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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.
6738. Stickler, F.C. and L.R. Frederick. 1959. Residue paritcle size as a factor in nitrate release from legume tops and roots.. Agonomy J. 51:271-274.
Tested different particle sizes of tops and roots of alfalfa, sweetclover, red clover, and white clover. Coarse particles immobilized less N with alfalfa and white clover, but not red clover. Most treatments immobilized some N for the first 40-50 days, after which net nitrate release curves tended to become parallel. There was greater release of nitrate and recovery from tops than from roots. After 100 days incubation, recovery ranged from 43% for alfalfa, 34% for sweetclover, 25% for red clover, to 19% for white clover.
8064. Welty, L.E., L.S. Prestbye, R.E. Engel, R.H. Lockerman, R.S. Speilman, J.R. Sims, R.A. Larson. 1988. Nitrogen contribution of annual legumes to subsequent barley production.. Applied Agric. Res. 3:98-104.