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Fertilizer Nitrogen Recovery in a No‐Till Wheat–Sorghum–Fallow–Wheat Sequence
Author(s) -
Porter Lynn K.,
Follett Ronald F.,
Halvorson Aedell D.
Publication year - 1996
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1996.00021962008800050012x
Subject(s) - agronomy , sorghum , fertilizer , leaching (pedology) , mineralization (soil science) , cropping system , crop , poaceae , nitrogen , biology , chemistry , soil water , organic chemistry , ecology
No‐till cropping in the semiarid Central Great Plains increases water storage during fallowing, which allows farmers to use an intensive cropping sequence of winter wheat ( Triticum aestivum L.)‐sorghum [ Sorghum bicolor (L.) Moench]‐fallow‐winter wheat. The purpose of this 15 N field study was to provide as complete accounting as possible of fertilizer N dynamics (changes in the NO 3 −N pool, fertilizer N uptake by plants, fertilizer N carryover effects, and mineralization and uptake of labeled N from wheat residues) for this intensive cropping sequence. Main‐plot treatments were 0, 56, and 112 kg N ha −1 . Eight microplots were established within all main plots. For the main plots that received 56 and 112 kg N ha −1 , two microplots received no K 15 NO 3 , and one of these microplots had its nonlabeled wheat residues exchanged with labeled residues. Six microplots were treated with K 15 NO 3 , one‐third received K 15 NO 3 the first year, one‐third the second year, and one‐third both years. There was no detectable NO 3 leaching. Mineralization, fertilizer application, and plant uptake had dramatic effects on the soil NO 3 −N pool. Both N rates increased the total N concentration and N uptake of aboveground biomass of the first wheat crop and the sorghum crop over the unamended treatment, whereas only the highest fertilizer N rate increased the total N uptake of the unfertilized second wheat crop. Plant N uptake transferred the majority of fertilizer NO 3 to aboveground biomass, and crop residue deposition, immobilization, and mineralization maintained the fertilizer N in the top 60 cm of soil. At the end of the 4‐yr cropping sequence, 90 and 87% of the applied fertilizer N was accounted for at the 56 and 112 kg N ha −1 rates, respectively. Of this N, generally 24 to 28% remained in the soil. The 10 to 13% of the applied fertilizer N that was unaccounted for was probably lost by denitrification or NH 3 volatilization.