C, N, and S mineralization of crop residues as influenced by crop species and nutrient regime
The mineralization of C, N, and S from residues of three different crop species (wheat, lentil, and rape) grown under diverse nutritional regimes was measured over a 12-week incubation period under controlled conditions. The rate of decomposition, as measured by CO2 evolution, varied considerably among treatments and appeared to be controlled almost entirely by N content of the residue (R2=0.98). Similarly, N mineralization was strongly tied to N concentration. The critical N concentration, below which significant immobilization of N occurred, declined over time, ranging from 1.9% at day 14 to 1.1% at day 84. Mineralization of S was positively correlated with initial S concentration (R2=0.95) and negatively related to N concentration, apparently because of a dilution effect. The results demonstrate that decomposition and N and S mineralization of crop residues, under conditions prevalent in the experiment, are primarily a function of their nutrient concentrations rather than biochemial composition related to crop species. As a result, it should be possible to enhance rate of residue decomposition, increase quantities of N and S mineralized, and avert detrimental immobilization losses in the following year by governing the nutritional regime under which the crop is grown.
Key wordscarbon crop residue mineralization nitrogen organic matter sulfur
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