Cereals and legumes

Summary

Part 1a – Weeds

I – Methods for mechanical weed control in cereal and pulse fields with and without undersown ley. Weed control is not possible when grass clover is broadcasted at the sowing time of barley. The risk of a poor established grass clover ley is high when pre-emergence weed harrowing is carried out before establishment of the ley. Using a special sowing technique where the grass clover is sown simultaneously with barley in the same row (24 cm row spacing) has two advantages: Firstly, an early sowing gives better conditions for a well established ley and secondly, the technique gives the possibility for both weed harrowing and hoeing after the establishment of the ley, because the cereal row protects the ley from mechanical damages. However, at low weed infestation levels the technique of broadcasting grass clover without mechanical weed control is enough to achieve a well-established and relatively clean grass clover ley.

Lupin is tolerant to pre-emergence harrowing, post-emergence harrowing and hoeing as long as the majority of the plants are not up-rooted. The trials proved that lupin is very tolerant to intense weed harrowing. A crop soil cover of as much as 80% did not cause any significant yield losses. The combination of hoeing and weed harrowing turned out to be a very effective weed control strategy (96% effect). The narrow leafed lupin did not compete well against high weed pressure due to the low ramification of the lupin, and controlling the weeds resulted in a yield increase.

II – Interaction between weed control and fertilizer placement. Injection of animal slurry increased the early growth (during tillering) of spring barley and the later growth (after tillering) of naked spring oats. In both crops injection improved the yield potential by 15 – 35 %. The injection reduced the weed biomass by up to 50 %, depending on the relative competitiveness between the actual crop and weed species. In some cases the injection of slurry improved the effect of weed harrowing and reduced the crop damage.

III – Row distance, row architecture and plant density. Sowing of spring wheat in a two-dimensional uniform pattern resulted in 30 % less weed biomass at all three densities. At high crop density (700 seeds m-2), the uniform pattern had 60 % less biomass and 60 % higher yield than under normal sowing practices (400 seeds m-2, sown in 13-cm rows). There were large differences in the ability of different varieties to suppress weeds, and this was most clear at higher densities.

IV – Development of strategies for weed control. A review about prevention and control of weeds in organic plant production has been written. A workshop about plant protection was arranged for farmers, extension workers and researchers. Late sowing of winter wheat reduces the yield under weed-free conditions, but late sowing reduces the germination of weeds. At high weed densities and mechanical weed control the weed infestation was reduced at late sowing. Stale seedbed did not seem to have any effect on weeds or yield, but may effect the weed seed reserve in the soil in the long run. At high weed densities, large row distance and row hoeing combined with weed harrowing is most effective, but at low weed densities, normal row distances and weed harrowing is sufficient.

Part 1b – Diseases

I – Development of direct control methods for smut of wheat with plant extracts and analysis of infection level in cereal samples of common bunt of wheat and stem smut of rye. Soil borne inoculum of common bunt can infect a wheat crop at least 5 years after last infected crop in the area. Also stem smut in rye can infect after several years without susceptible crops. Seed treatment with mustard flour can control common bunt and stem smut (>95% disease reduction) without significant reduction in germination vigour of the seeds. Seed treatment with milk powder can be used in control of the two diseases, but disease control has a lower reduction potential, and the risk of decreased germination vigour is higher. Several different biocontrol agents have a potential in control of common bunt, and in combination with milk powder the potential increases. The threshold for contamination of bunt spores in a seed lot should not be increased, but if possible it should be decreased in earlier propagation generation in order to minimise the risk of early multiplication of the disease. The threshold for contamination of stem smut spores in a seed lot can possibly be increased without significant risk of multiplication.

II – Resistant varieties against common bunt of wheat. A screening procedure has been established for testing resistance against common bunt (Tilletia caries). Most Danish winter wheat varieties have now been tested on different populations of T. caries with great variation in resistance. Varieties like Stava (19 test populations) and Tjelvar (13 test populations) are highly resistant. Varieties like Trintella and Aspect were only attacked 1-2 % when tested on 9 different populations. A group of varieties had only moderate attack in repeated test. The varieties grown on most of the area in Denmark are very susceptible to common bunt. There seems to be a good basis for introducing resistance against common bunt in breeding programmes but it has to be a long lasting and continuos process. The resistance is based on specific genes and only little is known on the population structure of the diseases and more information is needed especially on the virulence structure.

Part 1c – Insect pests

Control of beet aphids in Faba beans by use of varieties with bad host qualities. Different varieties of broad bean were tested in climate chamber-, mini glasshouse- and field trials to test their susceptibility to black bean aphids. For only one variety the results were corresponding. For the other varieties the results were not quite clear. It is concluded that field trials are necessary to have a more precise picture of the potential of the different varieties against black bean aphids.

Part 3 – Choice of crop and cultivar in relation to quality and yield

I – Selection and evaluation of genotypes of lupines. Narrow leafed lupine is more thermo-neutral and earlier ripening than yellow lupin, which also is very susceptible to the seed borne disease anthracnose. Early flowering and reduces branching are essential for timely ripening. The yield of selected varieties, mainly un-branched types, was between 3.1 and 4.9 tons ha-1. Whole crop silage of inter-grown lupin and barley is a good protein source; however, the energy availability and digestibility are slightly lower than in barley whole crop silage.

II – The ability of naked oats to produce protein and essential amino acids. Yield potential is lower in naked oats than in husked oats, however, grain quality is considerably higher in naked oats

III – The content of antioxidants in varieties of barley and naked oats under varying conditions. Development of a new method was carried out in order to determine the phenolic compounds. 15 phenolic compounds were found in barley leaves, comprising of 2 phenolic acids and 13 flavonoids. 8 of these were purified and the structures determined. One of these was a completely new compound, 3 were reported earlier in barley, 3 in other grasses and one was reported earlier only in dicots.