Citation: Halloran, J.M., Larkin, R.P., Defauw, S.L., Olanya, O.M., He, Z. 2013. Economic potential of compost amendment as an alternative to irrigation in Maine potato production systems. American Journal of Plant Sciences. 4:238-245. Interpretive Summary: Potato yield is strongly influenced by water. Even in the northeastern United States where annual rainfall can exceed 40 inches per year, potato yield is generally improved by over 30% with irrigation. Another way of increasing water availability to plants is by improving the soil’s water holding capacity. This approach can result in making rainfall more effective, thereby reducing the need to apply irrigation water. We evaluated the economics of producing potato under natural rainfall in compost amended soil compared to potato under irrigation without compost. We found that the compost treatment under natural rainfall was more profitable than irrigation as long as compost cost less than approximately $8/ton. In addition, we found that growers relying on natural rainfall can improve their profitability by adding compost as long as it does not cost more than approximately $25/ton. This research shows that compost is a potentially viable substitute to irrigation for potato in the northeastern U.S.; however, such potential does depend on the cost of producing and applying the compost.
Technical Abstract: Potato productivity in the northeastern U.S. has been relatively constant for over fifty years, raising questions about what factors are limiting productivity. Research was initiated in 2004 to identify key constraints to potato productivity by evaluating Status Quo, Soil Conserving, and Soil Improving cropping systems under both rainfed and irrigated management. We employed partial budgeting to determine cost differences and their impact on net revenue. Differences across these systems were primarily associated with tillage operations, compost and its application, and water management practices. When compost was annually applied at 19 Mg/ha and evaluated over the entire three-year crop rotation cycle, the compost amended (rainfed Soil Improving) system cost more than the irrigated Soil Conserving system once compost cost exceeded $9.15/Mg. Average yields were used to calculate gross and net revenue for each system. Because average potato yield for the irrigated SQ system (28.4 Mg/ha) equaled that in the rainfed SI system (28.3 Mg/ha), we were able to compare cost of irrigation vs. compost for achieving the same yield. The compost amended system under rainfed management generated more net revenue from the potato crop than the irrigated SQ system for compost costing less than $7.42/Mg. Comparing potato following compost amendment in the SI system with potato in the unamended SQ system indicates higher net revenue may be achieved in the commonly used rainfed barley-potato rotation as long as compost costs less than $22.95/Mg. This research shows that compost is a potentially viable substitute to irrigation for potato in the northeastern U.S.; however, such potential is highly dependent on compost production and application costs.