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Losses of soluble nutrients from cropland and their transport to surface and groundwater are a continuing water quality concern. In this study, we evaluated tillage impacts on dissolved losses of ammonium (NH4-N), nitrate nitrogen (NO3-N), chloride (Cl), and potassium (K) during rotational cotton and peanut production. Tillage treatments were strip tillage (ST), in which crops were planted into 15 cm strips tilled into cover crop residue mulch, and conventional tillage (CT), in which all crop residues were turned into the soil prior to planting. Winter cover crops were used in both tillage systems. Tillage and irrigation treatments were uniformly applied within two 0.6 ha fields located on a moderately sloping hillslope in the southern Atlantic Coastal Plain region of south-central Georgia. Tile drains were installed at the base of the slope of each field to capture and measure lateral subsurface flow. Each field was subdivided into three 0.2 ha plots, with the three plots making up a single tillage block. H-flumes were used for flow measurement and sample collection. During the five-year study, annual precipitation ranged from 910 to 1488 mm, with an annual average of 1201 mm. Annual surface runoff averaged 17% of annual rainfall from the CT field and 11% from the ST field. Because of relatively low variability in concentrations, surface runoff loads closely tracked surface runoff volumes. Annual surface runoff loadings of NH4-N, NO3-N, and Cl from the ST treatment were found to be significantly less than those from the CT treatment. The total five-year load of N (NH4-N and NO3-N) in surface runoff from CT was 8.3 kg ha-1, while it was 5.6 kg ha-1 from ST, equivalent to 1.5% of the total N applied to CT and 1.0% of that applied to ST. Annual subsurface flow averaged 12% of annual precipitation for CT and 21% for ST. Annual average subsurface flow loadings of NH4-N, NO3-N, and K from ST were significantly greater than from CT. The total five-year load of N (NH4-N and NO3-N) in subsurface flow was 45 kg ha-1 from CT and 99 kg ha-1 from ST, equivalent to 8.3% and 18.4% of the total N applied to CT and ST, respectively. Data showed that subsurface flow was the primary hydrologic pathway for dissolved N and Cl loss in both tillage systems. Overall, ST was found to be an effective method for reducing surface runoff and associated soluble losses, but increased infiltration with this practice significantly increased subsurface losses. This introduces a challenge to nitrogen management in reduced tillage systems such as ST in the region. [ABSTRACT FROM AUTHOR]

Widespread implementation of conservation tillage systems during cotton (Gossypium hirsutum L.) and peanut (Arachis hypogea L.) production in the Atlantic Coastal Plain region of the U.S. has substantially reduced erosion and sediment loss. However, the benefits of conservation tillage in these cropping systems are being threatened by weather shifts that include increased frequency of high-intensity rainfall, policies that encourage the removal of crop residues as cellulosic feedstocks for energy production, and increased herbicide resistance in weeds. Long-term integrated studies are needed to quantify potential impacts. We evaluated runoff and sediment loss from six 0.2 ha fields located on a gently sloping hillslope in a Southern Atlantic Coastal Plain landscape over ten years (2000-2009) during rotational cotton-peanut production, with a rye (Secale cereale) winter cover crop. Half of the fields were in conventional tillage (CT; inversion tillage with cover crop residue incorporation prior to planting), and half were in strip tillage (ST), which is a commonly used conservation tillage practice in the region. Fields were laid out as contrasting tillage pairs at upper, middle, and lower landscape positions and irrigated as needed. Runoff and sediment load from CT fields was significantly greater than from ST fields at each landscape position. Over the 10-year study period, mean annual total sediment load was 1823 kg ha-1 year-1 from CT fields and 237 kg ha-1 year-1 from ST fields (an 87% difference), and runoff was reduced by 41%. A soil tolerance value (T) of 2,200 kg ha-1 year-1 was exceeded in three out of ten years in CT fields and never exceeded in ST fields. On a monthly basis, extreme events (>90th percentile; 10%) accounted for 61% to 72% of the 10-year total sediment load for the CT system (341 to 2,828 kg ha-1 month-1) and 73% to 84% for the ST system (49 to 593 kg ha-1 month-1). The rainfall and irrigation total was above the normal monthly rainfall in 83% of these extreme monthly periods (mean 179 mm, range 81 to 316 mm). Sediment load was greatest in summer and spring, and during cotton production. The study results improve estimates of the increase in rainfall event size tolerated by CT vs. ST cropping systems, demonstrate the benefits of conservation tillage management during cotton and peanut production, and are expected to guide management decisions that focus on reducing sediment loss in this landscape. Specifically, the results point to the use of cover crops and strip tillage as essential best management practices for this purpose. [ABSTRACT FROM AUTHOR]

The elemental composition of soil plays an essential role in crop nutrition, but losses from croplands can negatively impact soil fertility and water quality. We compared the impact of strip tillage (ST) and conventional tillage (CT) on element concentrations and loads in surface runoff and subsurface flow from plots under rotational cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production with winter cover cropping. Total element concentrations (calcium [Ca], iron [Fe], potassium [K], magnesium [Mg], manganese [Mn], sodium [Na], phosphorus [P], sulfur [S], silicon [Si], and zinc [Zn]) in surface runoff and subsurface flow samples were measured using Inductively Coupled Plasma with Optical Emission Spectroscopy (ICP-OES). Element loads were estimated by multiplying the element concentrations by the surface runoff and drainage volumes. Significantly greater (p = 0.05) surface runoff loads for all elements (with the exception of K and Zn) were observed from the CT compared with the ST treatment plots only in 2006, likely due to the combined effects of hydrology and the timing of gypsum amendments that year. Surface runoff was the primary hydrologic pathway for Fe, K, Mn, P, Si, and Zn loss while subsurface flow was the primary hydrologic pathway for Ca, Mg, and S loss with both tillage treatments. Lower concentrations of Ca, Mg, Na, and S in the subsurface flow with ST compared to CT suggest that this tillage practice, in conjunction with the proper timing of fertilizer and soil amendment applications (e.g., poultry litter and gypsum) can be an effective method for reducing element losses from croplands. This finding highlights the importance of conservation practices in sustaining healthy cropland soils while reducing element losses and associated environmental impacts. [ABSTRACT FROM AUTHOR]

Conservation tillage (CsT) involves management that reduces soil erosion by maintaining crop residue cover on farm fields. Typically, both infiltration and soil organic matter increase over time with CsT practices. We compared the impact of a commonly used CsT practice, strip tillage (ST), to conventional tillage (CT) management on soil nitrogen (N) dynamics and leaching and examined associations to soil N availability and microbial biomass. A winter cover crop was used in both tillage treatments. The study was conducted over a five-year period during rotational cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production in the Atlantic Coastal Plain region in Georgia, United States. Fertilizer and poultry litter were applied ahead of the cotton crops. Sets of PVC cylinders were filled with soil from each of six plots, three in ST and three in CT, and maintained in situ in their respective plots for 16 intervals of about 90 days. After retrieval, the soil in each cylinder was analyzed for inorganic N (ammonium and nitrates [NH4+ and NO3−]), total N, total carbon (C), and microbial biomass. Leached NO3−-N was captured on anion exchange resin-filled bags attached to the bottom of each cylinder. After the five-year study period, the ST and CT soil C content increased by 22% and 23%, respectively. Total soil N content increased 27% with ST compared to 22% with CT. Temporal patterns in NO3−-N leaching were not different between CT and ST treatments, and a high amount of NO3−-N leaching was observed after the application of poultry litter. The cumulative amount of NO3−-N leached from soils throughout the five-year study was 141 and 122 kg N ha−1 (126 and 109 lb N ac−1) with CT and ST practices, respectively. Results suggest that leaching from the top 15 cm (6 in) of soil may be an important pathway of N loss from both CT and ST cropping systems in the region. Regardless of tillage, soil microbial biomass N was equal to or higher than the total inorganic N, but still represented a small percentage (up to 9%) of the total soil N. Overall, microbial biomass N was higher in ST compared to CT. Minimizing NO3−-N in the soil from reaching ground and surface waters while increasing crop productivity represents a major challenge. The use of ST in conjunction with winter cover crops may improve plant N availability by more than 27 kg ha−1 y−1 (24 lb ac−1 yr−1) in the sandy landscapes of the southeastern Coastal Plain region through microbial cycling of organic N while reducing subsurface NO3−-N losses. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the relationship of somatic cell count (SCC; cells/mL) with milk yield, energy-corrected milk yield (ECM; kg/d), dry matter intake (DMI; kg/d), feed efficiency for milk (FE MY ; kg of milk/kg of DMI), and feed efficiency for ECM (FE ECM ; kg of ECM/kg of DMI) in lactating dairy cows. We analyzed an SCC database consisting of 7 experiments, which were conducted at The Pennsylvania State University's Dairy Teaching and Research Center between 2009 and 2015. The experiments included in the SCC database were randomized block designs and investigated dietary effects on cow performance over 6 to 11 wk. Each experiment took repeated measurements of SCC, milk yield, milk composition, and DMI. After exclusion of records from cows without lactation number, days in milk, and only 1 measurement, the database comprised 1,094 observations of 254 cows for estimating the effect of SCC on milk yield, DMI, and FE MY and 1,079 observations of 250 cows for estimating the effect of SCC on ECM and FE ECM . Data were analyzed in R using a linear mixed model with natural logarithm of SCC, lactation number (1, 2, and ≥3), days in milk, and the interactions of the linear predictors as fixed effects and cow within block and experiment as random effect. Natural logarithm of SCC was negatively correlated with milk yield, ECM, DMI, FE MY , and FE ECM . Our results suggest that a cow with relatively high SCC (250,000 cells/mL) compared with a cow with a relatively low SCC (50,000 cells/mL) produces, on average, 1.6 kg/d less milk, consumes 0.3 kg/d less DMI, produces 0.04 kg less milk per kg of DMI, and produces 0.03 less ECM per kg of DMI. The observed decrease of feed efficiency with increased SCC adds to previously known economic losses and environmental impacts associated with mastitis, which should provide a further incentive to control mastitis in dairy cows., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)