Irrigation and fertilization coupling of drip irrigation under plastic film promotes tomato's nutrient uptake and growth

The low irrigation and fertilizer use efficiency of the greenhouse vegetables is a serious problem in semi-arid northwest areas of China. The purpose of this study was to investigate the effect of fertigation on tomato growth, yield, nutrient absorption and utilization efficiency in a solar greenhouse, thereby providing a theoretical and experimental basis for the irrigation and fertilizer management of tomato greenhouse in this area. From March to July 2013, the plot experiments were carried out on a greenhouse tomato cultivar of Jinpeng 10 at Yangling District of Shaanxi Province. Two factors of irrigation(W) and fertilizer(F: N-P2O5-K2O) were set up in this study. There were 3 irrigation levels(W1:100%ET0; W2:75%ET0; W3:50%ET0, ET0 is the reference crop evapotranspiration), 3 fertilizer levels(N:P2O5:K2O in F1: 240: 120: 150 kg/hm2, F2: 180: 90: 112.5 kg/hm2, F3: 120: 60: 75 kg/hm2), and a control treatment irrigated by conventional furrow method(W: 100%ET0, N:P2O5:K2O was 240: 120: 150 kg/hm2). The results showed that the dry matter accumulation, tomato yield and partial factor productivity of fertilizer for the drip fertigation treatment(W1F1) were 144.77 kg/hm2, 97.15 t/hm2 and 190.5 kg/kg, respectively, which were 60.0%, 46.9% and 47.0% higher than those of the control treatment with the same amount of irrigation and fertilizer. The absorptive amount of nitrogen, phosphorus and potassium in the plant organs were 1.82-2.41, 1.56-2.03, and 1.36-1.90 times higher than those of the control treatment, respectively. Except for the harvest period, the distribution rates of nitrogen, phosphorus and potassium in fruits were greater than those of the control treatment. The drip fertigation treatment also significantly increased the absorption efficiency of nitrogen, phosphorus and potassium as well as the partial factor productivity of fertilizer(PFP). Under drip irrigation and fertilization condition, the dry matter accumulation increased with the increase of irrigation water. Under the irrigation treatments W1 and W2, the dry matter accumulation first increased and then decreased as the fertilizer increased, while it continuously increased with the increase of the fertilizer under the treatment W3. The maximum dry matter accumulation was recorded in the W1F2 treatment(9 258.3 kg/hm2). Tomato yield was significantly affected by the irrigation, fertilization and irrigation-fertilization interaction, increased with the increase of irrigation water and fertilizer. The maximum tomato yield was recorded in the W1F1 treatment(97.15 t/hm2). Tomato yield in the W1 and W2 treatments were 19.0% and 6.5% higher than that of the W3 treatment, while the tomato yield in the F1 and F2 treatments were 18.3% and 12.9% higher than that of the F3 treatment. The absorptive amount of nitrogen, phosphorus and potassium increased with the increase of irrigation and fertilization amount except for the second fruit enlargement period, when the maximum absorptive amount of phosphorus and potassium were recorded in the F2 treatment. With the advance of the growth period, the difference of nutrient uptake under the F2 and F3 treatments increased, while the difference decreased compared to the F1 treatment. The amount of irrigation and fertilizer significantly affected the absorption and use efficiency of nitrogen and phosphorus, the use efficiency of potassium, and the PFP. The irrigation-fertilizer interaction significantly affected the PFP, but it exerted no significant interaction effects on the nutrient use efficiency(NUE) and the nutrient uptake efficiency(UPE). The higher the irrigation amount was used, the smaller the NUE was, but the higher the UPE and the PFP were. The higher the fertilizer amount was used, the smaller the NUE, UPE and PFP were. The results indicated that fertigation treatment obviously increased the tomato yield. With the highest dry matter accumulation, higher nutrient uptake efficiency and partial factor productivity of fertilizer, the W1F2(100%ET0, N:P2O5:K2O was 180:90:112.5 kg/hm2) treatment was recommended as an appropriate schedule for irrigation and fertilization due to its high yield-increasing potential.