Crop Rotation Effects on N03-N Leaching and Corn Yields Under Manure Management Practices

Nonpoint source nutrient pollution is recognized as an important environmental and social issue for several reasons. First, manure from swine production facilities can have serious impacts on the quality of surface and ground water resources. Second, several states are in the process of creating laws to reduce nitrogen and phosphorus loadings from manure to soil and water resources. Third, pollution of water resources from nutrients supplied by manure to croplands will set parameters for developing public policies on the management of manure

Impact of Manure and N-Management Systems on Water Quality

Nitrate from fertilizers and manure application have been detected in the surface and ground water in many agricultural regions of the country including Iowa. The current practices of fertilizer application methods and rates are believed to be contributing significantly in the contamination of groundwater. Therefore, it is imperative that tillage and planting systems, regarded as best management practices for agricultural sustainability, minimize the potential for chemical runoff and leaching losses to groundwater with alternative chemical management systems. If the potential for contamination is not reduced by developing and successfully demonstrating the innovative nitrogen and pesticide management practices, the potential for contamination will remain and could result in additional regulations. Because of these concerns, researchers must develop alternative farming practices with the goals of reducing the input costs, and preserving the resource base for the sustainability of our agriculture and protecting the environment

Spatial Variability Analysis: A First Step in Site-Specific Management

Small-scale spatial variability of selected soil-test parameters in two adjacent central Iowa fields is discussed. We used semivariance analysis to detect the distance to which parameters were correlated and to estimate the strength of each correlation. Distinct differences in spatial dependence patterns were observed for the two farming systems

AN AUTOREGRESSION MODEL FOR A PAIRED WATERSHED COMPARISON

Analysis of water quality data from a paired watershed design is needed to determine if a best fertilizer management practice reduces a specific water quality variable compared to a conventional fertilizer management practice. This study examines an existing recommended method of analysis for paired watershed designs, simple analysis of covariance (ANCOVA) on time aggregated data, then offers two autoregression analyses (AR) as alternatives. The first approach models the sequence of paired differences and estimates its 95% confidence band. The second approach develops individual watershed AR models then examines the joint 95% confidence interval about the predicted difference. A reliability analysis on the water quality data reveals that the data for the controlled watershed, i.e., the covariate, has a sizable measurement error, a factor that is not considered in the usual ANCOVA model. The AR methods avoid the measurement error and other inherent problems with the published recommended method. Graphically both AR analyses are similar and reveal three distinct trend phases: a period of continued similarity; a period of transition; and a period of sustained change. The model for the sequence of paired differences is the easier one of the two AR methods to use and interpret because its trend model of splined linear segments readily defines each response phase. Hence, we recommend it over the given alternatives. It offers water resources researchers an effective and readily adoptable analysis option

Assessing the Operationalization of Cultural Theory through Surveys Investigating the Social Aspects of Climate Change Policy Making

Cultural theory (CT) provides a framework for understanding how social dimensions shape cultural bias and social relations of individuals, including values, view of the natural world, policy preferences, and risk perceptions. The five resulting cultural solidarities are each associated with a “myth of nature”—a concept of nature that aligns with the worldview of each solidarity. When applied to the problem of climate protection policy making, the relationships and beliefs outlined by CT can shed light on how members of the different cultural solidarities perceive their relationship to climate change and associated risk. This can be used to deduce what climate change management policies may be preferred or opposed by each group. The aim of this paper is to provide a review of how CT has been used in surveys of the social aspects of climate change policy making, to assess the construct validity of these studies, and to identify ways for climate change protection policies to leverage the views of each of the cultural solidarities to develop clumsy solutions: policies that incorporate strengths from each of the cultural solidarities’ perspectives. Surveys that include measures of at least fatalism, hierarchism, individualism, and egalitarianism and their associated myths of nature as well as measures of climate change risk perceptions and policy preferences have the highest translation and predictive validity. These studies will be useful in helping environmental managers find clumsy solutions and develop resilient policy according to C.S. Holling’s adaptive cycle

Whole-profile soil organic matter content, composition, and stability under cropping systems that differ in belowground inputs

Subsoils have been identified as a potential carbon sink because they typically have low soil organic carbon (SOC) concentrations and high SOC stability. One proposed strategy to increase SOC stocks is to enhance C inputs to the subsoil by increasing crop rotation diversity with deep-rooted perennial crops. Using three long-term field trials in Iowa (study durations of 60, 35, and 12 years), we examined the effects of contrasting cropping systems [maize (Zea mays L.)-soybean (Glycine max (L.) Merr) (= two-year system) vs. maize-soybean-oat (Avena sativa L.)/alfalfa (Medicago sativa L.)-alfalfa or maize-maize-oat/alfalfa-alfalfa (= four-year system)] on above- and below-ground C inputs, as well as the content, biochemical composition, and distribution of SOC among physical fractions differing in stability to 90 cm depth. Average annual total C inputs were similar in the two-year and four-year systems, but the proportion of C delivered belowground was 20–35 % greater in the four-year system. Despite the long duration of these studies, the effect of cropping system on SOC content to 90 cm was inconsistent across trials, ranging from −7 % to +16 % in the four-year relative to the two-year system. At the one site where SOC was significantly greater in the four-year system, the effect of cropping system on SOC content was observed in surface and subsoil layers rather than limited to the subsoil (i.e., below 30 cm). Cropping system had minimal effects on biochemical indicators of plant-derived organic matter or on the proportions of SOC in labile particulate organic matter versus stable mineral-associated organic matter. We conclude that adoption of cropping systems with enhanced belowground C inputs may increase total profile SOC, but the effect is minimal and inconsistent; furthermore, it has minor impact on the vertical distribution, biochemical composition, and stability of SOC in Mollisols of the Midwest U.S