WINTER RYE AS A COVER CROP FOLLOWING SOYBEAN UNDER CONSERVATION TILLAGE

Rotation of corn (Zea mays L.) with soybean [Glycine max (L.) Merr.] p rovides certain economic and environmental advantages over monoculture corn. Low soybean residue production and persistence, however, promot e potentially excessive soil erosion following soybean harvest. An irr igated field experiment was conducted in eastern Nebraska for 4 yr (19 90-1993) under various tillage treatments and N rates to evaluate the effects of a winter rye (Secale cereale L.) cover crop following soybe an on (i) rye dry matter yield, (ii) surface residue cover for erosion protection, and (iii) corn establishment and production. The soil was a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Arg iudolls). Treatments were (i) no-tillage and disk tillage; (ii) corn f ollowing soybean with a winter rye cover crop (CBR), corn following so ybean without rye (CB) and corn following corn (CC); and (iii) 0, 50, 100, 150, and 300 kg N ha(-1) (applied to corn). Rye aboveground dry m atter yield, surface residue cover, and corn yield parameters were est imated. Rye dry matter yield ranged from 0.25 to 2.9 Mg ha(-1) and was influenced by tillage, N rate, and weather conditions in different ye ars. During the years of high rye dry matter yield, presence of rye in the corn-soybean system gave approximately 16% additional surface res idue cover prior to planting through cultivation, compared with soybea n residue alone. Surface cover by rye and soybean residues in CBR was equivalent to corn residue in CC under both disk and no-till managemen t. In 1 of the 3 yr, corn plant population and grain yield were reduce d following rye (CBR) compared with the no rye system (CB), possibly d ue to apparent allelopathic effects related to the age of rye. No sign ificant difference in N response was observed between CBR and CB corn yields. In general, rotation of corn with soybean (with and without ry e) resulted in an increase of approximately 27% in corn grain yield an d N uptake over continuous corn. During the years of high rye dry matt er production, rye accumulated approximately 45 kg N ha(-1) through ab oveground dry matter. Overall, including a winter rye cover crop in th e corn-soybean rotation system was beneficial.