Role of phosphorus fertiliser banding and the ratio of nitrate to ammonium on the uptake of phosphorus and wheat growth: a glasshouse study

While it is known that nitrogen fertilisers improve phosphorus uptake depending on soil type and pH, the role in phosphorus uptake of the ratio of nitrate to ammonium in nitrogen fertiliser banded with phosphorus fertiliser is unclear. The present glasshouse study investigated the wheat growth response to different rates of application and banding depths (5 and 15 cm) of nitrogen and phosphorus, and mixing of phosphorus fertiliser with soil. The effect of 2 forms of nitrogen (ammonium and nitrate) banded with phosphorus fertiliser was also studied. Both banding depths increased phosphorus uptake and wheat growth more than mixing fertiliser throughout the soil. Banding at the 5 cm depth increased phosphorus uptake efficiency and wheat growth more than banding at the 15 cm depth. The highest shoot and root growth and phosphorus content were found when the nitrate:ammonium ratio was 50:50 and 75:25, with a slight decline at 100:0. The treatments with a large proportion of ammonium suppressed the growth of wheat and, consequently, reduced total phosphorus content. It was concluded that banding nitrate and ammonium at ratios 50:50, 75:25 and 100:0 with phosphorus fertiliser at 5 cm depth was optimal for increasing phosphorus uptake and wheat growth.