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483. Army, T.J. and J.C. Hide. 1959. Effects of green manure crops on dryland wheat production in the Great Plains area of Montana.. Agron. J. 51:196-198.
This paper summarizes the results from the green manure treatments which were a part of a 38-year study (1914-1951) of numerous small grain rotations involving wheat, barley, oats, corn, and fallow in various combinations. The rotation experiments were carried out at several Great Plains experiment stations including Havre, Huntley, and Moccasin, Montana, and Sheridan, Wyoming. The results indicated that winter rye, field pea, and sweetclover green manures had no effect at all or a depressing effect on small grain yields the following year as compared to ordinary fallow. The results of this unreplicated study are the most likely reason that research on dryland legume-cereal rotations essentially ceased in Montana until 1978. Although legume green manures, ideally, may impart several beneficial effects on ensuing cereal crops, the primary benefit is the release of symbiotically fixed nitrogen. The legume green manures in the long-term study at Moccasin and Huntley had little chance of improving wheat yields compared to ordinary fallow for several reasons. First, the soils involved, and most Montana soils indeed, had not yet become deficient in N as they are today. Organic matter had begun to decline by the 1950's but it still provided ample N to meet the needs of wheat yield potentials of that era. Also, the management of the legumes in these early studies is questionable as one passage from the report suggested that when the green manure crops were not successfully established, thee was invariably a good crop of Russian thistle (Salsola kali L.) to plow under. Possible other factors lending to their failure include inefficient storage of winter precipitation, late seeding, poor timing of plow down, and a lack of nodulation which continues to be a problem of dryland legume culture today, especially with small-seeded legumes. The above substantiate their conclusion that the main effect of the green manures was to reduce the water available to the ensuing grain crops. A re-examination of the Moccasin and Huntley, Montana data indicates that grain yields after green manures were slightly higher than grain yields after fallow for eight of the last ten years of the study.
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 unpublished.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.
826. Bezdicek, D. and R. Lockerman. no date. Crop rotation and the response of cereal crops to nitrogen in the PNW. unpublished.
Experiments conducted at Pullman, WA and Bozeman, MT. Year 1 - legumes (rainfall -Pullman 500 mm, Bozeman 480 mm). Year 2 -Pullman winter wheat + N (rainfall 350 mm); Bozeman barley + N (rainfall 200 mm). Compared fababean, pea, lentil, chickpea, fallow at both locations. Pullman legumes were used as green manure, Bozeman legumes were harvested for seed. N fertilizer equivalents ranged from 30-86 kg/ha N at Pullman (fallow = 125) and from 27-81 kg/ha N at Bozeman (fallow = 53). All cereals responded to added N, although less so at Pullman. More N was removed in seed than was fixed. Seed legumes appeared to fix 50-100 kg/ha N. The rotation effect was more significant at Pullman. T: cereal yields; fertilizer N equivalent; moisture depletion.
3589. Kirby, E.M.. 1987. Soil moisture depletion and wheat yield response from annual legumes in the Pacific Northwest. M.S. Thesis, Dept. of Agronomy and Soils, WSU, Pullman, WA.
Legumes included chickpea, spring pea, lentil, fababean, sweetclover, rose clover, black medic, barrel medic. Sweetclover depleted more soil moisture than other legumes. Wheat yield increased following legumes relative to that after barley. Highest yield followed legume green manure with additional fertilizer N. Grain yields were similar for fallow, lentil, pea, chickpea, and fababean. T: soil moisture depletion; yield, N content of soil and grain.
7930. Sims, J.R.. 1988. Research on dryland legume-cereal rotations in Montana.. Symposium on Crop Diversification in Sustainable Agriculture. Univ. of Saskatchewan, Saskatoon.
This paper opens with a review of the long-term findings of historic rotation studies for dry farming in Montana and concludes that improved varieties and management abilities call for a re-examination of alternatives to the crop-fallow system. A short description of ley farming in Australia follows, and then research on adapting it to Montana conditions is presented. Results to date indicate the potential for both grain and forage legumes to successfully precede a cereal crop without significant cereal yield losses, and with a reduced need for nitrogen fertilizer. T: medic soil water use and N contribution; wheat yields after medics; pulse and cereal grain yields; annual legume forage yields; fertilizer response curves for barley with various forecrops.