A conservation tillage research update from the Coastal Plain Soil and Water Conservation Research Center of South Carolina: A review of previous research
In the U.S. Southeastern Coastal Plains conservation tillage (CT) became useful as a management
system with the development of in-row subsoiling systems capable of planting into heavy residues.
Research priorities associated with the development of CT included: reducing cover crop water loss,
improving stand establishment, assessing nutrient and water management requirements, determining
optimal subsoiling strategies, understanding long-term conservation tillage effects on soil properties,
evaluating the interaction of crop residue removal with tillage systems, and documenting tillage impact
on pests and beneficial organisms. Since the late 1970s the Coastal Plains Soil and Water Conservation
Research Center in Florence, SC has made a concerted effort to study these interactions and
alleviate them as obstructions to the use of CT management. These studies showed that for Coastal
Plain soils such as Norfolk sandy loam ( fine-loamy, siliceous thermic, Typic Paleudults ) winter cover
crops such as rye (Secale cereale L.) desiccated the soil profile by evapotranspiration in the spring.
This delayed emergence and early season growth of corn (Zea mays L.) but not full-season soybean
(Glycine max ( L. ) Merr. ). Conservation tillage helped manage soil strength by gradually increasing
soil organic matter content, restricting traffic patterns and maintaining higher soil water contents.
Laboratory studies demonstrated a negative correlation (R2=0.85 ) between proctor soil strength and
organic matter content. Conservation tillage affected nematode, Bradyrhizobium japonicum and Heliothis
species populations. Alternate cropping systems using rapeseed (Brassica napus L.) as a winter
crop or sunflower (Helianthus annuus L.) either before soybean or after corn provided crop cover
against potential soil loss from late autumn through early spring, when bare soil is exposed to intense
rainfall. Water quality questions associated with CT have been raised but remain unanswered. Although
CT can reduce runoff and erosion, the crop residues can support higher insect populations and
pathogen inoculum levels, and thus prompt greater pesticide use. Quantifying relationships between
soil strength, macropore formation and persistence, and water infiltration with surface and subsurface
water quality is the focus of new long-term evaluations. The findings of these studies, published to
date, are summarized in this paper
