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Salinity, Sodium, and Potassium in an Irrigated Soil Treated with Bovine Manure¹

ABSTRACT

Results of a 4-yr field experiment with liquid feedlot and solid dairy manures and two irrigation rates on a Hanford soil (Typic Xerorthents) are reported. Objectives were to measure the effects of manures on yields of barley and sudangrass forages, the accumulation of salts in the root zone, and the leaching of salts to groundwater. The leaching fraction (LF) calculated from chloride (Cl^-) balances ranged from 0.21 to 0.37. Salinity in the root zone, as measured by the electrical conductivity of the saturation extract (EC_e), decreased with increase in LF and was related to the rate and type of manure. Salinity appeared to have no negative effects on yields at manure rates up to 79 Mg ha^–1 yr^–1. The solid manure at 158 Mg ha^–1 yr^–1 reduced yields of sudangrass and the EC_e for this treatment was in the range of values reported to reduce yields. Manures did not increase the sodium adsorption ratio (SAR). The calculated SAR agreed well with measured SAR values. The potassium adsorption ratio (PAR) increased with increase in rate of manure, but the measured PAR was consistently less than the calculated PAR. There was no effect of irrigation on potassium (K) concentration in the saturation extract or on measured PAR. The data indicated that the soil profile still had considerable capacity to fix K in nonexchangeable forms. The amount of sodium (Na) leached from the root zone exceeded the Na input in water and in manures. The ratio of leached Na to input Na was correlated with LF. The long-term hazard of the use of manures on well leached irrigated lands appears to be more from K than from Na accumulation.

¹ Contribution from the Dep. of Soil and Environmental Sciences, Univ. of California, Riverside, CA 92521.

² Professor of Soil Science, Univ. of California, Riverside, CA 92521.

Received for publication December 6, 1983. Accepted for publication March 13, 1984.