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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.
555. Auld, D.L., G.A. Murray, and R.V. Withers. 1983. Austrian winter peas: a green manure crop for Idaho.. ID Agr. Expt. Sta. CIS #652.
Good % of pea N is from soil; best to plow under right after flowering; Melrose contributed 278 lb/ac of vine N; winter peas produced slightly more biomass than spring peas, but fall peas can be plowed 2 weeks earlier; spring peas accumulated 70 lb N/ac more than winter peas; variable cost of WW-SB-SF = $63/ac, uses 120 lb N/ac; for WW-SB-pea GM = $59/ac, with only 40 lb N/ac; must consider intangible benifits; recommended green manure crop every 3-5 years. T: organic matter yield, nitrogen content, costs.
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.
835. Bezdicek, D.F.. 1990 Jan.. Crop rotation studies. presentation at STEEP Annual Review, Moscow, ID.
Several studies were described in which different legume green manures were grown before winter wheat and treated with different residue management. Wheat yields were consistently depressed following chemically-killed legumes in the first study, but not in the second. Under chemical kill, there was a 40 bu/ac wheat yield response to soil fumigation. Part of the fumigation response appeared to be higher available N. Also, it appeared that chemical kill may be increasing N mineralization. Results are being prepared for publication.
1113. Buffum, B.C.. 1900. Alfalfa as a fertilizer and soil improver.. WY Agr. Expt. Sta. Bulletin 44.
Five years of alfalfa in the rotation increased the yield of the following crops by 65, 108, and 55% for spring wheat, oats, and potatoes respectively.
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.
3955. Mahler, R.L. and D.L. Auld. 1989. Evaluation of the green manure potential of Austrian winter peas in northern Idaho.. Agron. J. 81:258-264.
Austrian winter peas were evaluated as a green manure (GM) or seed pea (SP) crop, along with soil N levels, and subsequent yields of winter wheat (WW) and spring barley (SB). Four rotations were tested: GM-WW-SB; SP-WW-SB; SB-WW-SP; SF-WW-SB. Average N fertilizer equivalent values of 94, 75, and 68 kg/ha were provided by GM, SP, and SF (fallow) respectively, to the following wheat crop. Yield differences due to crop rotation or N fertilization rate were not observed in the third year of the cropping sequence. Austrian winter peas used as either a GM or SP provided more inorganic N than SF or SB. Although cereal crop yields were comparable, the SP-WW-SB was more profitable than GM-WW-SB or SF-WW-SB, due to the extra harvested crop.
4921. Oien, David. no date. Black medic information packet.. Timeless Seeds, RR 3 Box 461, Conrad, MT 59425.
This packet is sent to growers who purchase seed. The seeding rate is recommended at 8-10 lb/ac, planted 1/2" deep into a firm seedbed. Field trials have indicated successful medic establishment with barley, oats, spring wheat, and flax as nurse crops, but a second year of medic growth is then necessary for adequate seed production. On-going experiments in Montana (Jim Sims, MSU) are examining several rotations: medic-cereal, sweetclover-cereal, fallow-ceral, and continuous cereal, with different nitrogen rates. Results indicate that the green manures used 1-3" more soil moisture than the other treatments. Wheat yields after medic and sweetclover (25 bu/ac) were significantly higher than all other treatments. An herbicide screening tested a number of alfalfa herbicides on black medic. Poast, Fusilade, Treflan, and Kerb did not injure medic, while paraquat, Pursuit, and 2,4-DB ester caused minor injury. Solicam provided the best overall weed control with little injury to the medic.
5705. Rasmussen, P.E., H.P. Collins, and R.W. Smiley. 1989. Long-term management effects on soil productivity and crop yield in semi-arid regions of eastern Oregon.. OR Agr. Expt. Sta. Bulletin 675.
Summary of over 50 years of plot research at Pendleton, OR, with some results from Weston and Moro. Focuses on results from a continuous set of plots at the Pendleton station. Manure maintained highest yields, highest soil organic matter, highest pH compared to other treatments. Nitrogen fertilizer had a more marked effect on water infiltration than various tillage treatments. Green manure systems are generally not economic in the drier areas, due to competition for moisture with wheat, which is the most profitable crop. Legumes can contribute between 40 and 80 lb/ac N to the following crop. Varietal improvement over the past 50 years has been the most significant factor in increasing wheat yields. Burning straw accelerated organic matter losses from the soil and eventually reduced yields. Marginal returns have generally been lower from alternative crops than from wheat.