Factors affecting the loss of yield of sugar beet caused by beet yellows virus. II. Nutrition and variety

The effect of beet yellows virus on the yield of sugar beet was tested in the presence and absence of various fertilizers and farmyard manure. In general the manorial treatments increased the root and sugar yields of both infected and healthy plants, but the losses caused by infection increased proportionally as the mean yields increased. When the effects of nitrogen, farmyard manure and salt on mean yield were large, the losses caused by infection were increased more than proportionally.

The fertilizers had little effect in varying the symptoms of the disease. There was some indication that the red colour associated with some varieties of sugar beet was intensified by deficiency of phosphate and potash.

The effect of fertilizers on rate of spread of infection was variable, and again appeared to depend largely upon the magnitude of the fertilizer effects on mean yield. Nitrogen, phosphate and potash occasionally had positive effects, and salt had a fairly consistent negative effect. None of the effects appeared to be of any economic importance.