Break crops

Although winter wheat is grown on more land than any other crop in England and Wales, it is not usually grown continuously, because of problems from pests and diseases. Break crops are grown to interrupt the build-up of these problems, so we need to look at the behaviour of nitrogen under these and other crops, but much less information is available than for winter wheat. 

Up to Harvest. Oilseed rape and field beans are used as break crops for winter wheat on a variety of soils, and potatoes are used on the lighter soils. Sugar beet may also be grown, but this depends not only on the soil but also on the proximity of a sugar beet processing factor. Four Rothamsted-based experiments compared the effectiveness of winter wheat and winter oilseed rape in their use of labelled nitrogen fertilizer. Potatoes were included in two of these experiments and sugar beet and field beans in one experiment each. Two criteria based on the... 

A sound crop rotational system is of basic importance to the organic farmer. It reduces the risk of diseases and pests associated with monoculture, gives better control of weeds, spreads the labour requirements more evenly over the year, reduces the financial risk if one crop yields or sells badly and provides more interest for the farmer. For instance, take-all is a disease that cannot even be controlled chemically. Winter crops are more susceptible to take-all than spring sown crops and wheat is more susceptible than barley, so the safest position for winter wheat is immediately after a break crop. 

Robson, M C, Fowler, S M, Lampkin, N H, Leifert, C, Leitch, M, Robinson, D, Watson, C A and Litterick, A M (2002) The agronomic and economic potential of break crops for ley/arable rotations in temperate organic agriculture , Journal of Agronomy, 77, 370-427. 

Evans, J., Scott, G. Lemerle, D. Kaiser A., Orchard, B., Murray, G.M. and Armstrong, E.L. 2003. The impact of legume break crops on the yield and grain quality of wheat and relationship with soil mineral N and crop N content. Australian Journal of Agricultural Research 54 777-788. 

Smith, B.J., Kirkegaard, J.A. and Howe, G.N. 2004a. Impacts of Brassica break crops on soil biology and yield of following wheat crops. Australian Journal of Agricultural Research 55(1) 1-11. 

Alternative crops in a break crop system should do several important things ... 

This rotation can be lengthened by the inclusion of some second wheats or three-year leys, or can be shortened by the removal of a break crop and one of the first wheats. 

Northern Ireland and the hill areas of England and Wales where substantial seed potato enterprises still continue. The main advantages of these areas ate that the low temperatiues and strong winds keep aphid populations in check. This means that the severe virus diseases (leaf roll and the mosaics) which are spread from diseased to healthy plants by aphids, are less likely to occur. However, recent advances in aphid control and concerns over the quality of seed from some traditional areas have seen successful seed production extended to some of the English arable areas as a profitable break in predominantly cereal and break crop rotations. As with other forms of seed production the certifying authority in England and Wales is FERA, for Scotland SASA (Science and Advice for Scottish Agriculture) and DARD in Northern Ireland. In all cases the same basic Seed Potato Classification Scheme (SPCS) obtains. 

Oats can be taken at almost any stage in a rotation of crops. They are a useful take-all break crop and are often a lower input crop than other cereals. 

Abstract This chapter opens with an introduction to the concept of world markets for oilseeds and proteins and how this affects farmers decisions to grow break crops. It then tackles the agronomy of the main combinable break crops including oilseed rape, linseed, field peas and field beans. It briefly covers more esoteric crops such as flax, lupins, navy beans and sunflowers. Each crop is dealt with by describing the variety choice, tire establishment, crop nutrition, crop protection, and harvesting and storage, as well as a brief discussion of their markets and quality aspects requited. 

Because of the comparatively small area grown, pests and diseases are not generally a serious problem. Nevertheless, linseed should not be grown more often than one year in five. It is not related to atty other break crop so it can be grown in all rotations. It leaves a good seedbed for a following crop of wheat with a fine tilth and few slugs. 

Combinable break crops 355 Table 14.5 Field beans indicative yields (t/ha)... 

Peas can be a valuable break crop in cereal-based rotations. Peas are N-fixers and the crop debris contains high levels of N. Legumes (peas and beans) should be grown no more than one year in five to prevent the build-up of pests and diseases. 

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