Soil water storage and its temporal association with other water-atmospheric variables in a tomato field under different irrigation regimes

Abstract

This study was conducted to evaluate the effect of different irrigation regimes on soil water dynamics and temporal associations with other water-atmospheric variables in a tomato field under different drip irrigation regimes in southwestern Nigeria. The experiment was 3 x 3 randomized complete block design (RCBD) with a split plot arrangement of treatments in three replicates. Irrigation frequencies of applying water every 7, 5 and 3 days designated as F1, F2, and F3, respectively serve as the main plot of the experiment while irrigation depth of 100, 75 and 50% of crop water requirement ( ) designated as D1, D2 and D3 are the sub-plots. During the growing season, soil water storage (SWS) was monitored in soil depths of 0-5, 5-10, 10-20 and 20-30 cm using oven dry method while daily rainfall and crop evapotranspiration ( ) were obtained using rain gauge and daily weather data, respectively. Both classical statistics and time series (state-time) analyses were applied to the data of SWS, P (rainfall + irrigation) and ETc.  Irrigation water regimes significantly (p<0.05) affected SWS. The trend of water stored was F3D1>F3D2>F2D1>F3D3D2<F2D2>F2D3>F1D1>F1D2>F1D3. There was high amplitude of temporal variability of soil water storage while the maximum SWS was obtained in all depths at 86 DAP of tomato. There was strong temporal association between SWS and  but not with P. Classical regression of  from combinations of  and  gave low values of coefficient of determination (R²) (not more than 24%) while about 4 times as that value was obtained from state-time analysis. Employing the state-time approach, the effect of irrigation on soil water dynamics and how stored water is related to other variables was clearly recognized. Therefore, the state-time approach can be a specialized statistical tool for evaluating temporal associations among soil properties and processes under different management scenarios.