Crop Diversification Effects On Soil Nutrient Levels in Long-Term Dryland Cropping Systems in Montana.

Adoption of diversified no-till and organic cropping systems in semiarid regions of Montana has increased due to potential for soil quality, pest control, and economic benefits; however, relatively little research has been conducted to quantify these potential benefits in long-term experiments. Our current study objective was to evaluate the effects of crop diversification and nitrogen (N) fertilizer rate (full vs ˝ rate) on soil nutrient test levels in a long-term dryland cropping system. The field plot study was conducted at the 12-yr crop diversification rotation study located at the Post Agronomy Farm near Bozeman, Montana. Soil was collected at four-year intervals beginning in 2004. Soil samples were separated into depth segments of 0-15, 15-30, and 30-60-cm and each depth composited from four subsamples per plot. Soils were analyzed for a suite of parameters including ammonium, nitrate, total N, Olsen phosphorus, exchangeable potassium, sulfate, and organic carbon. Study results are pending as spring 2012 samples continue to be processed, but will be completed in time for the annual meeting.