Water use and production of a greenhouse pepper crop under optimum and limited water supply

Sweet pepper, grown from Autumn to Spring, is a major crop in greenhouse vegetable production systems of the Mediterranean coast in south-eastern Spain. Irrigation water is limited in this region, yet little information is available to assist in irrigation management at the farm and regional levels. The aim of this work was to determine crop evapo-transpiration, water-use efficiency and the effect of continuous water deficits on crop growth and production of pepper grown in plastic greenhouses in two growing seasons. Three irrigation treatments were applied: T1, watered with 100% of the estimated crop water requirement; and T2 and T3 watered with 50% and 20% of the estimated crop water requirements, respectively. Seasonal crop evapo-transpiration (ETc) in treatment T1 was 346-362 mm. The effect of water deficit on crop growth became apparent approximately 80 d after transplanting. The contributions of soil water uptake to total ETc for treatments T2 and T3 were 20-22% and 43-47%, respectively. The response of ETc to water stress was apparent at a threshold value of 55% of available water content (AWC), suggesting an allowable depletion of soil moisture equivalent to 27 mm. For treatments T2 and T3, reductions in total fruit production (relative to treatment T1) were 33% and 62%, respectively; and reductions in marketable fruit production were 47% and 67%, respectively. Water deficit had little effect on total fruit number, but substantially increased the proportion of unmarketable fruits due to their small fruit size, and to high incidences of sunburn and blossom-end rot. Linear relationships were found between both shoot biomass and marketable fresh fruit production with ETc. Mean water use efficiency values for shoot dry matter (WUEb) were 4.5 - 4.7 g m(-2) mm(-1); for total fresh fruit production (WUEt) between 24 - 33 g m(-2) mm(-1); and for marketable fresh fruit production (WUEm) between 16.9 - 25.9 g m(-2) mm(-1). Water stress did not induce early fruit production, or influence the relative distribution of assimilates within the plant.