High yield indicators of greenhouse tomato under non-pressure irrigation

Taking the 20 cm diameter pan evaporation as the calculation reference for irrigation water, the greenhouse tomato yield and the morphological indicators were studied with different crop-pan coefficients (Kcp) under non-pressure irrigation technology. Taking the stem diameter, stem height, above-ground fresh weight, above-ground dry weight and root dry weight as the monomial indicators, the direct and indirect path coefficients among these indicators and yield were calculated through path analysis. Results indicated that when Kcp was equal to 1.0～1.2, the irrigation water could improve tomato yield obviously, but when Kcp was equal to 0.2～1.0, it had less effect on tomato yield. The irrigation water had greater effect on tomato stem diameter than that on stem height. The relationships among stem diameter, above-ground fresh weight, above-ground dry weight, root dry weight and yield were obviously significant. Stem diameter and root dry weight could be considered as the monomial indicators for evaluating the high tomato yield, but above-ground fresh weight and above-ground dry weight had an indirect influence on tomato yield through the interaction with other indicators. Through the analysis of root-shoot ratio which was a relatively high yield indicator, it showed that the irrigation water influenced the distribution ratio of root system in different soil layers and its total development. High yield of tomato can be obtained when the root-shoot ratio is maintained in a range. Results provide guidance to cultivate tomato with high yield morphological indicators.