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The Balance Sheet Method as a Conceptual Framework for Nitrogen Fertilization of Wheat in a Pampean Agroecosystem
Author(s) -
Alvarez R.,
Steinbach H. S.,
Grigera S. M.,
Cartier E.,
Obregon G.,
Torri S.,
García R.
Publication year - 2004
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/agronj2004.1050
Subject(s) - agroecosystem , fertilizer , agronomy , mineralization (soil science) , nitrogen , nitrogen balance , yield (engineering) , crop yield , environmental science , human fertilization , soil water , mathematics , chemistry , agriculture , soil science , biology , ecology , materials science , organic chemistry , metallurgy
Yield response curves to fertilizer are needed to determine N rates for wheat ( Triticum aestivum L.) in the Argentine Rolling Pampa. Relationships between yield and available N have not been developed for this region. The balance sheet method can be use to define N fertilization strategies when yield data are not available. The shortcoming of this method is that profitability cannot be assessed. This study was conducted to: (i) determine N requirements for wheat in the Rolling Pampa, (ii) develop algorithms for predicting crop available N, and (iii) develop a model for making N fertilizer recommendations. Fifty‐eight field plots were selected with contrasting soil and management conditions. Soil mineral N content and N in residues of preceding crop were determined at initial and harvest stages of wheat from 1997 to 1999. Plant N accumulation was measured, and N mineralized from organic soil pools was calculated using a mass balance approach. Nitrogen available in the mineral and organic soil pools limited N uptake and yield. As available N increased, crop use efficiency and agronomic efficiency decreased. The model prediction agreed well with measured plant N uptake ( R 2 = 0.82) and explained 51% of yield variability. The model estimated the impact of increasing fertilizer N on yield in soils differing in N mineralization capacity. The economic optimum N requirement in the Rolling Pampa is 140 kg ha −1 for soil having an average capability to supply N from organic pools and at a mean fertilizer price/grain price ratio. This optimum increased or decreased 30 kg ha −1 across the range of N mineralization rates observed. Despite the empirical nature of the algorithms developed, the concepts may be used in other regions where response functions to N are not available.