281. Winter rye as a cover crop following soybean under conservation tillage

• Authors:
  • Walters, D. T.
  • Kessavalou, A.
• Source: Agronomy Journal
• Volume: 89
• Issue: 1
• Year: 1997
• Summary: Rotation of corn (Zea mays L.) with soybean [Glycine max (L.) Merr.] provides certain economic and environmental advantages over monoculture corn. Low soybean residue production and persistence, however, promote potentially excessive soil erosion following soybean harvest. An irrigated field experiment was conducted in eastern Nebraska for 4 yr (1990-1993) under various tillage treatments and N rates to evaluate the effects of a winter rye (Secale cereale L.) cover crop following soybean 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 Argiudolls). Treatments were (i) no-tillage and disk tillage; (ii) corn following soybean with a winter rye cover crop (CBR), corn following soybean 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 matter yield, surface residue cover, and corn yield parameters were estimated. 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 years. During the years of high rye dry matter yield, presence of rye in the corn-soybean system gave approximately 16% additional surface residue cover prior to planting through cultivation, compared with soybean residue alone. Surface cover by rye and soybean residues in CBR was equivalent to corn residue in CC under both disk and no-till management. In 1 of the 3 yr, corn plant population and grain yield were reduced following rye (CBR) compared with the no rye system (CB), possibly due to apparent allelopathic effects related to the age of rye. No significant difference in N response was observed between CBR and CB corn yields. In general, rotation of corn with soybean (with and without rye) resulted in an increase of approximately 27% in corn grain yield and N uptake over continuous corn. During the years of high rye dry matter production, rye accumulated approximately 45 kg N ha(-1) through aboveground dry matter. Overall, including a winter rye cover crop in the corn-soybean rotation system was beneficial.

282. Soil-plant nitrogen dynamics following incorporation of a mature rye cover crop in a lettuce production system

• Authors:
  • Schulbach, K. F.
  • Jackson, L. E.
  • Wyland, L. J.
• Source: The Journal of Agricultural Science
• Volume: 124
• Year: 1995
• Summary: Winter non-leguminous cover crops are included in crop rotations to decrease nitrate (NO3-N) leaching and increase soil organic matter. This study examined the effect of incorporating a mature cover crop on subsequent N transformations. A field trial containing a winter cover crop of Merced rye and a fallow control was established in December 1991 in Salinas, California. The rye was grown for 16 weeks, so that plants had headed and were senescing, resulting in residue which was difficult to incorporate and slow to decompose. Frequent sampling of the surface soil (0-15 cm) showed that net mineralizable N (anaerobic incubation) rapidly increased, then decreased shortly after tillage in both treatments, but that sustained increases in net mineralizable N and microbial biomass N in the cover-cropped soils did not occur until after irrigation, 20 days after incorporation. Soil NO3-N was significantly reduced compared to winter-fallow soil at that time. A N-15 experiment examined the fate of N fertilizer, applied in cylinders at a rate of 12 kg N-15/ha at lettuce planting, and measured in the soil, microbial biomass and lettuce plants after 32 days. In the cover-cropped soil, 59% of the N-15 was recovered in the microbial biomass, compared to 21% in the winter-bare soil. The dry weight, total N and N-15 content of the lettuce in the cover-cropped cylinders were significantly lower; 28 v. 39% of applied N-15 was recovered in the lettuce in the cover-cropped and winter-bare soils, respectively. At harvest, the N content of the lettuce in the cover-cropped soil remained lower, and microbial biomass N was higher than in winter-bare soils. These data indicate that delayed cover crop incorporation resulted in net microbial immobilization which extended into the period of high crop demand and reduced N availability to the crop.

283. Winter cover crop suppression practices and natural enemies of armyworm (Lepidoptera: Noctuidae) in no-till corn

• Authors:
  • Luna, J. M.
  • Laub, C. A.
  • Pimentel, D.
• Source: Environmental Entomology
• Volume: 21
• Issue: 1
• Year: 1992
• Summary: Rye, Secale cereale L., used as a winter cover crop was killed by the herbicide paraquat or by mowing with a rotary mower. In subsequent no-ill corn, Glyptapanteles militaris (Walsh) (Hymenoptera: Braconidae) and Periscepsia laevigata (Wulp) (Diptera: Tachinidae) were the most abundant of twelve species of parasitoids that emerged from field-collected larvae of the armyworm, Pseudaletia unipuncta (Haworth). No effects of cover crop suppression practices were detected for parasitism rates for any individual species or for total armyworm parasitism. Seasonal parasitism rates ranged from 32 to 45%. HIgher numbers of Pterostichus spp. and Scarites spp. (Coleoptera: Carabidae), and wolf spiders (Araneae: Lycosidae) occurred early in the corn season in the mowed cover crop treatment compared with the herbicide killed cover crop treatment. Subsequent reduction oflarval densities of armyworm in mowed plots following higher predator densities suggests the role of these generalist predators in biological control of armyworm.