The 2011 ASHS Annual Conference

Common organic amendments that can be used in conventional and organic vegetable production include: 1) cover crops (legumes and non-legumes); 2) compost generated from yard wastes, biosolids, municipal solid waste, and animal manures, and other biodegradable waste by-products; and 3) raw animal manure (poultry, dairy, horse, swine, and cattle with and without bedding).  These organic amendments directly affect soil bulk density, water holding capacity, soil structure, soil carbon content, macronutrients and micronutrients, pH, soluble salts and cation exchange capacity, and biological properties (microbial biomass).  Although organic amendments are sometimes not considered as a nutrient source when used as part of a fertility program, their nutrient contribution should be calculated. For example, the first step in building a conventional tomato fertility program is to take a soil sample and send it to a soil laboratory for analysis of N-P-K and micronutrients. These results can be compared to the local crop recommendations for N-P₂O₅-K₂O (in Florida 200 lb/acre of NO₃ is required for a tomato crop). Second, select the organic amendments based on local available cover crops and organic amendment such as Sorghum-sudangrass (7,842 lb/acre of dry weight, 1.5% N, and 23% mineralization rate) and poultry manure compost (10 ton/acre with 50% moisture and 3% N content and 10% mineralization rate). Then, determine the available nutrients of the cover crop (27 lb/acre of NO₃) and poultry manure compost (30 lb/acre of NO₃). Finally, a 143 lb/acre of NO₃ of inorganic fertilizer is needed based in nutrient crop requirement for a conventional fertility program on tomato in Florida.