Evaluation and development of empirical models for wetted soil fronts under drip irrigation in high-density apple crop from a point source

Accurate measurement of soil wetting pattern from the point source of drip irrigation system plays an important role for designing of the irrigation system. The study evaluated a novel empirical method for predicting soil wetted dimensions surrounding a drip emitter. The study conducted at Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Srinagar, in a high-density apple orchard during 2018-2020. The field data were used to evaluate the five different semi-empirical models, namely, Al-Ogaidi (A-O), Malek and Peters (M-P), Amin and Ekhmaj (A-E), Jiusheng Li (J-L) and Schwartzman and Zur (S-Z). The model's results were compared with field data for predicting the wetted pattern. The soil wetting front was measured using three different capacity emitters (2, 4, 8 lph) under a point source of a drip irrigation system. The results were evaluated on the basis of statistical comparisons [mean absolute error (MAE), root mean square error (RMSE), Nash-Sutcliffe efficiency (NSE) and coefficient of determination (R-2)] between model-predicted and field-observed data. The newly developed empirical model has shown close agreement as compared to other models with MAE, RMSE, NSE and R-2 for wetted soil width 0.205 (cm), 0.246 (cm), 0.996 and 0.997, respectively, and for wetted soil depth 0.421 (cm), 0.522 (cm), 0.992 and 0.993, respectively. The developed model accurately predicts the whole wetting pattern and performs well in reproducing from known experimental data. The study revealed that the higher the emitter discharge capacity, the more were the vertical soil wetting front advances with increased time duration of irrigation. The information of accurate wetting pattern of drip from a point source will be useful for the optimal design of drip irrigation systems.