ALFALFA YIELD AND QUALITY ARE AFFECTED BY SOIL HYDROLOGIC CONDITIONS

Soil water management practices may affect crop growth by reducing per iods of excess or shortage of soil water The objective of this study w as to evaluate forage yield and quality as affected by soil hydrologic conditions imposed by four water management practices. The experiment was conducted on a Muskellunge sandy clay loam soil (fine, mixed, fri gid Aeric Ochraqualf) in northern New York during three growing season s (1989-1991), each involving three cuttings of an alfalfa (Medicago s ativa L.)-timothy (Phleum pratense L.) intercrop. Treatments consisted of (i) drain open at all times (OD); (ii) drain closed at all times ( CD); (iii) drain open in winter, closed in summer (SC); and (iv) drain open in winter and the water table at a target 0.6-m depth using a we ir and supplemental irrigation in the summer (SW). Lack of drainage un der CD resulted in longer periods of soil saturation and reduced yield s by 9 and 16% compared with OD in the first and second growth cycle o f 1990 and by 17% during the first growth cycle of 1991. Increased soi l wetness after drain closure under SC did not result in yield increas es compared with conventional drainage during dry periods and caused a small decrease during a wet growth cycle. Maintaining a water table a t 0.6-m depth resulted in 30% yield increase in the dry year 1991, but none in 1989 and 1990. Soil temperatures were not affected by water m anagement. When yields were reduced, crude protein and elemental (P, C a, K, Mg) concentrations were generally higher, and fiber and lignin l evels were generally lower, indicating that increased forage quality p artially compensates for lower yields, especially under excess water c onditions.