Nitrate reductase as a possible predictive test of crop yield

Abstract

NITROGEN supply is one of the key factors affecting the quality and quantity of crops. The amount of nitrogen fertiliser used is increasing year by year; on a worldwide basis we now use seven times the total fertiliser used in 1939 (ref. 1). In many developed countries the use of excess nitrogenous fertiliser is already causing environmental disturbance, especially in inland rivers and lakes, and represents a potential danger to drinking water supplies. By contrast, in much of the world crops are grown in conditions of nitrogen deficiency. Lacking in each situation is the availability of a reliable method for determining the amount of nitrogenous fertiliser, if any, which should be applied for optimal yield with minimum cost and environmental side effect, or for maximum use of limited resources. We have found that early season assays of nitrate reductase provide such a method.