Estimation of tomato yield gaps for greenhouse in Uruguay

Yield gap analysis is a powerful method to explore gap's breadth between potential yields, attainable and those realized in farmers' fields, identifying constraints to production and assess opportunities to yield increase. We assessed yields and yield components across two seasons, in 110 greenhouse tomato (Solanum lycopersicum) crops during 2014/15 and 2015/16 in the south region of Uruguay, and compared them with potential and attainable yield. Potential yield was calculated with a simulation model based on photosynthetic active radiation (PAR) and light use efficiency, and TOMSIM to estimate assimilate partition and fruit yield. Since yield was primarily determined by cumulative PAR intercepted, a boundary function was fitted to estimate attainable yield as a function of cumulative PAR intercepted. Our study quantified a yield gap of 10.7 kg m(-2) or 44 % relative to potential. Overall gap was divided into three components: difference between actual and attainable (45 % of total gap), attainable and potential with actual greenhouse PAR transmissivity (29 % of total gap) and between potential with actual transmissivity and potential with 70 % of greenhouse transmissivity (26 % of total gap). For long summer and short spring/summer crops the greatest impact in yield could be obtained by increasing leaf area index by reducing plant lowering operations and leaf pruning intensity, and by increasing plant density. For autumn crops, yield could be improved by earlier planting, reducing leaf pruning intensity after harvest beginning, and increasing greenhouse transmissivity by more frequent plastic cover renewal and removing roofs' shading screens and whitening.