Irrigating and Liming Alfalfa on Coastal Plain Soil

Abstract

AbstractAlfalfa (Medicago sativa L.) stands do not persist for longer than 2 or 3 yr in many regions of the southern USA. A 3‐yr experiment was conducted to determine if alfalfa yield and stand persistence could be improved by irrigating and liming. Water management treatments were no irrigation and spinkle irrigation with about 25 mm of water when soil moisture reached approximately 50% of available water. Dolomitic lime treatments included 0 lime, 2.2 Mg lime ha−1 applied before planting, and 4.4 Mg lime ha−1 applied before planting, and 2.2 Mg time ha−1 applied every year. Soil samples were taken and analyzed for pH, exchangeable Ca, Mg, and Al and available Mn. In addition, plant density was monitored. Annual dry matter yields averaged 13, 10, and 3 Mg ha−1 in 1987, 1988, and 1989, respectively. The progressive decrease in seasonal yield over time was due to a decline in plant population density from an average of 191 to 26 plants per square meter between Years one and three of the study. Dry matter yield was not changed by irrigation, but decreased by an average of 0.9 Mg ha−1 when lime was not applied. Crop annual dry matter yield showed a positive correlation with soil Ca, Mg, and pH and a negative correlation with soil Al. Growing conditions resulting from lime application and irrigation should have been favorable for alfalfa production; therefore, stand reduction was probably not due to acid condition or drought stress in the surface soil.