Water conservation under reduced tillage systems

Water is important for dryland crop production. Seldom is rainfall sufficient or adequately distributed during a growing season so that dryland crops can produce to their fullest potential. It is necessary to have stored water available in the soil to supplement inadequate growing season rainfall for economical crop production. Stored water is especially important in the Inland Pacific Northwest of north central Oregon, southeastern Washington, and northern Idaho, where 65% of annual precipitation occurs during the six-month (Sept. 1 to Feb. 28) winter period and 30% during the four-month (March 1 to June 30) growing season. Stored water is also important in the Eastern Idaho Plateau where the low annual precipitation is nearly evenly distributed over the months of the year. The water balance equation tells us that change in water content in the soil - precipitation + inflow - runoff + upward flow - drainage - evapotranspiration (ET). Any cultural practice that decreases runoff or ET can result in increased water in the soil. To store adequate quantities of water, deep soils (> 60 inches) with good infiltration and water holding capacity are required. Summer fallow has long been the traditional practice for storing water in soils for later use by crops. Fallow periods vary from 14 to 15 months where winter small grains are seeded to 21 months where spring small grains are seeded. Water storage efficiency for fallow is low, ranging from 10 to 35% in the Great Plains and the Southwest; to 30-37% in eastern Idaho and northern Utah; to 40-45% of precipitation in the Inland Pacific Northwest (Evans and Lemon, 1957). Good water conservation yields increased crop production, stability of production, and increased water use efficiency. Soil tillage and residue management play significant roles in collection and storage of precipitation in the soil. Our objectives are to discuss insights in water conservation gained under the STEEP (Solutions to Economic and Environmental Problems) program (Oldenstadt et al., 1982) during these last ten years and problems that remain. New research information will be discussed under topics of crop residues, conservation tillage systems, fallow and models

A Regression Model to Estimate Regional Ground Water Recharge

A regional regression model was developed to estimate the spatial distribution of ground water recharge in subhumid regions. The regional regression recharge (RRR) model was based on a regression of basin-wide estimates of recharge from surface water drainage basins, precipitation, growing degree days (GDD), and average basin specific yield (SY). Decadal average recharge, precipitation, and GDD were used in the RRR model. The RRR estimates were derived from analysis of stream base flow using a computer program that was based on the Rorabaugh method. As expected, there was a strong correlation between recharge and precipitation. The model was applied to statewide data in Minnesota. Where precipitation was least in the western and northwestern parts of the state (50 to 65 cm/year), recharge computed by the RRR model also was lowest (0 to 5 cm/year). A strong correlation also exists between recharge and SY. SY was least in areas where glacial lake clay occurs, primarily in the northwest part of the state; recharge estimates in these areas were in the 0- to 5-cm/year range. In sand-plain areas where SY is greatest, recharge estimates were in the 15- to 29-cm/year range on the basis of the RRR model. Recharge estimates that were based on the RRR model compared favorably with estimates made on the basis of other methods. The RRR model can be applied in other subhumid regions where region wide data sets of precipitation, streamflow, GDD, and soils data are available

Water conservation under reduced tillage systems

Water is important for dryland crop production. Seldom is rainfall sufficient or adequately distributed during a growing season so that dryland crops can produce to their fullest potential. It is necessary to have stored water available in the soil to supplement inadequate growing season rainfall for economical crop production. Stored water is especially important in the Inland Pacific Northwest of north central Oregon, southeastern Washington, and northern Idaho, where 65% of annual precipitation occurs during the six-month (Sept. 1 to Feb. 28) winter period and 30% during the four-month (March 1 to June 30) growing season. Stored water is also important in the Eastern Idaho Plateau where the low annual precipitation is nearly evenly distributed over the months of the year. The water balance equation tells us that change in water content in the soil - precipitation + inflow - runoff + upward flow - drainage - evapotranspiration (ET). Any cultural practice that decreases runoff or ET can result in increased water in the soil. To store adequate quantities of water, deep soils (> 60 inches) with good infiltration and water holding capacity are required. Summer fallow has long been the traditional practice for storing water in soils for later use by crops. Fallow periods vary from 14 to 15 months where winter small grains are seeded to 21 months where spring small grains are seeded. Water storage efficiency for fallow is low, ranging from 10 to 35% in the Great Plains and the Southwest; to 30-37% in eastern Idaho and northern Utah; to 40-45% of precipitation in the Inland Pacific Northwest (Evans and Lemon, 1957). Good water conservation yields increased crop production, stability of production, and increased water use efficiency. Soil tillage and residue management play significant roles in collection and storage of precipitation in the soil. Our objectives are to discuss insights in water conservation gained under the STEEP (Solutions to Economic and Environmental Problems) program (Oldenstadt et al., 1982) during these last ten years and problems that remain. New research information will be discussed under topics of crop residues, conservation tillage systems, fallow and models