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Managing Annual Green Manures to Improve Yield and Soil Health in Organic Production Systems
Clare Sullivan, Dr. Diane Knight and Dr. Steve Shirtliffe
Abstract
Organic grain producers rely on green manures (GM) to return essential nutrients to their cropping systems; however, growers on the semiarid prairies are concerned with the tillage and depletion of soil moisture reserves associated with using GM. Legume green manures supplying high amounts of N and P, and management techniques optimizing nutrient cycling and soil moisture retention are needed for successful GM use.
This two-year field study conducted in Saskatoon and Vonda, SK explores the effect of termination timing and method of field pea (Pisum sativum) on subsequent wheat (Triticum aestivum) yield and soil health indicators. Field pea was terminated at early flower, late flower and budding of 2009 by either tillage or rolling/crimping. The roller-crimper kills GM by crimping the stems, leaving a layer of mulch on the soil surface expected to reduce surface evaporation. Soil and plant samples were taken from those plots being terminated within one week of termination, with soil sampling repeated in October 2009.
Green manure total N and P uptake and soil concentrations of NO3–, NH4+ and PO4- and moisture content will be presented for 2009. Microbial biomass C, N and P, metabolic quotient, alkaline phosphatase, protease, and dehydrogenase determined for the fall soil samples will be presented as indicators of soil health and potential N and P availability. In 2010, spring wheat will be planted on all of the treatment plots and a subsample analyzed for total N and P uptake three times throughout the summer. At harvest, yield, grain protein content, and total N and P of the wheat will be determined. Soil sampled at wheat sampling and in fall will be analyzed for NO3–, NH4+ and PO4- concentrations and gravimetric soil moisture content. Effects of GM management on nutrient availability, soil moisture and soil health indicators from 2009 will be discussed.
Source
Proceedings of the Joint Conference of the Canadian Society of Soil Science and the Canadian Society of Agronomy, Beyond Organics session. Saskatoon, Saskatchewan. 20-24 June 2010.
Author Locations and Affiliations
Department of Soil Science, College of Agriculture and
Bioresources, University of Saskatchewan
Posted July 2010