Compost Science & Utilization, (2008), Vol. 16, No- 4,220-227 Effects of Mulching Blueberry Plants With Cranberry Fruits and Leaves On Yield, Nutrient Uptake and Weed Suppression U. Krogmann , B.F. Rogers , and S. Kumudini 2, Department of Environmental Sciences, Rutgers University, Neiv Brunswick, New jersey 2. Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky Integration of local organic wastes as mulches into farm production can provide waste management op- tions and an alternative to landfilling. In 2000, cranberry growers needed ways to dispose of excess cran- berries caused by overproduction and a federal regulation limiting the fruit's marketable production. This study examined the use of excess cranberry fruits and leaves as mulches on established blueberry plants. The objective of this study was to determine the effects of these novel mulches on established blueberry plant nutrient uptake, fruit yield, selected soil chemical properties and weed suppression. A randomized block design was set up and maintained for two years with four different mulch treatments (no mulch, 5.1- cm cranberry fruit, 10.2-cm cranberry fruit and 10.2-cm cranberry leaves). Leaf tissue nutrients (N, P, K, Ca, Mg, Mn, Fe, Cu, Zn, S, B, Al), fruit yield and average fruit size, selected soil properties, weed biomass and number of weed types were determined. In the second year, the fruit yield in the mulched treatments was lower than in the control (P<0.05), but not the fruit size. One possible reason is a significant decrease in leaf nitrogen uptake observed in some mulch plots. Weed biomass was significantly reduced along with species diversity. This study shows that novel mulches need to be carefully evaluated before being used due to their potential environmental and plant impacts. Introduction Identifying beneficial uses of organic wastes can provide farmers, food processors and municipalities with much-needed organic waste management op- tions. Organic wastes have been used as mulches with positive effects on plant productivity, soil physical and chemical properties and weed growth inhibition. Typically, studies have shown mulches decrease tem- perature fluctuation, increase water retention in soil (Bristow 1988, Mbagwu 1991, Monks ct al. 1997, Pick- ering et al. 1998, Pinamonti 1998, Movahedi Naeini and Cook 2000) and suppress weed growth (Monks ct al. 1997, Ashworth and Harrison 1983). While increas- es in available nitrogen and organic matter are often recorded in mulched soils (Pinamonti 1998, Movahedi Naeini and Cook 2000), son:\e studies with organic mulches, typically with high C/N ratios, have shown nitrogen immobilization and little change in soil or- ganic matter after mulch application (Pickering and Shepherd 2000, Lloyd et al. 2002). These variations in nutrient availability are often dependent on soil type and type of organic mulch applied. Therefore, it is im- portant to identify the organic mulch characteristics in order to understand the potential effects the mulch will have on soil and plants. An overproduction of cranberries and a dramatic decrease in cranberry prices in 1999 in the United States resulted in a federal regulation to limit mar- ketable production of cranberry fruit in 2000 (USDA 2000). The nahire of perennial crop production meant that producers did not have any means of limiting pro- duction of their crop, but were forced to find ways of disposing of the crop produced that was in excess of their federally regulated limit. Cranberry growers throughout the United States urgently needed ways to manage and dispose of excess cranberry fruit harvest in a cost-effective and environmentally sound manner. In New Jersey, cranberry production is in proximity to blueberry acreage. Since blueberry plants require a soil pH in the range of 4.8 to 5.5 (Eck 1988) and the cran- berry fruit is Wghly acidic, investigators proposed the use of cranberry fruit waste as a mulch in blueberry fields to integrate a locally produced organic waste with the agricultural market. The close proximity of the cranberry fruit waste to the blueberry plants places the organic mulch source close to its end use, keeping hauling costs relatively low. Many studies have found that mulches can be ben- eficial to blueberry plant growth and yield. However, most of these studies only tested the effects of mulch on newly planted blueberry bushes and mainly looked 2 2 0 Compost Science & Utilization Autumn 2008