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The effects of certain micronutrients on seed production by legumes, particularly double-cut red clover (Trifolium pratense), and pole beans (Phaseolus vulgaris L.) Phillips, Arthur Harold

Abstract

The inconstancy of legume seed set has been recognized for some time, but the basic factors responsible for this irregularity have remained somewhat of a mystery. The literature on the subject is quite extensive and contains a diversity of opinions. Oddly enough the role of micronutrients seems scarcely to have been considered as a possible basic factor in legume seed setting. A study therefore has been made of the effects certain elements have on legume seed yields. The addition of lime to plots provided with molybdenum or phosphate on an acid clay soil in the Fraser Valley of British Columbia, with 900-1200 P.P.M. available calcium, markedly increased red clover seed yields. Without lime, the only response was obtained from additions of phosphate and potash. The addition of nitrogen to plots, on similar soil, which received molybdenum, sulphur, and phosphate resulted in markedly increased seed yields of double-cut red clover over the control. Without nitrogen there was a greater response on this soil to additions of phosphate, molybdenum and sulphur. The response to molybdenum was much greater, in both seed and forage, where plants were not provided with combined nitrogen, but where they largely depended on symbiotic nitrogen fixation for their nitrogen supply. The increased yield from sulphur attributable to this element having an indirect effect upon legumes through its direct' action, or effect, upon the nitrogen fixing organisms. Pole beans grown on a sandy loam soil with a pH 5.5 and 900 P.P.M. "available" calcium, produced more seed following applications of phosphate. The response was noted at several levels of lime and nitrogen. Molybdenum with lime, and sulphur with nitrogen also Improved seed yields. On a clay soil with a pH 4.8 and 500 P.P.M. "available calcium" the addition of lime increased all seed yields regardless of other treatments. The only other treatment to show a uniform and greatly increased seed yield, was an application of boron. On this clay soil pole bean plots receiving nitrogen outyielded the "no nitrogen" plots, but only phosphate, or potash, in combination with nitrogen showed much higher yields than the check. An experiment with double-cut red clover on a sandy loam soil with pH 5.5 and 900 P.P.M. "available" calcium showed a direct response to nitrogen regardless of the micronutrients added. On this soil boron with molybdenum gave higher seed yields than boron or molybdenum alone. These results were eon-firmed by a greenhouse experiment using silica sand.

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