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ABSTRACT
The leaching of cations (Ca, Mg, K, Na) from the soil root zone as a function of rate of manure and irrigation treatments, which controlled the leaching fraction and the volume of leachate, was measured during a 4-year field experiment. Large amounts of Ca, Mg, and K were accumulated in the soil, but there was a net loss of Na. Practically no K moved beyond the 1.5-m depth, which was considered the bottom of the root zone. The percent leaching of the cations added in water and in manures decreased as the rate of manure increased.
Extrapolation of the field data to a basin having 18,200 ha of irrigated land, and a production of 364,000 metric tons of dairy manure per year, showed that the total mass of salt leached to ground water in the basin would be reduced by concentrating the manure at relatively high rates on a fraction of the irrigated land, and by export of manure from the basin. However, these reductions were small compared to the effects of irrigation water management to obtain small leachate volumes. The concentration of manure on soils having low water transmissivities, and consequently giving low leachate volumes with most irrigation systems, might be a viable management approach.
Key Words: leaching of cations volume of leachate irrigation mass of salt leached
1 Contribution from the Dep. of Soil Science and Agric. Eng., Univ. of California, Riverside, CA 92521; and the ARS-USDA. Financial support of the ARS-USDA through Cooperative Agreement USDA 12-14-100-10431(41) and Western Consumers Industries, Inc. through a Grant-in-Aid is hereby gratefully acknowledged.
2 Professor of Soil Science; Agricultural Engineer, USDA; and Staff Research Associate, respectively.
Received for publication December 15, 1976.
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