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The Lower Chesapeake Bay (LCB) Long-Term Agroecosystem Research (LTAR) Common Experiment (CE) located in Beltsville, MD, focuses on research of concern to producers of the major regional crops, which are corn (Zea mays L.), soybean [Glycine max (L.) Merr.], wheat (Triticum aestivum L.), and various forage species. Livestock production in the region includes broiler and laying chickens (Gallus gallus domesticus L.) and dairy and beef cattle (Bos taurus L.). The LCB region is among the most heavily populated in the United States. Urban development pressure is high for both farms and natural areas. The need to restore Chesapeake Bay water quality is a major influence on regional agricultural practices. Conservation practices such as cover cropping, no-till agriculture, and nutrient management planning are more common in the region compared to nationally. However, farmers still face management challenges implementing practices that address water quality and the rise of herbicide-resistant weeds. Researchers at the LCB site recognize the need to protect the Chesapeake and Delaware Bays and maintain farmer profitability. The LCB CE compares a 3-year crop rotation system featuring alternative crop management (cover crop intensification, crop rotation diversification, and integrated weed management [IWM]) with a prevailing 2-year system (no cover crops and no IWM), both under continuous no-tillage, to identify the optimal balance to promote the sustainability of regional cropping systems. The LTAR LCB site provides data-driven tools and solutions to support farmers in the mid-Atlantic region., (© 2024 The Author(s). Journal of Environmental Quality © 2024 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

Cover crops reduce nitrate leached, but effects on nitrous oxide (N 2 O) emissions are mixed. Cover crops can reduce N 2 O emissions by reducing levels of mineral nitrogen (N) and surface soil moisture during spring. Cover crops can also increase N 2 O emissions by adding organic substrates, releasing N during decomposition, or increasing summer soil water content. Winter-killed cover crops can increase soluble organic C and N during periods of typically low microbial activity. We hypothesized that planting a cover crop mix of radish (Raphanus sativus)-crimson clover (Trifolium incarnatum)-rye (Secale cereale) would increase direct N 2 O emissions relative to no cover crop, and result in lower direct and indirect N 2 O emissions than planting radish alone. We also hypothesized that extending the cover crop growing season, by planting earlier and killing later, would increase direct N 2 O emissions during winter, decrease direct N 2 O emissions during summer, and decrease indirect N 2 O emissions. To address these hypotheses, we conducted two field experiments (on sandy and silty soils) over four site-years. We measured cover crop biomass and N content, soil mineral N concentrations, soil moisture, green canopy cover, soil porewater nitrate, direct N 2 O emissions, and estimated indirect N 2 O emissions. Nitrous oxide emissions were ~ 7.8 times greater at the silty than the sandy sites due to greater soil moisture retention. Site-years with high radish biomass exhibited greater direct N 2 O emissions than sites with low radish biomass following winter-kill. Indirect N 2 O emissions were decreased ~7 % by planting cover crops and by ~70 % by planting cover crops early. Fertilizer induced emission peaks were 8.2 times greater than all previous N 2 O emissions combined at a silty site. Our results suggested that soil texture and fertilization played an important role in direct N 2 O emissions, while cover crop species, biomass, and timing played a more important role in NO 3 leached, and thus, indirect N 2 O emissions., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Nathan Sedghi reports financial support was provided by Shore Rivers. Ray R. Weil reports financial support was provided by Shore Rivers. Nathan Sedghi reports financial support was provided by Maryland Soybean Board. Ray R. Weil reports financial support was provided by Maryland Soybean Board. Ray R. Weil reports financial support was provided by National Institute of Food and Agriculture., (Copyright © 2024. Published by Elsevier B.V.)

Land application of biochar reportedly provides many benefits, including reduced risk of nutrient transport, greenhouse gas (GHG) emission mitigation, and increased soil C storage, but additional field validation is needed. We evaluated the effectiveness of biochar in controlling the lability of nutrients in agricultural land. This study was designed to evaluate the impacts of biochar co-applied with various N and P sources on GHG fluxes from a subtropical grassland. Nutrients (inorganic fertilizer and aerobically digested Class B biosolids) were surface applied at a rate of 160 kg plant available N ha -1  yr -1 with or without biochar (applied at 20 Mg ha -1 ). Greenhouse gas (CO 2 , CH 4 , and N 2 O) fluxes were assessed using static chambers and varied significantly, both temporally and with treatments. Greenhouse gas fluxes ranged from 1,247 to 23,160, -0.7 to 42, and -1.4 to 376 mg m -2 d -1 for CO 2 , N 2 O, and CH 4 , respectively. Results of the 3-yr field study demonstrated strong seasonal variability associated with GHG emissions. Nutrient source had no effect on soil CO 2 and CH 4 emissions, but annual and cumulative (3-yr) N 2 O emissions increased with biosolids (8 kg N 2 O ha -1  yr -1 ) compared with inorganic fertilizer (5 kg N 2 O ha -1  yr -1 ) application. Data suggested that environmental conditions played a more important role on GHG fluxes than nutrient additions. Biochar reduced CO 2 emissions modestly (<9%) but had no effects on N 2 O and CH 4 emissions., (© 2020 The Authors. Journal of Environmental Quality © 2020 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

Despite the numerous benefits of biosolids, concerns over nutrient losses restrict the extent to which biosolids can be beneficially reused. We evaluated the effectiveness of biochar in controlling the lability of nutrients in agricultural land. This study was designed to investigate the potential impacts of co-applying biochar with biosolids or inorganic fertilizer on N and P leaching losses. A companion paper focuses on greenhouse gas responses. Nutrients were surface applied as biosolids (aerobically digested Class B) and inorganic fertilizer (ammonium nitrate and triple superphosphate) to an established perennial pasture at equivalent annual rates typical of field practices. Biochar was applied at an annual rate of 20 Mg ha -1 . Leachate N and P were monitored using passive-capillary drainage lysimeters. Results demonstrated significant temporal variability in leachate N and P, with larger pulses generally occurring during periods of high water table levels or after intensive rainfall. Inorganic fertilizer generally resulted in greater leachate N and P losses than biosolids. No differences in leachate N and P losses between biosolids and control were observed. Approximately 1% of applied N was lost via leaching from biosolids treatments vs. 16% for inorganic fertilizer. Regardless of the P source, negligible (0.1-0.2% of applied P), cumulative P leaching occurred during the 3-yr study. Biochar had no effect on P leaching but reduced N leaching from treatments receiving inorganic fertilizer by 60%. Prudent nutrient management is possible even on biosolids-amended Spodosols with high water tables., (© 2020 The Authors. Journal of Environmental Quality © 2020 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

To improve our ability to predict SOC mineralization response to residue and N additions in soils with different inherent and dynamic organic matter properties, a 330-day incubation was conducted using samples from two long-term experiments (clay loam Mollisols in Iowa [IAsoil] and silt loam Ultisols in Maryland [MDsoil]) comparing conventional grain systems (Conv) amended with inorganic fertilizers with 3 yr (Med) and longer (Long), more diverse cropping systems amended with manure. A double exponential model was used to estimate the size (Ca, Cs) and decay rates (ka, ks) of active and slow C pools which we compared with total particulate organic matter (POM) and occluded-POM (OPOM). The high-SOC IAsoil containing highly active smectite clays maintained smaller labile pools and higher decay rates than the low-SOC MDsoil containing semi-active kaolinitic clays. Net SOC loss was greater (2.6 g kg(-1); 8.6%) from the IAsoil than the MDsoil (0.9 g kg(-1), 6.3%); fractions and coefficients suggest losses were principally from IAsoil's resistant pool. Cropping history did not alter SOC pool size or decay rates in IAsoil where rotation-based differences in OPOM-C were small. In MDsoil, use of diversified rotations and manure increased ka by 32% and ks by 46% compared to Conv; differences mirrored in POM- and OPOM-C contents. Residue addition prompted greater increases in Ca (340% vs 230%) and Cs (38% vs 21%) and decreases in ka (58% vs 9%) in IAsoil than MDsoil. Reduced losses of SOC from residue-amended MDsoil were associated with increased OPOM-C. Nitrogen addition dampened CO2-C release. Clay type and C saturation dominated the IAsoil's response to external inputs and made labile and stable fractions more vulnerable to decay. Trends in OPOM suggest aggregate protection influences C turnover in the low active MDsoil. Clay charge and OPOM-C contents were better predictors of soil C dynamics than clay or POM-C contents.

The basal amounts of metallothionein (MT) and its rates of biosynthesis were compared in resting and proliferating Chang liver (CCl-13) cells. In resting cells the total amounts of the detectable isoforms MT-2 and MT-1e were approx. 1.6x10(6) and 4x10(5) molecules per cell respectively. In exponentially growing cultures the cellular contents of both isoforms increased co-ordinately approx. 4-fold and decreased again to the initial values within 48 h after entering density-mediated growth arrest. As documented for MT-2 its transient accretion was attributable to a 10-fold rise in the rate of biosynthesis of this protein during the growth phase. Measurements of the relative amounts of MT-2 mRNA indicated the occurrence of a more than 50% increase within the first 12 h after subculturing of the cells, followed by a return to basal levels thereafter. These results denote a direct link between the programming of MT synthesis and proliferation and thus attest to a central housekeeping function of the MTs.

We studied the comparative effects of beta-adrenergic blockade with propranolol (PROP) and bucindolol (BUC), a beta-adrenergic agonist having both alpha-adrenergic blocking properties and intrinsic sympathomimetic activity (ISA) on airway and cardiovascular responses, in 38 mongrel dogs in situ. Intravenous infusion of 0.6 mg/kg + 6 micrograms/kg/min BUC and 2.0 mg/kg + 20 micrograms/kg/min PROP caused identical shifts in the isoproterenol (ISO) EC50 for chronotropic and hypotensive arterial blood pressure responses. After PROP administration, resting heart rate (HR) decreased from 188 +/- 15 to 142 +/- 12 beats/min (p less than 0.02); BUC caused no decrease in HR. In contrast, the effects of BUC and PROP on mean arterial blood pressure response to ISO were similar. No change in bronchomotor tone was observed after bolus injection of either BUC or PROP. Beta-Adrenergic relaxation to ISO and alpha-adrenergic contraction to norepinephrine (NE) were studied simultaneously in tracheal and bronchial airways using chronotropically equivalent beta-adrenoceptor blocking doses of PROP and BUC. Comparable inhibition of ISO-induced airway relaxation after contraction with 120 micrograms/kg/min i.v. serotonin was demonstrated in both PROP (n = 5) and BUC (n = 5) groups (p less than 0.01 for doses greater than 5 X 10(-11) mol/kg). Similarly, both BUC (n = 5) and PROP (n = 5) blocked beta-adrenergic relaxation and caused identical alpha-adrenergic airway contraction to intravenous NE. We conclude that the ISA of the beta-adrenergic blocking drug BUC can be demonstrated on the spontaneous rate of the heart but not on the activity of bronchial smooth muscle. BUC neither augments ISO-induced relaxation nor inhibits NE-induced contraction of airways after effective chronotropic blockade.