Rapid Estimation of Crop Water Stress Index on Tomato Growth

Abstract

The goal of this research is to use a WORKSWELL WIRIS AGRO R INFRARED CAMERA (WWARIC) to assess the crop water stress index (CWSI _W) on tomato growth in two soil types. This normalized index (CWSI) can map water stress to prevent drought, mapping yield, and irrigation scheduling. The canopy temperature, air temperature, and vapor pressure deficit were measured and used to calculate the empirical value of the CWSI based on the Idso approach (CWSI _Idso). The vegetation water content (VWC) was also measured at each growth stage of tomato growth. The research was conducted as a 2 × 4 factorial experiment arranged in a Completely Randomized Block Design. The treatments imposed were two soil types: sandy loam and silt loam, with four water stress treatment levels at 70–100% FC, 60–70% FC, 50–60% FC, and 40–50% FC on the growth of tomatoes to assess the water stress. The results revealed that CWSI _Idso and CWSI _W proved a strong correlation in estimating the crop water status at R ² above 0.60 at each growth stage in both soil types. The fruit expansion stage showed the highest correlation at R ² = 0.8363 in sandy loam and R ² = 0.7611 in silt loam. VWC and CWSI _W showed a negative relationship with a strong correlation at all the growth stages with R ² values above 0.8 at p < 0.05 in both soil types. Similarly, the CWSI _W and yield also showed a negative relationship and a strong correlation with R ² values above 0.95, which indicated that increasing the CWSI _W had a negative effect on the yield. However, the total marketable yield ranged from 2.02 to 6.8 kg plant ⁻¹ in sandy loam soil and 1.75 to 5.4 kg plant ⁻¹ in silty loam soil from a low to high CWSI _W. The highest mean marketable yield was obtained in sandy loam soil at 70–100% FC (0.0 < CWSI _W ≤ 0.25), while the least-marketable yield was obtained in silty loam soil 40–50% FC (0.75 < CWSI _W ≤ 1.0); hence, it is ideal for maintaining the crop water status between 0.0 < CWSI _W ≤ 0.25 for the optimum yield. These experimental results proved that the WWARIC effectively assesses the crop water stress index (CWSI _W) in tomatoes for mapping the yield and irrigation scheduling.