2018 ASHS Annual Conference

Compost application studies conducted in potato production systems have reported yield increases with compost application or no difference in yield between compost applied treatments and commercial fertilizer only applied treatments. Rate of compost application may explain the lack of yield increase when compost is applied compared to commercial fertilizer application only. Studies were conducted at Colorado State University San Luis Valley Research Center, to evaluate the effect of compost application rate with optimum or reduced nitrogen (N) (one half of the optimum N rate) application on the performance of fresh market Russet potato. Treatments included application of 1, 3, and 5 tons per acre of compost, and each compost application rate combined with optimum or reduced N application rate. A control treatment was included where only commercial fertilizer was applied with optimum N rate. Application of compost combined with varied N application rates influenced plant uptake of nitrate nitrogen, phosphorus, and potassium. Application of compost at rates of 3 or 5 tons per acre with optimum N fertilizer application rate did prolong green leaf area duration (LAD), delayed leaf senescence, and enhanced early tuber bulking. For each rate of compost applied, optimum and reduced N application rates produced similar tuber yields. However, one ton per acre of compost applied with reduced N rate produced economically higher marketable (> 4 oz.) and large marketable size (> 6 oz.) tuber yields compared to all other treatments. The yield increases were 13.0% and 28.0%, respectively, when compared to the control treatment. In this study, the application of compost combined with N fertilizer application reduced tuber external and internal defects, when compared to the control treatment. Data from this study indicate that application of the proper rate of compost with appropriate N rate improves marketable tuber yield and reduces tuber external and internal defects. To improve economic yield of Rio Grande Russet, application of 1 ton compost per acre with reduced N rate is recommended.