WATER QUALITY IMPLICATIONS OF CROP WATER USE PATTERNS

摘要

Water quality impacts are a result of the soil water balance for any given soil and position within a watershed.These effects have been recognized but there is little direct assessment of the impacts of crop water use patterns on waterquality. Studies have been conducted within the Walnut Creek watershed since 1990 to quantify the daily and seasonal waterbalance of different tillage and cropping systems. Water use patterns vary among years due to differences in energy inputand precipitation amounts and within a year due to tillage practice, crop residue cover, crop, and soil water holding capacity.Soils with lower organic matter content have a reduced soil water holding capacity and begin to drain earlier in the springcompared to higher organic matter content in soils. These lower organic matter soils are more subject to surface runoffconditions because they refill faster during intense precipitation events and cropping practices that can continually removesoil water will have a positive impact on environmental quality. Understanding the soil water balance at the watershed scaleand the interactions with crop management will enhance water quality when best management practices are coupled with theunderstanding of the seasonal water balance.