Alternate Partial Root-Zone Drip Nitrogen Fertigation Reduces Residual Nitrate Loss While Improving the Water Use but...

The efficient utilization of irrigation water and nitrogen is of great importance for sustainable agricultural production. Alternate partial root-zone drip irrigation (APRD) is an innovative water-saving drip irrigation technology. However, the coupling effects of water and nitrogen (N) supply under APRD on crop growth, water and N use efficiency, as well as the utilization and fate of residual nitrates accumulated in the soil profile are not clear. A simulated soil column experiment where 30-40 cm soil layer was ¹⁵NO₃-labeled as residual nitrate was conducted to investigate the coupling effects of different water [sufficient irrigation (W₁), two-thirds of the W₁(W₂)] and N [high level (N₁), 50% of N₁ (N₂)] supplies under different irrigation modes [conventional irrigation (C), APRD (A)] on tomato growth, irrigation water (IWUE) and N use efficiencies (NUE), and the fate of residual N. The results showed that, compared with CW₁N₁, AW₁N₁ promoted root growth and nitrogen absorption, and increased tomato yield, while the N absorption and yield did not vary significantly in AW₂N₁. The N absorption in AW₂N₂ decreased by 16.1%, while the tomato yield decreased by only 8.8% compared with CW₁N₁. The highest IWUE appeared in AW₂N₁, whereas the highest NUE was observed in AW₂N₂, with no significant difference in NUE between AW₂N₁ and CW₁N₁ at the same N supply level. The ¹⁵N accumulation peak layer was almost the same as the originally labeled layer under APRD, whereas it moved 10-20 cm downwards under CW₁N₁. The amount of ¹⁵N accumulated in the 0-40 cm layer increased with the decreasing irrigation water and nitrogen supply, with an increase of 82.9-141.1% in APRD compared with that in CW₁N₁. The utilization of the ¹⁵N labeled soil profile by the tomato plants increased by 9-20.5%, whereas the loss rate of ¹⁵N from the plant-soil column system decreased by 21.3-50.1% in APRD compared with the CW₁N₁ treatment. Thus, APRD has great potential in saving irrigation water, facilitating water use while reducing the loss of residual nitrate accumulated in the soil profile, but has no significant effect on the NUE absorbed.