A research trial to evaluate the effectiveness of green waste compost, as compared to the standard orchard fertilizers of ammonium nitrate, manure, composted manure, and pelletized chicken manure, was initiated in 1992 and is currently in its final season of evaluation (1996). All soil amendments were applied at a rate of 100 pounds of nitrogen per acre in a replicated block of Elegant Lady peaches. Plot size is 49 trees per treatment plot and each treatment is replicated four times. All nitrogen sources are compared to an unfertilized control. Both furrow and microsprinklers are utilized in this 15-year-old orchard.
The following parameters have been evaluated: yield, disease incidence, insect damage, plant nutritional analysis, soil nitrate movement, trunk circumference, number of fruit per tree, fruit size, leaf water potentials, light bar readings, soluble solids content, acidity, fruit flesh pressure, postharvest characteristics related to storage, internal browning, etc. In addition to the cultural aspects and the postharvest storage aspects, a consumer taste test evaluation was performed on fruit which was harvested during the 1995 season. Two consumer taste tests were performed to evaluate fruit which was ripened for three days following harvest and on fruit that was held in cold storage for one week; then ripened to simulate shipments to the east coast.
The data thus far indicates that green waste compost compares favorably to our standard orchard fertilizers, when applied at the same rate of nitrogen. Significant differences are developing in leaf nutrient levels, organic matter content in the upper six inches of soil, and in the movement of the nitrate ion in the soil. An interesting observation with regard to brown rot disease was noted where the green waste compost was applied. In 1993 and 1994, less storage brown rot developed on the peaches where the green waste compost had been applied. This reduction in disease incidences has been attributed to the presence of Aureobasidium pullalan spores located on the surface of the fruit. When there are 2,500,000 spores or more, there appears to be no brown rot developing in stored fruit. Why the green waste compost treatment seems to accumulate more of these spores on the surface of the fruit than the other treatments is still under study.
The consumer taste test evaluation included three of the treatments from this study. This evaluation included fruit from the ammonium nitrate plots (petroleum based fertilizer) and from the manure and the green waste compost treatments. All fruit were comparable in size, color, firmness, and soluble solid content. Consumers were allowed to handle, smell, and evaluate fruit from each treatment prior to their tasting of similar fruit from each treatment (from which the soluble solid content and pressure had been predetermined). The results indicated that the consumers could not determine differences among the fruit except for texture. The consumers determined that the fruit flesh from the petroleum based fertilizer treatment was firmer than either of the organic fertilizer treatments. This was validated through statistical analysis, by using a UC firmness tester on each fruit prior to it being tasted by the consumers. The consumers could not determine any differences in any of the other parameters of color, size, shape, texture, or soluble solids. Prior to tasting the fruit, the consumers were asked to choose which of the three peaches they would prefer to buy. After tasting the fruit they were told the fertilizers used and then asked which fruit they would prefer to buy. When shown information about the fertilizer treatment used on the peaches, 84% of those who initially selected the peach that was later identified as "grown with conventional, petroleum-based fertilizers," switched to one of the two peaches labeled as 4 6 grown with natural fertilizers." None of the respondents who initially preferred a peach grown with one of the two natural fertilizers switched to the fruit grown with petroleum based fertilizer.