Timing the Removal of a Legume Intercrop to Optimize Soil Nitrogen and Moisture In An Organic Dryland Wheat System.

Crop diversification is a common practice among growers interested in organic and sustainable farming practices. Wheat growers could benefit from intercropping a legume as a source of biological nitrogen (N) for wheat if competition for other resources is not a concern. The main objective of this experiment was to determine the optimal time to mechanically remove a winter pea intercrop to provide the greatest amount of fixed N and perhaps other benefits to winter wheat while reducing soil moisture stress. Removal times were based on percent canopy cover of the intercrop. At each removal time, subsamples of crop biomass were collected in each treatment plot and previously swept plots and analyzed for dry weight and total N. Soil samples (0 to 60 cm depth) were collected at each removal time for treatment plots, non-intercropped controls and previously swept plots, and for all plots after harvest. Soil samples were analyzed for gravimetric water content and inorganic N. Grain was harvested at maturity and analyzed for yield, test weight and protein. Precipitation was approximately 6 cm above normal during the sampling period (April to June). Although wheat vegetative biomass was greater when the intercrop was removed earlier, preliminary results indicate that crop biomass N concentration, grain yield, grain test weight and protein content did not vary among removal treatments. No difference was found among treatments for inorganic soil N and moisture, indicating that the legume intercrop did not compete with wheat for these resources. Wheat grain yield and quality did not appear to be affected when intercropped with a legume when resources were abundant enough to prevent competition stress.