Effect of Nitrogen to Phosphorus Atom Ratio of Ammonium Phosphates on Emergence of Wheat (Triticum vulgare)1

Abstract

AbstractAmmonium phosphates providing five N:P atom ratios (1.00, 1.25, 1.50, 1.75, and 2.00:1) were applied in solution in the row with wheat seed at planting in greenhouse experiments. The soils used were Oneida clay loam (CEC 18.3 meq/100 g) and Fox sandy loam (CEC 8.2 meq/100 g) each adjusted to pH levels ranging from 5.4 to 7.4. Soil pH, over the range studied, had no effect on emergence with any of the ammonium phosphate materials tested. Neither early nor final emergence changed when the N:P atom ratio was varied in the clay loam soil when the molarity of the fertilizer solution was held constant (equal rates of P but varying rates of N). In the sandy loam soil early emergence was markedly lower with high N:P atom ratio materials than with low ratio materials. Final emergence showed the same trend as early emergence with the sandy loam soil but differences between materials were much smaller. The difference in results between the two soils is attributed to the effect of cation exchange capacity on the toxicity of ammonia in the soil.