Fate of Fertilizer Nitrate Applied to Coastal Bermudagrass on a Swelling Clay Soil
1978
Kissel, D. E. | Smith, S. J.
The purpose of this study was to determine why N fertilizer recovery by Coastal bermudagrass (Cynodon dactylon L.) is lower on swelling clay soils than on coarse-textured soils. The disposition of N fertilizer applied to Coastal bermudagrass in the field over two growing seasons was determined by applying 560 kg N/ha as Ca(NO₃)₂ tagged with 7.599 atom % ¹⁵N to a field microplot during 1974 and measuring various components of the N balance. Plant uptake of residual N was measured during 1975. Forty-nine percent of the applied N was recovered in harvested forage in 1974. About 40% of the applied N remained in the soil as residual N at the end of 1974. About 10% of the N was unaccounted for, indicating that denitrification losses were no more than 10% of the applied N. Most of the residual N at the end of the first growing season was immobilized N or was present in the root system of the grass. Immobilization is, therefore, a major factor causing low recovery of applied N by Coastal bermudagrass on swelling clay soils. Moreover, since only 17% of the residual N was recovered in forage during 1975 (7% of the N applied in 1974), most of the immobilized N was not available the following year.
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