Nitrate-nitrogen Removal from Soil Profiles by Alfalfa
1975
Mathers, A. C. | Stewart, B. A. | Blair, Betty
Alfalfa (Medicago sativa L. ‘Cody’) was established in the fall of 1971 on plots previously treated with 0, 22, 45, 112, or 224 metric tons/ha of manure annually for 3 years. Additional plots had received 224 kg N/ha (as NH₄NO₃) annually for 3 years. Nitrate-nitrogen and water contents of the soil profile were determined by 30-cm increments to 6 m prior to planting. Nitrate-nitrogen was found to 6 m, but the largest concentrations were in the top 1.8 m, where amounts of NO₃⁻-N varied from 100 to 2,400 kg/ha. Additional profile samples were taken in 1972 and 1973 after the final cutting of alfalfa. The data showed that alfalfa removed water and NO₃⁻-N to a 1.8-m depth the first year and to 3.6 m the second year. These results indicate that alfalfa could remove NO₃⁻-N from the lower depth of soil profiles where annual crops were not effective. Yield, NO₃⁻-N, and P contents of alfalfa were increased by manure. Total N taken up by the crop was directly related to the yield.
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