Objectives This study explored the influences of negative pressure irrigation on the phosphorus uptake and phosphorus content in various organs of maize, and total phosphorus and available phosphorus content in rhizosphere soil, aiming to provide a theoretical basis for improving the efficiency of negative pressure water supply.
Methods Negative pressure irrigation pot experiments were conducted in a rain-proof shed at the experimental base of Heilongjiang Bayi Agricultural University in 2019 and 2020 respectively, using maize variety Xianyu 335. Three negative pressure irrigation pressure levels, namely −5 kPa, −10 kPa, and −15 kPa, were established, with conventional irrigation as the control (CK). Plant height, stem diameter, and yield of maize were measured, phosphorus uptake and phosphorus content in various organs at different growth stages were analyzed. Total phosphorus and available phosphorus content in maize rhizosphere soil were also determined.
Results The yield of the −5 kPa treatment was 38.7% and 16.2% higher than that of the CK in 2019 and 2020, respectively. The yield of the −15 kPa treatment was significantly lower than that of the control and the −5 kPa treatment. At the maturity stage, the root, stem, leaf, cob, grain, and whole plant phosphorus uptake of the −5 kPa treatment were 120.8%, 86.6%, 26.4%, 66.9%, 15.2%, and 43.3% higher than those of the CK in 2019, and were 15.4%, 22.4%, 47.0%, 29.7%, 30.0%, and 21.3% higher than those of the CK in 2020, respectively. The phosphorus uptake in the roots, stems, and leaves of the −10 kPa treatment was 47.1%, 53.0%, and 10.7% higher than that of the CK, respectively, in 2019, and the phosphorus uptake in the leaves was 10.1% higher than that of the CK in 2020, while the total phosphorus uptake of other organs was all lower than that of the CK. The phosphorus uptake in various organs and the total phosphorus uptake of the −15 kPa treatment were significantly lower than those of the CK and the −10 kPa treatment. In 2019, the phosphorus content in the root, stem, leaf, bract, and axis of the −5 kPa treatment was 22.4%, 71.8%, 10.1%, 10.0%, and 43.7% higher than that of the CK, respectively. The phosphorus content in the stem, leaf, bract, shaft, and grain of the −10 kPa treatment was 102.8%, 17.9%, 13.8%, 19.8%, and 11.5% higher than that of the CK, and the phosphorus content in the stems, leaves, bracts, and axes of the −15 kPa treatment was 136.9%, 38.9%, 98.2%, and 66.1% higher than that of the CK, respectively. In 2020, the phosphorus content in the roots, stems, leaves, and axes of the −5 kPa treatment was 34.1%, 17.2%, 13.6%, and 28.4% higher than that of the CK, respectively. The phosphorus content in the root system, leaves, and axis of the −10 kPa treatment was 30.5%, 27.6%, and 22.6% higher than that of the CK, respectively. The phosphorus partial productivity and phosphorus efficiency of the −5 kPa treatment were 38.7% and 41.7% higher than those of the CK, respectively, in 2019, and were 16.2% and 18.8% higher than those of the CK, respectively, in 2020. At the tassel stage and maturity stage, the total phosphorus in the rhizosphere soil of the −5 kPa treatment was 8.1% and 10.9% lower than that of the CK in 2019, and was 5.4% and 6.0% lower than that of the CK in 2020. There was no significant difference between the −10 kPa and −5 kPa treatments, and there was no significant difference between the −15 kPa treatment and the CK. When the maize was at the tasseling stage and maturity stage, the soil available phosphorus content in the −5 kPa treatment was 17.6% and 36.0% lower than that of the CK in 2019, and 19.2% and 21.9% lower than that of the CK in 2020, respectively. There was no significant difference between the −10 kPa and −5 kPa treatments. The available phosphorus content in the rhizosphere soil of the −15 kPa treatment was significantly lower than that of the CK and the −5 kPa treatment in 2019, and the −15 kPa treatment was significantly lower than the CK at maturity in 2020.
Conclusions Negative pressure irrigation with −5 kPa water supply pressure has better effects on promoting maize growth, increasing yield and phosphorus uptake than CK, −10 kPa and −15 kPa treatments. At the same time, the contents of total phosphorus and available phosphorus in rhizosphere soil was reduced.
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