Evaluating how weather, farm management, and soil conditions impact phosphorus (P) loss from agricultural sites is essential for improving our waterways in agricultural watersheds. In this study, rainfall characteristics, manure application timing, tillage, surface condition, and soil test phosphorus (STP) were analyzed to determine their effects on total phosphorus (TP) and dissolved phosphorus (DP) loss using 125 site-years of runoff data collected by the University of Wisconsin Discovery Farms and Discovery Farms Minnesota. Three linear mixed models (LMMs) were then used to evaluate the influence of those factors on TP and DP losses: (1) a model that included all runoff events, (2) manured sites only, and (3) precipitation events only. Results show that the timing of manure application relative to the timing of a runoff event only had a marginal association with P loads and concentrations, although the majority of the runoff events were collected after 10 days of manure application. Tillage was as influential factor, with greater DP loads and concentrations associated with no-till, especially during frozen conditions. Fields in this study had high STP values, but the model results only showed positive associations between DP load and DP flow-weighted mean concentration (FWMC) loss at the 0- to 15-cm depth. The precipitation event LMM (which included precipitation characteristics) was the model that resulted in the largest R2 value. While the predictive capacity of the LMMs was low, they did illuminate the relative importance of management and environmental variables on P loss, and can be used to guide future research on P loss in this region.

The accumulation of soil organic matter (SOM) is vital to the agronomic and environmental functioning of agroecosystems, yet the relative influence of inherent soil properties and agricultural management practices on SOM dynamics are not often addressed in individual studies. Using a network of 218 operating farm fields across Wisconsin and southern Minnesota, USA, this research employs single variable analysis (ANOVA and regression) and regression tree analysis to assess the effects of soil properties (texture, drainage class, and pH) and management variables related to crop rotation, tillage, cover cropping, and manure application on SOM, as well as total organic carbon (TOC) and total nitrogen (TN) in the upper 15 cm. Single variable analysis revealed that greater SOM, TOC, and TN were associated with poorly drained soil, tile-drained fields, high clay content soil, and high biomass crop rotations. SOM and TOC were strongly related (R-2 = 0.71), but different regression trees were produced; SOM was most influenced by clay content, while TOC was most influenced by drainage class. Future assessment for the building of SOM or TOC should be conducted with drainage and texture class categories and on a regional basis, given that these factors influence the practices that occur within landscapes. A rapid building of datasets through unstructured sampling, including an abundance of metadata, should be a research priority in agricultural science to identify practices to build SOM on a regional basis.

Soil health can differ across cropping systems because of variation in edaphic and management factors. We evaluated how biological indicators of soil health (soil organic matter [SOM], permanganate oxidizable carbon [POXC], mineralizable carbon [MinC], autoclaved‐citrate‐extractable [ACE] protein, and potentially mineralizable nitrogen [PMN]) compared across four common Wisconsin cropping systems: grazed cool‐season pastures, forage‐based rotations that included perennial legumes or grasses, annual rotations receiving manure, and annual rotations receiving synthetic fertilizers. Biological indicators of soil health were up to 195% greater in pastures than other cropping systems. MinC, POXC and PMN were 10%–90% greater in forage‐based rotations than annual cropping systems, but only MinC and POXC were greater in annual systems with manure compared to those without manure by 35% and 7%, respectively. Perennial vegetation and livestock integration offer the greatest potential to increase biological indicators of soil health in agricultural lands.

The amount of soil organic matter (SOM) is considered a key indicator of soil properties associated with higher fertility. Despite the ubiquity of assumptions surrounding SOM's contributions to soil functioning, we lack quantitative relationships between SOM and yield outcomes on working farms. We quantified the relationship between SOM and yields of corn (Zea mays L.) and silage for a dataset of 170 fields arrayed across 49 farms in a network of growers based in Wisconsin and Minnesota, USA. As SOM concentrations increase so do yields, though gains start to level off around 4% SOM. When examining the relationship between yield and soil health indicators representative of biologically active C pools, we found that mineralizable C has a stronger relationship with yield than permanganate oxidizable C. Mineral fertilizer, manure, and SOM had relationships of similar magnitude with yield, highlighting that SOM in combination with exogenous inputs likely plays an important role in driving agricultural productivity in this region. An interaction between SOM and crop rotation indicated that the impact of SOM on crop yields varied depending on rotation (continuous corn vs. corn in rotation). That is, continuous corn had lower yields than corn in rotation despite higher SOM concentrations. Our findings provide insight into the relationship between indicators of soil health, farm management, and crop yields for a set of working farms and lend support to the goals of soil health initiatives that rest on building SOM in agricultural soils to improve agricultural outcomes.

Environmental conditions and management practices affect nutrient losses in surface runoff, but their relative impacts on phosphorus (P) loss during frozen and nonfrozen ground periods have not been well quantified. More specifically, the relative importance of manure application, tillage, and soil-test P (STP) has not been assessed at the field scale. In this study, we compiled a dataset composed of 125 site-years of data from 26 fields that were continually monitored for edge-of-field P loss during snowmelt and storm events. Regression tree analyses were performed to rank the level of influence each environmental and management factor had on nutrient loads. Dissolved P (DP) was the majority of the total P (TP) during frozen conditions, but a small portion of TP during nonfrozen conditions. Manure application had a greater influence on the flow-weighted mean concentrations (FWMCs) of TP and DP during frozen conditions than during nonfrozen conditions. No-till resulted in greater TP and DP FWMCs during frozen conditions than conventional tillage, whereas the opposite effect for TP FWMC was seen during nonfrozen conditions. However, regression tree analysis revealed that STP (0- to 5-cm depth) was the most important factor in predicting DP and TP FWMCs during frozen conditions and DP FWMC during nonfrozen conditions. Extremely high STP values were associated with late-frozen manure applications and grazed pastures. Reducing surface P loss in seasonally frozen landscapes will require prioritizing management strategies that avoid manure application through early- and late-frozen conditions and lead to a drawdown of STP, particularly in the top 5 cm.

Agriculture accounts for 34% of land use in Wisconsin (USDA NASS 2012), and nonpoint source pollution plays a significant role in water quality impairment (WDNR 2016). Out of 2,400 water bodies assessed by the Wisconsin Department of Natural Resources, 1,294 were considered impaired, 74% of which were impaired by either phosphorus (P) or sediment, which are typically contributed by agricultural fields (WDNR 2016). In 2010, revisions to Wisconsin's Phosphorus Water Quality Standards created water quality standards for P in surface waters. To implement these standards, permit holders and agricultural producers were encouraged to work together through the compliance options called Water Quality Trading and Adaptive Management (WDNR 2012). These options allow point sources to offset their pollution load by taking credit for other P reductions in the watershed. The implementation of an enhanced regulatory package raises questions about the best way to engage with farmers in a watershed in order to document current practices and make improvements in water quality through installation of best management practices.

Agriculture has been identified as a potential leading source of nutrients (nitrogen and phosphorus) and sediment enrichment of water bodies within the Mississippi River basin (MRB) and contributes to impaired water quality and biological resources in the MRB and the northern Gulf of Mexico (GOM). This study reviewed agriculture, impacts on water quality and biological resources, and a brief introduction of watershed conservation programs in the MRB. Agriculture has increased nutrients and sediment loads to the Mississippi River and the northern GOM since the 1950s. Fish and macroinvertebrate communities have shifted, and low oxygen and high-turbidity-tolerant groups became dominant. In addition to existing conservation practices such as the Conservation Reserve Program through the 1985 farm bill and other related programs (e.g., the Wetlands Reserve Program), a recent basin-wide conservation initiative the Mississippi River Basin Healthy Watersheds Initiative (MRBI) was launched by U.S. Department of Agriculture Natural Resources Conservation Service in 2010. The MRBI provides financial incentives (more than US$222 million) to producers and landowners in 640 watersheds of 13 states to implement voluntary conservation practices that improve water quality, restore wetlands, enhance wildlife habitat, and sustain agricultural profitability. Edge-of-field and watershed monitoring have been initiated through the MRBI and related agricultural conservation programs such as Section 319 of the U.S. Environmental Protection Agency Clean Water Act and new initiatives such as the Discovery Farms program in Arkansas, Wisconsin, Minnesota, and North Dakota, Pioneer Farm in Wisconsin, the Louisiana Master Farmer Program in Louisiana, and others in the MRB states. These efforts will greatly improve downstream watershed ecosystem health by avoiding, controlling, and trapping nutrient and sediment runoff from agricultural fields to the Mississippi River and GOM. Although there continues to be problems with nutrient transport, sedimentation, and depleted groundwater supplies, agriculture will likely have less influence on the future ecological health condition of the Mississippi River and GOM. Future restoration programs need to focus more on state or regional coordination by classifying restoration projects and standardizing the geographic scale and evaluation methods across the whole MRB.

•Large phosphorus losses occur in tile drains in eastern Wisconsin.•There was not a consistent drainflow-P flux relationship among sites.•The tile flow-P flux relationship was not significant when the tile drain intercepted groundwater flow.•Manure applications affected annual losses of P from tile drains.•Manure applications did not consistently lead to immediate increases in P concentrations.

Recent evaluations of soil water use by potato (Solanum tuberosum L.) plants have confirmed that a dry zone develops mid to late in the growing season when potatoes were grown in a ridge and furrow system under sprinkler irrigation oil some sandy soils. Although trickle irrigation has been shown to reduce the dry zone in potato hills, a more cost- and labor-effective solution Could be the use of a surfactant to change soil water surface tension and thereby promote more uniform water distribution into hills. Water content in surfactant-treated potato hills was compared with no-surfactant-treated hills using data from time domain reflectometry probes collected at 15-minute intervals, In addition, nitrate-nitrogen (NO3-N) concentration in soil water collected 1 m below the crop row with porous cup samplers was evaluated to assess NO3-N leaching below the root zone of potatoes. Data from surfactant applications at 9.35 L ha(-1) at Planting with the seed piece in 1998, 1999, and 2003 through 2005 generally resulted in significantly increased movement of water into the dry portion of potato hills and in many cases decreased soil water NO3- concentrations at a depth of I In beneath potato hills. Comparison of several surfactants suggested that water movement into the dry zone can be accomplished with a number of different products. Some trends of increased potato yield with surfactant applications as compared with no surfactant were noted in a few cases; but in all cases (P = 0.16-0.24), these were not statistically significant at the 95% level.

Text: The UW-Discovery Farms Program has been working with producers, USGS and others to collect water quantity and quality data from 21 monitoring sites on six privately owned farms in Wisconsin. These sites - a combination of edge-of-field, in-stream, and subsurface tile lines encompass a wide range of management systems from small organic grazing (MIRG) to large dairy confined animal feeding operations (CAFO). Meteorological stations were installed on each farm providing comprehensive climatologic data that can be used to predict the likelihood of runoff in the different regions of the state. These predictions could aid in the development of good on-farm management decisions, particularly those that may be environmentally sensitive such as when and where to spread manure. A Critical Condition Index (CCI) is being developed to assist producers with decision making. Multiple years of data suggest that the risk of runoff (either surface or tiles) is higher in the later months of the winter period (February and March) and in the early spring (April through June) when soils are wet and vegetation cover is minimal. These runoff periods are similar throughout the state and are particularly dependant on antecedent soil moisture conditions. Farmers who make proper management decisions during these critical periods will greatly reduce their risk of agricultural runoff and adverse environmental impacts. A programmatic goal is to develop a statewide network to provide producers with current climatic and soil moisture information to assist their decision making. One option is to make available hand held soil moisture meters calibrated to cover a range of conditions appropriate for manure applications (normal rate, reduced and none). An additional alternative would be to develop a web-based system that can provide producers, consultants and others with the information needed for these management decisions.

irrigation scheduling and nitrogen fertilizer placement and time of application have been studied extensively in an attempt to maximize utilization efficiency of nitrogen by potato (Solanum tuberosum L.) plants and reduce nitrate leaching to groundwater. Some researchers believe that drip irrigation, as compared to sprinkler irrigation, is more efficient in supplying irrigation water to potato hills. To investigate water distribution and movement through potato hills under drip and sprinkler irrigation time domain reflectometry (TDR) probes were installed into potato hills to monitor water content at 15-min intervals at various positions in the potato hill. On average, water content values within the centre of the potato hill were greater under drip irrigation (average for 1996 and 1997 was 0.104 and 0.110 m(3) m(-3), respectively) as compared to sprinkler irrigation (average for 1996 and 1997 was 0.085 and 0.066 m(3) m(-3), respectively) where similar amounts of irrigation water were applied weekly. Water content values in the centre portion of the potato hill, where the greatest densities of roots occur, were greater under drip irrigation than sprinkler irrigation by an average of 0.032 m(3) m(-3) for values averaged over the two growing seasons. Concurrently, water content values were less in the furrow of drip irrigation than sprinkler irrigation by an average of 0-025 m(3) m(-3). Decreased water content in the centre portion of the potato hill under sprinkler irrigation became more prominent as the growing season progressed, resulting in hydrophobic soil conditions midway through the growing season. Copyright (c) 2007 John Wiley & Sons, Ltd.

Preferential flow of water and excessive nitrate leaching commonly occur in potato production on sandy soils of Wisconsin, USA where groundwater is relatively close to the soil surface. The problem of nitrate leaching is serious with respect to the environment as nitrate has been linked to the hypoxic zone in the Gulf of Mexico. In potato production in Wisconsin, nitrogen is band-applied to the shoulder of the row in an effort to reduce nitrate leaching as this is a location where it is believed that less water infiltrates. However, we discovered that on these soils the center of the row, where most of the potato plant roots are located, becomes hydrophobic midway through the growing season causing greater preferential flow of water through the shoulders of the row resulting in excessive nitrate leaching. Following this discovery, we used a wetting agent applied to the center of the row, which increased soil water content in the center of the row by more than 50% at several locations over 3 years. This increase in water content remained throughout the growing season although the surfactant was only applied at planting. By improving water use efficiency we discovered as much as an 80% reduction in the peak soil nitrate nitrogen concentration at 1-m depth by using the surfactant in five out of 15 site-years, but the reduction was noted at three out of four different locations. We think this reduction in nitrate leaching was only observed in some years at different locations because the reduction is closely related to rainfall frequency and duration. However, we have not found a direct relationship between the use of surfactant and nitrate nitrogen concentration in the shallow groundwater. In addition to assessing N leaching we evaluated the use of surfactant in com-bination with different levels of N fertiliser use. In 2 of 3 years, surfactant-treated plots showed greater fertiliser N use efficiency than the non-treated plots and had a similar yield as the control with less N-fertiliser. Further research is needed to better understand if there is a potential benefit of using a surfactant to reduce nitrate leaching.