Intelligent fertigation improves tomato yield and quality and water and nutrient use efficiency in solar greenhouse production

Intelligent fertigation is a sustainable solution for optimising water and fertiliser input, thus minimising environmental pollution in vegetable cultivation facilities and reducing labour costs in agricultural practices. It is important to optimise irrigation scheduling parameters to specific crops to ensure water and nutrient use efficiency. A field experiment was conducted in Shouguang, Shandong Province, to investigate the effects of irrigation scheduling with different treatments (farmer drip irrigation FI, intelligent irrigation II1, and intelligent irrigation II2) on tomato growth, irrigation water and nutrient use efficiency over two growth seasons. Intelligent irrigation II1 and II2 utilised FDR sensors to control the moisture range within 80-95% and 80-85% field capacity (FC) for automatic irrigation scheduling, respectively. Intelligent irrigation (II1 and II2 treatments) reduced irrigation rate by 24.3-63.8% in comparison with FI treatment, significantly increasing total dry matter accumulation, nutrient uptake, yield and fruit quality of tomato. II2 treatment further reduced the irrigation rate by 31.6-32.3% compared to II1 treatment, with no significant difference in tomato yield and quality. Root dry matter, root-shoot ratio, 0-2 mm diameter root length and root surface area, 0-1.5 mm diameter root tips, and >3.5 mm diameter root volume were significantly increased under intelligent irrigation treatments. Positive correlations between irrigation water productivity; nitrogen, phosphorus, and potassium use efficiency; and the indices of length, surface area, tips, and volume of roots were highly significant. Intelligent fertigation system (IFS) maintained soil moisture within a suitable range through high-frequency irrigation scheduling, promoted the growth of 0-2 mm diameter roots, which were responsible for absorbing, acquiring, and transporting water and nutrients in the soil, and reduced water loss and nutrient leakage. Taken together, the intelligent fertigation system presented herein is an effective fertigation strategy to improve irrigation water and nutrient use efficiency.