Nitrogen-fixing Covercrops for California Rice Production (4/4)

G.S. Pettygrove and J.F. Williams
SUMMARY
Covercropping with nitrogen-fixing crops in a rice rotation can, under optimal conditions, provide nitrogen economically to the following rice crop. Covercrop biomass N is used by rice as efficiently, and in some cases more efficiently, than pre-plant fertilizer N. The N fertilizer value of a covercrop can be estimated by a grower at the time of covercrop incorporation in the spring by determining the fresh weight of the covercrop growing in a small area. Covercrops can be established in most years under a range of conditions, including where straw has been spread and left on the surface.
In two field experiments in the Sacramento Valley, one on a loam soil and one on a clay soil, the maximum rice yield (i.e., yield at the optimal N fertilizer rate) on covercropped plots exceeded by 2 to 5 cwt/acre the maximum yield on non-covercropped plots. This suggests a non-nitrogen related benefit of covercropping. There is some evidence to suggest that covercropping in a rice rotation increases soil organic matter, contributes to soil tilth, and influences rice straw breakdown, although long-term experiments have not been conducted to confirm this.
The energy consumed in planting and incorporating the covercrop is offset by the energy saved by the reduction in the use of synthetic N fertilizers, the manufacture of which uses large amounts of natural gas or electricity.
The economic return on covercropping in a rice rotation is often not favorable. However, under optimal circumstances, covercropping can pay off, even in the short run. Therefore growers are encouraged to experiment.
FURTHER INFORMATION ON COVERCROPPING IN RICE PRODUCTION
PRODUCTION
Miller, P.R., W.L. Graves, W.A. Williams, and B.A. Madson. 1989. Covercrops for California agriculture. Publication 21471. University of California, Division of Agriculture and Natural Resources, Oakland, CA.
Phillips, D.A. and W.A. Williams. 1987 (rev.) Range-legume inoculation and nitrogen fixation by root-nodule bacteria. Bulletin 1842. University of California, Division of Agriculture and Natural Resources, Oakland, CA.
SAREP. 1996. UC SAREP online cover crop database. World Wide Web, http://www.sarep.ucdavis.edu. Sustainable Agriculture Research and Education Program, University of California, Davis.
Williams, W.A., D.C. Finfrock, and M.D. Miller. 1957. Green manures and crop residues in managing rice soils. Leaflet No. 90. California Agricultural Experiment Station, Berkeley, CA.
COST STUDIES
1992 U.C. Cooperative Extension Sample Costs to Produce Organic Rice Water Seeded in the Sacramento Valley. Department of Agricultural and Resource Economics, University of California, Davis. CA 95616
Sample Cost to Produce Rice - Sutter, Yuba, Placer and Sacramento Counties. 1992. Department of Agricultural and Resource Economics, University of California, Davis CA 95616.
RESEARCH LITERATURE
Bossio, D.A. and K. M. Scow. 1995. Impact of carbon and flooding on the metabolic diversity of microbial communities in soil. Appl. Environ. Microbiol. 61(11):4043-4050.
Bouldin, D. 1988. The effect of green manure on soil organic matter content and nitrogen availability to crops. pp. 151-163 In Green manure in rice farming: Proceedings of a symposium on sustainable agriculture, 25-29 May 1987. International Rice Research Institute, Los Banos, Philippines.
Buresh, R.J. and S.K. De Datta. 1991. Nitrogen dynamics and management in rice-legume cropping systems. pp.1-59 In N.C. Brady (ed.), Advances in Agronomy, Vol. 45. Academic Press, N.Y.
Huang, Z. and F.E. Broadbent. 1989. The influences of organic residues on utilization of urea N by rice. Fertilizer Research 18:213-220.
Lauren, J.G., G.S. Pettygrove, and J.M. Duxbury. 1994. Methane emissions associated with a green manure amendment to flooded rice in California. Biogeochemistry 24:53-65.
Pettygrove, G.S. 1994. Interaction of rice straw incorporation and winter cover cropping: Demonstration of energy savings and soil quality effects. pp.43-51 In Annual Report Comprehensive Rice Research. Dept. of Agronomy and Range Science, University of California, Davis.
Pimentel, D. 1992. Energy inputs in agriculture. In R.C. Fluck (ed.) Energy in World Agriculture, Vol. 6. Energy in Farm Production. Elsevier Pub., New York.
Quixiao, W. and Y. Tianren. 1988. Effect of green manure on physiochemical properties of irrigated rice soils. pp. 275-287. In Green manure in rice farming: Proceedings of a symposium on sustainable agriculture, 25-29 May 1987. International Rice Research Institute, Los Banos, Philippines.
Sarrantonio, M. and T.W. Scott. 1988. Tillage effects on availability of nitrogen to corn following a winter green manure crop. Soil Sci. Soc. Am. J. 52:1661-1668.
Singh, Y., C.S. Khind, and B. Singh. 1991. Efficient management of leguminous green manures in wetland rice. pp. 135-188 In N.C. Brady (ed.), Advances in Agronomy, Vol. 45. Academic Press, N.Y.
Talley, S.N. and D.W. Rains. 1980. Azolla filiculoides Lam. as a fallow-season green manure for rice in a temperate climate. Agron. J. 72:11-18.
Westcott, M.P. and D.S. Mikkelsen. 1985. Comparative effects of an organic and inorganic nitrogen source in flooded soils. Soil Sci. Soc. Am. J. 49:1470-1475.
Westcott, M.P. and D.S. Mikkelsen. 1987. Comparison of organic and inorganic nitrogen sources for rice. Agron. J. 79:937-43.
Westcott, M.P. and D.S. Mikkelsen. 1988. Effect of green manure on rice soil fertility in the United States. pp. 257-73. In Green manure in rice farming: Proceedings of a symposium on sustainable agriculture, 25-29 May 1987. International Rice Research Institute, Los Banos, Philippines.
Williams, J.F., G.S. Pettygrove, J.Y. Deng, M. Cady, and J.E. Hill. 1993. Nitrogen fertilizer response of rice in continuous rotation with winter legume. Agronomy Abstracts. Am. Soc. of Agron., Madison, WI. p. 291.
Williams, W.A. 1968. Effects of nitrogen from legumes and crop residues on soil productivity. Rice J. 77(5):29-32. Williams, W.A. and J.H. Dawson. 1980. Vetch is an economical source of nitrogen in rice. California Agriculture. 34(8-9):15-16.
Williams, W.A. and L.D. Doneen. 1960. Field infiltration studies with green manures and crop residues on irrigated soils. Soil Sci. Soc. Am. Proc. 24:58-61.
Williams, W.A. and D.C. Finfrock. 1962. Effect of placement and time of incorporation of vetch on rice yields. Agron. J. 54:547-49.
Williams, W.A., D.C. Finfrock, L.L. Davis, and D.S. Mikkelsen. 1957. Green manuring and crop residue management in rice production. Soil Sci. Soc. Am. Proc. 21:412-415.
Williams, W.A., D.S. Mikkelsen, K.E. Mueller, and J.E. Ruckman. 1968. Nitrogen immobilization by rice straw incorporated in lowland rice production. Plant Soil 28:49-60. Williams, W.A., M.D. Morse, and J.E. Ruckman. 1972. Burning vs incorporation of rice crop residues. Agron J 64:467-468.

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Modified: 4 Dec 1997 Comments to jayoung@ucdavis.edu