Determination of optimal amount of irrigation and fertilizer under drip fertigated system based on tomato yield, quality, water and fertilizer use efficiency

Abstract: This study was aimed to investigate the effect of different combinations of irrigation and fertilizer on root growth, yield, quality, water and fertilizer use efficiency of drip fertigated greenhouse tomato. The multivariate regression analysis method was used to obtain the best combination of irrigation and fertilizer for maximum production of a single target. The spatial analysis method was further used to comprehensively evaluate the tomato yield, quality, water and fertilizer use efficiency to seek a high-yield, good-quality and low-water fertigation system for the closest acceptable production of multiple targets. The plot experiments were conducted in the greenhouse with two factors of irrigation and fertilizer (N-P2O5-K2O). There were three irrigation levels (high irrigation: 100%ET0; medium irrigation: 75%ET0; low irrigation: 50%ET0, ET0 was reference crop evapotranspiration) and three fertilizer levels (high fertilizer: 240-120-150 kg/hm2; medium fertilizer: 180-90-112.5 kg/hm2; low fertilizer: 120-60-75 kg/hm2). The results showed that irrigation and fertilizer treatments significantly affected the tomato yield, quality, water use efficiency and partial factor productivity of fertilizer. Tomato yield was very significantly affected by irrigation and fertilizer interaction and which had positive correlations with irrigation and fertilizer amount. The high irrigation-high fertilizer treatment had a maximum yield of 97.1t/hm2. The water use efficiency increased but the partial factor productivity of fertilizer decreased with the decreasing irrigation water and increasing fertilizer amount, at the same time, the water use efficiency decreased but the partial factor productivity of fertilizer increased with the increasing irrigation water and decreasing fertilizer amount. The maximum water use efficiency of 47.7 kg/m3 and partial factor productivity of fertilizer of 305.5 kg/kg were recorded for the low irrigation-high fertilizer treatment and high irrigation-low fertilizer treatment, respectively, and the minimum water use efficiency of 27.8 kg/m3 and partial factor productivity of fertilizer of 152.6 kg/kg were recorded for the high irrigation-low fertilizer treatment and low irrigation-high fertilizer treatment, respectively. Vitamin C and lycopene content first increased and then decreased with increasing fertilizer amount (except for medium irrigation treatment). Soluble solids content had significant difference between high and low fertilizers. Organic acid and soluble sugar content of low fertilizer had significant difference with high and medium fertilizers. Sugar acid ratio had no significant difference between different fertilizer treatments. The root dry weight was very significantly influenced by irrigation and fertilization interaction, total root length and total root volume were significantly influenced by single factor of fertilizer and irrigation amount, the total root surface area was only significantly influenced by fertilizer amount. The root dry weight first increased and then decreased with increasing fertilizer amount under high and medium irrigation treatments, and which was significantly reduced with decreasing irrigation amount under medium fertilizer treatment. The root weight, length, surface area and volume had obvious linear positive correlations with tomato yield. Through the multivariate regression analysis and the spatial analysis methods, the results showed that the maximum water use efficiency was obtained with a combination of irrigation 159 mm and fertilizer 479.4 kg/hm2; the maximum lycopene and sugar acid ratio were obtained with irrigation 159 mm and fertilizer 404.4 and 382.8 kg/hm2; the maximum yield was obtained with irrigation 279 mm and fertilizer 510 kg/hm2; the maximum partial factor productivity of fertilizer was obtained with irrigation 262 mm and fertilizer 225 kg/hm2. Acceptable yield and quality were (≥85% of corresponding maximum values) were obtained within the range of irrigation water 210~230 mm and fertilizer amount 385~453 kg/hm2, while the acceptable yield, lycopene and water use efficiency (≥85% of corresponding maximum values) were obtained within the range of irrigation water 198~208 mm and fertilizer amount 442~180 kg/hm2. The research provides a guidance basis for scientific management of water and fertilizer in greenhouse tomato production under the local drip fertigated condition.