Growth and N Supply from Legume Cover Crops in Organic Rye and Wheat Production

Harun Cicek and Martin Entz

Abstract
Organic farming systems rely heavily on legumes for N supply. The predominant legume system for prairie organic farmers is a full season legume. One disadvantage with this system is loss of economic crop production for that year. Late season legume cover crops have the advantage of being compatible with continuous cropping, but little is known about legume cover crops in prairie organic grain production.

The objective of this study was to test several legume cover crops grown with fall rye. Red clover and sweet clover were relayed cropped with rye by broadcast seeding the legumes into rye in early spring. Pea, lentil, cowpea, hairy vetch and soybean were double cropped by direct-seeding these legumes immediately after rye seed harvest. Field experiments were established at three Southern Manitoba locations in a randomized complete block design with 4 replicates.

At Glenlea in 2008, red and sweet clover and forage pea produced 4118, 1438 and 692 kg ha^-1 dry biomass by late autumn. Under drier conditions at Carman that year, forage pea resulted in higher late season biomass production than red and sweet clover. Legume N benefit was determined by measuring N uptake into the following spring wheat crop. At Glenlea, wheat after red clover and sweet clover yielded significantly more than the control. At Carman, in spite of dry conditions and relatively little legume biomass in the fall of 2008, spring wheat in 2009 following double cropped forage pea, hairy vetch and cow pea yielded 2523, 2153 and 2118 kg ha^-1 respectively (compared with 1991 kg ha^-1 for the control).

Results of year 1 indicate that late-season legumes have the ability to supply modest amounts of N resulting in wheat yield increases the following year. Work is continuing to learn more about adaptation of these legumes under different weather conditions


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 Plant Science, University of Manitoba


Posted July 2010