Impact of organic production practices on soil quality indicators

The impact of organic production practices on soil quality indicators, for selected farms in Nebraska and North Dakota, were evaluated to better understand their effects on soil quality and sustainability. Conventional production practices were the standard to which the effects of organic production were compared. Five organic and conventional farms, matched by soil type, were chosen for the study, Soil properties recognized as basic soil quality indicators were measured on each farm at depths of 0 to 7.6 and 0 to 30.5 cm, Averaged across locations, there was 22% more organic C (12 571 kg ha-(1)) and 20% more total N (970 kg ha(-1)) on organic farms than conventional farms in the surface 30.5 cm, At four of five locations, organic farms had soil pH closer to neutral, lower bulk density, and higher available-water holding capacity, microbial biomass C and N, and soil respiration as compared with conventional farms. Nutrient levels above crop needs were observed in both organic and conventional farms indicating the potential for negative environmental impacts. Despite this, organic farms often had more potentially mineralizable N (anaerobic incubation) relative to NO3-N in the surface 30.5 cm. For conditions of this study, the capacity of organic production practices to improve soil quality was mainly due to use of more diverse crop sequences, application of organic: amendments, and less frequent tillage.