Soil coverage by residue as affected by ten crop species under no-till in the northern Great Plains

Soil coverage by residue protects soil and land resources from erosion, conserves soil water, and maintains soil quality. No-till and chemical weed control are management practices that increase soil coverage by residue. On the other hand, crop diversification in dryland agriculture in the northern Great Plains promotes the use of crops that produce significantly less soil coverage by residue than small cereal grains. Within a 10 x 10 crop sequence project under no-till in south-central North Dakota [409 mm (16.1 in) mean annual precipitation], all two-year crop sequence combinations of ten crops (barley, canola, crambe, dry bean, dry pea, flax, safflower, soybean, spring wheat, and sunflower) were evaluated at two adjacent sites. Soil coverage by residue was measured by transect and photographic techniques following spring wheat seeding. Soil coverage ranged from 98 to 89 percent following crop sequences that included spring wheat and barley. Soil coverage values were intermediate for spring wheat-alternative crop sequences, 97 to 62 percent. Crop sequences not including spring wheat with alternative crops for two years had values ranging from 86 to 35 percent. Soil coverage values after two consecutive years of sunflower or dry pea (two years of data) and two years of dry bean or safflower (single year of data) were in a lower range, 48 to 35 percent. Soil erosion hazards were evaluated with equations based on residue effects alone that were taken from the Revised Universal Soil Loss Equation (RUSLE) water erosion and Revised Wind Erosion Equation (RWEQ) wind erosion models: calculated soil loss ratio values (SLR = 1 with no residue protection) for 35 percent coverage following a sunflower-sunflower sequence were 0.29 for water erosion and 0.21 for wind erosion. Even with use of no-till, especially on more fragile soils, producers should consider planting a higher residue-producing crop (e.g., wheat, flax) the year before seeding lower residue-producing crops in order to assure adequate protection of soil and land resources.