Cereal yield and quality as affected by N availability in organic and conventional crop rotations in Denmark: a combined modeling and experimental approach

The effects of nitrogen (N) availability related to fertilizer type, catch crop management, and rotation composition on cereal yield and grain N were investigated in four organic and one conventional cropping systems in Denmark using the FASSET model. The four-year rotation studied was: spring barley–(faba bean or grass-clover)– potato–winter wheat. Experiments were done at three locations representative of the different soil types and climatic conditions in Denmark. The three organic systems that included faba bean as the N fixing crop comprised a system with manure (stored pig slurry) and undersowing catch crops (OF+C+M), a system with manure but without undersowing catch crops (OF−C + M), and a system without manure and with catch crops (OF + C−M). A grass-clover green manure was used asNfixing crop in the other organic system with catch crops (OG+C+M). Cuttings of grass-clover were removed from the plots and an equivalent amount of total-N in pig slurry was applied to the cropping system. The conventional rotation included mineral fertilizer and catch crops (CF+C+F), although only non-legume catch crops were used. Measurements of cereal dry matter (DM) at harvest and of grain N contents were done in all plots. On average the FASSET model was able to predict the yield and grain N of cereals with a reasonable accuracy for the range of cropping systems and soil types studied, having a particularly good performance on winter wheat. Cereal yields were better on the more loamy soil. DM yield and grain N content were mainly influenced by the type and amount of fertilizer-N at all three locations. Although a catch crop benefit in terms of yield and grain N was observed in most of the cases, a limited N availability affected the cereal production in the four organic systems. Scenario analyses conducted with the FASSET model indicated the possibility of increasing N fertilization without significantly affecting N leaching if there is an adequate catch crop management. This would also improve yields of cereal production of organic farming in Denmark

SIMULATING WINTER WHEAT YIELD AND NITROGEN LEACHING FROM ORGANIC AND CONVENTIONAL CROP ROTATIONS

This work evaluates the effects of growing a green manure crop or a legume crop in winter wheat yield and on nitrate leaching, in an irrigated crop rotation. Results are also compared with a conventional cropping system. Simulations with the field version of the FASSET model (Berntsen et al., 2003) were done to evaluate the performance of the model to predict winter wheat dry matter yield. The simulated leaching from the different cropping systems was evaluated during the rotation period