Vegetable Crops Grown under High Soil Water Availability in Mediterranean Greenhouses

The soil water availability of six vegetable crop cycles, irrigated with water of 0.4 dS m(-1) electrical conductivity, was modified by varying the irrigation frequency in typical Mediterranean greenhouses at SE Spain. The soil matric water potential (SMP) in the middle of the loamy soil layer where most roots usually grow was maintained between -10 and -20 kPa (H), -20 and -30 kPa (C), and -30 and -50 kPa (L) for the crops grown under high, conventional and low soil water availability, respectively, while the total irrigation water applied was similar for the three treatments. The high soil water availability (H) did not improve the fresh weight of total, marketable and first class fruits, or the shoot biomass and partitioning. The irrigation frequency did not affect the total root biomass at the end of the autumn-winter cucumber, but the crop under L distributed its root biomass more homogenously throughout the soil profile than the crop under H. Regulating the soil water availability (maintaining the SMP higher than or close to the level at which crop water stress may occur) over the cycle as a function of crop conditions or farmers' requirements appears to be a useful management practice for controlling soil root distribution or shoot partitioning.