283 Water and Nutrient Management of Garlic in California

Garlic is a cool-season vegetable crop with a long growing season. The potential nutrient and water needs are high. Irrigation and fertilization trials were conducted in the San Joaquin Valley in varying weather and different soils. Objectives were to relate fertilizer and irrigation management to garlic yield and to the efficiency of water and fertilizer use;to develop crop coefficients relating crop ET to reference crop ET; to relate postharvest quality to water nutrient management; and to determine if slow-release nitrogen fertilizers are as effective as more soluble forms. N, P, and K rates and timing of applications were applied. Furrow irrigation variables included calendar timing, cutoff date of last irrigation, irrigation at different available soil moisture (ASM) depletion, and irrigation based on evapotranspiration. A line source sprinkler irrigation was also conducted. Response to fertilizer nitrogen and to irrigation were dependent on soil type and depth. Response in heavy, deep soil was poor; response in lighter texture and shallower soil was much greater. Garlic extracted water and nutrients to depths greater than 120 cm and suffered no yield loss at high ASM depletion (50%) in deep, heavy soil. In shallow or lighter texture soil, extraction was limited to 60 cm, with highest yields when irrigated at 25% ASM depletion. Yield and quality of garlic were affected by irrigation cutoff date. Nitrogen response varied from ≈100 to more than 300 kg/ha. Slow-release nitrogen fertilizers were effective, but not economical. Little or no response to P or K fertilizer was measured in these experiments. Effects of excessive fertilizer rates on postharvest quality was variable.