Fate of Nitrogen-15 Enriched Ammonium Nitrate Applied to Corn
1993
Reddy, G. B. | Reddy, K. R.
Nitrogen utilization by corn (Zea mays L.) is influenced by the form of inorganic N present in the root zone. A field experiment was conducted on Enon sandy loam (fine, mixed, thermic Ultic Hapludalf) to determine N use efficiency and its partitioning in various plant parts of corn. Ammonium nitrate labeled either as ¹⁵NH₄-N or ¹⁵NO₃-N and applied at 50, 100, or 200 kg N ha⁻¹ was evaluated. Microplots (1.06 m²) were established in the main N plots for ¹⁵N fertilizer application, and main plots were used to determine grain yield. After the crop harvest, soil N alone, fertilizer N used by the crop, and fertilizer N remaining in inorganic and organic forms in the top 75 cm of the soil were measured. Grain yield response to N application was significant (P < 0.01). Recovery of applied fertilizer N in corn and weeds ranged from 43 to 57% and 3 to 5%, respectively. Nitrogen sources showed no significant differences with respect to N accumulation in corn. Only 17 to 20% of the fertilizer N was recovered in the grain. The amounts of soil N utilized by the corn was about three-to sixfold higher than the fertilizer N, suggesting extensive turnover of soil and fertilizer N through immobilization and mineralization. More N was recovered (21–63% of added N) in the soil from ¹⁵NH₄ than from ¹⁵NO₃ (6–38%). Loss of N (unaccounted for) ranged from 11 to 18% at 100 kg N ha⁻¹ and from 34 to 48% at 200 kg N ha⁻¹. Nitrogen loss was higher in the plots receiving ¹⁵NO₃ than ¹⁵NH₄. Most of the fertilizer N remaining in the soil at the end of the growing season was in the organic fraction, suggesting immobilization into microbial and root biomass. Joint contribution from North Carolina A&T State Univ. and Univ. of Florida.
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