Russian thistle is the most problematic broadleaf weed for spring-sown crops in the low-precipitation (< 340 mm yr−1) region of the inland Pacific Northwest of the United States. A 6-yr field experiment was conducted at Lind, WA, to evaluate three postharvest control strategies for Russian thistle in continuous annual spring wheat. Postharvest treatments were (1) tillage with low-disturbance overlapping undercutter V-blade sweeps; (2) paraquat + diuron at the labeled rate, which is widely used by farmers; and (3) an untreated check (letting Russian thistle grow unhindered). The undercutter V-sweep consistently killed all Russian thistle with essentially no residue burial, and no seed was produced. In contrast, the paraquat + diuron treatment halted Russian thistle dry biomass production, but plants continued to extract soil water and produce an average of 310 seeds m−2 on the lower branches. In the check, Russian thistle produced an average of 700 kg ha−1 postharvest dry biomass and 5,670 seeds m−2. The undercutter V-sweep treatment had significantly more water in the 180-cm soil profile at time of wheat harvest, after a killing frost in October, and in mid March as well as greater spring wheat grain yield compared with the herbicide and check treatments. Results show that postharvest tillage with an undercutter V-sweep consistently achieved 100% control, retained ample wheat residue on the surface to control erosion, and was by far the most effective treatment in this experiment.

Sustainable rainfed cropping systems are needed in the Pacific Northwest of the United States to reduce or eliminate wind and water erosion, improve soil quality, and control weeds with reduced chemical inputs. A grass seed cropping system is excellent for improving soil quality and for controlling erosion, and can be grazed by sheep to produce meat and wool Tilla ge and residue management methods that create a rough surface to reduce wind and water erosion and increase water infiltration include: use of a chisel to create large clods; leaving residue on the surface; and use of the Paratill to shatter the soil to increase water infiltration with little disturbance of the soil surface. Including a legume in the rotation may help to break disease cycles, add N and C to the soil, and improve soil biological properties. The use of surface residues and tillage to control erosion and increase water infiltration may demand new approaches to weed contro I Rhizobacteria that attack the roots of weeds but not of wheat may reduce the need for chemica I herbicides. Research being conducted on these techniques in the Pacific Northwest of the United States and in other countries should soon result in guidelines for sustainable agricultural systems for the dryland, rainfed areas of the world.

Four land use options—annual cropping, agroforestry, agrihorticulture, and agrosilviculture—were tried on a Land Capability Class IVs Alfisol under rainfed conditions to find a farming system that would be profitable and sustainable. The agrihorticultural system required more cash input but gave a value/cost ratio of 2.16 compared with 1.95 with annual cropping, 1.69 with agroforestry and 1.52 with agrosilviculture. Runoff was 4.9% in the agrihorticultural system, and 10.6% with agroforesty. Economic and soil health considerations led to the conclusion that the agrihorticultural system would be a sustainable land use option for the semi-arid Alfisol However, other options also are profitable, with value/cost ratios of more than 1.50. Therefore, land users can choose among several systems, depending on their desired production level and their investment capacity.