Nitrogen fertigation of trickle-irrigated potato

This three-year field study, on Pellic Vertisol, was designed to investigate the response of trickle-irrigated potato (Solanum tuberosum L.) to four nitrogen levels continually applied with the irrigation stream. Waters containing 70, 130, 190, and 250 mg Nl^–1 and uniformly supplied with 50 and 120 mgl^–1 of P and K, respectively, were applied when the soil water potential was between 0.03 and 0.04 MPa. The amount of water applied at each irrigation was equivalent to 0.8 of pan evaporation from a screened USWB Class A pan. The resulting N application totals ranged from 205 to 735 kg ha^–1. Significant buildup of soil NO₃-N occurred below 45 cm depth with the two higher amounts of N but not with the 70 or 130 mg Nl^–1. A concentration of 130 mg Nl^–1 was adequate for maintaining petiole NO₃-N above the critical value throughout the growing period. The highest yield of good quality (58130 kg ha^–1; specific gravity 1.071) was obtained with 130 mg Nl^–1. It was concluded that fertigation (combined irrigation with fertilization) is a promising means for maintaining N concentration in the soil throughout the growing period at desirable levels, without undue losses by leaching.