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Organic & Integrated Tree Fruit Production

Saturday, September 22, 2018

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Browse on keywords: crop rotation green manure nitrogen fixation

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Search results on 09/22/18

805. Bezdicek, D.. no date. (STEEP green manure plots). unpublished.
Examined 3 legume green manures (red clover, Austrian winter pea, hairy vetch) and harvested spring pea, with 3 incorporations (plow, disk, chemical kill) and 3 N rates (0, 67, 134 kg N/ha). Prior to tillage, red clover and hairy vetch depleted 3.4 cm/m more moisture than spring pea, and AWP depleted 1.8 cm/m more. Soil residual N was highest under spring pea and lowest under red clover. N fixation estimates ranged from 76 for spring pea to 114 for AWP. Winter wheat yield was highest following red clover that had been plowed or disked. Chemical kill appeared to inhibit wheat yield, and N fertilizer could not overcome this depression. Yields after AWP were lower than red clover but higher than spring peas. Recovery of pea and wheat residue N ranged from 7-10% by a following wheat crop. Overseeding of red clover in a spring cereal was successful. T: residual moisture, N; yield response to the various treatments; recovery of N.

7524. White, J.G.H.. undated. Grain legumes in sustainable cropping systems; a review.. unpublished manuscript, Plant Science Dept..
This paper briefly reviews the role that grain legumes can play in sustaining cropping systems. It presents various estimates of N fixation of grain legumes, with lupin and fababean showing the highest rates, followed by peas and lentils, chickpeas, and soybeans. Phaseolus beans are generally poor N fixers. Fababeans are more tolerant of soil mineral N than other species and will still fix large quantities of N when mineral N is present. Under drought stressed conditions, peas and lentils were more efficient in N fixation than fababeans. Only in lupins and fababeans was N fixation normally greater than the N removed in the seed. The roots and nodules of grain legumes are likely to be the greatest source of N for following crops. This N is often quickly mineralized within several weeks after harvest, and strategies are needed to prevent its loss. Grain legumes are also beneficial break crops, particularly for soil-borne diseases, and can help to control certain grassy weeds. Preceding grain legumes with a brassica crop has reduced the incidence of Aphanomyces root rot in peas, due to sulfur containing compounds. Most grain legumes suffer reduced yields if soils are compacted and poorly aerated. The paper contains numerous references and tables on nitrogen relations.

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