Objectives The purpose of this study is to evaluate the effect of three kinds of ammonium polyphosphates(APP) with various polymerization degree (PD) as seed fertilizer on maize seedling growth.

Methods With mono-ammonium phosphate (MAP) as control, three ammonium polyphosphates were APP1 (mainly low to medium PD), APP2 (mainly medium to high PD) and APP3 (uniform PD distribution) and combinations of APP with MAP (APP∶MAP = 1∶1, P₂O₅ mass ratio) to compare the effect on maize seedlings when all APPs were used as seed fertilizer on laterite soil. There were 8 treatments including CK (no phosphate fertilizer), MAP, APP1, APP2, APP3, APP1∶MAP, APP2∶MAP, and APP3∶MAP. At 40 days after sowing, corn seedling plants and soil samples were collected, and plant height, stem diameter, dry matter weight of aboveground and underground parts, soil total phosphorus, soil available phosphorus, phosphorus uptake of plant and phosphorus use efficiency were determined or calculated.

Results The seedling growth was significantly different among the 8 treatments. When APPs was applied individually, the best corn growth was in APP3, followed by MAP and APP1 and the worst was in APP2. This information indicated that APP with uniform PD distribution had the best effect as seed fertilizer. Compared with the individual APP treatments, combination of APP with MAP could significantly increase seedling growth and phosphorus uptake. The best combination was APP3 with MAP, which resulted in 21.3% and 81.6% more plant dry matter weight and phosphorus use efficiency over the treatment of MAP alone, respectively.

Conclusions Ammonium polyphosphate with homogeneous distribution of polymerization degree (APP3) could steadily supply phosphorus, resulting in maximum plant height, dry weight and phosphorus uptake. Combined application of MAP with APP3 is proved to be capable of promote nutrient availability and corn growth significantly, which is a proper application way.