On-farm diagnosis for greenhouse tomato in south Uruguay: Explaining yield variability and ranking of determining factors

Knowledge about contributing factors to yield loss is essential for sustainable intensification of agriculture, which has the objective to increase both, yield and environmental sustainability. This study aimed to identify strategies to reduce the distance between under-performing and best-yielding greenhouse tomato crops in the south region of Uruguay. Gap to attainable yield was described and main causes of yield variability were explored by combining regional agronomic diagnosis and yield gap analysis. A sample of 110 tomato greenhouses within 23 farms during 2014/15 and 2015/16 were assessed. The variables assessed were classified in four groups: growth defining, growth limiting, growth reducing factors and yield components. Yield ranged from 0.9 to 24.3 kg m(-2). Cumulated photosynthetically active radiation (PAR) intercepted was the most correlated with yield. We analyzed two complementary ways of increasing yield: (1) modifying growth-defining factors to increase cumulated PAR intercepted and attainable yield, and (2) modifying growth-limiting and reducing factors responsible for the gap to attainable yield at a given level of cumulated PAR. PAR interception could be increased by adjusting transplanting dates to modify daily incident radiation, improving transmissivity of greenhouses and fraction PAR intercepted by canopy. We classified crops in three groups of cumulated PAR intercepted and yield. The average gap between actual and attainable yield was 34%. The strategy to close that gap differed among groups, but K nutrition was common to all. Results from this study allowed us to deliver relevant and actionable information to better inform discussions among farmers and their technical advisors.