Bridging the attainable yield gaps of watermelon through nitrogen and phosphorus nutrients management in North-West Ethiopia

Optimum fertilizer is essential for obtaining high yields of watermelon. This three location study was conducted to investigate the effect of nitrogen and phosphorus (NP) fertilizer on the growth and fruit yield of watermelon. The experiment consisted of five levels of nitrogen (0, 46, 92, 138 and 184 kg N ha−1) and four levels of phosphorus (0, 23, 46, and 69 kg P2O5 ha−1) combined full factorial. A randomized complete block design (RCBD) with three replications was used. NP interaction and location interactions had effects on the growth and yield. Earliness of maturity was observed with 92/46 kg N/P2O5 ha−1 at all locations. A biological maximum yield of 78. 8, 58. 4 and 64. 5 t ha−1 was obtained with 92/69, 138/46, and 184/46 kg N/P2O5 ha−1 at Ribb, Woramit and Koga, respectively. Based on the regression analysis, an optimum yield of 69. 0 t ha−1 was obtained with 117/98 kg N/P2O5ha−1 at Ribb while 111/70 kg N/P2O5 ha−1 gave 50. 2 t ha−1 at Woramit. High N (221 kg ha−1) interacted with 71 kg P2O5ha−1 gave an optimum yield of 59. 0 t ha−1 at Koga. Moreover, 115. 4/97. 8 kg N/P2O5 ha−1 gave a maximum net return of 684, 431. 10 Birr (US 18178. 78) at Ribb while 110. 2/69. 6 kg N/P2O5 ha−1 gave a maximum net return of 496942. 61Birr (US 13199. 00) at Woramit. At Koga, a maximum net return of 581, 229. 72 (US 15437. 71) was obtained with 218. 9/70. 2 kg N/P2O5 ha−1 application. Fruit weight ranged from 3. 2 kg with 0/0 kg N/P2O5 ha−1 to 5. 03 kg with 92/69 kg N/P2O5 ha−1at Ribb while from 3. 08 kg with 0/0 kg N/P2O5 ha−1 to 5. 36 kg with 184/46 kg N/P2O5 ha−1 at Woramit. At Koga, it ranged from 1. 67 kg with 0/0 N/P2O5 ha−1 to 4. 04 kg with 184/0 kg N/P2O5 ha−1. The highest N rate gave less TSS value at Ribb while the opposite was true at Woramit and Koga. It was concluded that 115/98, 110/70, and 219/70 kg N/P2O5 ha−1at Ribb, Woramit and Koga, respectively are economical optimum NP rates for the production of watermelon in northwest Ethiopia.