Search

Corn (Zea maysL.) stover demand as a forage or for an emerging bioeconomy has increased the importance of determining the long‐term effects of stover removal on grain yield and soil properties. Study objectives were to evaluate grain yield, soil organic carbon (SOC), and total soil N (0–150 cm) in a 20‐year, irrigated, continuous corn study, located in eastern Nebraska, under conventional tillage (CT) and no‐till (NT) with variable corn stover removal rates (none, medium, and high). After 20 years, grain yield was up to 6.0% greater under NT with stover removal compared with NT and no stover removal, while yield was similar for CT in all stover removal treatments. Grain yield was similar between NT with stover removal and CT in all stover removal treatments. High stover removal rates resulted in greater SOC loss at the surface soil layers (0–15 cm and 0–30 cm) after 20 years compared with no or medium stover removal. Corn stover retention under NT resulted in the same cumulative SOC stock loss as CT or stover removal. All management practices resulted in cumulative (0–120 cm) SOC stock loss (8% decrease) that occurred in the last 10 years of the study. Total soil nitrogen stocks were maintained or increased after 20 years at the surface soil layers (0–15 cm and 0–30 cm) and were similar between NT and CT. In an irrigated continuous corn system, neither NT nor stover retention was able to maintain cumulative SOC stocks over time. Corn yield increased under no‐till with stover removal but not under conventional tillage.Corn yield was similar in conventional tillage under no, medium, and high stover removal rates.High residue removal rates decreased SOC stocks at the soil surface (0–30 cm) under both no‐till and conventional tillage.All management practices resulted in a net loss of cumulative SOC stocks.

Alkenylboronates are versatile building blocks for stereocontrolled synthesis owing to the traceless nature of the boron group that can be leveraged to achieve highly selective geometric isomerization. Using thioxanthone as an inexpensive photocatalyst, the photoisomerization of these species continues to provide an expansive platform for stereodivergent synthesis, particularly in the construction of bioactive polyenes. Although mechanistic investigations are consistent with light-driven energy transfer, direct experimental evidence remains conspicuously absent. Herein, we report a rigorous mechanistic investigation using two widely used alkenylboronates alongside relevant reference compounds. Through the combination of irradiation experiments, transient absorption spectroscopic studies, kinetic modeling, and DFT calculations with all isomers of the model compounds, it has been possible to unequivocally detect and characterize the perpendicular triplet generated by energy transfer. Our results serve not only as a blueprint for mechanistic studies that are challenging with organic sensitizers, but these guidelines delineated have also enabled the development of more sustainable reaction conditions: for the first time, efficient organocatalytic isomerization under sunlight irradiation has become feasible.

Mesoporous hematite (α-Fe2O3) thin films with high surface-to-volume ratios show great potential as photoelectrodes or electrochemical electrodes in energy conversion and storage. In the present work, with the assistance of an up-scalable slot-die coating technique, locally highly ordered α-Fe2O3thin films are successfully printed based on the amphiphilic diblock copolymer poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) as a structure-directing agent. Pure PS-b-P4VP films are printed under the same conditions for comparison. The micellization of the diblock copolymer in solution, the film formation process of the printed thin films, the homogeneity of the dry films in the lateral and vertical direction as well as the morphological and compositional information on the calcined hybrid PS-b-P4VP/FeCl3thin film are investigated. Because of convection during the solvent evaporation process, a similar dimple-type structure of vertically aligned cylindrical PS domains in a P4VP matrix developed for both printed PS-b-P4VP and hybrid PS-b-P4VP/FeCl3thin films. The coordination effect between the Fe3+ions and the vinylpyridine groups significantly affects the attachment ability of the P4VP chains to the silicon substrate. Accordingly, distinct feature sizes and homogeneity in the lateral direction, as well as the thicknesses in the perpendicular direction, are demonstrated in the two printed films. By removing the polymer template from the hybrid PS-b-P4VP/FeCl3film at high temperature, a locally highly ordered mesoporous α-Fe2O3film is obtained. Thus, a facile and up-scalable printing technique is presented for producing homogeneous mesoporous α-Fe2O3thin films.

Understanding the impacts of long‐term agricultural practices on soil quality (SQ) is key for sustaining agroecosystem productivity. This study investigated conventional and no‐tillage (NT), residue burning and no burning, residue level (high and low), and irrigation (irrigated and dryland) effects on soil properties, SQ, and crop yields following 16 yr of a wheat (Triticum aestivumL.)–soybean [Glycine max(L.) Merr.] double‐crop system via the Soil Management Assessment Framework (SMAF). A field experiment was conducted in the Lower Mississippi River Delta region on a silt‐loam soil. Bulk density, soil organic C (SOC), total N (TN), pH, electrical conductivity (EC), and soil P and K from the 0‐ to 10‐cm soil depth were used as SQ indicators investigated individually and as an overall soil quality index (SQI). Following 16 yr, residue burning reduced SOC (1.1%) compared with no burning (1.24%). Irrigation resulted in greater soil TN than dryland management systems (p < 0.05). Reduced soil pH and extractable soil P and K occurred under NT, high residue, and irrigated treatments. Irrigation increased soybean yields, regardless of the tillage system. Burned, NT–high residue management increased wheat yields (3.45 Mg ha−1). Irrigation reduced SQ because of low EC and K scores. High residue reduced SQ compared with the low residue treatment within NT systems, owing to low pH scores. The SMAF indices identified the impacts of irrigation, NT, and optimal N fertilization on SQ. Monitoring of soil pH, P, and K may be needed to maintain SQ in long‐term wheat–soybean systems.

In situprinting gives insight into the evolution of morphology and optical properties during slot-die coating of active layers for application in organic solar cells and enables an upscaling and optimization of the thin film deposition process and the photovoltaic performance. Active layers based on the conjugated polymer donor with benzodithiophene units PBDB-T-2Cl and the non-fullerene small-molecule acceptor IT-4F are printed with a slot-die coating technique and probed in situwith grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and ultraviolet/visible light spectroscopy. The formation of the morphology is followed from the liquid state to the final dry film for different printing conditions (at 25 and 35 °C), and five regimes of film formation are determined. The morphological changes are correlated to changing optical properties. During the film formation, crystallization of the non-fullerene small-molecule acceptor takes place and polymer domains with sizes of some tens of nanometers emerge. A red shift of the optical band gap and a broadening of the absorbance spectrum occurs, which allow for exploiting the sun spectrum more efficiently and are expected to have a favorable effect on the solar cell performance.

Corn (Zea maysL.) residue or stover is harvested as supplemental feed for livestock and is a potential feedstock for cellulosic biofuels. Limited information is available on corn stover removal effects on grain yield under different irrigation rates, nitrogen (N) fertilizer rates, and practices to maintain soil carbon (C) and minimize soil erosion. We evaluated potential interactions between irrigation rate (full or limited), C amelioration practices (cover crop, surface‐applied manure, or no amelioration practice), fertilizer N management (125 or 200 kg N ha−1), and stover removal (residue removal or no residue removal), on no‐till continuous corn grain yield located on a silt loam soil in south‐central Nebraska (2011–2018). Stover removal increased (P= .0017) grain yield by 1.02 Mg ha−1and grain N uptake compared with no stover removal. Manure increased corn grain yield by 899 kg ha−1compared to either the control or cover crop with stover removal while C amelioration practices did not affect grain yield under stover retention. Grain N concentration was higher (P< .0001) with stover removal (13.2 g kg−1) than residue retained (12.7 g kg−1). Partial factor productivity (grain yield/N rate) was highest for manure treatments with residue removal. The farmgate N balance (N applied − N removed) from stover removal was negative, yet grain yield was not affected after eight growing seasons. Grain yield increased with stover removal and manure application resulting in a cost‐effective C amelioration practice whereas incorporating a winter cover crop resulted in similar grain yield as the control.

A major barrier to the impact of genomic diagnosis in patients with congenital malformations is the lack of understanding regarding how sequence variants contribute to disease pathogenesis and whether this information could be used to generate patient-specific therapies. Congenital diaphragmatic hernia (CDH) is among the most common and severe of all structural malformations; however, its underlying mechanisms are unclear. We identified loss-of-function sequence variants in the epigenomic regulator gene SIN3Ain two patients with complex CDH. Tissue-specific deletion of Sin3ain mice resulted in defects in diaphragm development, lung hypoplasia, and pulmonary hypertension, the cardinal features of CDH and major causes of CDH-associated mortality. Loss of SIN3A in the lung mesenchyme resulted in reduced cellular differentiation, impaired cell proliferation, and increased DNA damage. Treatment of embryonic Sin3amutant mice with anacardic acid, an inhibitor of histone acetyltransferase, reduced DNA damage, increased cell proliferation and differentiation, improved lung and pulmonary vascular development, and reduced pulmonary hypertension. These findings demonstrate that restoring the balance of histone acetylation can improve lung development in the Sin3amouse model of CDH.

Printing of active layers of high-efficiency organic solar cells and morphology control by processing with varying solvent additive concentrations are important to realize real-world use of bulk-heterojunction photovoltaics as it enables both up-scaling and optimization of the device performance. In this work, active layers of the conjugated polymer with benzodithiophene units PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F are printed using meniscus guided slot-die coating. 1,8-Diiodooctane (DIO) is added to optimize the power conversion efficiency (PCE). The effect on the inner nanostructure and surface morphology of the material is studied for different solvent additive concentrations with grazing incidence small-angle X-ray scattering (GISAXS), grazing incidence wide-angle X-ray scattering (GIWAXS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Optical properties are studied with photoluminescence (PL), UV/vis absorption spectroscopy, and external quantum efficiency (EQE) measurements and correlated to the corresponding PCEs. The addition of 0.25 vol % DIO enhances the average PCE from 3.5 to 7.9%, whereas at higher concentrations the positive effect is less pronounced. A solar cell performance of 8.95% is obtained for the best printed device processed with an optimum solvent additive concentration. Thus, with the large-scale preparation method printing similarly well working solar cells can be realized as with the spin-coating method.

Integrated crop–livestock systems (ICLSs) can help increase food production while benefiting soils and the environment. This review summarizes recent impacts of ICLSs on crop and livestock production and rural economics and discusses lessons learned in the northern Great Plains (NGP). Research on ICLS conducted in the NGP indicates that the crop residue grazing, swath grazing, and annual forage grazing can positively influence crop production; whereas, livestock performance varies with season, forage nutritive value, and grazing management. Furthermore, ICLSs can reduce the costs and risks of agricultural production. The success of ICLSs in NGP region depends on trade‐offs, planning, economic benefits, policies, regulations, community acceptance, and management skills. The ICLSs could play a strategic role in future agricultural production. The lessons learned from adopting ICLSs in the NGP include the lack of available land for fertilizer (manure) management, that to implement ICLS practices skills and knowledge must be maintained, and ICLS provides an entry point for young farmers and ranchers however capital is needed. These experiences and lessons could be valuable references for producers to adopt ICLSs in the NGP or other regions. Core IdeasIntegrated crop–livestock systems positively affect crop production by improving soil health.Common integrated crop–livestock system management techniques can enhance the northern Great Plains crop production.Integrated crop–livestock system livestock performance is impacted by season, forage selection, and management.Integrated crop–livestock systems can increase economic benefits and reduce economic risks.Experiences and lessons in the northern Great Plains could be valuable for other regions to adopt integrated crop–livestock systems. Integrated crop–livestock systems positively affect crop production by improving soil health. Common integrated crop–livestock system management techniques can enhance the northern Great Plains crop production. Integrated crop–livestock system livestock performance is impacted by season, forage selection, and management. Integrated crop–livestock systems can increase economic benefits and reduce economic risks. Experiences and lessons in the northern Great Plains could be valuable for other regions to adopt integrated crop–livestock systems.

Water vapor (H2O) is the strongest greenhouse gas in our atmosphere. Hence, accurate measurements and a correct representation in global models of H2O in the upper troposphere/lower stratosphere (UTLS) are important for understanding and projecting climate. Here we compare balloon‐borne measurements of UTLS H2O, performed by cryogenic frostpoint hygrometers (CFH) and meteorological radiosondes (Vaisala RS41) during two intensive field campaigns in the Asian summer monsoon anticyclone region, with humidity data from three products of the European Centre for Medium‐range Weather Forecasts (ECMWF): operational analysis and forecast (termed OPERA), ERA‐Interim reanalysis, and the newly released ERA5 reanalysis. Taking CFH as a reference, we show that OPERA and ERA5 provide a more accurate representation of UTLS H2O than ERA‐Interim. In particular, OPERA and ERA5 similarly overestimate H2O mixing ratios by on average 0.7–0.8 ppmv (14–15%) and 0.7–0.9 ppmv (15–17%) at pressures 60–100 hPa, respectively, and both provide a good representation of the observed vertical distribution (including fine structures) and natural variability of UTLS H2O. In contrast, ERA‐Interim underestimates UTLS H2O by 0.6–1.7 ppmv (14–30%), and it fails to capture relevant features of the vertical distribution of UTLS H2O. At pressures (p) lower than 60 hPa, all three ECMWF products are in good agreement with CFH. Humidity measurements by RS41 show an average dry bias of 0.1–0.5 ppmv (3–9%) compared to CFH for 60–100 hPa, and a moist bias increasing with altitude for p< 60 hPa, exceeding 100% for p< 40 hPa. ECMWF operational and ERA5 data show moist bias (14–17%) in UTLS water vapor compared to cryogenic frostpoint hygrometer (CFH)ERA‐Interim data shows dry bias (14–30%) in UTLS water vapor compared to CFHNew ERA5 reanalysis provides an improved representation of UTLS water vapor compared to ERA‐Interim reanalysis

In Brazilian sugarcane (Saccharumspp.) production systems, the practice of moving harvesting residue from row to inter‐row positions (i.e., raking) has increased in response to producer concerns over the potential negative effects of sugarcane straw on crop establishment and stalk yield. Despite increasing adoption among sugarcane farmers, the impacts of straw raking practices on plant growth and yield remain unclear. A 2‐yr experiment that included both dry and wet seasons was conducted at two sites in southeastern Brazil to evaluate straw management strategy effects on plant tillering, phytomass accumulation, plant nutritional status, and stalk yield. The experiments were established at the Bom Retiro mill and the Univalem mill. Experimental treatments included raking straw to inter‐rows (raked), total straw removal (bare soil), and no straw removal (straw cover). Raked and bare soil treatments improved plant tillering but did not influence final plant population. Straw management had a slight effect on phytomass accumulation. Reduction of phytomass yield was observed from the first to the second ratoon during both seasons at both sites. At Bom Retiro, phytomass yield decreased 37% for stands established during the dry season and 19% for stands established during the wet season. At Univalem, phytomass yield decreased 20% for stands established during the dry season and 30% for stands established during the wet season. Retaining straw in the field (regardless of treatment) increased leaf tissue P content but not stalk yield. Raking straw from row to inter‐row positions at these locations in southeastern Brazil had no benefit on sugarcane yield but may result in soil compaction and higher production costs over time.

Recombinant inbred lines (RILs) of winter wheat (Triticum aestivumL.) were used to determine whether the combination of low grain phytate (LPA) conditioned by lpa1‐1and Gpc‐B1(where GPC stands for grain protein content) alleles would simultaneously increase beneficial mineral concentrations and grain protein without pleiotropic effects on grain yield. Four different genotypes (LPA‐GPC, LPA‐wild type [WT], WT‐GPC, or WT‐WT) were used as treatments in field experiments in Nebraska. Genotypic effects on senescence, grain yield, grain volume weight, grain protein, Fe, Zn, and other mineral grain concentrations were determined. Low grain phytate alone and in combination with GPC increased dialyzed Zn, Ca, and Mn. Gpc‐B1had a slight effect on grain protein concentration in the tested genetic backgrounds and environments. The combination of LPA and GPC did not lower grain yield, grain protein, or total grain Fe and Zn concentrations. However, the LPA‐GPC combination significantly reduced grain volume weight. The LPA allele alone reduced grain protein concentration. Introgression of lpa1‐1alleles into adapted Great Plains winter wheat materials can improve dialyzed Zn, Ca, and Mn concentrations without reducing grain yield and, coupled with introgression of Gpc‐B1, provide more nutritious wheat kernels.

The western US Corn Belt is projected to experience major changes in growing conditions due to climate change over the next 50 to 100 yr. Projected changes include increases in growing season length, number of high temperature stress days and warm nights, and precipitation, with more heavy rainfall events. The impact these changes will have on soil organic carbon (SOC) needs to be estimated and adaptive changes in management developed to sustain soil health and system services. The process‐based model CQESTR was used to model changes in SOC stocks (0–30 cm) of continuous corn (Zea maysL.) and a corn–soybean [Glycine max(L.) Merr.] rotation under disk, chisel, ridge, and no‐tillage using projected growing season conditions for the next 50 yr. Input for the model was based on management and harvest records from a long‐term tillage study (1986–2015) in eastern Nebraska, and model output was validated using measured changes in SOC from 1999 to 2011 in the study. The validated model was used to estimate changes in SOC over 17 yr under climatic conditions projected for 2065 under two scenarios: (i) crop yields increasing at the observed rate from 1971 to 2016 or (ii) crop yields reduced due to negative effects of increasing temperature. CQESTR estimates of SOC agreed well with measured SOC (R2= 0.70, P< 0.0001). Validated model simulated changes in SOC under projected climate change differed among the three soil depths (0–7.5, 7.5–15, and 15–30 cm). Summed over the 0‐ to 30‐cm depth, there were significant three‐way interactions of year × rotation × yield (p= 0.014) and year × tillage × yield (p< 0.001). As yield increased, SOC increased under no‐tillage continuous corn but was unchanged under no‐tillage corn–soybean and ridge tillage regardless of cropping system. Under chisel and disk tillage, SOC declined regardless of cropping system. With declining yields SOC decreased regardless of tillage or cropping system. These results highlight the interaction between genetics and management in maintaining yield trends and soil C. Improvements in management and genetics will be needed to maintain or increase C sequestration.Conservation tillage practices that minimize soil disturbance sustain soil organic C.Decreasing crop yields will require additional input to sustain current soil organic C levels.

Balloon sounding with the Compact Optical Backscatter Aerosol Detector (COBALD) and Frost Point hygrometers (FPs) provides in situ data for a better understanding of the vertical distribution of cirrus clouds. In this study, eight summer balloon‐borne measurements in Kunming (2012, 2014, 2015, and 2017) and Lhasa (2013, 2016, 2018, and 2020) over the Tibetan Plateau were used to show the distribution characteristics of cirrus clouds. Differences of cirrus occurrence were compared by different indices: the backscatter ratio (BSR) at a 455 nm/940 nm wavelength (BSR455> 1.2/BSR940> 2), the color index (CI > 7), and the relative humidity with respect to ice (RHice> 70%). Analysis of the profiles indicated that BSR455> 1.2 was the optimal criterion to identify the cirrus layer and depict the distribution of the CI and RHicewithin cirrus clouds. The results showed that the median CI (RHice) within the cirrus clouds at both sites was mostly in the 18–20 (90%–110%) range at pressures below 120 hPa. Furthermore, the balloon‐borne measurements combined with Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements indicated a high frequency of cirrus occurrence near the tropopause in Kunming and Lhasa. The top height of cirrus occurrence at both sites was above the cold point tropopause and the lapse rate tropopause. Both Kunming and Lhasa had the highest frequency of thin cirrus clouds in the 0–0.4 km vertical cirrus thickness range. Balloon‐borne measurements of cirrus clouds are scarce over the Tibetan Plateau. The sounding water vapor, ozone, and particles (SWOP) campaign has collected Compact Optical Backscatter Aerosol Detector (COBALD) and Frost Point Hygrometers (FPs) data for eight summers in Kunming and Lhasa. The backscatter ratio at wavelengths of 455 and 940 nm (BSR455, BSR940) from COBALD, the color index (CI), and the relative humidity over ice (RHice) from the FPs are able to indicate the occurrence of cirrus clouds. BSR455>1.2/BSR940> 2 was the optimal criterion to identify the cirrus layer in the upper troposphere over the Tibetan Plateau. The results showed that the CI and RHicewithin the cirrus clouds at both sites have a consistent distribution. The median CI (RHice) remained essentially in the range of 18–20 (90%–110%) below 120 hPa. The top height of cirrus occurrence at both sites was above the cold point tropopause and the lapse rate tropopause. Thin cirrus clouds (less than 400 m thick) had the highest frequency in both Kunming and Lhasa. A backscatter ratio over 1.2/2 at a 455 nm/940 nm wavelength can effectively identify cirrus clouds over the Tibetan PlateauCirrus clouds were observed above the cold point tropopause (CPT) in both Kunming and LhasaAbout 38% (39%) of the cirrus clouds are thinner than 400 m in Kunming (Lhasa) A backscatter ratio over 1.2/2 at a 455 nm/940 nm wavelength can effectively identify cirrus clouds over the Tibetan Plateau Cirrus clouds were observed above the cold point tropopause (CPT) in both Kunming and Lhasa About 38% (39%) of the cirrus clouds are thinner than 400 m in Kunming (Lhasa)

Long‐term cropping system and fertilizer N studies are essential to understanding production potential and yield stability of corn (Zea maysL.), grain sorghum [Sorghum bicolor(L.) Moench], and soybean [Glycine max(L.) Merr.] in rain‐fed environments. A no‐till experiment (2007–2013) was conducted in eastern Nebraska to evaluate crop rotation (continuous corn, continuous grain sorghum, continuous soybean, corn–soybean, grain sorghum–soybean, corn–soybean–grain sorghum–oat [Avena sativa(L.)]/clover mixture [80% Melilotus officinalisLam. + 20% Trifolium pretenseL.], and corn–oat/clover–grain sorghum–soybean) and fertilizer N (corn and grain sorghum: 0, 90, 180 kg N ha−1; soybean and oat/clover: 0, 36, 67 kg N ha−1) on grain yield, plant N uptake, and N recovery efficiency. Diversified crop rotations increased corn and grain sorghum yields and improved yield stability. A positive corn grain yield response to fertilizer N was consistent across crop rotations, but fertilizer N addition with corn–soybean–grain sorghum–oat did not increase grain sorghum yield. Yield stability of soybean was less sensitive to management; all treatment combinations were found to be stable. Fertilizer N addition decreased soybean grain yield in 2 of 7 yr, but yields were similar in the remaining 5 yr. These results indicate that adoption of 2‐ and 4‐yr crop rotations in rain‐fed environments can result in high‐yielding, more stable corn, grain sorghum, and soybean grain production compared with shorter rotations or continuous cropping. Core Ideas Diversified 2‐ and 4‐yr crop rotations increased corn and grain sorghum yields.Corn and grain sorghum grain yields in 2‐ and 4‐yr rotations were more resilient to variable growing conditions.Soybean was less sensitive than corn and grain sorghum to crop rotation. Diversified 2‐ and 4‐yr crop rotations increased corn and grain sorghum yields. Corn and grain sorghum grain yields in 2‐ and 4‐yr rotations were more resilient to variable growing conditions. Soybean was less sensitive than corn and grain sorghum to crop rotation.

Long‐term experiments are essential to understand how crop rotation and tillage practices affect corn (Zea maysL.) and soybean [Glycine max(L.) Merr.] production and its resiliency to variable weather conditions. A 28‐yr rainfed experiment was conducted in Nebraska to evaluate continuous corn (CC), the corn phase of corn–soybean rotation (CS), continuous soybean (SS), and the soybean phase of corn–soybean rotation (SC), and tillage system (chisel [CH], tandem disk [DK], moldboard plow [MP], no‐till [NT], ridge‐tillage [RT], and subsoil tillage [ST]) on grain yield and yield stability. In 19 of 28 yr, CS yields were greater than CC, although the corn grain yield advantage in CS decreased as CC yield increased. Rotated soybean (SC) grain yield was greater than SS in 67% of cropping years, and similar in the remaining 33%. Stability analysis showed that all crop rotation and tillage combinations, except CH for soybean, resulted in stable grain yields across a range of seasonal weather patterns. Corn grain yields were affected by tillage in 29% of the years, while NT soybean resulted in consistently high and stable grain yields following an initial 11‐yr lag period. We conclude that crop rotation has a greater impact on corn and soybean production than tillage in the western Corn Belt, although nearly all combinations can produce stable yields if well managed.

Corn (Zea maysL.) stover (non‐grain aboveground biomass) in the US Corn Belt is used increasingly for livestock grazing and co‐feed and for cellulosic bioenergy production. Continuous stover removal, however, could alter long‐term agricultural productivity by affecting soil organic C (SOC) and soil physical properties, indicators of soil fertility and erosion potential. In this study, we showed that 12 consecutive yr of 55% stover removal did not affect mean grain yields at any N fertilizer rate (4.5, 6.3, and 6.0 Mg ha−1for 60, 120, and 180 kg N ha−1yr−1, respectively) in a marginally productive, rainfed continuous corn system under no‐till (NT). Although SOC increased in the top 30 cm of all soils since 1998 (0.54–0.79 Mg C ha−1yr−1), stover removal tended to limit SOC gains compared with no removal. Near‐surface soils (0–5‐cm depth) were more sensitive to stover removal and showed a 41% decrease in particulate organic matter stocks, smaller mean weight diameter of dry soil aggregates, and lower abundance of water‐stable soil aggregates compared with soils with no stover removal. Increasing N fertilizer rate mitigated losses in total water‐stable aggregates in near‐surface soils related to stover removal. Collectively, however, our results indicated soil structure losses in surface soils due to lower C inputs. Despite no effect on crop yields and overall SOC gains with time using NT management, annually removing stover for 12 yr resulted in a higher risk of wind and water erosion at this NT continuous corn site in the western Corn Belt.

Demand for corn (Zea maysL.) stover as forage or as a cellulosic biofuel has increased the importance of determining the effects of stover removal on biomass production and the soil resource. Our objectives were to evaluate grain yield, soil organic C (SOC), and total soil N (0–150 cm) in a 10‐yr, irrigated, continuous corn study under conventional disk tillage (CT) and no‐till (NT) with variable corn stover removal rates (none, medium, and high). Natural abundance C isotope compositions (δ13C) were used to determine C additions by corn (C4–C) to the soil profile and to evaluate the retention of residual C3–C. After 10 yr of management treatments, mean grain yields were 7.5 to 8.6% higher for NT when stover was removed compared with no stover removal, while grain yields were similar for CT in all stover removal treatments. Turnover of SOC occurred as C3–C stocks were replaced by C4–C in the 0‐ to 120‐cm soil profile. Total SOC and N stocks changed mainly in surface soils (0–30 cm), with no detectable cumulative changes at 0 to 150 cm. Specifically, SOC declined after 10 yr under CT at 0 to 15 cm and was affected by residue management at 15 to 30 cm. Total soil N was greater when no stover was removed (P= 0.0073) compared with high stover removal at 0 to 15 cm. Long‐term NT ameliorated medium stover removal effects by maintaining near‐surface SOC levels. Results support the need to evaluate SOC cycling processes below near‐surface soil layers.

Addition of cover crops and animal manure following corn (Zea maysL.) stover removal for expanded uses may mitigate negative soil property effects of stover removal. We studied the short‐term (3 yr) cumulative impacts of stover removal with and without winter rye (Secale cerealeL.) cover crop or animal manure application on near‐surface (0‐ to 5‐cm depth) soil properties under irrigated no‐till continuous corn on a Hastings silt loam (fine, smectitic, mesic Udic Argiustolls) (<3% slope) near Clay Center, NE. Treatments were irrigation levels (full and deficit), amelioration practices (none, cover crop, or animal manure), stover removal (no removal or maximum removal), and N fertilization (125 or 200 kg N ha−1). Data collected after 3 yr indicate that stover removal (63%) reduced geometric mean diameter of dry aggregates 93%, increased erodible fraction sixfold, and reduced aggregate stability 32% compared with plots without stover removal. Stover removal from plots with cover crop or manure reduced dry aggregate size and stability and increased erodible fraction compared with plots without removal and amelioration practices, indicating that amelioration practices did not offset stover removal effects. Stover removal reduced wet aggregate stability and soil organic C (SOC) concentration in the 0‐ to 2.5‐cm depth, but cover crop or manure mitigated these small reductions. Stover removal did not change water infiltration rates and had small effects on particulate organic matter (POM). Overall, in the short term, cover crop or manure may not provide sufficient protection from raindrop impact and wetting and drying cycles to maintain soil structure, resulting in increased susceptibility to wind erosion. Use of these amelioration practices, however, may offset changes in surface layer wet aggregate stability and SOC after high rates of stover removal in this region.

Soil biotic and abiotic factors strongly influence nitrogen (N) availability and increases in nitrification rates associated with the application of manure. In this study, we examine the effects of edaphic properties and a dairy (Bos taurus) slurry amendment on N availability, nitrification rates and nitrifier communities. Soils of variable texture and clay mineralogy were collected from six USDA–ARS research sites and incubated for 28 d with and without dairy slurry applied at a rate of ∼300 kg N ha−1. Periodically, subsamples were removed for analyses of 2 M KCl extractable N and nitrification potential, as well as gene copy numbers of ammonia‐oxidizing bacteria (AOB) and archaea (AOA). Spearman coefficients for nitrification potentials and AOB copy number were positively correlated with total soil C, total soil N, cation exchange capacity, and clay mineralogy in treatments with and without slurry application. Our data show that the quantity and type of clay minerals present in a soil affect nitrifier populations, nitrification rates, and the release of inorganic N. Nitrogen mineralization, nitrification potentials, and edaphic properties were positively correlated with AOB gene copy numbers. On average, AOA gene copy numbers were an order of magnitude lower than those of AOB across the six soils and did not increase with slurry application. Our research suggests that the two nitrifier communities overlap but have different optimum environmental conditions for growth and activity that are partly determined by the interaction of manure‐derived ammonium with soil properties.

The cob fraction of corn (Zea maysL.) residue has characteristics that reduce concerns associated with residue removal making it a potential biofuel feedstock. The contribution the cob makes to soil C and nutrient dynamics is unknown. A litterbag study was conducted in no‐tillage plots under irrigated and rainfed conditions in eastern Nebraska. Litterbags containing cobs were placed in corn rows on the soil surface or vertically in the 0‐ to 10‐cm soil depth following grain harvest and collected after 63, 122, 183, 246, 304, and 370 d. Samples were analyzed for dry matter, C, N, P, K, S, Ca, Mg, Fe, Mn, Cu, and Zn. Dry matter loss was greater for buried (59% loss rainfed site vs. 64% irrigated site) than surface cobs (49% loss rainfed site vs. 42% irrigated site). Cob N, P, S, content did not change over the duration of the study and these nutrients would play a limited role in nutrition for the subsequent crop. Cob K content declined exponentially over the study suggesting that cob K would be available to the subsequent crop. Cob Ca, Mg, Zn, Fe, Mn, and Cu content increased during the study representing immobilization. With the exception of K, nutrients contained in the cob are immobilized the year following harvest and play a minor role in mineral nutrition of the subsequent crop. As cellulosic conversion technology becomes available cobs represent a feedstock that can be harvested with minor effect on crop nutrient availability.

Abstract: One-pass harvest equipment has been developed to collect corn (Zea mays L.) grain, stover, and cobs that can be used as bioenergy feedstock. Nutrients removed in these feedstocks have soil fertility implication and affect feedstock quality. The study objectives were to quantify nutrient concentrations and potential removal as a function of cutting height, plant organ, and physiological stage. Plant samples were collected in 10-cm increments at seven diverse geographic locations at two maturities and analyzed for multiple elements. At grain harvest, nutrient concentration averaged 5.5 g N kg−1, 0.5 g P kg−1, and 6.2 g K kg−1 in cobs, 7.5 g N kg−1, 1.2 g P kg−1, and 8.7 g K kg−1 in the above-ear stover fraction, and 6.4 g N kg−1, 1.0 g P kg−1, and 10.7 g K kg−1 in the below-ear stover fraction (stover fractions exclude cobs). The average collective cost to replace N, P, and K was $11.66 Mg−1 for cobs, $17.59 Mg−1 for above-ear stover, and $18.11 Mg−1 for below-ear stover. If 3 Mg ha−1 of above-ear stover fraction plus 1 Mg of cobs are harvested, an average N, P, and K replacement cost was estimated at $64 ha−1. Collecting cobs or above-ear stover fraction may provide a higher quality feedstock while removing fewer nutrients compared to whole stover removal. This information will enable producers to balance soil fertility by adjusting fertilizer rates and to sustain soil quality by predicting C removal for different harvest scenarios. It also provides elemental information to the bioenergy industry.

The cob fraction of corn (Zea maysL.) residue has been identified as a potential feedstock for ethanol production. However, the role of the cob in soil and water conservation is largely unknown. A rainfall simulator study was conducted in an irrigated corn field in Nebraska having replicated strips where corn residue was removed (6.0 ± 1.0 Mg ha−1residue remaining, 49.5% cover) or retained (12.9 ± 1.0 Mg ha−1residue remaining, 77% cover). Duplicate plots were installed in each strip and cobs were removed from one and retained in the other. Simulated rainfall was applied for 30 min at a mean rate of 83 mm h−1to plots at antecedent moisture and 24 h later at near saturated soil moisture conditions. Time to initiate runoff, runoff and sediment loss, and water quality parameters were measured. Residue removal reduced the time to initiate runoff (195.9 ± 1.0 vs. 239.5 ± 4.8 s) and increased sediment loss (0.36 ± 0.02 Mg ha−1vs. 0.27 ± 0.01 Mg ha−1). Cob removal reduced time to initiate runoff during the antecedent run but not during the saturated run. Residue removal and rainfall treatment (antecedent vs. saturated) affected runoff water quality parameters (NO3–N concentration, pH, soluble P concentration, and NO3–N loss). Cob removal did not affect runoff, sediment loss, runoff pH, NO3–N, NH4–N, or soluble P loss. Cob removal when adequate stover was retained did not negatively affect erosion and runoff nutrient loss at this site.

Swine (Sus scrofa) manure can serve as a fertilizer source for crop production, but it typically contains more P relative to N than the crop requires, creating the potential for P losses in runoff. A 3-year study was conducted to compare runoff losses of NO3-N, NH4-N, total N, dissolved P, and total P under natural rainfall conditions from no-tillage sorghum plots Sorghum bicolor(L.) Moench receiving inorganic fertilizer, manure from swine fed low-phytate corn (Zea maysL.) diet, or manure from swine fed a traditional corn diet. Runoff (26.5 mm in 1999, 14.2 mm in 2000, and 1.6 mm in 2001), sediment loss (2.9 kg ha−1in 1999, 0.9 kg ha−1in 2000, and 0.4 kg ha−1in 2001), and runoff nutrient losses differed among years but were similar among treatments within a year. Runoff losses of NO3-N (5.3 g ha−1in 1999, 1.0 g ha−1in 2000, and 2.6 g ha−1in 2001), NH4-N (2.9 g ha−1in 1999, 0.6 g ha−1in 2000, and 5.6 g ha−1in 2001), total N (89.7 g ha−1in 1999, 8.4 g ha−1in 2000, and 100.2 g ha−1in 2001), dissolved P (1.5 g ha−1in 1999, 0.5 g ha−1in 2000, and 3.1 g ha−1in 2001), and total P (3.8 g ha−1in 1999, 0.9 g ha−1in 2000, and 3.5 g ha−1in 2001) from these plots represented less than 1% of that applied each year. Although use of low-phytate corn reduces manure P content, it did not decrease runoff P under these no-tillage conditions.

The Soil Management Assessment Framework (SMAF) was developed to assess conservation effects on soil, and uses multiple soil quality indicator measurements to compare soil functioning. Our objective was to develop a SMAF‐compatible scoring equation for soil β‐glucosidase (BG) activity using published data sets representing different soils and management. The resulting equation was an S‐shaped curve: y= a/[1 + bexp(−cx)], where xis the measured BG activity (mg p‐nitrophenol [PNP] released kg−1soil h−1), aand bare constants, and cis a factor modified by soil classification, texture, and climate. Data from a study conducted near Mandan, ND were used to test the model for sensitivity to crop management systems. Soil organic C (SOC) content at the site measured 247 to 687 g kg−1, while BG activity ranged from 33 to 675 mg kg−1h−1Using SMAF, SOC indicator scores ranged from 0.25 to 0.73, while BG activity scores varied from 0.17 to 0.93. As the work progressed, it became apparent that when BG activity values were normalized to the SOC content, the resulting ratio could indicate C sequestration trends, with ratios of 10 to 17 g PNP kg−1SOC h−1reflective of systems in equilibrium. Ratios >17 were mostly from recently altered management systems with SOC contents trending upward, while ratios <10 were generally from soils that were expected to continue to lose soil C. The application of a sensitive C cycling enzyme activity such as BG should improve the SMAF soil quality assessments for soil functions where soil metabolic activity or C‐cycle enzyme activity play a role.

Field application of swine (Sus scrofa) slurry provides essential nutrients for crop production. The N to P ratio for slurry is lower than needed by most crops resulting in P accumulation when applied at N rates required for crop growth. Low phytate corn (Zea maysL.) (LPC) contains similar amounts of total P but less phytate P than traditional corn (TC) resulting in improved P bioavailability and reduced P excretion by monogastric animals. While manure from swine-fed LPC diets has a higher N to P ratio than that from TC diets, field studies comparing crop utilization of nutrients from LPC manure have not been conducted. A field study was conducted to compare N and P utilization by no-tillage rainfed sorghum [Sorghum bicolor(L.) Moench.] receiving three annual surface applications of nutrients (inorganic fertilizer, LPC slurry, and TC slurry) and by irrigated corn receiving one incorporated application of nutrients. Sorghum grain and total dry matter N utilization exhibited a year by treatment interaction but total dry matter N utilization was similar for both manure types in all years (61.2 ± 2.6% for TC and 53.8 ± 2.6% for LPC). Grain P utilization was similar for inorganic fertilizer and manure but differed among years (44.4 ± 7.0% in 1999, 25.1 ± 1.4% in 2000, and 57.0 ± 2.2% in 2001). Corn grain N and P utilization did not differ among nutrient sources in the year of application (50.7 ± 2.4% for N and 40.4 ± 3.0 for P) and increased little in the year following application (62.2 ± 3.0% for N and 50.2 ± 4.5% for P). Crop N and P utilization from LPC manure and TC manure was similar and nutrient guidelines developed for TC swine slurry should also apply for LPC slurry.

Swine (Sus scrofa) slurry contains nutrients essential for crop production but usually contains more P relative to N than is required by most crops, creating the potential for negative environmental impacts. Diet modifications such as low‐phytate corn (Zea maysL.) have resulted in improved bioavailability of P and reduced manure P content. A field study was conducted to compare in situ availability of N and P at two sites. One site received three annual additions of manure from swine fed low‐phytate corn or traditional corn diets or inorganic fertilizer, surface applied to rainfed no‐till sorghum [Sorghum bicolor(L.) Moench]. A second site received a one‐time application and incorporation of the same nutrient treatments to irrigated corn. Nutrient treatments were applied at rates intended to meet crop N needs. At both sites, an in situ soil core resin bag technique was used to determine available N and P during the growing season. Potentially mineralizable N was 70% of applied N and extractable P was 100% of applied P for manure from both diets. Incorporation of swine slurry reduced potentially mineralizable N to 40% the year of application and 30% the year after application and reduced extractable P to 60% the year of application and 40% the year after application for both diets. Modified diets reduced the P content of the manure but not the availability of N or P.

Soils exhibit spatial variability in their properties. One approach for delineating field‐scale variability involves mapping the variation in apparent soil electrical conductivity (ECa). The objectives of this study were to evaluate the physical and chemical soil characteristics that define ECa classification and the association of specific soil microbiological communities with these soil properties. In May 2003, ECa was measured in a field in Buffalo County, Nebraska, and processed to create four ECa zones based on ranges of horizontal and vertical ECa measurements using unsupervised classification. Soil properties (0–90 cm) that showed higher correlations with vertical ECa included total C (r= 0.87), clay (r= 0.83), total dissolved solids (r= 0.68), and depth of topsoil (r= 0.70). These properties influence soil water availability in this field. Soil microbial groups were correlated with different soil C fractions in the 0‐ to 15‐cm depth and were similar across ECa zones. Bacterial (r= 0.85) and actinomycetes (r= 0.71) biomarker concentrations were more highly correlated with fine particulate organic matter (POM) than coarse POM (bacteria r= 0.69 and actinomycetes r= 0.48). In contrast, fungal (r= 0.77) and my‐corrhizal (r= 0.48) biomarker concentrations were correlated only with coarse POM. Given current knowledge of the spatial distribution of POM and aggregates, we hypothesize that microorganisms are also spatially distributed and that fungal groups are closely associated with coarse POM early in the growing season.

13CH4was injected through graphite and tungsten spherical limiters in reproducible TEXTOR discharges. These materials were chosen, as they represent the actual compromise for the plasma facing components in the ITER divertor. 13C was used in order to distinguish injected and intrinsic carbon in the layer deposited on the limiter surface. Shot-by-shot video recordings show a continuous growth of the deposit near the injection hole. A pronounced difference in the 13C deposition pattern on the graphite and tungsten limiters was observed. Post-mortemsurface analysis showed that the ratios of the locally deposited to the injected amount of carbon are 4% for graphite and 0.3% for tungsten. The margins of the carbon layer deposited on tungsten are significantly steeper in comparison with the graphite limiter case. The large difference in the 13C deposition efficiency can be explained by direct reflection of carbon from tungsten and the enhanced sputtering of carbon on the tungsten substrate. Nucleation is suggested to be an important mechanism for carbon deposition on tungsten. Monte Carlo impurity transport calculations by the ERO code reproduce reasonably the experimental results for the graphite limiter.

The aim of this study was to determine the immunomodulatory effects of IL-12, IL-18 and CD154 (CD40 ligand, CD40L) in DNA-vaccination against the classical swine fever virus. Four recombinant plasmids were constructed including the CSFV coding region for the glycoprotein gp55/E2 alone or together with porcine IL-12, IL-18 or CD154 genes. Five groups of four pigs each were immunized intramuscularly (i.m.) three times with the respective constructs. The control group was inoculated with empty plasmid DNA. Eighteen days after the final immunization, the pigs were challenged with a lethal dose of CSFV strain Eystrup and monitored for a further 16 days. This study showed that co-delivery of IL-18 and CD154 induced an earlier appearance of serum antibodies, reduced B-cell deficiency after infection and protected pigs against a lethal CSFV infection. In contrast, co-delivery of IL-12 led to a reduced titer of neutralizing antibodies and protection against a lethal CSFV challenge in comparison to the other pigs and to pigs that were immunized with a gp55/E2 plasmid alone.

To utilize manure P for crop production, P release and plant availability needs to be quantified. An incubation study was conducted to determine P availability from swine (Sus scrofa) and cattle (Bos taurus) feedlot manure in three soils. Treatments for each manure included temperature (11, 18, 25, and 32°C), water regime [constant 60% water‐filled pore space (WFPS) vs. four dry‐down cycles of 60 to 30% WFPS], time, and soils (Catlin silt loam, Sharpsburg silty clay loam, and Valentine fine sand). In another study, synthetic P fertilizer was used to determine the fraction of P that becomes unavailable with time to compare with manure P. Time, soil, and manure application were factors that influenced soil test P and water‐soluble P during incubation. At the low synthetic P fertilizer rate of 6 μg g−1, about 12 kg P ha−1, none of the applied P remained available in the Catlin soil while about one‐third remained plant available in the Sharpsburg soil and two‐thirds in the Valentine soil. At the high P rate, 68 mg kg−1, 38 to 83% of fertilizer P remained available in the three soils. Phosphorus availability was 60 to 100% of applied cattle manure P and 52 to 100% of swine slurry P in the three soils. Phosphorus availability in the Sharpsburg soil was 100% of P in both manure types. Phosphorus availability from manure is high, and manure can be used similar to inorganic P fertilizer in soils where P‐based application is made in areas susceptible to P loss in runoff. In P‐deficient soils, a P availability of 70% should be used.

AbstractLimiter lock systems on the top and the bottom of the TEXTOR vessel are essential elements for experimental investigations of plasma-wall interaction in a tokamak. The lock systems are designed as user facilities that allow the insertion of wall elements (limiter) and tools for diagnostic (electrical probes, gas injection) without breaking the TEXTOR vacuum. The specially designed holder on top of the central carrier and a powerful vacuum pump system permit the exchange of components within ~1 h. Up to ten electrical signals, four thermocouples, and a gas supply can be connected at the holder interface. Between discharges, the inserted component can be positioned radially and turned with respect to the toroidal magnetic field. Additionally, the central carrier is electrically isolated to apply bias voltages and currents up to 1 kV and 1 kA, respectively.An important feature of the lock system is the good access for optical spectroscopic observation of the inserted components in the vicinity of the edge plasma. The whole spectrum from ultraviolet to infrared is covered by spectrometers and filters combined with cameras. Toroidally and poloidally resolved measurements are obtained from the view on top of the probes while the tangential poloidal view delivers radially and toroidally resolved information.A programmable logic controller (Simatic S5) that is operated inside the TEXTOR bunker and from remote locations outside the concrete wall drives all possible features of the lock system.

Swine (Sus scrofa) slurry can serve as an excellent fertilizer source. Application at rates to meet crop N requirements can result in excess soil P due to low manure N/P ratios. Low phytate corn (LPC) (Zea maysL.) stores a greater proportion of P as phosphate than does traditional corn (TC) increasing bioavailability of P in pig feed grain. Improved utilization of feed P reduces P concentration in manure and soil P accumulation. However, the potential effects of LPC manure on other soil properties are not known. Changes in soil attributes over 3 yr were compared for soils receiving LPC manure, TC manure, inorganic fertilizer, and no nutrients in no‐tillage sorghum [Sorghum bicolor(L.) Moench] on a Sharpsburg clay loam (fine, smectitic, mesic Typic Argiudolls). Soil physical properties exhibited values that should not inhibit crop growth. Several soil chemical properties differed by year and treatment. Particulate organic matter (POM), NO3–N, pH, and extractable P increased with manure additions. Extractable P content was greater with addition of TC than LPC manure. Soil chemical properties exhibited values acceptable for crop production, but increasing extractable P increases the potential for environmental contamination. Biological soil properties varied in their response to treatments. Microbial biomass C decreased in the control and increased in manure treatments. The Soil Management Assessment Framework (SMAF) was used to conduct a dynamic soil quality assessment. The SMAF index values were similar across years in the control and inorganic fertilizer treatments and increased in both manure treatments. Manure additions improved soil properties affecting crop production, with P accumulation and the potential for environmental contamination being lower with LPC manure. LPC manure applied at rates to meet crop N requirements will have slower soil P accumulation rates and a lower potential for P contamination of the environment.

Soil biological response to management is best evaluated in field-scale experiments within the context of the soil environment and crop; however, cost-effective methods are lacking to relate these data which span multiple spatial scales. We hypothesized that zones of apparent electrical conductivity (ECa) could be used to integrate soil properties (sampling-site scale), microbial-scale measures of vesicular-arbuscular mycorrhizal (VAM) fungi, and field-scale wheat yields from yield maps. An on-farm dryland experiment (∼250 ha) was established wherein two (∼32-ha) fields were assigned to each phase of a winter wheat (Triticum aestivumL.) – corn (Zea maysL.) – proso millet (Panicum miliaceumL.) – fallow rotation. Each field was mapped and classified into four zones (ranges) of ECa. Soil samples were collected from geo-referenced sites within ECazones and analyzed for multiple soil properties associated with productivity (0–7.5 and/or 0–30 cm). Additionally, VAM fungi were assessed using C16:1(cis)11 fatty acid methyl ester biomarker (C16vam), glomalin immunoassay, and wet-aggregate stability (WAS) techniques (1–2mm aggregates from 0- to 7.5-cm soil samples). Concentrations of C16vamand WAS increased among cropping treatments as: fallow < wheat < corn < millet. Glomalin across crops and replicates, C16vamand WAS in fallow (crop effect removed), soil properties associated with productivity, and wheat yields were negatively correlated with ECaand different among ECazones (P≤ 0.05). Zones of ECaprovide a point of reference for relating data collected at different scales. Monitoring cropping system parameters and profitability, over time, may allow linkage of microbial-scale processes to farm-scale economic and ecological outcomes.

Traditional corn (Zea maysL.) (TC), the primary grain used in swine (Sus scrofa) diets, stores a majority of its P as phytate, which is largely unavailable for digestion by nonruminant animals. Low‐phytate corn (LPC) contains similar amounts of total P but a smaller percentage of P as phytate. When fed to swine, LPC increases P utilization and reduces P content of manure. While differences in P content between manure from animals fed TC and LPC diets have been documented, solubility and lability of manure P have not been compared. Manure P was characterized in manure from swine fed either LPC or TC diets in 2000 and 2001. Total P was lower (20 vs. 34 g kg−1) and N to P ratio was higher (4.5 vs. 3.3) in LPC manure than in TC manure. Manures were sequentially extracted with deionized water, 0.5 MNaHCO3, 0.1 MNaOH, and 1.0 MHCl. Extracts were analyzed for inorganic and total P. Most P (approximately 80%) in the extracts was in the inorganic form. Concentration of P in the water‐extractable fraction was lower for LPC manure (10.2 g kg−1in 2000 and 9.7 g kg−1in 2001) than for TC manure (13.6 g kg−1in 2000 and 17.0 g kg−1in 2001). Percentage of total P in each extract was in the order of: H2O (60%), HCl (22%), NaHCO3(12%), NaOH (8%), and residue (<1%). Total P and distribution of P in extracts indicates swine are able to utilize more P contained in LPC feed but the composition of P excreted in LPC manure is similar to TC manure. Solubility, crop availability, and lability of P in LPC manure should be similar to that of TC manure.

Agronomic researchers are increasingly accountable for research programs and outcomes relevant to producers. Participatory research—where farmers assume leadership roles in identifying, designing, and managing on‐farm field‐scale research—addresses this directive. However, replication is often unfeasible at this level of scale, underscoring a need for alternative methods to estimate experimental error. We compared mean square errors to evaluate: (i) within‐field variability for estimating experimental error (in lieu of replication) and (ii) classified within‐field variability, using apparent electrical conductivity (ECa), for estimating plot‐scale experimental error. Eight 31‐ha fields, within a contiguous section of farmland (250 ha), were managed as two replicates of each phase of a no‐till winter wheat (Triticum aestivumL.)–corn (Zea maysL.)–millet (Panicum miliaceumL.)–fallow rotation. The section was ECa–mapped (approximately 0‐ to 30‐cm depth) and separated into four classes (ranges of ECa). Georeferenced sites (n= 96) were selected within classes, sampled, and assayed for multiple soil parameters (0‐ to 7.5‐ and 0‐ to 30‐cm depths) and residue mass. Within‐field variance effectively estimated experimental error variance for several evaluated parameters, supporting its potential application as a surrogate for replication. Comparison of data from the field‐scale experimental site to that from a nearby plot‐scale experiment revealed that ECa–classified within‐field variance approximates plot‐scale experimental error. We propose using this relationship for a systems approach to research wherein treatment differences and their standard errors, derived from ECa–classified field‐scale experiments, are used to roughly evaluate treatments and identify research questions for further study at the plot scale.

Site‐specific management (SSM) can potentially improve both economic and ecological outcomes in agriculture. Effective SSM requires strong and temporally consistent relationships among identified management zones; underlying soil physical, chemical, and biological parameters; and crop yields. In the central Great Plains, a 250‐ha dryland experiment was mapped for apparent electrical conductivity (ECa). Eight fields were individually partitioned into four management zones based on equal ranges of deep (ECDP) and shallow (ECSH) ECa(approximately 0–30 and 0–90 cm depths, respectively). Previous experiments documented negative correlations between ECSHand soil properties indicative of productivity. The objectives of this study were to examine ECSHand ECDPrelationships with 2 yr of winter wheat (Triticum aestivumL.) and corn (Zea maysL.) yields and to consider the potential applications of ECa–based management zones for SSM in a semiarid cropping system. Within‐zone wheat yield means were negatively correlated with ECSH(r= −0.97 to −0.99) and positively correlated with ECDP(r= 0.79–0.97). Within‐zone corn yield means showed no consistent relationship with ECSHbut positive correlation with ECDP(r= 0.81–0.97). Equal‐range and unsupervised classification methods were compared for ECSH; within‐zone yield variances declined slightly (0–5%) with the unsupervised approach. Yield response curves relating maximum wheat yields and ECSHrevealed a boundary line of maximum yield that decreased with increasing ECSH. In this semiarid system, ECSH–based management zones can be used in SSM of wheat for: (i) soil sampling to assess residual nutrients and soil attributes affecting herbicide efficacy, (ii) yield goal determination, and (iii) prescription maps for metering inputs.

Inorganic nitrogen in the soil is the source of N for non-legume plants. Rapid methods for monitoring changes in inorganic N concentrations would be helpful for N nutrient management. The effect of varying soil moisture content on soil mineral nitrogen, electrical conductivity (EC), and pH were studied in a laboratory experiment. Soil NO3-N increased as soil water-filled pore space (WFPS) increased from 0 to 80 cm3cm−3. At soil moisture levels greater than 80 cm3cm−3, NO3-N concentration declined rapidly and NH4-N concentration increased, likely due to anaerobic conditions existing at higher WFPS levels. Soil pH did not change as soil moisture increased from 100 g kg−1to 400 g kg−1and increased from 6.2 to 6.6 at higher levels of soil moisture. Soil EC was correlated with soil mineral N concentration when measured in situwith a portable EC meter (R2=0.85) or in the laboratory as 1:1 soil water slurries (R2=0.92). Results suggest that EC can be used to rapidly detect changes in soil inorganic N status in soils where salts and free carbonates are not present in large amounts.

Soil C sequestration can improve soil quality and reduce agriculture's contribution to CO2emissions. The long‐term (12 yr) effects of tillage system and N fertilization on crop residue production and soil organic C (SOC) sequestration in two dryland cropping systems in North Dakota on a loam soil were evaluated. An annual cropping (AC) rotation [spring wheat (SW) (Triticum aestivumL.)–winter wheat (WW)–sunflower (SF) (Helianthus annuusL.)] and a spring wheat‐fallow (SW‐F) rotation were studied. Tillage systems included conventional‐till (CT), minimum‐till (MT), and no‐till (NT). Nitrogen rates were 34, 67, and 101 kg N ha−1for the AC system and 0, 22, and 45 kg N ha−1for the SW‐F system. Total crop residue returned to the soil was greater with AC than with SW‐F. As tillage intensity decreased, SOC sequestration increased (NT > MT > CT) in the AC system but not in the SW‐F system. Fertilizer N increased crop residue quantity returned to the soil, but generally did not increase SOC sequestration in either cropping system. Soil bulk density decreased with increasing tillage intensity in both systems. The results suggest that continued use of a crop‐fallow farming system, even with NT, may result in loss of SOC. With NT, an estimated 233 kg C ha−1was sequestered each year in AC system, compared with 25 kg C ha−1with MT and a loss of 141 kg C ha−1with CT. Conversion from crop‐fallow to more intensive cropping systems utilizing NT will be needed to have a positive impact on reducing CO2loss from croplands in the northern Great Plains.

Understanding long‐term management effects on soil properties is necessary to determine the relative sustainability of cropping systems. Soil physical, chemical, and biological properties were measured in a long‐term cropping system study in the Western Corn Belt. Properties were evaluated after 16 yr in four crop sequences [continuous corn (zea maysL.) (CC), corn–soybean [Glycine max. (L.)] (C–SB), corn–oat (Avena sativaL.) + clover (80% sweet clover [Melilotus officinalisL.] and 20% red clover [Trifolium pratenseL.])–grain sorghum [(Sorghum bicolor(L.) Moench)–soybean (C–OCL–SG–SB), and corn–soybean‐grain sorghum–oat + clover (C–SB–SG–OCL)] each at three N fertilization rates (ZERO, LOW, and HIGH) to a soil depth of 30.5 cm on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudolls). Nitrogen fertilization had a greater impact on soil properties than crop sequence, with management effects most pronounced at 0 to 7.6 cm. Increased N rate resulted in greater organic C, total N, and particulate organic matter (POM), but lower soil pH. Increased N rate also reduced microbial biomass by ∼20% between the HIGH and ZERO N‐rate treatments. The C–SB–SG–OCL sequence possessed more potentially mineralizable N (PMN) (57 vs. 46 kg ha−1for average of CC and C–SB) and a higher percentage of POM present as soil organic matter (17.1% for the C–SB–SG–OCL sequence vs. 13.9% for other sequences). Within the context of soil functions and cropping system performance, results from this study indicate the C–SB–SB–OCL sequence enhanced nutrient cycling efficiency, while N fertilization resulted in a trade‐off between its positive effect on biological productivity and negative effect on nutrient cycling efficiency.

Management practices for conversion of land supporting perennial vegetation to crop production are needed. Effect of haying (hayed or not hayed), cropping (annual crop with no‐tillage, minimum tillage, or conventional tillage, and no‐tilled perennial crop), and N fertilization (0 or 67 kg ha−1) on soil properties were measured in 1995 and 1997 at a Conservation Reserve Program (CRP) site in North Dakota having an Amor loam (Fine‐loamy, mixed, superactive, frigid, Typic Haplustoll) soil in a spring wheat (Triticum aestivumL.), winter wheat, pea (Pisum sativumL.) rotation. Soil physical properties were not affected negatively by the management practices used. Haying and tillage practices influenced soil chemical properties. Organic C and total N content declined (1.2 Mg ha−1for C and 0.1 Mg ha−1for N) from 1995 to 1997. In hayed plots, organic C and total N increased as tillage intensity decreased while in non‐hayed plots no pattern was observed. Haying and tillage influenced soil biological properties. Potentially mineralizable N at 0 to 0.05 m increased as tillage intensity decreased in 1997. In the 0.05‐ to 0.15‐m depth, potentially mineralizable N increased from 1995 (118 kg ha−1) to 1997 (146 kg ha−1). By 1997, soil properties in hayed plots responded to cropping practices similarly to those in established cropping systems in this region. In non‐hayed plots, management induced patterns had not developed by 1997. Haying, conservation tillage, and annual cropping are viable approaches for converting land to annual crop production.

Traditional sampling methods are inadequate for assessing the interrelated physical, chemical, and biological soil properties responsible for variations in agronomic yield and ecological potentials across a landscape. Recent advances in computers, global positioning systems, and large‐scale sensors offer new opportunities for mapping heterogeneous patterns in soil condition. We evaluated field‐scale apparent electrical conductivity (ECa) mapping for delineating soil properties correlated with productivity and ecological properties. A contiguous section of farmland (250 ha), managed as eight fields in a no‐till winter wheat (Triticum aestivumL.)–corn (Zea maysL.)–millet (Panicum miliaceumL.)–fallow rotation, was ECamapped (≈0‐ to 30‐cm depth). A geo‐referenced soil‐sampling scheme separated each field into four ECaclasses that were sampled (0‐ to 7.5‐ and 7.5‐ to 30‐cm depths) in triplicate. Soil physical parameters (bulk density, moisture content, and percentage clay), chemical parameters (total and particulate organic matter [POM], total C and N, extractable P, laboratory‐measured electrical conductivity [EC1:1], and pH), biological parameters (microbial biomass C [MBC] and N [MBN], and potentially mineralizable N), and surface residue mass were significantly different among ECaclasses (P≤ 0.06) at one or both depths (0–7.5 and 0–30 cm). Bulk density, percentage clay, EC1:1, and pH were positively correlated with ECa; all other soil parameters and surface residue mass were negatively correlated. Field‐scale ECaclassification delimits distinct zones of soil condition, providing an effective basis for soil sampling. Potential uses include assessing temporal impacts of management on soil condition and managing spatial variation in soil‐condition and yield‐potential through precision agriculture and site‐specific management.

Spring wheat (Triticum aestivumL.) is generally produced in the northern Great Plains using tillage and a crop–fallow system. This study evaluated the influence of tillage system [conventional‐till (CT), minimum‐till (MT), and no‐till (NT)] and N fertilizer rate (0, 22, and 45 kg N ha−1) on grain N, grain N removal from cropping system, and changes in residual postharvest soil NO3–N during six rotation cycles of a dryland spring wheat–fallow (SW–F) cropping system. Grain N concentration increased with increasing N rate and was higher with CT (33.3 g kg−1) than with NT (32.3 g kg−1) at 45 kg ha−1N rate. Grain N removal per crop was greater with CT (70 kg N ha−1) and MT (68 kg N ha−1) than with NT (66 kg N ha−1) and tended to increase with increasing N rate, but varied with rotation cycle. Total grain N removal in six rotation cycles was in the order: CT > MT > NT. Total grain N removal by six SW crops was increased by N fertilization, with only 21 and 17% of the applied N removed in the grain for the 22 and 45 kg ha−1N rates, respectively. Postharvest soil NO3–N levels in the 150‐cm profile varied with N rate and rotation cycle, with residual NO3–N increasing during consecutive dry crop cycles. In contrast, some leaching of NO3–N below the SW root zone may have occurred during wetter crop cycles. Soil profile NO3–N levels tended to be greater with CT and MT than with NT. Variation in precipitation during rotation cycles and N fertilization impacted grain N removal and residual soil NO3–N levels more than tillage system within this SW–F cropping system.

Increasing the frequency of cropping in dryland systems in the northern Great Plains requires the application of N fertilizer to maintain optimum crop yields. A 12‐yr annual cropping rotation [spring wheat (Triticum aestivumL.)–winter wheat–sunflower (Helianthus annuusL.)] under dryland conditions was monitored to determine the influence of tillage system [conventional till (CT), minimum till (MT), and no till (NT)] and N fertilizer rate (34, 67, and 101 kg N ha−1) on N removed in grain and annual changes in postharvest soil NO3–N. Nitrogen removal in the grain increased with increasing N rate in most years. Total grain N removal was lowest with NT at the lowest N rate and highest with NT at the highest N rate compared with CT. Total grain N removal after 12 cropping seasons was 144, 84, and 61% of the total N applied for the 34, 67, and 101 kg N ha−1fertilizer rates, respectively. Residual soil NO3–N levels were not affected by N rate or tillage system in the first 3 yr, but they increased significantly following consecutive drought years. Residual NO3–N in the 150‐cm soil profile tended to be higher with CT and MT than with NT. Soil NO3–N movement below the crop root zone may have occurred in 1 or 2 yr when precipitation was above average. Results indicate that NT, with annual cropping, may reduce the quantity of residual soil NO3–N available for leaching compared with MT and CT systems.