Using RZWQM to search improved practices for irrigated maize in Fergana, Uzbekistan

Abstract

Located in the Aral Sea Basin, Uzbekistan suffers from environmental problems related to soil salinization and water scarcity. The arid climate requires that cultivated crops be intensively irrigated. Under conditions of limited resources, crop production must be maintained at expense of minimum inputs but aiming at achieving maximum returns. The search of the best combination between the available resources and crop yield can be eased by the use of system modelling. In this work, the Root Zone Water Quality Model (RZWQM) was used. The research was conducted in an experimental field located in the Fergana Valley, Usbekistan. The soil is a Sierozem cropped with maize ( Zea maïs) and irrigated with saline water. The soil hydraulic and crop growth components of the model were calibrated against field data. Initial values for the soil hydraulic properties were determined by a combination of the in situ method of the soil monolith and two alternative laboratory methods. After calibration, the model was run as a management tool to predict the impact of different irrigation and fertilization practices upon crop yield. Soil moisture, soil water potential, water table depth and plant development were monitored during the 2001 growing season and used for model evaluation. Results from the comparison of field and simulated data show a good calibration of the soil hydraulic and plant growth model components. Soil water was simulated for five soil layers with an average deviation from the measured values of 3.6%. Crop yield was estimated by the model with an error of 13%. The results from the simulation of various agricultural management scenarios can be used for further agro economical analysis and assessment in view of economic profitability. Nevertheless, other model components like the chemical modules must be calibrated against detailed field experiments.