Effects of humic acid-enhanced phosphate fertilizer on wheat yield, phosphorus uptake, and soil available phosphorus content

Humic acid (HA) can improve the use efficiency of phosphate fertilizer, although its optimal proportion in fertilizers remains unknown. In this study, we conducted soil column experiments over two growing seasons to compare the effects of different HA proportions in phosphate fertilizer on wheat yield and phosphorus uptake, utilization, and soil available phosphorus. At harvest, grain yields were 0.23%-13.21% higher under HA-enhanced phosphate (HAP) compared to treatments with conventional phosphate fertilizer (P). Among different HAPs, wheat treated with HAP with 1.0% HA (HAP10) or 2.0% HA (HAP20) had the highest 2-year grain yield. Furthermore, total phosphorus uptake and its allocation in grains were both higher under HAP treatments compared to P treatment. The apparent use efficiency, agronomic efficiency and partial productivity of phosphorus in HAP10 and HAP20 treatments were also significantly higher than those treated with P in both growing seasons. In addition, HAP10 and HAP20 treatments resulted in the highest content of available phosphorus in the 0-60 cm soil layer compared with other HAPs or P alone. Incorporating HA into phosphate fertilizer at proportions of 0.5%-5.0% can increase wheat yield, phosphorus uptake, phosphate fertilizer use efficiency, and soil available phosphorus content, 1.0% or 2.0% HA in HAP shows the highest effects on these indexes. Given the economic benefits, 1.0% level is an optimal level for enhancing the effects of phosphate fertilizer in winter wheat crops.