The Effects of Salinity and Nutrient Deficiency on Spinach Growth, Physiology, and Nutrition Value

Salinity is a major constraint to crop production in all important spinach districts of the United States and nutrient-depleted soil is an increasing concern for farmers, especially vegetable growers. The effects of salinity and nutrient deficiency on spinach were evaluated in sand cultures under greenhouse conditions. Plants were watered every day with Hoagland nutrition solution, deprived of nitrogen (N), phosphorous (P) or potassium (K) for nutrient deficiency, either with or without 20/10 mM NaCl/CaCl₂ for salinity treatment. Salinity itself decreased shoot fresh and dry weight (FW and DW), leaf relative water content, and specific leaf area (SLA), and increased chlorophyll and carotenoid contents, photochemical yield [Y(II)] and maximum photochemical efficiency (Fv/Fm). The N deficiency greatly reduced shoot FW and DW, SLA, and the contents of chlorophyll and carotenoids. However, the reduction in shoot FW and DW was much smaller under salt stress than under control (68% versus 85% for FW and 61% versus 79% DW). Also N deficiency decreased Y(II) and Fv/Fm under salinity treatment. Both P and K deficiency similarly reduced shoot FW and DW under both control and salt stress, and increased chlorophyll content under control condition. The P deficiency increased Fv/Fm under both control and salt stress, and Y(II) under control condition. Salinity and nutrient deficiency also affected spinach nutrition value.