Index of water stress of lettuce crop (Lactuca sativa), through infrared thermometry to different irrigation sheets

Marcelo Tarqui Delgado; René Chipana Rivera; Freddy Carlos Mena Herrera; Juan Javier Quino Luna; Rubén Tallacagua Terrazas; Susana Gutiérrez Villalobos

Abstract

Infrared thermometry is a widely used method in Bolivia, it measures the IEHC which is a reliable tool in irrigation scheduling, combined with efficient irrigation systems for increasing yields of crop yields and greater efficiency of use of Water resources based on the physiological needs of the crop. The research was carried out at the Cota Cota Experimental Station, with the objective of determining the IEHC of lettuce crop produced with drip irrigation, to a relation with irrigation sheets for irrigation scheduling and prediction of the yield of both green and dried matter. The experimental design was unifactorial with three levels of irrigation: 50, 75 and 100% of the ETo. The treatments were distributed in a completely randomized design with 20 samples per treatment. The IEHC was calculated from the crop temperature, air, relative humidity and vapor pressure deficit. When the crop transpires, this relationship is: Tc -Ta = 1.2851 - 2.3915 DPV (r2 = 0.68, P <0.01, n = 42) and, the upper limit was 2.8 ° C when the crop does not transpire. The yield of the crop was directly correlated with mean IEHC values ​​and the linear equation was obtained: Y = 52.53-69.7IEHC (r2 = 0.5151 and n = 82), which indicates the limit where the lettuce plant is not in stress. Values ​​from 0 to 0.23 of the IECH, the values ​​with relative stress and timely irrigation requirement are in the ranges of 0.24 to 0.31 to obtain yields of 3.17 to 3.44 kg m-2, the values ​​in which the plant presents a stress of greater magnitude is in the values ​​of 0.32 to 0.50 decreasing the yield up to 1.7 kg m-2. The values ​​of the water stress index in the ranges 0.56 to 1.00 result in the death of the crop.