Soil Water and Solute Distributions Under Drip Fertigation: Effects of Soil Type, Phosphate Source, Irrigation Parameters and Fertigation Strategies

ABSTRACT The analysis of water and nutrient distributions across different soil types optimizes drip fertigation design and improves nutrient management precision. Soil column experiments were conducted to investigate water, NO 3 ‐N, NH 4 ‐N, Olsen‐P and total P distributions under varying emitter flow rates (1.0, 2.0 and 4.0 L/h), irrigation volumes (7.5, 10 and 12.5 L), fertigation strategies (full cycles, 1/4 W‐1/2 F‐1/4 W [first applying water {W} for one‐fourth of the total irrigation time, then applying fertilizer solution {F} for one‐half of the total irrigation time, followed by applying water {W} for the remaining one‐fourth of the total irrigation time], 1/2 F‐1/2 W and 1/2 W‐1/2 F), soil types (sandy and loam) and P sources (monoammonium phosphate [MAP] and ammonium polyphosphate [APP]). The results revealed that increasing the emitter flow rate increased NO 3 ‐N and Olsen‐P transport to the 20‐ to 30‐cm layer but did not affect NH 4 ‐N. The irrigation volume, fertigation strategy and soil type influenced the distributions of NO 3 ‐N, NH 4 ‐N and Olsen‐P, whereas the P source primarily affected Olsen‐P and total P. In sandy soils, nutrients were applied during mid‐to‐late irrigation (M1, M2) to reach the 10‐ to 35‐cm layer, with M2 favouring APP. In loam, early‐to‐mid fertilization (M1, M3) was used to avoid nutrient accumulation in the 0‐ to 10‐cm layer and target the 10‐ to 25‐cm layer, with MAP preferred for higher post‐fertilization irrigation volumes. These findings can inform practical cofertigation with N and P fertilizers.