Objectives The property of phosphorus (P) fertilizers affects the movement and distribution of P in soil. We studied the distribution characteristics of different water-soluble P fertilizers in calcareous soil and the absorption and utilization of P by maize with fertigation.
Methods The field test of drip irrigation corn was carried out at the experimental station of Shihezi City, Xinjiang from 2018 to 2020. The maize variety ‘Zhengdan 958’ was selected as the test material. Six treatments were set up in the experiment: urea phosphate (UP), potassium dihydrogen phosphate (MKP), ammonium polyphosphate (APP), diammonium phosphate (DAP), monoammonium phosphate (MAP), and no phosphate fertilizer (CK). The irrigation and total NPK input amount were the same for the five fertilizer treatments except for CK. Soil samples were collected at 0–10, 10–20, and 20–40 cm layer in the vertical direction at three sites of the dripper in the horizontal direction, the root system, and the wide row at the flowering and mature stages of maize. The pH value, available phosphorus and total phosphorus content of the samples were measured. The aboveground plant samples of maize were collected, and the phosphorus content in stem, leaf and ear organs were determined. The maize yield was measured at the mature stage of maize, and the fertilizer utilization efficiency and other indicators were calculated.
Results Compared with CK and DAP, acid water soluble phosphorous fertilizer reduced soil pH to some extent. UP significantly reduced soil pH in 0–40 cm of soil around dripper: the decrements were 0.20 and 0.32 units at flowering stage, and 0.24 and 0.31 units at maturity. MKP, APP and MAP reduced soil pH within 0–10 cm distance to the drippers. UP increased soil available P in 0–40 cm soil depth and the available P was evenly distributed across 0–40 cm soil layer. The available P in 0–20 cm soil depth under UP was lower than APP, but higher than that of MAP. Compared with DAP, the soil available P content in 0–20 cm soil of APP, UP and MAP treatments were 65.47%, 44.18% and 23.14% higher at maize flowering stage, and 58.08%, 40.13% and 127.89% higher at mature stage, respectively. APP treatment had the highest P accumulation in ears, leaves and the entire plant of maize, which were 29.22%, 43.97% and 22.43% higher than DAP at flowering stage , and 65.39%, 26.63% and 50.60% higher at mature stages (P<0.05). The yield in APP, UP and MAP was similar, but was 18.03%, 11.64% and 9.46% higher than DAP. The phosphate fertilizer utilization rate in APP, UP and MAP was 29.62, 13.65 and 9.93 percentage points higher than DAP, respectively. The phosphorus fertilizer partial factor productivity and phosphorus fertilizer agronomic efficiency treated by APP increased by 18.03% and 174.96%, respectively, compared with DAP. The correlation analysis showed that the yield and P accumulation of maize were significantly correlated with the soil available P content in 0–20 cm layer, weakly correlated with the soil available P content in 20–40 cm layer.
Conclusions The distribution of P in soil was highly correlated with that of soil pH. The drip application of acidic water-soluble phosphate fertilizers could reduce the soil pH to varying degrees. Urea phosphate could significantly reduce soil pH in 0 to 40 cm range around dripper, so it had the higher and uniform available P content in 0–40 cm soil layer, while the other fertilizers’ impacts were limited within a distance of 10 cm near the dripper. However, APP had the highest available P in the 10–20 cm soil layer, and recorded the highest P accumulation in maize. APP had higher correlation of soil available P accumulation within 10–20 cm depth , and the highest P fertilizer utilization rate. Overall, ammonium polyphosphate, urea phosphate and monoammonium phosphate could be selected for maize fertigation in Xinjiang, and diammonium phosphate should be avoided.
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