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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.
3117. Rasmussen, P.E.. 1989. unpublished data on soil pH from long-term plots at Pendleton, OR. Columbia Basin Agr. Res. Center, P.O. Box 370, Pendleton, OR 97801.
Plots have received various tillage and fertility treatments since 1931. The original pH (1:2 water) was 6.3. Addition of 10 T/ac manure every other year raised the pH to 6.9, while addition of 1 T/ac pea vines raised it to 6.5. Fall burn lowered the pH to 6.2. The decline in soil pH was essentially linear with increasing total N fertilizer added over the years. A nearby permanent pasture had a pH of 7.3.
10079. Cowie, A.L., R.S. Jessop, D.A. MacLeod and G.J. Davis. 1990. Effect of soil nitrate on the growth and nodulation of lupins (Lupinus angustifolius and L. albus).. Austral. J. Expt. Agric. 30:655-659..
The effect of increasing external nitrate concentration on the nodulation of Lupinus albus and L. angustifolius lines was examined in two sand culture experiments. In the first experiment four lines, three L. albus and one L. angustifolius, were grown at nitrate concentrations of 0, 2, 8, 16, and 30 mmol/L for 49 days. Increasing the nitrate concentration reduced nodule weight in all varieties to a similar extent. In a second experiment, 18 L. angustifolius lines were grown at nitrate concentrations of 2 and 8 mmol/L for 49 days. The ratio of nodule weights at the 8 and 2 mmol/L nitrate treatments varied widely, from 23 to 71%, between the lines. There appears to be potential for selection of L. angustifolius varieties able to maintain nitrogen fixation at increased levels of soil N.