Alfalfa Production Improved by Shallow Drains on Marine Sediments

Abstract

ABSTRACT ALFALFA responded favorably to shallow subsurface drainage at three spacings compared to no drainage on a silty clay loam marine sediment under cool humid climate field conditions over a four year period. There were four replications each of four drain spacings (none, 3, 6, and 12 m) of 7.5 cm diameter drain tubing at 60 cm depth. Soil water content at 30 cm depth intervals to 120 cm and water-table depths were measured to characterize the seasonal soil moisture regimes. Total hay yields on the drained plots during four growing seasons with three intervening winters were significantly higher than without drainage. Alfalfa persistence as measured by crop botanical analysis and live crown counts was also greater on the drained treatments. Favorable crop response due to subsurface drainage can be attributed to a change in the rooting environment. Water tables were lowered by drains which improved the soil water regime in the upper 60 cm of the root zone. Aeration or oxygen diffusion rate in the soil surface horizon was enhanced by drainage during early spring. Subsurface drains 60 cm deep and spaced at 12 m in these slowly permeable soils will provide suitable conditions for alfalfa growth.