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Performance evaluations and corrections of soil water sensors have not been studied using different installation orientations under various irrigation treatments in the Texas High Plains. This study evaluated the performance of four sensors using factory calibration and derived field corrections as compared to calibrated neutron moisture meters (NMMs). Sensor performance was assessed using horizontal insertion, laid horizontal placement, and vertical insertion at 15.2, 45.7, and 76.2 cm depths in a clay loam soil with three irrigation treatments. Results indicated the factory-calibrated Acclima 315 L performed satisfactorily using horizontal insertion as compared to NMM measurements at 45.7 and 76.2 cm depths with a ±2% mean difference (MD) and <3.5% root mean square error (RMSE). The factory-calibrated Acclima 315 L using horizontal insertion also performed satisfactorily across all irrigation treatments according to soil profile water storage (MD = 0.36% and RMSE = 3.25%). Generally, the factory-calibrated Decagon GS1 and Campbell Scientific 655 using vertical insertion agreed more closely with NMM measurements compared with other installation orientations. There was a significant underestimation of water storage (>60 mm) in the 0.9 m soil profile using the Watermark 200SS. In summary, field corrections are required for Decagon GS1, Campbell Scientific 655, and Watermark 200SS sensors.

Net ecosystem exchange (NEE) of carbon dioxide (CO 2 ) and water vapor (H 2 O) fluxes from irrigated grain sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.) fields in the Texas High Plains were quantified using the eddy covariance (EC) technique during 2014-2016 growing seasons and examined in terms of relevant controlling climatic variables. Eddy covariance measured evapotranspiration (ET EC ) was also compared against lysimeter measured ET (ET Lys ). Daily peak (7-day averages) NEE reached approximately -12 g C m -2 for sorghum and -14.78 g C m -2 for maize. Daily peak (7-day averages) ET EC reached approximately 6.5 mm for sorghum and 7.3 mm for maize. Higher leaf area index (5.7 vs 4-4.5 m 2  m -2 ) and grain yield (14 vs 8-9 t ha -1 ) of maize compared to sorghum caused larger magnitudes of NEE and ET EC in maize. Comparisons of ET EC and ET Lys showed a strong agreement (R 2  = 0.93-0.96), while the EC system underestimated ET by 15-24% as compared to lysimeter without any corrections or energy balance adjustments. Both NEE and ET EC were not inhibited by climatic variables during peak photosynthetic period even though diurnal peak values (~2-weeks average) of photosynthetic photon flux density (PPFD), air temperature (T a ), and vapor pressure deficit (VPD) had reached over 2000 μmol m -2  s -1 , 30 °C, and 2.5 kPa, respectively, indicating well adaptation of both C 4 crops in the Texas High Plains under irrigation. However, more sensitivity of NEE and H 2 O fluxes beyond threshold T a and VPD for maize than for sorghum indicated higher adaptability of sorghum for the region. These findings provide baseline information on CO 2 fluxes and ET for a minimally studied grain sorghum and offer a robust geographic comparison for maize outside the United States Corn Belt. However, longer-term measurements are required for assessing carbon and water dynamics of these globally important agro-ecosystems., (Published by Elsevier B.V.)

Nutrient management on US dairy farms must balance an array of priorities, some of which conflict. To illustrate nutrient management challenges and opportunities across the US dairy industry, the USDA Agricultural Research Service Dairy Agroecosystems Working Group (DAWG) modeled 8 confinement and 2 grazing operations in the 7 largest US dairy-producing states using the Integrated Farm System Model (IFSM). Opportunities existed across all of the dairies studied to increase on-farm feed production and lower purchased feed bills, most notably on large dairies (>1,000 cows) with the highest herd densities. Purchased feed accounted for 18 to 44% of large dairies' total operating costs compared with 7 to 14% on small dairies (<300 milk cows) due to lower stocking rates. For dairies with larger land bases, in addition to a reduction in environmental impact, financial incentives exist to promote prudent nutrient management practices by substituting manure nutrients or legume nutrients for purchased fertilizers. Environmental priorities varied regionally and were principally tied to facility management for dry-lot dairies of the semi-arid western United States (ammonia-N emissions), to manure handling and application for humid midwestern and eastern US dairies (nitrate-N leaching and P runoff), and pasture management for dairies with significant grazing components (nitrous oxide emissions). Many of the nutrient management challenges identified by DAWG are beyond slight modifications in management and require coordinated solutions to ensure an environmentally and economically sustainable US dairy industry., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).)

Accurate estimates of actual crop evapotranspiration (ET) are important for optimal irrigation water management, especially in arid and semi-arid regions. Common ET sensing methods include Bowen Ratio, Eddy Covariance (EC), and scintillometers. Large weighing lysimeters are considered the ultimate standard for measurement of ET, however, they are expensive to install and maintain. Although EC and scintillometers are less costly and relatively portable, EC has known energy balance closure discrepancies. Previous scintillometer studies used EC for ground-truthing, but no studies considered weighing lysimeters. In this study, a Surface Layer Scintillometer (SLS) was evaluated for accuracy in determining ET as well as sensible and latent heat fluxes, as compared to a large weighing lysimeter in Bushland, TX. The SLS was installed over irrigated grain sorghum ( Sorghum bicolor (L.) Moench) for the period 29 July-17 August 2015 and over grain corn ( Zea mays L.) for the period 23 June-2 October 2016. Results showed poor correlation for sensible heat flux, but much better correlation with ET, with r² values of 0.83 and 0.87 for hourly and daily ET, respectively. The accuracy of the SLS was comparable to other ET sensing instruments with an RMSE of 0.13 mm·h -1 (31%) for hourly ET; however, summing hourly values to a daily time step reduced the ET error to 14% (0.75 mm·d -1 ). This level of accuracy indicates that potential exists for the SLS to be used in some water management applications. As few studies have been conducted to evaluate the SLS for ET estimation, or in combination with lysimetric data, further evaluations would be beneficial to investigate the applicability of the SLS in water resources management., Competing Interests: The authors declare no conflict of interest.

High grazing pressure can lead to soil erosion in pastures, causing increased sediment delivery to waterways. The objectives of this research were to evaluate the impact of grazing management and buffer strips on soil erosion by assessing soil physical properties, hydrology, and sediment loads from pastures fertilized with broiler litter. Field studies were conducted for 12 yr on 15 small watersheds. Five management strategies were evaluated: hayed (H), continuously grazed (CG), rotationally grazed (R), rotationally grazed with a buffer strip (RB), and rotationally grazed with a fenced riparian buffer (RBR). Broiler litter was applied every year at a rate of 5.6 Mg ha. Bulk density and penetration resistance were highest for CG watersheds. Runoff volumes, sediment concentrations, and loads were lowest for the H and RBR treatments and highest for CG. Average runoff amounts were 48, 84, 77, 60, and 81 mm yr for the H, R, RB, RBR, and CG treatments, respectively. Annual average sediment loads were 25, 30, 58, 71, and 110 kg ha for H, RBR, R, RB, and CG, respectively. The Revised Universal Soil Loss Equation, Version 2 was reasonably effective at predicting soil loss for the R, RB, and RBR treatments, but it greatly overpredicted soil loss from the CG and H treatments. Converting a pasture to a hay field or using rotational grazing in conjunction with a fenced riparian buffer appear to be effective options for reducing soil erosion and runoff to waterways from pasture soils., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

An 84-d grazing experiment was conducted in 2 growing seasons to evaluate interactions of stocking rate and steroidal implants with BW gain and symptoms of toxicosis in yearling steers grazing endemic endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.). A 4 x 2 factoral design was used to evaluate 4 stocking rates (3.0, 4.0, 5.0, and 6.0 steers/ ha) with or without steroidal implants (200 mg of progesterone + 20 mg of estradiol benzoate). Treatment combinations were randomly assigned to eight 1-ha pastures of E+ Kentucky-31 tall fescue (i.e., treatments were not replicated). Treatment effects were analyzed for ADG, total BW gain per hectare, forage availability, and hair coat ratings. At the conclusion of grazing in the second year (22 June), steers were placed on a bermudagrass [Cynodon dactylon (L.) Pers.] pasture, and rectal temperatures and serum prolactin concentrations were monitored for 10 d to assess carryover effects of stocking rate and steroidal implants on recovery from toxicosis-related heat stress. Forage availability differed (P < 0.001) between years, but there were no year x treatment interactions (P > 0.10). There was an implant x stocking rate interaction (P < 0.05) on ADG. Differences between the slopes in the regression equations indicated that ADG responded to implantation when stocking rates were low, but the response diminished as stocking rate increased. Stocking rate did not influence (P = 0.89) postgraze rectal temperature, but the regression intercept for implanted steers was 0.4 degrees C greater (P < 0.05) than for nonimplanted steers, and the difference was consistent across the entire 10-d fescue-free grazing period. Concentrations of prolactin increased during the 10-d fescue-free grazing period, but trends differed due to an implantation x stocking rate interaction (P < 0.05). Results indicate that implantation with progesterone + estradiol benzoate increases ADG with lower stocking rates, but the effect diminishes with increased grazing intensity. Implantation with steroid hormones increased rectal temperatures, but during a fescue-free grazing period rectal temperatures and serum prolactins for implanted and nonimplanted steers returned to values indicative of a stable and healthy status in a 192- to 240-h (i.e., an 8- to 10-d) period. However, because the treatments used in this study were not replicated, these observations need to be confirmed with replicated studies.

The objective of the experiment was to determine the effectiveness of copper oxide wire particles (COWP) in pregnant ewes and safety to lambs. COWP have been used recently as an anthelmintic in small ruminants to overcome problems associated with nematode resistance to chemical dewormers. Doses of COWP (

Several laboratories have determined the surface charge density of membranes utilizing methods based on vesicle-induced quenching of the fluorescence of 9-aminoacridine and its relief by other cations. However, the computational methods by which surface charge density were calculated have not been verified in a model system. In this study, the quenching of 9-aminoacridine fluorescence by liposomes made from varying amounts of digalactosyldiacylglyceride and phosphatidic acid and relief of quenching by salts was examined. Quenching of 9-aminoacridine fluorescence increased with increasing amounts of phosphatidic acid added, independent of the composition of the added liposomes. In certain instances, the computational methods did not yield the surface charge density of the liposomes expected from their composition. However, when the effects of background ionic strength on surface potential were considered, there was a positive correlation between expected and calculated values. Therefore, the data support the contention that changes in the fluorescence of 9-aminoacridine can be used to calculate surface charge density of membranes.

To further elucidate the mechanisms of differential genotypic tolerance to Al, plasma membrane (PM) vesicles were isolated from whole roots, root tips, and tipless roots of Al3+-sensitive and Al3+-tolerant cultivars (cv) of wheat (Triticum aestivum L. cv Scout 66 and cv Atlas 66, respectively). Vesicles from cv Scout root tips sorbed more Al than vesicles prepared from any other source. The intrinsic surface-charge density of vesicles isolated from cv Scout was 26% more negative than vesicles from cv Atlas (-37.2 versus -29.5 millicoulombs m-2). Growth experiments indicated that cv Scout is slightly more sensitive to La3+ than is cv Atlas, that the cultivars are equally sensitive to H+, and that cv Atlas is slightly more sensitive to SeO42-. The difference in sensitivity to Al3+ was very large; for a 50% inhibition, a 16-fold greater activity of Al3+ was required for cv Atlas. Using a newly developed Gouy-Chapman-Stern model for ion sorption to the PM together with growth-response curves, we estimate that the difference in surface-charge density can account for the slightly greater sensitivity of cv Scout to cationic toxicants and the slightly greater sensitivity of cv Atlas to anionic toxicants. According to our estimates the differences in PM surface negativity and Al sorptive capacity probably account for some of the difference in sensitivity to Al3+, but the greater part of the difference probably arises from other tolerance mechanisms expressed in cv Atlas root tips that reduce the amount of Al3+ that can reach the PM.

A general model for the sorption of trivalent cations to wheat-root (Triticum aestivum L cv. Scout 66) plasma membranes (PM) has been developed and includes the first published coefficients for La3+ and Al3+ binding to a biological membrane. Both ions are rhizotoxic, and the latter ion is the principal contributor to the toxicity of acidic soils around the world. The model takes into account both the electrostatic attraction and the binding of cations to the negatively charged PM surface. Ion binding is modeled as the reaction P- + IZ <==> 'PIZ-1 in which P- represents a negatively charged PM ligand, located in an estimated area of 540 A2, and IZ represents an ion of charge Z. Binding constants for the reaction were assigned for K+ (1 M-1) and Ca2+ (30 M-1) and evaluated experimentally for La3+ (2200 M-1) and H+ (21,500 M-1). Al sorption is complicated by Al3+ hydrolysis that yields hydroxoaluminum species that are also sorbed. Binding constants of 30 and 1 M-1 were assigned for AlOH2+ and Al(OH)+2, respectively, then a constant for Al3+ (20,000 m-1) was evaluated experimentally using the previously obtained values for K+, Ca2+ and H+ binding. Electrostatic attraction was modeled according to Gouy-Chapman theory. Evaluation of parameters was based upon the sorption of ions to PM vesicles suspended in solutions containing variable concentrations of H+, Ca2+ and La3+ or Al3+. Use of small volumes, and improved assay techniques, allowed the measurement of concentration depletions caused by sorption to vesicles. Some independent confirmation of our model is provided by substantial agreement between our computations and two published reports of La3+ effects upon zeta potentials of plant protoplasts. The single published report concerning the electrostatic effects of Al on cell membranes is in essential agreement with the model.

The biochemical events utilized by transport proteins to convert the chemical energy from the hydrolysis of ATP into an electro-chemical gradient are poorly understood. The inhibition of the plasma membrane ATPase from corn (Zea mays L.) roots by N-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline (EEDQ) was compared to that of ATPase solubilized with N-tetradecyl-N,N-dimethyl-3-ammonio-1-propane-sulfonate (3-14) to provide insight into the minimal functional unit. The chromatographic behavior of the 3-14-solubilized ATPase activity during size exclusion chromatography and glycerol gradient centrifugation indicated that the solubilized enzyme was in a monomeric form. Both plasma membrane-bound and solubilized ATPase were inhibited by EEDQ in a time- and concentration-dependent manner consistent with a first-order reaction. When the log of the reciprocal of the half-time for inhibition was plotted as a function of the log of the EEDQ concentration, straight lines were obtained with slopes of approximately 0.5 and 1.0 for membrane-bound and 3-14-solubilized ATPase, respectively, indicating a change in the number of polypeptides per functional ATPase complex induced by solubilization with 3-14.