EFFECT OF FERTILIZERS AND OF LIMING ACID SOIL ON COMMON ROOT-ROT IN WHEAT, AND OF CHLORIDE ON THE DISEASE IN WHEAT AND BARLEY

Field experiments were conducted in Saskatchewan to ascertain the effect of fertilizers and of liming acid soil at Scott [pH 4.8 (CaCl2)] on common root rot (CRR) and yield of wheat, and of potassium chloride (KCl) fertilizer on these variables in wheat and barley at several locations. Application of lime to raise soil pH to 6.5 or 7.0 in 1963 or 1965 had no influence on CRR severity in spring wheat that was rated in 8 years between 1973 and 1982. However, grain yields were improved significantly by the lime treatments in 5 of 7 years with an overall mean increase of about 15% for the wheat on soil limed to pH 6.5. On soil limed to pH 7.0, mean yields over 3 years were improved by 27%. Severity of disease was not affected by phosphate (P) and nitrogen plus phosphate (NP) fertilizer. It was significantly reduced by KCl in 5 of the 8 years. A yield increase averaging about 12% was associated with P fertilization. The response to P fertilizer was most pronounced in the untreated soil and least in the limed soil. This differential response likely was due to the lower availability of soil P in the unlimed than limed soil. In an experiment on fertilizer rates and K sources, both added K and Cl significantly reduced CRR of wheat in 1 of 4 trials conducted from 1980 to 1982, and over the 4 trials. However, applied K reduced the average yield compared to the control. Mean disease severity and grain yield increased as rates of NP increased. Chloride, but not K, reduced the severity of CRR significantly in 4 of 11 wheat trials and in 7 of 11 barley trials conducted in 1987 to 1989. The Cl effect was consistent in wheat at Swift Current, and in barley at Saskatoon and Scott, suggesting a differential influence of the fertilizer on CRR in these crops. Yields were obtained in 7 trials for each of wheat and barley. Neither K nor Cl provided a yield benefit. The total N and P content of wheat and barley foliage were not modified consistently by K or Cl fertilizers. Cochliobolus sativus was the primary cause of CRR. It was isolated from more than 80% of subcrown internodes from wheat and barley plants in the 1988 and 1989 trials.