Using Hydrus-2d Model for Simulating Soil Water Dynamics in Drip-Irrigated Citrus

Abstract

The demand of water for irrigation is gradually increasing due to escalating competition for fresh water by urban, industrial, and agricultural users. To sustain or increase agricultural productivity, there is a need to adopt highly efficient irrigation technologies such as drip irrigation in crop production. Studies related to water dynamics in crop root zone is the pre-requisite for efficient and economic design of any irrigation system. In the present study, the water dynamics under drip irrigation was evaluated taking citrus as a test crop in sandy loam soil. The soil water content observed in effective root zone (0–60 cm) of the crop showed that water availability was higher in top 15 cm soil, whereas at 45–60 cm soil depth the water content remained unchanged. Drip emitter placement in tree basin had a good influence on water distribution in root zone. The soil water content was simulated using HYDRUS-2D model to compare the observed data of water distribution in the soil in root zone of the crop. The calibrated model predicted all the parameters close to observed values with root mean square (RMSE) values ranging from 0.013 to 0.015. However, lower RMSE values were observed at deeper soil layers. At fruit maturity stage, water present at 45-60 cm soil depth was predicted to be 12.5% higher in comparison to measured values. Overall, HYDRUS-2D model has proved it’s ability to predict soil water dynamics with higher accuracy in the present crop and soil condition.

Potrebe za vodom za navodnjavanje se postepeno povećavaju zbog povećanih potreba za svežom vodom u urbanim, industrijskim i poljoprivrednim područjima. Za održavanje i povećanje poljoprivredne proizvodnje potrebno je prilagođavanje visoko efikasnih tehnologija navodnjavanja kao što je navodnjavanje kap po kap. Proučavanje dinamike zemljišne vlage u zoni korenovog sistema je preduslov za efikasno i ekonomično projektovanje sistema za navodnjavanje. U ovom istraživanju analizirana je dinamika vlage kod navodnjavanja kap po kap plantaže citrusa kao oglednog zasada na peskovito-ilovastom zemljištu. Sadržaj zemljišne vode praćen je u efektivnoj zoni korena (0–60 cm) i uočeno je da je dostupnost vode bila veća u gornjih 15 cm zemljišta, dok je na dubini od 45–60 cm sadržaj vode ostao nepromenjen. Položaj kapalice u osnovi stabla uticao je na raspodelu vode u zoni korena. Sadržaj zemljišne vlage bio je simuliran modelom HYDRUS-2D radi poređenja izmerenih podataka raspodele vode u zoni korena biljaka. Kalibrisani model je predvideo sve parametre blizu izmerenih vrednosti, sa srednjim kvadratnim odstupanjem od 0.013 do 0.015. Ipak, manje vrednosti odstupanja su uočene u dubljim zemljišnim slojevima. Pri stanju pune zrelosti voća, procenjeni sadržaj vode prisutne na dubini od 45-60 cm bio je 12.5% veći u poređenju sa izmerenim vrednostima. Ukupno, model HYDRUS-2D je pokazao svoju sposobnost da predvidi dinamiku zemljišne vlage sa visokom tačnošću kod ovig zasada i i u ovim zemljišnim uslovima.