Crop yields and supply of nitrogen compared in conventional and organic farming systems

The aim of organic agriculture is to produce food of high nutritional quality in sufficient quantity. Field experiments were conducted to evaluate the effect of organic and conventional growing systems on (i) total amounts and supply of N taken up or applied to plants during a five year crop cycle period and (ii) crops total dry matter (DM) yield obtained during same period. The total DM yields from the organic treatments were 25–33% smaller than from the conventional treatments. The ratio of N output/N input was significantly the smallest in the organic treatment with cattle manure, where only 37% of all supplied N was used by plants during the crop cycle period. The organic fertiliser with faster mineralisation rate and splitting the application of organic N during crop cycle period would be more appropriate to supply sufficient quantities of N during rapid plant growth and to obtain higher crop yields in organic farming systems.