The presence of crop residue on the soil surface is important in controlling soil erosion, but residue amounts from lentil (Lens culinaris Medik.) are often insufficient to control soil erosion during subsequent phases of the cereal-grain legume cropping systems of the U.S. Pacific Northwest. To gain knowledge of residue production by lentil in typical production environments, six lentil cultivars were grown at four slope positions in southeastern Washington over 3 yr. Residue and seed production varied significantly among cultivars and slope positions (P < 0.01). Total residue production ranged from four to 20 times the 290 lb/acre required by conservation standards, however, the amount remaining after sowing of the subsequent winter wheat (Triticum aestivum L.) crop was much less, indicating that large losses occurred during harvesting and tillage operations. On lower slope positions, grain and residue yields were inversely correlated for all cultivars. On upper slope positions, grain yields were nearly constant among cultivars, but ‘Laird’ produced an average of 42% more residue than ‘Brewer’. No single cultivar met yield and residue production criteria across all landscape positions. Growers can improve erosion control by site-specific sowing of high-residue cultivars such as Laird. Breeding programs should consider the differences in the upper and lower slope positions for seed and residue production when selecting for cultivars with improved biomass production. Research Question Surface residue is a very important factor in preventing erosion on the steep slopes in the Palouse region of the Pacific Northwest. Lentils produce relatively small amounts of residue compared with wheat and other small grains and, in order to maintain sustainable farming systems in the region, this study was undertaken to identify lentil cultivars that produce large amounts of residue across a wide range of slope positions. Literature Summary The soils on the rolling hills of the Palouse region of eastern Washington, northern Idaho, and northeastern Oregon are becoming increasingly eroded. Soils on these slopes vary considerably in type and productivity. In general, the upper slope positions are less productive than the lower slope positions due to poorer soil types caused by erosion, leaching of nutrients, and reduced moisture content. Ironically it is the upper slope positions that are in greatest need of residue, however they are the positions that have the lowest potentia1 for residue production. In order to meet regulations regarding minimum surface residue levels set up by the Natural Resource Conservation Service, many fmers have incorporated tillage practices that leave a rough soil surface over the winter while others are eliminating lentil from their rotations altogether. Eliminating lentil from the current rotations could be quite detrimental to the small grain crops, since lentil crops return N to the soil and break up disease cycles. In order to make it more equitable for the farmer, lentil cultivars that produce high levels of residue in the poorer, upper slope positions must be identified. Study Description This study involved growing six lentil cultivars at the four main slope positions (topslope, backslope, footslope, and toeslope) determining their production potential at each. The experiment was conducted at three different locations over 3 yr (1984, 1985, and 1986). Samples of the mature crop were harvested from a 4 ft segment of the middle two rows in each plot. Total biomass, seed, and residue yields were recorded for each cultivar and harvest index was calculated by dividing seed yield by total biomass yield. Applied Questions How can lentil residues be increased to a sufficient level on the upper slope positions to significantly reduce erosion? This may be accomplished through site specific farming. Farmers would grow high residue producing cultivar on the upper slope positions while growing a cultivar that produced less residue on the lower positions. One caution with thi approach is that the two cultivars have to mature at nearly the same time. Often the crop on the upper positions will mature earlier than those on the lower posi tions due to lower moisture reserves. Can future cultivars be developed to produce adequate levels of residue? Lentil breeding programs should consider using residue production as a selection criteria when developing new cultivars. Recommendation Growers may consider site specific farming where a cultivar producing large amounts of residue are planted on the upper slope positions while a cultivar producing less residue could be planted on the lower slope positions where smaller amounts are needed.