TOMATO YIELD AS RELATED TO DRIP LATERAL SPACING AND FERTILIZER APPLICATION ON TOTAL AND WETTED AREA BASIS

Abstract

With drip irrigation systems, a part of the area is wetted at the soil surface. This raises the question of whether to program fertilizer rates on the total or wetted area of the plot. The objective of this investigation was to study the response of unstaked tomato plants (Lycopersicon lycopersicum L. Karst.) to drip application of fertilizers on the basis of total versus wetted surface area. Apart from the conventional broadcast and drip application of NPK fertilizers in liquid form, four other treatments were applied consisting of two rates of NPK, i.e., 224, 88 and 168 kg ha−1 on total plot area basis, and 56, 22 and 42 kg ha−1 on wetted surface area basis, factorially combined with 1.2- and-2.4-m lateral spacings, with N through drip, P and K banded. The study also included drip irrigation at 1.0 and 0.5 times the daily evapotranspiration (ET) rate factorially combined with drip application of NPK at 1.0, 0.75 and 0.5 times and broadcast application at 1.0 times the NPK rate. The NPK were, respectively, at 224, 88 and 168 kg ha−1. At the full grown stage, available water in the plant root zone was 60–100%. Root growth, soil temperature, and thermal conductivity were positively influenced by canopy cover and soil moisture regime. The development pattern indicated that 74% of the total root weight was confined to the top 15-cm soil layer. At the time of fruiting, the root weight declined in the soil layer with high water content. Drip irrigation equal to 0.5 ET required 25% less fertilizer than irrigation equal to ET, but irrigation at the latter rate and application of fertilizers to supply 224, 88 and 168 kg ha−1 of NPK, respectively, gave the highest yield of 90 t ha−1.Key words: Drip irrigation, root growth, spacing, multiple rows, fertilizer