husbandry as it can provide high quality feed in winter and in the early spring. However, the lack of methods to build highly sown forage is still a bottleneck limiting the potential of hulled oats. In these areas, oat cultivar introduction and evaluation are a crucial means of increasing oat production potential (Zhang, et al., 2002). More and more personnel and agencies are providing oat germplasm to areas of China as a valuable input to accelerate oat extension and cultivar improvement. A Canadian oat breeder, Dr Burrows, visited the Baicheng area of Jilin province to help guide the oat production programme and donated 260 germplasm lines and more than 160 hybrid combinations (not included in Table 8.7). His generosity and contribution to the agricultural development of China is truly appreciated (Ren et al., 2002; Chen, 2002).

However, cultivar introduction is not the ultimate way to solve the problems appearing in oat production, so some areas in Tibet Autonomous Region and Qinghai province have set up seed production bases (Jin, 2000; Chen et al., 2002). For instance, the biggest oat seed multiplication base, established in Huangzhong county of Qinghai province, sponsored by the Agricultural Ministry of China, has been in use since 2003 and can produce more than 5 000 t of seed annually. Unfortunately, for a long time, most effort was put into the improvement of naked rather than fodder oats, so the small number of fodder oat cultivars is another limiting factor in the development of fodder production in pastoral areas. In the longer term, much more attention should be paid to fodder oat breeding, with a target of early maturity, high green feed or hay yield, cold tolerance and high protein in grain.

Plant breeding alone will not be enough. A multidisciplinary and integrated approach is needed, including associated livestock improvement, and mechanization of seeding, harvesting, grain cleaning and storage, hay storage and silage ensiling. Agencies are also needed to facilitate effective cooperation with inter national agencies to bring Chinese fodder oat production up to world standards.

Perspectives

In China, continuous population growth and loss of farming land encourages protection of the living environment and promotion of living quality. Unfortunately, in past decades, overproduction of cereals and overstocking of livestock have resulted in environmental deterioration and degradation of arable land and grasslands. The agricultural production structure has to be adjusted to meet the requirement for healthy economic growth in rural areas, especially in cooler regions of China, where maize and soybean cannot be grown successfully because of low temperatures and where oats could be an ideal option in the production of forage and could provide livestock with ample feed in the winter and early spring. According to the Tenth Five-Year Plan (2000-2005), grassland development and feeding domestic animals with straw have received more attention by the government, and livestock development has been placed in a very important position to face competition from all around the world after entry to the WTO. In these five years, 1.3 million hectares of grassland will be established, 20 forage breeder’s seed bases and 136 forage seed multiplication bases will be constructed. Oats, as a most valuable fodder, will be further recognized and used widely in most grazing areas. For instance, 9 000-13 000 t of fodder oat seeds will be needed in Qinghai and nearby regions of other provinces, but only 31 percent of this requirement can be met through the current seed market (Zhou, 2003). So in the near future, fodder oats should develop rapidly because this crop can bring good returns to farmers and ranchers.

Conclusion

Oats have been grown in China for at least 2100 years and were always a staple food. Its importance lessened after 1974 because maize, wheat and soybean production expanded and supplanted it. However, the yield per unit area has increased rapidly as a result of successful oat breeding programmes in areas where oats are grown widely. The main areas for oat production are in the northwest, north and northeast of China, with the cool, moist climates to which oats are best adapted. Oats are adapted to a wide range of soil types, but temperature and moisture conditions are the limiting factors in production. In recent years, the importance of oats as fodder - pasture, hay, silage and feed grain - has been recognized more by farmers and government because of its high feeding value and environmental conservation function. Naked oats are considered a cash crop in rotations and will become a grain of commerce with the development of food processing industry. The potential is so high as to permit this crop to play a very important role in the development of the agricultural economy of China.