See more from this Session: Organic Management Systems Community: II (Includes Graduate Student Competition)
Tuesday, October 18, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
Organic grain producers commonly rely on green manures to return essential nutrients to their cropping systems. However, concerns with the use of green manures on the semiarid prairies are depletion of soil moisture and potential negatives effects associated with excessive tillage. Legume green manures supplying high amounts of N and P, and management techniques optimizing nutrient cycling and soil moisture retention are needed for successful green manure use. The objective of a two-year field study conducted in Saskatchewan was to find a compromise between reducing tillage and the necessity of using tillage to maintain profitable yields in organic agriculture. The study explored the effect of termination timing and method of field pea (Pisum sativum) on subsequent wheat (Triticum aestivum) yield. Field pea was terminated at early flower, late flower and budding of 2009 by either tillage, mowing or rolling. The roller-crimper kills green manures by crimping the stems, leaving a layer of mulch on the soil surface expected to reduce surface evaporation. Green manure shoot biomass N and soil concentrations of NO3-, NH4+ and moisture content were recorded in 2009. Shoot biomass N was significantly lower at early flower, and tended to be highest when terminated at late flower. No consistent trend was detected for soil moisture, while fall inorganic N was highest for late flower treatments terminated with tillage. In 2010 spring wheat was planted on all of the treatment plots and a subsample analyzed for N uptake three times throughout the summer. Harvest yield, grain protein content, and wheat N uptake were measured, with no consistent temporal relationship detected. The results from this study suggest reduced tillage in the green manure termination year is possible without compromising wheat yield.