Undersown Crops Research Articles

Design and use of a time-sorting pitfall trap for predatory arthropods

An electronically-controlled time-sorting pitfall trap was designed which improves upon earlier models in having a 24-h rotation time, and in being capable of running continuously for at least one week without attention. Four prototypes were built, using readily available, inexpensive components, and used from June to October, 1995, to collect carabid beetles and linyphiid spiders in clover-undersown and weeded cabbages. The traps operated without malfunction during the hottest weather ever recorded in Aberdeen, when soil surface temperatures exceeded 40°C, and also during periods of torrential rain. Three spider and two carabid species dominated the catch, their nocturnal and diurnal patterns of activity being in general agreement with other published data. Some predators were apparently able to adapt to the contrasting vegetation in the two treatments, two species of Erigone spiders being nocturnal in weeded cabbages but tending to be diurnal in undersown crops.

A behavioural study to help clarify how undersowing with clover affects host‐plant selection by pest insects of brassica crops

AbstractLaboratory and field‐cage tests were done to determine how undersowing brassica plants (Brassica oleraceae L. and B. rapa L.) (Cruciferae) with subterranean clover (Trifolium subterraneum L.) (Papilionaceae) affected host‐plant selection by eight pest insect species of brassica crops. The pest species tested were Pieris rapae (Lepidoptera: Pieridae) (the small white butterfly), Pieris brassicae (Lepidoptera: Pieridae) (the large white butterfly), Delia radicum (Diptera: Anthomyiidae) (the cabbage root fly), Phaedon cochleariae (Coleoptera: Chrysomelidae) (the mustard beetle), Plutella xylostella (Lepidoptera: Yponomeutidae) (the diamond‐back moth), Evergestis forficalis (Lepidoptera: Pyralidae) (the garden‐pebble moth), Mamestra brassicae (Lepidoptera: Noctuidae) (the cabbage moth) and Brevicoryne brassicae (Hemiptera: Aphididae) (the cabbage aphid). In all tests, except two in which the brassica plants were about three times as high as the clover background, 39%–100% fewer of the pest insect stage monitored were found on host plants presented in clover than on those presented in bare soil. Contrary to claims supporting the ‘enemies hypothesis’, differences in colonization alone appeared sufficient to account for the lower numbers of insects found when host plants are undersown with clover. To be effective in reducing plant colonization, the clover must cover 50%, and preferably more, of the vertical profile of the crop plants. As clover used as an undersown crop often has to be cut to make it less competitive with the main brassica crop, temporal aspects of the condition of the clover during critical periods of pest activity need to be recorded carefully before concluding that undersowing does not produce the effect desired against certain pest species under field conditions. The effective clover barrier is like any other treatment, if it is not present at the appropriate time it cannot be expected to reduce pest insect numbers.

Strategies to Reduce Nitrogen Losses via Leaching and to Increase Precrop Effects when Growing Faba Beans

ABSTRACT In four year field trials faba bean cultivation techniques were tested with the primary aim to reduce nitrate losses via leaching by increasing crop soil-nitrate uptake. This aim did not generally contradict the aims of gaining high faba bean grain yields, high amounts of symbiotically fixed nitrogen and an increased precrop effect. As a function of poor rooting systems and poor soil-nitrate uptake faba bean pure stands left high amounts of nitrate in the soil before winter, which is suspected to be leached during winter. A more homogenous rooting-distribution via narrow faba bean row distances increased soil-nitrate uptake and slightly reduced residual- nitrate content before winter. Increasing crop rooting-density by intercropping with cereals or undersown non-legumes considerably reduced soil residual-nitrate content. Undersown brassicas like oil-radish or white mustard were more efficient than ryegrass and intercropping with cereals. Undersown crops showed no negative effect on faba bean grain yield and N2-fixation. Intercropping with cereals considerably reduced faba grain yield and N2-fixation. Underseed variety in faba beans and intercropping considerably affected precrop effects to the successive crop oats as a function of different amounts and temporary availability of nitrogen.

Mitigation of Agricultural Water Pollution in Finland: An Evaluation of Management Practices

This paper summarizes the results of recent studies concerning the agricultural nutrient load to surface waters in Finland and possible management practices for reducing nutrient losses from agricultural land. Both the nitrogen and the phosphorus load exceed the loads from municipal and industrial sources together, thus being mainly responsible for the eutrophication of surface and coastal waters. 25% of the total agricultural phosphorus load is bioavailable dissolved reactive phosphorus, and 5% of the paniculate phosphorus load is available for algae. Reduced tillage, filter strips and permanent grassland on the set-aside land are means investigated for reducing erosion and nutrient losses. Based on experiments and model simulations, it is estimated that a wide adoption of all these practices would reduce total phosphorus load by about 40%. Soluble phosphorus and nitrogen losses can be reduced by adjusting the amount and timing of fertilization and manure application to the actual needs of plants. If the whole set-aside area was under permanent grassland, the nitrogen loss would decrease by about 17%, but the effect of cover or undersown crops in Finnish conditions is still unknown. More investigations are also needed of the effects of all these management practices on the soluble phosphorus load.