A field experiment was conducted to evaluate the response of potato crop to foliar applied potassium nitrate in terms of vegetative growth, tuber yield and tuber size of potatoes grown on a loam-sandy soil in the semi-arid environment of Central East of Tunisia. The experimental layout was a randomized complete block design with 4 treatments and 3 replications. The four treatments were 0, 0,5, 1 and 2 g KNO3/L and were supplied as a foliar spray at 45, 55 and 70 days after planting. Increasing potassium nitrate rates resulted in a significant increase (P<0,05) in plant height, leaves number, leaf area, leaf relative water content and chlorophyll a concentration.
All potassium nitrate treatments showed significant increases in mean tuber weight and tuber diameter (Table 1). The foliar KNO3 sprays increased the tuber yield compared to the control, although statistically non-significant (Table 1). The treatments were applied early in the growing season, so possible more pronounced effects on yield may be obtained with later applications during the tuber-bulking or tuber maturating stages.
Table 1. Effect of foliar potassium nitrate applications on tuber quality and tuber yield of potato.