Effect of Phosphorus Fertilizer Placement Depth, Amount, and Soil Water Content on Early Maize Growth

ABSTRACT Background Drought stress (DS) reduces soil phosphorus (P) availability by limiting P diffusion and uptake, while global P resource scarcity exacerbates nutrient limitations for crops. Aim This study investigated whether deep subsurface P placement could alleviate the combined effects of P deficiency and DS on maize growth. Methods A greenhouse trial with maize (cv. Ricardinio) was conducted involving three factors: three P fertilizer amounts (0 mg P pot −1 [NP], 109 mg P pot −1 [LP], and 655 mg P pot −1 [HP]), three placement depths (0–9 cm [U, upper layer], 9–18 cm [L, lower layer], and uniformly mixed throughout 0–18 cm [M]), and two soil water contents (45% of soil water holding capacity [WHC] [DS] and 75% WHC [WW]). Root and shoot traits were assessed at the fourth‐ and tenth‐leaf stages. Results LP significantly reduced shoot biomass and P content compared to HP treatment. At the fourth‐leaf stage, DS increased root biomass by 69.3% and 27.1% in the 9–18 cm and 0–18 cm layers compared to WW treatment. At the tenth‐leaf stage, DS reduced root biomass by at least 41% across layers and decreased shoot growth and P uptake. Under DS, L‐DS increased root growth and root length in the 9–18 cm layer compared to M‐DS and U‐DS treatments but did not improve shoot traits. Conclusion Deep subsurface P placement promoted deeper root development under drought and P deficiency. However, its benefits on shoot growth were not evident in early stages, indicating the need for longer term field validation.