Managing soil fertility in organic farming systems

Complex relationships exist between different components of the organic farm and the quantity and quality of the end products depend on the functioning of the whole system. As such, it is very difficult to isolate soil fertility from production and environmental aspects of the system. Crop rotation is the central tool that integrates the maintenance and development of soil fertility with different aspects of crop and livestock production in organic systems. Nutrient supply to crops depends on the use of legumes to add nitrogen to the system and limited inputs of supplementary nutrients, added in acceptable forms. Manures and crop residues are carefully managed to recycle nutrients around the farm. Management of soil organic matter, primarily through the use of short-term leys, helps ensure good soil structure and biological activity, important for nutrient supply, health and productivity of both crops and livestock. Carefully planned diverse rotations help reduce the incidence of pests and diseases and allow for cultural methods of weed control. As a result of the complex interactions between different system components, fertility management in organic farming relies on a long-term integrated approach rather than the more short-term very targeted solutions common in conventional agriculture

A comparison of butterfly populations on organically and conventionally managed farmland

Habitat loss and reduction in quality, together with increasing homogeneity of the farmed landscape and more intensive field management, are believed to be major drivers of biodiversity loss on farmland. Organic farms demonstrate features that are now rare elsewhere in UK farming systems, such as crop rotations incorporating grass leys, exclusion of synthetic pesticides and fertilizers, and reliance on animal and green manures. They may also contain greater densities of uncropped habitats such as hedgerows. In this study, we examined whether organic farming affected populations of one group of insects of conservation interest, butterflies, on farmland. The abundance of butterflies on pairs of organically and conventionally managed farms was recorded over 3 years and a number of habitat and crop variables, likely to be related to butterfly abundance, were also measured. Organic farms attracted significantly more butterflies overall than conventional farms. Significantly more butterflies in both farming systems were recorded over the uncropped field margin than the crop edge. The difference in butterfly abundance between crop edge and field margin was relatively greater in conventional than organic systems. Species richness of butterflies tended to be greater on organic farms. Five species of butterfly were significantly more abundant on organic farms in at least 1 year, while no species was significantly more abundant on conventional farms. Organic and conventional cropping patterns differed, the former having proportionally more grass leys, and hedgerows were larger on organic farms. Although no significant effects of farming system on the numbers of grass or forb species present in the field margin or crop edge were detected, some individual plant species showed differences in frequency between organic and conventional field boundaries. Increasing the extent of organic farming, or practices associated with it, could help to restore biodiversity in agricultural landscapes