Pulses Fix More Nitrogen with Less Tillage

Doug Derksen, AAFC Brandon Research Centre, A. Matus and C. van

Kessel, University of Saskatchewan & H. Loeppky, AAFC Saskatoon

Research Centre.

Research at Indian Head has shown that with less tillage we have found that legumes fix more N. Several explanations exist for this discovery. Firstly, legumes in conservation tillage grow in a less stressful environment. There is more available soil water and less heat stress.

Secondly, the soil surface layer is more biologically active in conservation tillage. This area has not been explored by researchers in Canada, however, soil samples taken from this study are being analyzed by M. Monreal at the Brandon Research Station to see if a difference in microorganisms will explain the difference between the tillage systems.

Thirdly, since cultivation releases nitrogen from the soil, legumes grown in conventional tillage use released nitrogen rather than fix new nitrogen.

To date, a yield benefit from legumes has occurred in the next years wheat crop. This has been about 10%. Coupled with the yield benefits of conservation tillage, putting lentils or peas in your rotation makes dollars and sense. The following long term rotation work was done at Indian Head in the early 1990's.

Clearly peas were most encouraged to fix atmospheric N without tillage, but the same was true for lentils. This has also been shown true for soybeans in the US and observed with lupins in Australia.