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Evaluation of Composts for Managing Phytophthora capsici 2003

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Project Leader(s):

Dale Moyer, Cornell Cooperative Extension, Suffolk County

Meg McGrath, Dept. of Plant Pathology, Cornell

Anu Rangarajan, Dept. of Fruit and Vegetable Science, Cornell

Type of grant:

Cultural methods; sanitation; physical controls

Project location:

throughout the Northeast


The primary goal of this long-term project is evaluating yearly soil amendment of commercially-available composts plus 3-year rotation for managing Phytophthora blight. This disease is a major concern for many growers because an effective management program (including fungicides) has not been identified and severe losses have resulted in cucurbit crops, especially pumpkin, and pepper. Research is being done where blight occurred in 1999 through 2001. Additionally, compost is being examined as a soil-building amendment and fertilizer for rotation crops. Yearly amendments of compost were demonstrated to be having a long-term impact on nutrient availability and organic matter content of soil. Soil samples collected in mid June before applying compost or chemical fertilizer in 2003 revealed that plots receiving compost in 2001 and 2002 had significantly higher organic matter content and more available phosphorus, potassium, magnesium, manganese, and zinc than non-compost-amended plots. A one-year-old compost made of leaves and fruit waste was used. Its nitrogen content was 0.77%, thus applying it at 40 ton/acre was expected to provide 30 lb/acre nitrogen assuming 10% availability of the nitrogen in the compost. More available nitrogen was detected 22 days after applying fertilizer and compost in soil of non-compost plots that received 50 lb/A nitrogen from a conventional chemical fertilizer (15-15-15) than in plots receiving a combination of compost and chemical fertilizer to achieve this same nitrogen rate. The compost may not have provided the expected quantity of nitrogen or it provided nitrogen more slowly than chemical fertilizer. However, nitrogen content of leaves did not differ significantly. Compared to non-compost plots, compost plots had a smaller plant canopy, numerically more weeds (but not a significant difference), and yielded slightly less based on data from the first harvest done 15-22 Sep (24.4 vs 20.7 marketable-sized pods/plant, respectively). In conclusion, amending soil with compost yearly is having a long-term impact. Compost appears to be a suitable source of nitrogen to at least partly replace chemical fertilizer. Results may be improved by applying compost more than a few days before planting or by using a lower estimate for the percent available nitrogen in this compost. Availability of nitrogen is known to vary substantially among composts.