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The Toxicity of Banded Urea or Diammonium Phosphate to Corn as Influenced by Soil Temperature, Moisture, and pH
Author(s) -
Creamer F. L.,
Fox R. H.
Publication year - 1980
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1980.03615995004400020019x
Subject(s) - urea , diammonium phosphate , loam , chemistry , nitrification , zoology , phosphorus , coated urea , phosphate , ammonia , moisture , nitrogen , agronomy , soil water , biology , biochemistry , ecology , organic chemistry
A laboratory and greenhouse study, using a Hagerstown silt loam (Typic Hapludalf, fine, mixed, mesic) was designed to determine the effect of initial soil pH, soil temperature, and soil moisture on NH 4 + + NH 3 ‐N movement and concentration, pH change, and NO 2 ‐ ‐N production and accumulation around urea or diammonium phosphate (DAP) banded at 80 or 100 kg N/ha (assuming 76 cm between bands). Observations were also made in the greenhouse on corn root growth around banded urea plus triple superphosphate (TSP), NH 4 NO 3 plus DAP, urea plus DAP, urea plus DAP with 100 kg Mg/ha, and urea plus DAP with a nitrification inhibitor (nitrapyrin). Root growth around those treatments was compared to banded NH 4 NO 3 plus TSP and no‐starter controls. Nitrogen and phosphorus were applied at 100 kg/ha and 60 kg/ha in the band, respectively. Increasing the initial soil pH and decreasing soil moisture increased the proportion of total NH 4 + + NH 3 ‐N present as free NH 3 around banded urea or DAP. Lowering soil temperature appeared to inhibit nitrification and help maintain high pH and NH 4 + + NH 3 ‐N concentrations for a longer time. With both urea and DAP, NH 3 toxicity appeared to be the main cause for root growth inhibition around the band. Magnesium did not decrease toxicity symptoms nor did NO 2 ‐ accumulate to toxic levels. Ammonia toxicity potential from DAP was lower than an equivalent amount of urea due to the smaller pH increase adjacent to the band of DAP. At a banded rate of 100 kg N/ha, urea increased the pH in Hagerstown silt loam from 6.8 to 9.1 whereas DAP increased pH to only 7.3.