Impacts of vegetable processing and cheese making effluent on soil microbial functional diversity, community structure, and denitrification potential of land treatment systems.

The cheese making and vegetable processing industries generate immense volumes of high-nitrogen wastewater that is often treated at rural facilities using land applications. Laboratory incubation results showed denitrification decreased with temperature in industry facility soils but remained high in soils from agricultural sites (75% at 2.1°C). 16S rRNA, phospholipid fatty acid (PLFA), and soil respiration analyses were conducted to investigate potential soil microbiome impacts. Biotic and abiotic system factor correlations showed no clear patterns explaining the divergent denitrification rates. In all three soil types at the phylum level, Actinobacteria, Proteobacteria, and Acidobacteria dominated, whereas at the class level, Nitrososphaeria and Alphaproteobacteria dominated, similar to denitrifying systems such as wetlands, wastewater resource recovery facilities, and wastewater-irrigated agricultural systems. Results show that potential denitrification drivers vary but lay the foundation to develop a better understanding of the key factors regulating denitrification in land application systems and protect local groundwater supplies. PRACTITIONER POINTS: Incubation study denitrification rates decreased as temperatures decreased, potentially leading to groundwater contamination issues during colder months. The three most dominant phyla for all systems are Actinobacteria, Proteobacteria, and Acidobacteria. The dominant class for all systems is Nitrosphaeria (phyla Crenarchaeota). No correlation patterns between denitrification rates and system biotic and abiotic factors were observed that explained system efficiency differences.

Autonomous high-throughput in situ soil nitrogen flux measurement system.

Nitrogen (N) behavior in soil is a major component of the global N cycle. Climate scientists seek to accurately measure N flux to the atmosphere, farmers want to maximize plant N uptake and reduce input costs, and industries land-applying wastewater must mitigate potential N leaching to drinking water supplies. The need to quantify denitrification rates of wastewater disposed of by vegetable processing and cheese making industries in Wisconsin drove the development of an autonomous high-throughput in situ sampling and analysis system for soil N flux. The system was deployed to six unique industry sites with different soil types for 7 days once per quarter and data collected continuously. Additional seasonal data collection allowed for the determination of system N mass balances. The system can deliver quality data under challenging conditions where staffing would be impractical and provide detailed information about soil gas emissions under a range of environmental conditions.

Tillage and manure effects on runoff nitrogen and phosphorus losses from frozen soils.

In cold regions, nutrient losses from dairy agroecosystems are a longstanding and recurring problem, especially when manure is applied during winter over snow-covered frozen soils. This study evaluated two tillage (fall chisel tillage [CT] and no-tillage [NT]) and three manure-type management treatments (unmanured control, liquid manure [<5% solids], and solid manure [>20% solids]). The liquid and solid manure used in this study were from the same animal species (Bos taurus) and facility. The six management treatments were field tested in south-central Wisconsin during the winters (November-April) of 2017-2018 and 2018-2019 with a complete factorial design. Seasonal runoff losses were significantly lower from fall CT compared with NT during both seasons. Manure applications (both liquid and solid) on top of snow significantly increased most of the nutrients (NH4 + , dissolved reactive phosphorus, total Kjeldahl nitrogen, and total phosphorus) in runoff compared with unmanured control. Irrespective of tillage and multiple runoff events, solid manure was present on the surface for longer periods, potentially releasing nutrients each time it interacted with runoff. In contrast, liquid manure infiltrated the snowpack and was partly lost with snowmelt and infiltrated soil depending upon soil frost and surface conditions. Overall, results indicate that wintertime manure applications over snow-covered frozen soils pose a risk of nutrient loss irrespective of tillage and manure type, but in unavoidable situations, prioritizing tillage × manure type combination can help reduce losses.

Fall Tillage Reduced Nutrient Loads from Liquid Manure Application during the Freezing Season.

Reducing agricultural runoff is important year round, particularly on landscapes that receive wintertime applications of manure. No-tillage systems are typically associated with reduced runoff loads during the growing season, but surface roughness from fall tillage may aid infiltration on frozen soils by providing surface depressional storage. The timing of winter manure applications may also affect runoff, depending on snow and soil frost conditions. Therefore, the objective of this study was to evaluate runoff and nutrient loads during the freezing season from combinations of tillage and manure application timings. Six management treatments were tested in south-central Wisconsin during the winters of 2015-2016 and 2016-2017 with a complete factorial design: two tillage treatments (fall chisel plow vs. no-tillage) and three manure application timings (early December, late January, and unmanured). Nutrient loads from winter manure application were lower on chisel-plowed versus untilled soils during both monitoring years. Loads were also lower from manure applied to soils with less frost development. Wintertime manure applications pose a risk of surface nutrient losses, but fall tillage and timing applications to thawed soils can help reduce loads.

Dynamics of Measured and Simulated Dissolved Phosphorus in Runoff from Winter-Applied Dairy Manure.

Agricultural P loss from fields is an issue due to water quality degradation. Better information is needed on the P loss in runoff from dairy manure applied in winter and the ability to reliably simulate P loss by computer models. We monitored P in runoff during two winters from chisel-tilled and no-till field plots that had liquid dairy manure applied in December or January. Runoff total P was dominated by nondissolved forms when soils were bare and unfrozen. Runoff from snow-covered, frozen soils had much less sediment and sediment-related P, and much more dissolved P. Transport of manure solids was greatest when manure was applied on top of snow and runoff shortly after application was caused by snowmelt. Dissolved P concentrations in runoff were greater when manure was applied on top of snow because manure liquid remained in the snowpack and allowed more P to be available for loss. Dissolved runoff P also increased as the amount of rain or snowmelt that became runoff (runoff ratio) increased. The SurPhos manure P runoff model reliably simulated these processes to provide realistic predictions of dissolved P in runoff from surface manure. Overall, for liquid dairy manure applied in winter, dissolved P concentrations in runoff can be decreased if manure is applied onto bare, unfrozen soil, or if runoff ratio can be reduced, perhaps through greater soil surface roughness from fall tillage. Both management approaches will allow more manure P to infiltrate into soil and less move in runoff. SurPhos is a tool that can reliably evaluate P loss for different management and policy scenarios for winter manure application.

Soil health indicators impacted by long-term cattle manure and inorganic fertilizer application in a corn-soybean rotation of South Dakota.

Manure impacts labile pools of soil organic carbon (SOC) and nitrogen (N) which can influence soil microbial composition (MCC) and enzyme activities, and hence soil health. The present study was conducted to investigate the impacts of long-term dairy manure and inorganic fertilizers (INF) on soil carbon (C) as well as nitrogen (N) fractions, enzyme activities, and microbial community structure in different time horizons at planting (P), one month after planting (1MAP), and after harvesting (H) under corn (Zea mays L.)-soybean (Glycine max L.) rotation. Study treatments included three manure application rates (low, phosphorus-based recommended rate; medium, nitrogen-based recommended rate; and high, the double rate of medium nitrogen based recommended rate), two INF rates (medium only nitrogen additions; and high nitrogen, phosphorus, potassium, zinc, and sulfur additions) and a control (no application of manure and/or inorganic fertilizer). In comparison to the INF, the dairy manure not only significantly increased chemical fractions of C and N but also impacted the enzyme activities. Average urease activity after manure was applied was shown to be 26.8% higher than it was with INF applied at planting. The ß-Glucosidase activity was 6 and 14% higher with manure than it was with INF at 1MAP and harvesting, respectively. The cold-water extractable nitrogen (CWEN) was enhanced with high manure rate at all timings of sampling compared to the high fertilizer rate (53%), and CK (90%). Principal component analysis indicated that MCC under manure differed from those under the INF treatments. The total bacteria/total fungi ratio at planting was increased with the INF compared to the manure addition. Pearson's correlation analysis showed that CWEC, CWEN, and enzyme activities especially ß-Glucosidase activity were the key determinants of MCC. Data from this study showed that, compared to inorganic fertilizers, manure can be beneficial in enhancing soil health indicators.

Temperature and Manure Placement in a Snowpack Affect Nutrient Release from Dairy Manure during Snowmelt.

Agricultural nutrient management is an issue due to N and P losses from fields and water quality degradation. Better information is needed on the risk of nutrient loss in runoff from dairy manure applied in winter. We investigated the effect of temperature on nutrient release from liquid and semisolid manure to water, and of manure quantity and placement within a snowpack on nutrient release to melting snow. Temperature did not affect manure P and NH-N release during water extraction. Manure P release, but not NH-N release, was significantly influenced by the water/manure solids extraction ratio. During snowmelt, manure P release was not significantly affected by manure placement in the snowpack, and the rate of P release decreased as application rate increased. Water extraction data can reliably estimate P release from manure during snowmelt; however, snowmelt water interaction with manure of greater solids content and subsequent P release appears incomplete compared with liquid manures. Manure NH-N released during snowmelt was statistically the same regardless of application rate. For the semisolid manure, NH-N released during snowmelt increased with the depth of snow covering it, most likely due to reduced NH volatilization. For the liquid manure, there was no effect of manure placement within the snowpack on NH-N released during snowmelt. Water extraction data can also reliably estimate manure NH-N release during snowmelt as long as NH volatilization is accounted for with liquid manures for all placements in a snowpack and semisolid manures applied on top of snow.

Quantifying the Impact of Seasonal and Short-term Manure Application Decisions on Phosphorus Loss in Surface Runoff.

Agricultural phosphorus (P) management is a research and policy issue due to P loss from fields and water quality degradation. Better information is needed on the risk of P loss from dairy manure applied in winter or when runoff is imminent. We used the SurPhos computer model and 108 site-years of weather and runoff data to assess the impact of these two practices on dissolved P loss. Model results showed that winter manure application can increase P loss by 2.5 to 3.6 times compared with non-winter applications, with the amount increasing as the average runoff from a field increases. Increased P loss is true for manure applied any time from late November through early March, with a maximum P loss from application in late January and early February. Shifting manure application to fields with less runoff can reduce P loss by 3.4 to 7.5 times. Delaying manure application when runoff is imminent can reduce P loss any time of the year, and sometimes quite significantly, but the number of times that application delays will reduce P loss is limited to only 3 to 9% of possible spreading days, and average P loss may be reduced by only 15% for winter-applied manure and 6% for non-winter-applied manure. Overall, long-term strategies of shifting manure applications to low runoff seasons and fields can potentially reduce dissolved P loss in runoff much more compared with near-term, tactical application decisions of avoiding manure application when runoff is imminent.

Climate-induced reduction in US-wide soybean yields underpinned by region- and in-season-specific responses.

The United States is one of the largest soybean exporters in the world. Production is concentrated in the upper Midwest(1). Much of this region is not irrigated, rendering soybean production systems in the area highly sensitive to in-season variations in weather. Although the influence of in-season weather trends on the yields of crops such as soybean, wheat and maize has been explored in several countries(2-6), the potentially confounding influence of genetic improvements on yields has been overlooked. Here we assess the effect of in-season weather trends on soybean yields in the United States between 1994 and 2013, using field trial data, meteorological data and information on crop management practices, including the adoption of new cultivars. We show that in-season temperature trends had a greater impact on soybean yields than in-season precipitation trends over the measurement period. Averaging across the United States, we show that soybean yields fell by around 2.4% for every 1 °C rise in growing season temperature. However, the response varied significantly among individual states, ranging from -22% to +9%, and also with the month of the year in which the warming occurred. We estimate that year-to-year changes in precipitation and temperature combined suppressed the US average yield gain by around 30% over the measurement period, leading to a loss of US$11 billion. Our data highlight the importance of developing location-specific adaptation strategies for climate change based on early-, mid- and late-growing season climate trends.

Impact of a real-time controlled wastewater subsurface drip disposal system on the selected chemical properties of a vertisol.

The operation of onsite septic effluent disposal without considering seasonal moisture changes in drain field conditions can be a major cause of the failure of conventional septic systems. This study addressed this issue from a soil hydraulic perspective by using real-time drain field soil moisture levels to limit septic effluent disposal in a vertisol via subsurface drip irrigation. A prototype system was field-tested in a Houston clay soil and results describe the subsequent impact on selected soil chemical properties. After one year of hydraulic dosing with a synthetic wastewater, soil total carbon and nitrogen concentrations increased, but no increase in soil total phosphorus concentration was observed. Soil NO3-N leaching potential was noted, but soil NH4-N concentrations decreased, which could be ascribed to NH4-N nitrification, fixation within clay sheets and NH3 volatilization. Soil K+, Mg2+ and Na+ concentrations increased in soil layers above the drip lines, but decreased in soil layers below drip lines. Soil electrical conductivity accordingly increased in soil layers above drip lines, but the range was significantly lower than the threshold for soil salinity. Although the moisture-controlled effluent disposal strategy successfully avoided hydraulic dosing during unfavourable wet drain field conditions and prevented accumulation of soil salts in the soil profile beneath the drip lines, soil salts tended to accumulate in top soil layers. These adverse effects warrant system corrections before large-scale implementation of subsurface drip irrigation of effluent in similar vertisols.

Natural Migration of Rotylenchulus reniformis In a No-Till Cotton System.

Rotylenchulus reniformis is the most damaging nematode pathogen of cotton in Alabama. It is easily introduced into cotton fields via contaminated equipment and, when present, is difficult and costly to control. A trial to monitor the natural migration of R. reniformis from an initial point of origin was established in 2007 and studied over two growing seasons in both irrigated and non-irrigated no-till cotton production systems. Vermiform females, juveniles and males reached a horizontal distance of 200 cm from the initial inoculation point, and a depth of 91 cm in the first season in both systems. Irrigation had no effect on the migration of vermiform females and juveniles, but males migrated faster in the irrigated trial than in the non-irrigated trial. Population density increased steadily in the irrigated trial during both years, exceeding the economic threshold of 1,000 per 150 cm(3), but was highly correlated with rainfall in the non-irrigated trial. The average speed of migration ranged from 0- to 3.3-cm per day over 150 days. R. reniformis was able to establish in both the irrigated and non-irrigated trials in one season and to increase population density significantly.