| dc.description.abstract | Winter wheat is a valuable crop in Southern Great Plains (SGP) of the U.S. that grows from fall to spring; then the cropland is kept fallow during summer. Introducing cover crops to this system may reduce soil erosion and weeds. Moreover, grazing cover crops might increase farm profitability. The objective of this work was to evaluate different cover crops' grazing potential and their effect on the following wheat crop in the SGP. Nine summer cover crops including three legumes, three grasses and two mixes were established late spring 2016 and 2017 in Chickasha and Perkins, OK. At 6 weeks after planting (WAP), three simulated grazing regimes such as severe, proper grazing, and dedicated cover crops (no grazing) were performed in all cover crops. Cover crops regrowth were chemically terminated at 14 WAP, and winter wheat seeded over standing residues. Finally, wheat was harvested in May 2017 and 2018. Cover crop available forage dry matter (AFDM), ADFM species composition, forage nutritive value parameters, daily steer gain (DSG), and total steers gain per area (TSGA) were measured at 6 WAP. Final dry matter residue (FDMR), and FDMR species composition were measured at 14 WAP; and wheat grain yield and wheat grain protein content were also measured. Results indicated that triple treat sorghum-sudan (TTSS, Sorghum bicolor x S. bicolor var. sudanese) produced the highest ADFM under no water limiting conditions, and all tested grasses except for pearl millet [PM, Pennisetum glaucum (L.) R. Br.] produced enough FDMR for total soil coverage. Overall, grasses and mixes were more effective in controlling weeds than legumes; however, the cover crop's weed suppression varied according to rainfall and soil fertility. Under low rainfall, cover crop produced limited amount of ADFM and FDMR (less than 2 Mg ha-1) which did not allow enough forage nor final residue. Even though TTSS showed the highest ADFM potential, other cover crops such as mungbeans (MB, Vigna radiata) and PM+MB in Perkins and Chickasha, respectively allowed the highest DSG and TSGA. Finally, wheat yield and quality variations among site-year were mainly affected by weather and soil fertility rather than previous cover crop. | |
