Improving Seed Potato Leaf Area Index, Stomatal Conductance and Chlorophyll Accumulation Efficiency through Irrigation Water, Nitrogen and Phosphorus Nutrient Management

Abstract

A study was conducted in a Rainshelter (RTrial) at Horticultural Research and Teaching Farm, Egerton University to determine the effect of integration of irrigation water, nitrogen (N) and phosphorus (P) application on seed potato leaf area index (LAI), stomatal conductance and chlorophyll content. The treatments arranged in a split-split plot layout in a completely randomised block design, consisted of three irrigation water rates (40%, 65% and 100% field capacity), four N rates (0, 75, 112.5 and 150 kg N/ha) supplied as urea (46% N), and four P rates (0, 50.6, 75.9, 101.2 kg P/ha) supplied as triple superphosphate, replicated three times and repeated once. During the growth leaf area, stomatal conductance, and chlorophyll content were measured. Data collected were subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at P≤0.05. Leaf area index was greater with high irrigation water at 100%, N at 150 kg N/ha and P at 101.2 kg P/ha, which was 2.6 and 1.3 at 51 days after planting (DAP) and 3.5 and 3.1 at 64 DAP. Furthermore, low irrigation water rate at 40% together with low N and P rates of 0 kg N/ha and 0 kg P/ha had the least LAI, which was 0.28 and 0.19 at 51 DAP and 0.28 and 0.24 at 64 DAP both in RTrials I and II, respectively. Subjecting potato to 100% compared to 40% irrigation rate increased stomatal conductance at 87 days after planting (DAP) by 32.82 and 31.99 mmolm⁻²s⁻¹, leaf chlorophyll content index by 16.2 and 16.5, 19.8 and 19.6, and 15 and 20.3, when integrated with high compared with low N and P application rates at 59, 73 and 87 DAP, in RTrials I and II respectively. Irrespective of N and P rates LAI, stomatal conductance and chlorophyll content were significantly greater with high irrigation water at 100% followed by 65% and was lowest with 40% irrigation water rate.