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Water and Olsen-P distribution as affected by phosphate fertilizer types and emitter discharge rates from a point source

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2021 ASABE Annual International Virtual Meeting  2100767.(doi:10.13031/aim.202100767)
Authors:   Zhen Wang, Yanhong Guo, Jiusheng Li
Keywords:   phosphorus, fertigation, emitter discharge rate.

Abstract. Water and solute dynamics in the soil are important for the design, operation, and management of the fertigation system by drip irrigation. Experiments were conducted to study the effects of emitter discharge rates on wetting patterns and Olsen-P distribution in the soil from a surface point source. Three widely used phosphate fertilizers of diammonium phosphate (DAP), potassium dihydrogen phosphate (KDP), and urea phosphate (UP) were tested. A 30° wedge-shaped plexiglass container was used to represent one twelfth of the complete cylinder. Monitoring of the wetting front movement in the tested sandy soil revealed that the increase in the surface wetted radius and in the vertical plane with water volume applied can be represented by a power function with power values of about 0.38 and 0.44, respectively. The dimensions of the wetted soil volume were clearly related to the emitter discharge rate. An increase in rate resulted in an increase in the wetted horizontal distance and a decrease in the wetted soil depth. The distribution of Olsen-P content in soil generally decreased with distance from the point source in the radial and vertical directions for all the three phosphate fertilizers. The absorption of phosphorus to soil increased with pH of the fertilizer solutions in an order of UP (2.78) < KDP (6.21) < DAP (8.62). The maximum Olsen-P contents in soil at depth of 20 cm were 97, 62, and 37 mg kg-1 for the treatments with UP, KDP and DAP fertigated, respectively. Greater radial and smaller vertical distributed range of Olsen-P were observed in soil with higher discharge rates. The application strategy of phosphate fertilizer should be developed considering the absorption of fertilizers and emitter discharge rates.

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