Early irrigation cut-off before the intended harvest date (40-45 days) is common practice in several regions (e.g., California), to increase the Brix value of tomato without a significant decrease in yield. The time to stop irrigation before harvest should be decided by taking into account not only the harvesting predictions but also local environmental conditions and certain soil, plant physiology, and agronomic factors. Stopping irrigation of tomatoes under furrowing (a widely used system) is an agronomic technique not commonly used in southwestern Spain, although traditionally farmers interrupt irrigation approximately 10 days before harvest to facilitate mechanical operations. According to practical experience, water cut-offs exceeding 20 days have a drastic impact on yield and quality. This experiment studied the influence of irrigation cut-off 15 days before the predicted harvest date (heat unit calculated at Nestle-Miajadas factory) on yield and Brix. The trials were performed over 4 years on a typical soil (sandy loam, 0.5-0.7% organic matter, and 50 cm depth) in a Mediterranean climate. The experimental results showed that irrigation cut-off about 15 days before the ideal harvest date produced a net yield decrease of acceptable raw material (ARM) of around 13% and an approximate Brix increase of 0.2 units, resulting in a lower ARM per yield per hectare. Based on these results and taking into account the characteristics of the traditional tomato production structure in southwestern Spain, we consider that irrigation cut-off could only be recommended with furrow irrigation in our area if carried out less than 15 days before harvest.
