The postharvest quality of vegetable crops from conventional and organic production\nsystems depends on pre-harvest factors such as variety genetic potential, fertilization, and irrigation.\nThe five principles of plant nutrition (plants absorb ions, not fertilizers; Leibeigââ?¬â?¢s law of the\nminimum; nutrient application requires a source, a rate, a placement and a time of application;\nno correlation exists between total nutrient presence in the soil and availability; and plant nutrient\nconcentration and yield are related) must be followed throughout the crop growth cycle. In certified\norganic production in the United States, cover crops, manure and composts may be used together\nwith Organic Materials Review Instituteââ?¬â??approved fertilizer products. A fertilization program\nusually includes (1) soil sampling and understanding the recommendation; (2) adjusting pH if\nnecessary; (3) applying preplant fertilizer and developing a schedule for sidedressing or fertigation;\n(4) using foliar fertilization; (5) monitoring plant nutrient status; and (5) keeping fertilization records.\nThe components of an irrigation schedule are (1) determining a target irrigation volume based\non reference evapotranspiration and crop age; (2) adjusting this amount based on soil moisture\ncontent; (3) determining the contribution of rainfall; (4) developing a rule for splitting irrigation;\nand (5) keeping irrigation records. A poorly designed irrigation program can negate the benefits\nof a sound fertilization program. Challenges encountered in conventional and organic production\ninclude predicting nutrient release rates from organic materials, supplying enough N throughout\nthe cropping season, identifying rescue strategies, keeping production costs low, and meeting the\nadditional legal requirements of the food safety and best management practices programs.
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