Submitted to: Conservation Research Report
Publication Type: Other
Publication Acceptance Date: 6/15/2003
Publication Date: 6/30/2003
Citation: Banuelos, G.S. 2003. Orchard study of long-term biosolids application shows no significant negative effects on apricot fruit.. Conservation Research Report. California Agr. Research Initiative Report #00-1-002-1B, 5pp. Interpretive Summary: Biosolids have been applied to agricultural land for decades due to their beneficial properties for plant growth and development. They contain all essential macro- and micronutrients for plants, as well as other trace elements that are potentially inhibitory to plant growth. The actual content of any element is however dependent on the biosolids' source and the associated treatment process. Use of a non-industrial source biosolids in tree fruit production may be an ideal fertilizer and disposal option for excessive biosolids. Moreover, biosolids will not come into direct contact with fruit produced on the tree. In a long-term study the WMRL applied composted biosolids at different rates to field-grown apricot trees for 7 years. The soluble nutrients increased in the soil to a depth of 60cm. All essential nutrients increased in leaves and in fruit. For all biosolid treatments, fruit maturation was delayed, and fruit were firmer than fruit collected from control trees. Using a non-industrial source of biosolids in apricot production may be advantageous for growers who transport fruit over long distances and for growers who wish to have a staggered fruit maturity.
Technical Abstract: Composted biosolids of a non-industrial source were applied to apricots at rates of 0, 1.9, 5.8, and 11.7 Mg/ha (dry basis) based on providing the following amounts of total N in Kg N/ha): 0 (control), 57, 170, and 340. After 7 years of biosolids applications total and soluble concentrations of macro- and micronutrients increased in soils amended with biosolids. No increases in soluble nutrients were observed, however, beyond 60 cm in the soil. Heavy metals were not significantly detected in soils or in tested plant tissues, while all macro- and micronutrients were greater in fruits from trees grown with applied biosolids. Fruit were firmer and maturation was delayed with biosolids application. Other parameters used for the determination of fruit quality (juice pH, total acidity, and organic acids) were temporarily affected during fruit development. Using a non-industrial source biosolids in apricot production may be advantageous for growers transporting fruit over long distances and for growers who wish to have a delay in fruit maturity.