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Tuesday, June 19, 2018

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4022. Mahler, R.L.. 1990. Nitrogen database project - final report.. unpublished report for Dryland Cereal/Legume LISA project.
This project had two components: 1) development of a comprehensive database on winter wheat response to nitrogen fertilizer rates; 2) evaluation of the potential of peas, alfalfa, and wheat straw as nitrogen sources for a following wheat crop in rotation. The database study examined winter wheat yield response to 41 nitrogen rates. When soil test N + mineralizable N + fertilizer N ranged from 101 to 175 kg/ha, a requirement of 2.75 lb N per bushel of wheat was calculated. This agrees with the figure calculated by Leggett in the 1950's, indicating that modern varieties have not changed in their basic nitrogen requirement, when nitrogen fertilizer efficiency is assumed to be 50%. At total available N rates greater than 175 kg/ha, the N requirement per bushel of wheat increased dramatically. Low rates did not show a large increase in efficiency on a per bushel basis. At Moscow, N fertilizer application rates less than 95 kg/ha resulted in greater than 50% N use efficiency. Efficiency declined rapidly at rates above this. The green manure study compared alfalfa, pea, and green wheat straw residues applied at 1, 2, and 3 mt/ha. In general, higher rates of pea and alfalfa resulted in higher wheat yields. The highest yields were with the high rate of pea residue. It was more effective than alfalfa residue, probably due to faster decomposition. Alfalfa provided more N per ton of residue (31 kg/mt) than the peas (29 kg/mt), while straw added 19 kg/mt.

5065. Patten, A.G.. 1982. Comparison of nitrogen and phosphorous flows on an organic and conventional farm.. M.S. Thesis, Dept. of Agronomy and Soils, WSU, Pullman, WA.
Two adjacent farms, one organically managed and the other conventionally managed, located in the Palouse region of eastern WA, were studied for 2 years. Soil organic matter, total N, extractable P, and extractable K tended to be higher in the top 30 cm of soil from the organic farm. Mineral nitrogen in the top 30 cm of soil from the conventional farm was higher than or equal to that of the organic farm. Average long-term changes calculated in soil N and P pools resulted in substantial deficits of 44 and 14 kg/ha/yr, respectively, for the organic farm and 23 and 5 kg/ha/yr for the conventional farm. However, nutrients deficits were not reflected in lower soil N and P levels in the plot area tested on the organic farm as compared to the plot area on the conventional farm.

6545. Smith, V.T.. 1948. Green manure crops for Idaho farms.. U. of Idaho Ext. Circ. #105.
Estimates legume N contribution and dollar value: alfalfa - 260 lb N, $40/ac; sweetclover - 160 lb N, $24/ac; clover - 140 lb N, $21/ac; peas/beans - 50lb N, $7/ac; green manure provides nitrogen, improved soil condition, organic matter; results from 10 yr experiment; grow legume seed for cash crop.

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.

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