Contributions of Food Processing By-products Land Application to Soil Nutrient Availability.

The use of land-applied non-hazardous wastes, for example those come from food processing by-products, as an agricultural soil amendment or fertilizer replacement is projected to rise. Because public concerns regarding environmental impact and economic constraint of their disposal in landfill or incineration as well as presumed inherent agricultural benefits are the major driven force. This practice is important not only for recycling nutrients but also for minimizing concentration of elements of concern (e.g. sodium, chloride, and trace elements) that would otherwise be concentrated elsewhere. However, the impact of food processing by-products (which contain high moisture content, low pH, high total dissolved salts, and trace elements) are that they may impair soil and water quality upon application to California farmlands. The primary goal of this project was to develop best management practices for sustainable reuse of food processing by-products as a soil amendment on California farmlands. Quantifying soil nutrient availability from these by-products is critical to growers to carefully establish fertilizer replacement value to improve their crop use efficiency on their farms. This greenhouse study was established to study a potential loading rate for land-application of food processing by-products. The current application rate of these by-products to farm soils prior to planting forage crops is at 1:8 v/v. The objective of this study is to assess soil nutrient mineralization after various application rates of peach- or tomato by-products on two farm soils. These by-products were in semi-solids or slurry form and contained as high as 90% moisture content. Each by-products was mixed with each soil type at the rate equal to none (control), 1:8, 3:8, and 5:8 v/v, respectively. Macro- and micro nutrient, and trace element contributions from soil-byproduct mixtures were recorded at 0, 7, and 30 days after their applications. The results from this study will be discussed in detail.