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UC Dads Vegetable Research and Information Center Fertility Manacement of Dno-Imoated Veoetahbles <br /> FERTILITY MANAGEMENT OF DRIP-IRRIGATED VEGETABLES <br /> T.K. Hartz <br /> Department of Vegetable Crops <br /> University of California, Davis, CA 95616 <br /> G.J. Hochmuth <br /> Horticultural Sciences Department <br /> University of Florida, Gainesville, FL 32611 <br /> Additional Index Words: trickle irrigation, nutrients, fertigation <br /> L <br /> Summary: <br /> Drip irrigation provides an efficient method of fertilizer delivery virtually free of cultural <br /> constraints that characterize other production systems. Achieving maximum fertigation efficiency <br /> requires knowledge of crop nutrient requirements, soil nutrient supply, fertilizer injection <br /> technology, irrigation scheduling, and crop and soil monitoring techniques. If properly managed, <br /> fertigation through drip irrigation lines can reduce overall fertilizer application rates and minimize <br /> adverse environmental impact of vegetable production. <br /> 6- Drip irrigation allows precise timing and uniform distribution of fertilizer nutrients. Improved <br /> efficiency results from small, controlled fertilizer applications throughout the season, in contrast <br /> to large preplant or early-season sidedress applications. Fertilizer application through drip <br /> 6. irrigation (fertigation) can reduce fertilizer usage and minimize groundwater pollution due to <br /> fertilizer leaching from rain or excessive irrigation. Significant technical skill and management are <br /> required to achieve optimum performance. The following discussion highlights the main elements <br /> 4- of formulating and evaluating a fertigation plan. <br /> Soil Nutrient Supply: <br /> ■- Proper fertigation management begins with knowledge of the nutrient status of the soil. Most <br /> soils contain substantial quantities of available macronutrients and are frequently sufficiently <br /> supplied with micronutrients; using a standard drip fertigation program without soil testing will <br /> +� often lead to wasteful fertilizer application and, less frequently, result in a nutrient deficiency. <br /> Analytical procedures for soil analysis differ widely from location to location; it is important to <br /> employ a laboratory using test procedures calibrated for the geographic area of interest. <br /> Both mineral (NO3-N and NH,-N) and organic forms of N are present in all soils. Analysis for <br /> mineral N often is confined to NO3-N, because in most situations NH4-N constitutes <20% of <br /> mineral N content. Estimating the rate at which soil organic N is mineralized is problematic, but <br /> consideration of N mineralization potential can be important; net N mineralization rates of 0.5 to <br /> 2.0 kg Naha-t/day are common (Magdoff, 1991). Provided that the soil is drained adequately, <br /> mineralization potential generally increases with increasing organic N content; a low C/N ratio of <br /> recently incorporated plant residues and organic amendments also will favor more rapid <br /> mineralization. <br /> L Page 1 <br />