Browse on keywords: crop rotation WA nitrogen fixation
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1015. Bowren, K.E. (ed.).. 1986. Soil improvement with legumes.. Saskatchewan Agriculture, Soils and Crops Branch.
This excellent publication summarizes research over the past 40 years pertaining to the use of legumes for soil improvement in Saskatchewan. The role of legumes in maintaining soil nitrogen was crucial prior to available fertilizer. But their value extends beyond their nitrogen contribution to the improvement of soil physical properties. One study found the tillage draft requirement to be up to one-third lower where legumes had been a regular part of the rotation. The positive effects of alfalfa were measured for over ten years in a series of wheat crops compared to plots with no alfalfa. Over 17 years, the average grain yield from a wheat-wheat/clover-clover green manure rotation with no fertilizer were 30% higher that a wheat-wheat-fallow rotation with fertilizer. Moisture depletion by legumes is the biggest hurdle to their use in very dry areas. Adequate fertility for the legumes is necessary to maximize their benefit. Use of selected Rhizobium strains can improve nitrogen fixation, especially on acid soils. Several varieties of sweetclover are mentioned with adaptation to forage or green manure use. The booklet has numerous color photos and many data tables and figures.
6620. Speilman, R.S.. 1984. Nitrogen economy and agronomic evaluation of annual legume-cereal grain rotations.. M.S. Thesis, Plant and Soil Science, Montana State Univ., Bozeman, MT.
Legume biomass and seed yield were best for fababean, fieldpea, and chickpea. Potential for use of legumes for hay or silage. Barley yield after legumes was comparable to barley after fallow, and better than barley after barley or wheat. N contributions to the cropping system, except for field bean, were greater for legumes than for fallow. High N fertility levels from legume N plus fertilizer N resulted in premature soil moisture depletion. Optimum rotation performance will depend on balancing nitrogen fertility with expected available moisture.