Effective nitrification inhibitors may improve fertilizer recovery in irrigated cotton
1996
Rochester, I. | Constable, G. | Saffigna, P.
N fertilizer is often poorly recovered in irrigated cotton production, due to N loss through denitrification. We researched the ability of inhibitors to delay nitrification and reduce the availability of NO3 to denitrifying microorganisms and thus improve N fertilizer recovery. 2-Ethynylpyridine, etridiazole, and nitrapyrin proved highly effective nitrification inhibitors, although nitrification was evident several weeks after their application. CaC2 was relatively ineffective, even when wax-coated to prolong the evolution of C2H2. Phenylacetylene and ethynylcyclohexanol were also ineffective, despite having a chemical structure similar to 2-ethynylpyridine. A strong association was identified between each compound's ability to inhibit nitrification and its capacity to improve N fertilizer recovery. In one experiment, N fertilizer recovery was increased by approximately 50% with 2-ethynylpyridine, etridiazole, or nitrapyrin application, from 33% without inhibitors. The inhibitors had little effect on fertilizer recovery where N losses were relatively small. 3-Methyl pyrazole significantly increased N uptake and lint yield, but the nitrification inhibitors had no significant effect on N uptake or on yield in two of the three of the cotton crops. A laboratory study confirmed that nitrification inhibitor effectiveness declined in the order 2-ethynylpyridine>etridiazole>nitrapyrin> 3-methyl pyrazole>phenylacetylene> CaC2>ethynylcyclohexanol.
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