Green Manure - 86


 

 

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Project Leader and Principal UC Investigators

D.S. Mikkelsen, Department of Agronomy and Range Science, University of California, Davis

 

Objective

  • Compare the benefits of nitrogen from vetch green manure with nitrogen from commercial fertilizer.

This project, completed in 1985, was conducted near Woodland and was supported by University of California and industry grants from sources other than the Rice Research Board. It was developed in response to interest in growing vetch or horse beans as a winter crop in rotation with rice. The practice is an attractive way to decrease nitrogen fertilizer costs.

The experiments on Clear Lake clay soils compared vetch and ammonium sulfate as sources of nitrogen when incorporated into the soil prior to flooding for rice planting. Thirty days after flooding, available nitrogen levels were higher from fertilizer than from vetch, but from 30 to 60 days after flooding the two sources of nitrogen were the same. Plant nitrogen content was higher with fertilizer nitrogen when compared with an equal amount of vetch nitrogen. Grain yields were correlated with nitrogen availability, with the ammonium sulfate producing the highest rice yields. Residual soil nitrogen from vetch would benefit second crops more than residual soil nitrogen from ammonium sulfate.

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