Precision irrigation decision system for protected vegetables based on cumulative PAR and its application in tomato cultivation

Precision irrigation regulates water application based on crop physiological demands and environmental dynamics. Precision irrigation decision system based on cumulative photosynthetically active radiation ( PAR )—a fundamental determinant of crop water demand and directly influences the photosynthetic rate, transpiration, and overall metabolic activity—data can optimize quantitative relationships between environmental inputs and crop water needs. However, relevant research integrating PAR for protected tomatoes remains limited. Therefore, we designed a precision irrigation decision and control system, based on cumulative PAR , comprising irrigation training and decision-making systems. The irrigation-training system used cumulative PAR as a triggering mechanism for irrigation. By incorporating the reference crop evapotranspiration ( ET 0 ) under varying cultivation modes, irrigation frequencies, and irrigation amounts, optimal irrigation strategies were established through a comprehensive analysis of facility vegetable yield and quality, thereby constructing an intelligent irrigation model that links cumulative PAR with actual irrigation volume. To validate the effectiveness of the system, a two-factor factorial experiment was conducted on greenhouse tomato cultivation involving three irrigation levels (100% ET 0 , 120% ET 0 , and 140% ET 0 ) and two irrigation frequencies with irrigation intervals of 2 and 4 days. The results demonstrated that under the 4-day irrigation frequency, the intelligent irrigation system based on cumulative PAR achieved optimal overall yield and quality at the 140% ET 0 irrigation level. This study provides an innovative and efficient precision irrigation solution for soil cultivation in protected greenhouses.