Simulation of Mulch and No-Mulch Conditions for Various Soil Matric Potential Thresholds for Drip-Fertigated Guava (Psidium guajava L.) in the Semiarid Region of Northwest India
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2016 American Society of Civil Engineers. Field experiments were conducted in a semiarid region of Punjab state, northwest India, for 2 years to evaluate an efficient irrigation schedule for guava under mulch and no-mulch conditions. The experiment involved the effect of mulching and three irrigation threshold values [I1 (-20 kPa); I2 (-40 kPa); and I3 (-60 kPa)] on guava plants under drip irrigation and fertigation. Soil matric potential, irrigation amount, soil water content, and fertilizer (N, P, and K) content were measured, and seasonal crop evapotranspiration as well as water and fertilizer use efficiency were computed regularly during the growing period of the crop. The calibrated two dimensional (2D)/three-dimensional (3D) model was used to simulate soil matric potential, and water and fertilizer movement in the soil under guava trees for mulch and no-mulch conditions. Simulated water movement, soil matric potential, and N, P, and K movement statistically matched those measured using the tensiometers, soil water probes, and soil sampling techniques. Results show that for mulch plants, if no irrigation was applied for a period extending to 6-7 days, i.e., for I3 (-60 kPa), irrigation treatment and dry periods without rainfall, the soil matric potential was lower for mulch plants than for no-mulch plants. Statistical measures [root mean square error (RMSE), average absolute error (AAE), relative root mean square error (RRMSE), correlation coefficient (r2), and model efficiency (EF)] indicate a close correspondence between measured and simulated values. The modeling efficiency (EF) and the root-mean square error (RMSE) for soil matric potential varied from 0.80 to 0.95 and 4.07 to 8.35 kPa, respectively, and for fertilizer movement from 0.61 to 0.87 and 0.0094 to 1.78 mg/cm-1, respectively. A water and mass balance was performed using commercially available software to estimate the water and fertilizer (N, P, and K) performances and relate these with amount of water and fertilizer applied. Modeling also revealed that lower leaching losses was for -40 kPa soil matric potential. The amount and frequency of irrigation application at this soil matric potential perfectly suited the growth of the plants.
