Phosphorus partly compensates for low‐temperature stress in maize by improving early seedling growth under limited growing degree days

Abstract

Chilling stress at the seedling stage and low phosphorus (P) use efficiency are major constraints to maize ( Zea mays L.) yield in North China. However, the interaction between early‐season thermal accumulation and soil P availability remains insufficiently understood. This study tested the hypothesis that adequate soil available P can partly compensate for insufficient growing degree days (GDD) by promoting early maize (cv. Xianyu 335) growth. Based on a long‐term field experiment involving two annual sowing dates and five P application rates, we assessed the correlations among seedling biomass, soil available P levels, GDD, and grain yield. P fertilization increased soil Olsen‐P content and seedling biomass, which plateaued when V3 (vegetative stage with the third leaf collar visible) biomass exceeded approximately 1.15 g plant ^{− 1} . A biomass‐contour model relating seedling biomass with soil Olsen‐P and GDD was developed, enabling identification of P targets associated with maximum yield. Based on meteorological data, GDD zones were classified as low (<220°C day), moderate (220°C day–295°C day), and high (>295°C day). The model indicated that lower‐GDD zones require higher soil Olsen‐P (>78 mg P kg ^{− 1} ) to achieve the same seedling biomass threshold, whereas high‐GDD zones require lower Olsen‐P (58 mg P kg ^{− 1} ). The results indicate that site‐specific P management based on local thermal conditions and soil Olsen‐P status is a feasible strategy to stabilize maize production across thermal zones. This approach improves the matching between P input and regional thermal conditions, thereby enhancing agronomic efficiency of increased P input while balancing crop productivity with environmental safety.