Effect of Double Cropped On Yield and Biomass Accumulation of Cover Crops in Kansas.

The contribution of nitrogen (N) by cover crops is an important component of sustainable agriculture and alternative source of N. Legume summer and winter cover crops can decrease inorganic N fertilizer requirements and production costs through symbiotic N₂ fixation. It is also vital to make maximum use of the available land during the growing season. However, summer crop yields may be decreased due to shortened length of growing season and risk of water shortage. The objectives of this research were to (a) to evaluate the performance of doubled cropped soybean and grain sorghum yield following winter wheat, and (b) to determine total biomass production, N and carbon accumulation of various cover crops following winter wheat. Field experiments were conducted at two locations (Ashland Bottoms and North Farm both in Riley County, Kansas) in 2012. The experimental design was a randomized complete block design with four replications. Five crops, cowpea [Vigna unguiculata (L.) Walp], sunn hemp (Crotolaria juncea), pigeon pea [Cajanus cajan (L.) Millsp], soybean [Glycine max (L.) Merr.], and grain sorghum [Sorghum bicolor (L.) Moench] were randomly assigned to the experimental units. Nitrogen and carbon concentrations in the above ground parts were determined. There was a significant interaction between location and crop (P<0.05) for most physiological, growth and yield traits. Pigeon pea recorded the greatest plant N and carbon accumulation, while sorghum and sunn hemp had the lowest plant N and carbon accumulation respectively. Also, pigeon pea produced the maximum above ground biomass followed by sorghum when averaged across both locations. Grain sorghum produced the highest grain yield when compared to soybean across both locations. Overall, preliminary data suggest that there were significant differences in above ground biomass, plant carbon and N accumulation among the various crops. Also, there was strong positive linear relationship between biomass and plant nitrogen and carbon accumulation.