EFFECT OF NITROGENOUS FERTILIZER APPLIED AT DIFFERENT DATES ON TAKE-ALL, EYESPOT AND YIELD OF WINTER WHEAT GROWN ON LIGHT SANDY LOAM

In a replicated field experiment on light sandy loam at Woburn, where winter wheat is a very uncertain crop, Cappelle and Holdfast, grown after potatoes with dung, yielded 50 and 41 cwt./acre of grain, respectively, when given 6 cwt./acre of Nitro-Chalk in April, compared with 19 and 20 cwt./acre when unfertilized. The same fertilized plots yielded 29 and 19 cwt., respectively, in the second, and 25 and 17 cwt./acre, respectively, in the third year on the same land, whereas unfertilized plots of both varieties yielded only 9 and 5 cwt./acre. The decrease in mean yield from 27 cwt. in the first, to 15 and 10 cwt./acre in the second and third crops was associated with a decrease in ear number from 16.7 to 14.6 and 12.2, respectively, and with a striking decrease in weight of grain per ear, caused partly by a large increase in the proportion of small grains. Eyespot (Cevcosporella herpotrichoides Fron.) although present each year did not become prevalent; an increase in the percentage straws affected by take-all (Ophiobolus graminis Sacc.) from 9 to 15 and 26%, respectively, and a severe increase in weed infestation (Agrostis gigantea) appeared to be the main factors reducing yield. Nitro-Chalk applied in April yielded most grain every year, and wheat fertilized at this time had less eyespot and take-all than that fertilized in March. Fertilizer applied in May increased weed growth, failed to decrease take-all and yielded fewer ears, less grain, and a higher proportion of tailcorn than did earlier applications.