The effect of fertilization on the susceptibility of potatoes to late blight

Summary

Experiments were conducted in the field and the greenhouse to study the effects of N, P and K nutritions on the incidence of late blight in potatoes.

In the N experiments the results of the field and greenhouse were variable. In the field excessive amounts of N fertilizer had a marked tendency to increase the size of the late blight lesions on the potato leaves. In the greenhouse excessive use of N fertilizer did not increase the late blight lesions on the potato leaves.

The amount of P applied in the fertilizer was the most significant factor in determining the size of the late blight lesions. Large applications of P decreased the size of the late blight lesions on the potato leaves, while the progress in the size of the late blight lesions was most rapid in leaves receiving no application of P.

Significant decreases in the size of the late blight lesions resulted from the high applications of K fertilizers, but K was not as efficient as P in decreasing the size of the late blight lesions.