The understanding of soil and nutrient dynamics under drip fertigation is relevant for crop production as well as water and nutrient management. The aim of this study was to generate information about the distribution of phosphorus (P) under different fertigation strategies for onion production on sandy clay loam soil during 2007-2008 to 2008-2009. The study involved field experiment, laboratory analysis and modeling of P distribution. The phosphorus distribution data in the field were collected, analyzed and used to calibrate and validate the solute transport model HYDRUS-2D for sandy clay loam soil. The performance of HYDRUS-2D was evaluated by comparing its simulated values with the observed values of soil moisture and nutrient concentration. The coefficient of determination (R2), root mean square error (RMSE) and mean absolute error (MAE) were used as model performance indicators. The range of R2 between 0.72-0.99 for water as well as nutrient distribution indicates good correlation between the observed and simulated values. The MAE and RMSE values for water and nutrient distribution were in between 0.0009 to 0.0039 which indicated the accuracy of the model. From these results, it can be concluded that the model is performing well for predicting the P concentration in the soil as well as the soil moisture distribution for onion crop grown under sandy clay loam. The model was also validated for water and phosphorus distribution with the observed values at the end of the crop season and found to be performing well. The HYDRUS-2D model may be used to carry out simulations for different soil types and with different fertigation and irrigation strategies for developing guidelines.
HYDRUS-2D, Fertigation strategy, Phosphorus distribution, Onion
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