Management & sustainability of stockless organic arable and horticultural systems

Summary

The essential difference between stockless and stocked systems is that the fertility building clover ley and other “forage crops” are not processed through an animal but instead are grown as green manures which are returned directly to the soil by mulching, incorporation or occasionally through composting of the green manure. Stockless systems provide no opportunity for the creation of straw and animal manure based farm yard manure or compost. While there is no research evidence that the lack of animals or manure based compost affects overall soil fertility and crop yield, there is some research evidence that animal manure enhances soil mychorrizae populations and soil organic matter accumulation. This effect might also be seen from the use of plant based compost, sometimes sourced off-farm as “green waste” in stockless systems, but there is no comparative work available. While the use of manures has the advantage of allowing movement of fertility around the farm within a rotation, grazing animals have the drawback of uneven dispersal of manure and urine and manure storage is liable to poor management and loss of nutrients. Green manures are fundamental to stockless systems, both as one or two year crops which are either mulched or incorporated or grown as short term catch crops or undersown crops. With appropriate selection and management of green manures there is potential for enhanced fertility building over that which is possible with grazed leys. The practical commercial experience of farmers using stockless rotations is stronger than the research would suggest in terms of supporting its technical success and viability. Weed control remains a serious problem for arable farms which requires very high standards of management. The demand for organic livestock products is increasing and the area of organic land producing feed grains is insufficient to support the required expansion. World demand for organic grains is increasing. The introduction of livestock on to specialist conventional cereal producing farms in many instances requires prohibitively expensive infrastructure costs. Stockless rotations utilising green manures to fix nitrogen as part of the rotation provide a technically feasible and profitable alternative. Stockless horticultural systems operated with or without the use of imported manure or compost offer potential for technically and financially viable systems provided that there is an appropriate balance of fertility building green manures and cash crops.