Abstract

The environmental impact of using chemical fungicides to suppress disease in potato production is becoming a concern in recent years. The use of compost tea as a disease suppressant is becoming popular. A study was conducted at Colorado State University, San Luis Valley Research Center, U. S. A. from 2007 to 2009, to evaluate the interactive effect of nitrogen fertilizer rate and compost tea or fungicide application on tuber yield, tuber size distribution and quality of potato cultivars Russet Norkotah and Russet Nugget. Treatment combinations included nitrogen fertilizer (N) applied at 90 and 134 kg/ha with compost tea or fungicide applied. Two control treatments were established where N was applied at 90 and 134 kg/ha with no compost tea or fungicide application. Medium size tuber yield (114–284 g tubers) increased significantly in all three years for Russet Norkotah when compost tea was applied with 90 kg N/ha (2007) or with 134 kg N/ha (2007, 2008 and 2009). Marketable size tuber yield (114–454 g tubers) of Russet Norkotah was significantly increased when compost tea was applied with 134 kg N/ha (2007 and 2009), compared to the control treatment. For Russet Nugget, medium size tuber yield increased significantly in all three years of the study when compost tea was applied with 90 kg nitrogen fertilizer/ha, compared to the control treatment. The yield of large marketable size (170–340 g and 170–454 g tubers) increased when compost tea was applied with 90 kg N/ha in two of the three years study. For Russet Norkotah, the application of fungicide increased tuber specific gravity, compared to the application of compost tea and the control treatments. However, for Russet Nugget tuber specific gravity was similar in the fungicide and compost tea treatments in two of the three years study. Results of these studies suggest that compost tea can be used with reduced or no fungicide application to produce optimum tuber yields in potato production.