Fertilizer and varietal effects on take-all in irrigated wheat

Abstract

A severe infection of take-all (Ophiobolus gramtnis Sacc.) occurred in an irrigated wheat experiment combining four rates of sulphate of ammonia, two rates of superphosphate, and two varieties. The extent of disease affected areas was measured and from this and from crop sample data the yield loss due to takeall was estimated. Increasing rates of nitrogen fertilizer from 0 to 120 lb N an acre progressively reduced the mean area affected from 60 per cent to 14 per cent and the mean yield loss from 22.2 to 3.4 bushels an acre. There was little response to the higher level of superphosphate apart from an interaction with nitrogen in the proportion of area affected. The varieties differed in the mean proportion of area affected, this being 38 per cent for Pinnacle and 28 per cent for NBJ 115. However NBJ 115 yielded more than Pinnacle in the absence of take-all and the varietal difference in yield loss per acre was not significant. Data are also presented on the influence of nitrogen, variety, and take-all on straw and grain yields and on yield components.