Systems for returning conservation reserve program land to wheat (Triticum aestivum) production

Experiments were conducted near Duke and Forgan, OK, on land enrolled in the Conservation Reserve program (CRP) that had been seeded to Old World bluestem (OWB) to evaluate tillage systems for returning CRP grassland to winter wheat production. Glyphosate controlled OWE 72% or less in no-till (NT) wheal. Disk tillage (DT) and moldboard plow tillage (MPT) for wheat seedbed preparation controlled OWB 87 and 99%, respectively, at Forgan and 96 and 100%, respectively, at Duke. At Forgan, OWE control in NT was higher when glyphosate was applied in July than when applied in May. Soil water content to a depth of 120 cm at planting was as high in DT and MPT without herbicide as in NT with 1,680 g ae/ha glyphosate. Within NT and MPT, glyphosate did not consistently increase soil water content compared to the respective nontreated checks. in DT, soil water content to a depth of 120 cm was greater following glyphosate at 1,680 g/ha than without glyphosate. Wheat density was greater in DT and MPT than in NT. Compared to the NT no herbicide treatment, tillage tripled wheat yields. Wheat yields were often greater where glyphosate was applied before tillage. No-till wheat production immediately after CPR in Oklahoma without prior destruction of accumulated OWE residue does not appear feasible.