, Volume 5, Issue 1, pp 1-76

Nitrification inhibitors in agriculture and horticulture: A literature review

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Preface

This literature survey is the English version of P. Kerkhoff and J.H.G. Slangen “Nitrificatieremstoffen in Land- en Tuinbouw, Interne Mededeling 54, Vakgroep Bodemkunde en Bemestingsleer, Landbouwhogeschool, Wageningen, 99 p, 1980”, supplemented by reference to the literature of 1980 and a partly of 1981. The literature cited has been taken from sources in East and West Europe and North America.

Only crops common in the regions mentioned are involved. For this reason rice has not been included in the cereals. Aspects of controlling the nitrogen status in soils by, for instance, “controlled release fertilizers” are not discussed and no details of the effects of pesticides on the NO3 - and or NH4 - contents in soils are given here.

Abstract

This review of literature is focussed on the readily available nitrification inhibitors N Serve (2-chloro-6-(trichloromethylpyridine), DCD (dicyandiamide) and AM (2-amino-4-chloro-6-methylpyrimidine). Compounds such as Terrazole (5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole), DCS (N-2,5-dichloro-phenyl-succinamic acid) and non synthetic inhibitors like “Neem” and “Karanjin” are only briefly discussed.

Some chemical characteristics of these inhibitors are summarized. The effects of such soil characteristics as texture, organic matter content, pH moisture content, O2-pressure and temperature on their efficiency are being discussed. These aspects are seen in relation to yield and to the chemical composition of a number of agricultural (wheat, maize, grassland, oats) and horticultural (lettuce, spinach, tomatoes) crops.

Phytotoxicity, residual effects and residues in soils and plants of the most interesting compounds are reviewed as well as aspects of some effects of inhibitors on plant diseases.

Most of the compounds are more or less effective in keeping nitrogen in the NH4-form thus leading to a relatively high content of NH4-N over a shorter or longer period. In a number of situations this leads to more effective use of nitrogen, but not necessarily to higher yields. This increase of nitrogen efficiency can be explained by a decrease in leaching and or denitrification of nitrogen. Lower NO3-contents in vegetables, found in some of the experiments with nitrification inhibitors, cannot be used to declare the products as generally useful in this respect. The uptake and assimilation of nitrogen by plants in their overall diversity cannot be regulated by adding a simple compound to the soil, not even in small quantities.