Effects of Nitrogen Fertilizer Application Time on Dry Matter Accumulation and Yield of Chinese Potato Variety KX 13

Abstract

Application time of nitrogen (N) fertilizer can significantly influence the yield and quality of potato tubers. The objective of this experiment was to assess the effects of N application time on dry matter accumulation in foliage and tubers, as well as on marketable tuber ratio, dry matter concentration, and specific gravity of the Chinese cultivar KX 13. The four treatments were as follows: all the 150 kg N ha−1 applied at planting (T1); 100 kg N ha−1 applied at planting and 50 kg N ha−1 applied 1 week before tuber initiation (20 days after emergence, DAE) (T2); 100 kg N ha−1 applied at planting and 50 kg N ha−1 applied 1 week before tuber bulking stage (35 DAE) (T3); and 100 kg N ha−1 applied at emergence and 50 kg N ha−1 applied 1 week before tuber bulking stage (35 DAE) (T4). For all treatments, 90 kg P2O5 ha−1 ((NH4)2HPO4) and 150 kg K2O ha−1 (K2SO4) were applied at planting. Thirty tons per hectare of marketable tuber yield was achieved with T3, while 23 t ha−1 marketable yield was achieved by applying all 150 kg N ha−1 at planting (T1). Relative to treatment T1, T3 also significantly increased harvest index (HI) from 0.76 to 0.86 and marketable tuber ratio from 64.8% to 79.2%. Applying N at planting in conjunction with dressing at 20 DAE (T2) gave a high marketable tuber ratio (74%) and HI (0.86), but the lower total tuber yield led to a lower marketable tuber yield. Without N application at planting (T4), N dressing did not increase the yield and HI. Treatments with N dressing had no significant effect on specific gravity or dry matter concentration of tubers.