Water management parameters in hydroponic tomatoes and sweet pepper under greenhouse.

Abstract

The optimal water interval based on volumetric moisture thresholds in the substrate (θvs), allows precise control of the volume and frequency of irrigation. The research determined the thresholds of θvs for irrigation management in tomato and sweet pepper crops in coconut fiber in the greenhouses at the Fabio Baudrit Moreno Agricultural Research Station (EEAFBM), Alajuela, Costa Rica, 2015. In both crops, there were 2 treatments: with irrigation (CR) and without irrigation (SR), in a completely random design. The content of water θvs, the water potential (ψh) and the leaf temperature (Th) were evaluated and the evapotranspiration of both crops was estimated by means of a water balance in the substrate. The θvs threshold for water management in coconut fiber and both crops could be established in the readily available water range of 56% to 38%, where the ψh values were below the critical threshold of < -1 MPa reported by different authors and the Th were similar to the air temperature. The averages of θvs in tomato (44%) and sweet pepper (50%) in CR treatments were within the range of readily available water (38% to 56%) of the coconut fiber. In the SR treatments of both crops, the θvs decreased to an average value of 32%, close to the permanent wilting point. The differences between treatments of the ψh and Th were of higher magnitude at midday of 2nd day. The ψh in CR treatments were -0.84 MPa and -0.98 MPa, meanwhile in SR treatments they were -1.24 MPa and -1.3 MPa, in tomato and sweet pepper respectively. At midday of 2nd day, the Th of both crops and treatments were similar and lower, respectively, to the air temperature (32.9°C).