Attempts to control potato late blight with cattle slurry

Abstract

Two years’ experiments concerning treatment of potatoes with diluted cattle slurry were carried out in an attempt to find a possible effect on potato late blight infection and to investigate whether slurry could be applied as an alternative to fungicides. The slurry was analysed for content of dry matter, total N and NH4 + N, and prior to each treatment the slurry was diluted with water in the ratio 1:1 to obtain a consistency similar to that of liquid manure. Treatment against potato late blight was carried out two and four times at 7–10‐day intervals from mid‐July. The dose was 10 tons diluted slurry per hectare per treatment. The results showed that diluted cattle slurry had no effect on the number of leaf lesions (sites of infection by late blight), tuber infection, yield or tuber content of total N and NO3 − N, and no effect was found on taste and boiling quality of tubers. Diluted cattle slurry applied at high global radiation caused considerable leaf scorching (necrosis) and a tendency to yield losses. Therefore, diluted cattle slurry cannot be used as an alternative to fungicides for control of potato late blight.