Matching water requirements of Chinese chives planted at different distances apart from the line emitter under negative pressure irrigation subsurface system

Abstract

To supply water to crop in a proper way by using subsurface negative pressure irrigation (NPI), the distribution of soil moisture around the emitter with different water supply pressure (N1: −2 kPa, N2: −4 kPa, N3: −6 kPa) was investigated with surface irrigation as control (CK), to discuss the match degree of soil moisture to root distribution of Chinese chives planted at different distance apart from the NPI emitter. In the first growth season (FG), it took more than 15 days to form the stable wetting body of NPI due to the very low initial soil moisture, as a result the soil moisture and soil water storage (W) in NPI was lower than CK. In the second growth season (SG), the wetting body of NPI is almost invariable along time, and the soil moisture was much higher in NPI system with N1 significantly larger than CK. The yield showed a significant positive relation with soil moisture and W in both growth period (R was 0.942 and 0.849, respectively). As a result, the yield in NPI was significantly lower than CK in the FG and the yield in N1 was much higher than CK in the SG (p < 0.05). IWUE in NPI was significantly lower than CK in the FG while significantly larger than CK in the SG (p < 0.05). At the same water supply pressure, the soil moisture content was larger near the emitter, resulting better crop growth (p < 0.05). From the perspective of long-term irrigation, NPI could obtain a better yield and IWUE with less irrigation water amount (p < 0.05). The water supply pressure of − 2 kPa was more feasible to supply water for 6 lines of Chinese chives, with the same yield to CK and much higher IWUE (p < 0.05). The results indicated that planting crops in regions with proper soil moisture contents within the unique wetting body of NPI maintained high crop yield and improved crop IWUE, thus it is feasible to supply water for multiple rows of dense planted crops of Chinese chives with one linear emitter of the NPI subsurface system.