Effects of Irrigation Water and Mineral Nutrients Application Rates on Tissue Contents and Use Efficiencies in Seed Potato Tuber Production

Soil fertility and unreliable rainfall have become important in seed potato (Solanum tuberosum L.) production in Kenya. Knowledge on water and mineral nutrient use efficiencies will help predict the best application rates for optimal seed potato production. A study was conducted at Egerton University, Horticultural Research and Teaching Farm to determine the effect of integration of irrigation water, nitrogen (N) and phosphorus (P) nutrient on water, N and P use efficiencies and tissue content. In a split-split plot, the irrigation water supply (40%, 65% and 100% field capacity) was assigned to main plots, N (0, 75, 112.5 and 150kg N/ha) to subplots and P (0, 50.6, 75.9, 101.2kg P/ha) to sub-subplots, each treatment replicated three times and trial repeated once. Irrigation water was drip applied throughout the potato growth period, with N supplied as urea (46% N) in two splits, and P as triple superphosphate (46% P2O5) at planting time. Data on seed potato yield collected from each treatment at harvest was used to calculate water, N and P use efficiencies. Oven dried ground tubers were used to determine N and P contents. Analysis of variance was done and significantly different means separated using Tukey’s Studentized Range Test at P≤0.05. High irrigation water at 100% compared to 65 and 40% rate resulted in relatively high N and P use efficiencies, but decreased water use efficiency. High (100%) compared to 40% irrigation rate when integrated with high compared with low N and P application rates reduced the WUE by 6.1 and 8.1kg/m3, increased NUE by 14.4 and 13.3kg/kg, and PUE by 73.4 and 69.5kg/kg, in Trials I and II respectively. Application of intermediate to high N and P nutrient increased the water, N and P use efficiencies. Regardless of irrigation water rate tuber tissue N and P contents increased with N and P application rate. Application of low to intermediate irrigation water, intermediate to high N and P will increase their use efficiencies and tissue contents during seed potato production.