Objectives The effects of water pressures and emitter materials on the growth and nutrient uptake of spinach were tested in order to provide technique parameters for the selection of negative irrigation of spinach.
Methods Pot experiments were carried out in a rain shelter. Two emitter materials of ceramic cop (T) and PVFM (P) were used, and three irrigation pressures of –4, –8, –12 kPa and one conventional irrigation were designed with each of the emitter material, recorded as W1, W2, W3, and CK in turn. The dynamic change of water consumption, soil water content, dry matter accumulation, yield and nutrient absorption of spinach were monitored.
Results The water consumption rate was slow at the early growth period and became fast at the late growth period. The soil water content in the negative pressure treatments was all higher than that in CK, and it could be controlled in range of 18.6%–27.4%. The coefficient of variation ranged from 0.039 to 0.052, belonging to weak variation, while that of CK was 0.103, belonging to moderate variation. Under the same water supply pressure, the cumulative water supply of PVFM was higher than that of ceramic. When the negative pressure of water supply was between –8 kPa and –4 kPa, the spinach grew well and the number of leaves was moderate (about 11–15 pieces), soil water content was higher and leaf area was larger. Compared with the dry matter of spinach of using ceramic cop as emitter material, that of using PVFM as emitter was significantly increased by 36.2% under the –8 kPa pressure. In the case of maintaining high yield and biomass, the W2P treatment showed superiorities in that the spinach yield was increased by 59.9%, water consumption decreased by 35.9%, and water use efficiency (WUE) increased by 88.3% compared with CK. With the decrease of water supply pressure, the content of total P and total K increased, total N content decreased, all the negative water supply treatments had higher N, P and K contents than CK. With the decrease of water supply pressure, the absorption of N, P and K increased first and then decreased, but all higher than that of CK. The highest absorption of N, P and K was under the water supply pressure of –8 kPa. The N, P and K absorption of PVFM emitter was all higher than that of ceramic cop emitter at the same water supply pressure.
Conclusions Under the experimental conditions, the best combination for spinach growth was using PVFM made emitter and the water supply pressure of –8 kPa, which could effectively improve water use efficiency, increase yield and nutrient uptake of spinach.
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