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Wednesday, April 25, 2018

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765. Benson, V., W. Goldstein, D. Young, J. Williams, and C. Jones. 1988. Impacts of cropping practices on nitrogen use and movement.. Proc. Intl. Conf. on Dryland Farming.
Conventional and PALS practices were used as inputs for the EPIC model to simulate the effects of the systems over 108 years on an Athena soil. Total erosion over 108 yr under PALS was 40% less than the conventional system. Nitrogen loss through water was 25% less under PALS than conventional. Percolation loss of N was zero for both systems. Neither system had significant increase or decrease in yields after 108 yr of erosion.

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 unpublished.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 unpublished.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.

1015. Bowren, K.E. (ed.).. 1986. Soil improvement with legumes.. Saskatchewan Agriculture, Soils and Crops Branch.
This excellent publication summarizes research over the past 40 years pertaining to the use of legumes for soil improvement in Saskatchewan. The role of legumes in maintaining soil nitrogen was crucial prior to available fertilizer. But their value extends beyond their nitrogen contribution to the improvement of soil physical properties. One study found the tillage draft requirement to be up to one-third lower where legumes had been a regular part of the rotation. The positive effects of alfalfa were measured for over ten years in a series of wheat crops compared to plots with no alfalfa. Over 17 years, the average grain yield from a wheat-wheat/clover-clover green manure rotation with no fertilizer were 30% higher that a wheat-wheat-fallow rotation with fertilizer. Moisture depletion by legumes is the biggest hurdle to their use in very dry areas. Adequate fertility for the legumes is necessary to maximize their benefit. Use of selected Rhizobium strains can improve nitrogen fixation, especially on acid soils. Several varieties of sweetclover are mentioned with adaptation to forage or green manure use. The booklet has numerous color photos and many data tables and figures.

1617. Doran, J., D. Fraser, M. Culik, and W. Liebhardt. 1987. Influence of alternative and conventional agricultural management on soil microbial processes and nitrogen availability.. Am. J. Alternative Agriculture 2:99-106.
Differences in soil biological factors between management systems (conventional cash grain; legume/cash grain; grain/forage plus manure) were related primarily to crop characteristics and, to a lesser extent, to soil physical properties. The use of ag chemicals had little effect on microbial populations, their activities, or the cycling of N. Competitiveness of alternative systems employing legumes as N sources for grain crops may depend largely on the grower's ability to synchronize supplies of available soil N with periods of maximum uptake by grain crops.

2249. Granatstein, D., D. Bezdicek, L. Elliott, V. Cochran, and J. Hammel. 1987. Long-term tillage and rotation effects on soil microbial biomass, carbon, and nitrogen.. Biol. Fertil. Soils 5:265-270..
This research examined plots that had been under different tillage and rotational management for 12 years. Rotations were WP (winter wheat-spring pea); WBP (winter wheat-spring barley-spring pea); WPA (winter wheat-spring pea undersown with red clover and alfalfa)-clover/alfalfa GM). The two tillages studied were moldboard plowing and no-till. There was little difference in microbial biomass, C or N below 5 cm in the no-till, with surface values being highest. Few differences due to rotation could be detected. The WPA rotation had the highest total C and N. Microbial biomass was higher in no-till surface soils where the preceding crop had provided high residue, while the opposite was true for tilled plots. Microbial biomass levels changed little from April to September, and then jumped higher in October with the advent of moisture.

2507. Heichel, G.H.. 1987. Legumes as a source of nitrogen in conservation tillage systems.. IN: J.F. Power (ed.) The role of legumes in conservation tillage systems..
A review of legume N contributions in crop rotations across the U.S. Covers nitrogen nutrition of legumes, legume nitrogen and companion plants, management effects, nonlegume yield response. T: examples of regional rotations with legumes; seasonal N fixation for various crops in various locations; N transfer from legume to grass; N budgets; N recovery.

2617. Hill, K.W.. 1954. Wheat yields and soil fertility on the Canadian prairies after a half century of farming.. Soil Sci. Soc. Am. Proc. 18:182-184.
T: soil properties X rotation; wheat yields X time

2756. Huggins, D.R., W.L. Pan, and J.L. Smith. 1989. Improving yield, percent protein, and N use efficiency of no-till hard red spring wheat through crop rotation and fall N fertilization.. Proceedings, 40th Far West Fertilizer Conference,.
In a field experiment near Pullman, WA, all fall and split fall-spring N applications significantly increased percent protein and N uptake efficiency as compared to all spring applications, while yields were unaffected. Protein increase was attributed to enhanced late season uptake, due to better positional availability of deep soil N. In another experiment, yield of hard red spring wheat was 10% greater when no-tilled into Austrian winter pea stubble (for seed) as compared to winter wheat stubble, while grain N and percent protein were not affected. The difference in yield was not eliminated by optimized N rates, indicating other rotation effects.

2965. Ingham, I.M.. 1924. Effect of legumes in rotation upon the nitrogen content of the soil.. M.S. Thesis, Washington State College, Pullman, WA.
Soils at WSC farm were sampled to show residual effect of legumes upon following crops of wheat, and upon the N content of soil. T: Effect of legumes upon the following crops as shown by yields of wheat. Changes in the N content of soils after 5 years of crop rotations. Influence of various rotations on the N/C ratio of the soil.

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