|Sudduth, Kenneth - Ken|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2015
Publication Date: 7/2/2015
Citation: Veum, K.S., Kremer, R.J., Sudduth, K.A., Kitchen, N.R., Lerch, R.N., Baffaut, C., Stott, D.E., Karlen, D.L., Sadler, E.J. 2015. Conservation effects on soil quality indicators in the Missouri Salt River Basin. Journal of Soil and Water Conservation. 70:232-246. DOI: 10.2489/jswc.70.4.232.
Interpretive Summary: The Salt River Basin in the Central Claypan Region of Missouri is challenged in attaining a balance of agronomic productivity with long-term sustainability and environmental protection. Contributing to these problems are the claypan soils found in this region, which are known for high runoff and soil erosion potential, and rapid soil degradation. Even so, nearly half of the land area in the basin is cultivated for crops, and grain crop production is dominated by the 2-yr, corn-soybean rotation. Conservation management practices have tremendous potential to improve profitability, reduce soil loss, and protect and improve water and soil quality. Soil quality can be broadly defined as the capacity of a soil to function for sustained plant and animal productivity, for environmental quality, and in support of human health and habitation. Soil quality can be evaluated using a range of soil chemical, physical, and biological measurements. The Soil Management Assessment Framework (SMAF) translates multiple laboratory measurements into comprehensive scores related to crop productivity, environmental protection, and other important soil functions. This study used the SMAF to evaluate the soil quality benefits of several different conservation management practices including Conservation Reserve Program (CRP) systems, prairie restoration, perennial working grasslands (i.e., pasture, forage, and hay production), tillage reduction, increased crop rotation diversity, and incorporation of cover crops. In the surface soil layer (0–2 in), SMAF soil quality scores were the highest for systems with permanent, vegetative cover and living roots (e.g., CRP), ranging from 88 to 98 percent. Annual cropping systems scored lower than perennial systems, ranging from 76 to 87 percent. Among annual grain cropping systems, systems that incorporated cover crops scored the highest (87 percent), followed by no-till systems without cover crops (85 percent), and tillage systems lacking cover crops (76–84 percent). Based on the results of this study, restoration of degraded or marginal soils would realize the greatest soil quality benefits from perennial CRP systems including either cool- or warm-season grasses with legumes, followed by working grasslands and pasture systems. Perennial systems such as these have dense roots that can protect highly erodible soil, increase soil organic matter, and stimulate nutrient cycling. Conversely, reversion of CRP acreage to annual row crops may potentially lead to substantial losses in soil quality under certain conditions. For cultivated, annual row cropping systems, prudent management integrating no-till with diverse cover crops and crop rotations can protect, improve, restore, and/or maintain soil quality. Overall, this study will benefit producers, scientists, and policy makers by demonstrating the benefits of vegetative cover and living roots on surface soil quality, and by documenting the importance of diversified cropping systems that reduce soil disturbance, maximize soil cover, and potentially increase profitability.
Technical Abstract: The Conservation Effects Assessment Project was initiated in 2002 to quantify the potential benefits of conservation management practices. Within the Central Claypan Region of Missouri, the Salt River Basin was selected as a benchmark watershed to assess long-term effects of conservation practices on soil quality. The objectives of this study were (1) to compare soil quality under 15 different perennial vegetation and annual cropping systems typically employed in this region and (2) to evaluate relationships among soil quality indicators. Annual cropping systems included varying nutrient management, crop rotation, cover crops, and tillage. Perennial vegetation systems included permanent cool- and warm-season grasses and legumes under varying management including Conservation Reserve Program (CRP) systems, prairie restoration, and working grasslands (i.e., pasture, forage, and hay production). Soil samples were obtained in 2008 from the surface (0-5 cm) and subsurface (5-15 cm) layers. Eleven biological, physical, chemical, and nutrient soil quality indicators (SQI) were measured. Soil quality was quantified using the Soil Management Assessment Framework (SMAF). The SMAF provides an integrated, comprehensive assessment of soil quality by using scoring algorithms to quantitatively relate soil quality indicators to important soil functions. Soil quality rankings among management systems varied with the SQI, the soil functional group, and with depth. In the surface layer, systems with permanent, vegetative cover and living roots demonstrated the greatest SMAF scores, ranging from 88 to 98 percent of the soil’s inherent potential. Scores for annual cropping systems ranged from 76 to 87 percent, in the order no-till with cover crops (87 percent) = mulch-till with cover crops (87 percent) > no-till without cover crops (85 percent) > mulch-till or intensive tillage without cover crops (76 – 84 percent). Across SQIs, biological and physical indicators were the most sensitive to management effects, reflecting significant differences in mineralizable N, water-filled pore space, organic C, bulk density, and ß-glucosidase activity. Biological soil quality under the diversified no-till system with cover crops was 11 percent greater than under no-till alone, and 20 percent greater than under mulch-till without cover crops. In the subsurface layer, SMAF scores were lower than in the surface layer across all management systems, and no-till cropping systems scored lower (60 – 64 percent) than mulch-till systems (65 – 72 percent). The results of this study demonstrate the strong influence of vegetative cover and living roots on surface soil quality, and emphasize the importance of diversified cropping systems that reduce soil disturbance and maximize soil cover.