Crosby Silt Loam Research Articles

Long-Term Effects of Single Application of Biochar on Physical and Hydrological Properties of Crosby Silt Loam Soil in Central Ohio, USA

Long-Term Effects of Single Application of Biochar on Physical and Hydrological Properties of Crosby Silt Loam Soil in Central Ohio, USA

Long-Term Effects of Biochar on Soil Physical and Hydrological Properties in Crosby Silt Loam in Central Ohio, USA

Long-Term Effects of Biochar on Soil Physical and Hydrological Properties in Crosby Silt Loam in Central Ohio, USA

Vehicular traffic effects on hydraulic properties of a Crosby silt loam under a long-term no-till farming in Central Ohio, USA

Changes in soil properties have been reported under several long-term no-till (NT) studies, however, the magnitude of changes in soil hydraulic properties with the use of new generation heavy machinery under NT farming is not widely documented on a long term basis. Therefore, a site under long-term NT production system was selected, where a known compaction force of 0 Mg axle load (control, C-0), two (C-2) and four (C-4) passages of 2.5 Mg water wagon axle load was applied to cover the entire plot for 20 consecutive years to assess changes in soil hydraulic properties at a site in the Central Ohio, USA. The field was under NT-based corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation since 1997. An additional three plots were established in a natural woodlot (30 m adjacent from the compaction field plots) as the baseline to compare the impact of compaction under a NT managed agricultural soil. Total of 24 (three per treatment for each depth) undisturbed soil cores was collected in November 2016 from 0 to 10 cm and 10 to 20 cm depths by using a hammer based manual core sampler for determination of soil hydraulic properties (soil water retention-SWR, plant available water), and to measure pore size distribution and air porosity. Results revealed that vehicular traffic induced significant changes in SWR at 0 and -6 kPa soil water potential (ψ). A reduction of SWR by 7.9 to 3.2% under C-2, by 6.6 to 0% under C-4 and by 2.4 to 0.8% under C-0 was observed at -6 to -300 kPa compared to that for the wooded soil. The soil under C-4 treatment had the lowest air porosity. Furthermore, the volume of pores with diameter >10 μm under C-4 was reduced by 8.3% compared to C-0 and by 7.6% compared to the wooded soil. Soil water content (transmission, plant available and residual water) followed a trend similar to that of the pore volume distribution for soil subjected to vehicular traffic-induced compaction. The data supports the conclusion that two or four passages of 2.5 Mg axle load of vehicular traffic under NT farming moderately changed SWR, plant available water, pores size distribution and air porosity compared to that of the wooded soil. However, the magnitudes of changes in soil hydraulic properties due to vehicular passages of 2.5 Mg axle load were not consistent under the NT production system. Thus, further monitoring of the impacts of compaction on soil hydraulic properties particularly on some other properties (e.g., water infiltration and air permeability) across the years is needed for better assessment of the relationships between crop production and soil hydraulic properties as well as soil resilience.

Long-Term Effects of Different Passages of Vehicular Traffic on Soil Properties and Carbon Storage of a Crosby Silt Loam in USA

The passage of vehicles with heavy axle loads causes soil compaction, and this adversely affects soil properties and crop yield. The adverse effects can persist for several years due to significant changes in key soil properties. However, the mechanisms of the aforementioned effects are not well understood for conservation agriculture (CA) (e.g., no-till (NT)) wherein the use of heavy machinery is considerably common. Therefore, known compaction forces (0 Mg load for compaction (NT-0, control), two passages of 2.5 Mg water wagon axle load (NT-2), and four passages of 2.5 Mg water wagon axle load (NT-4)) were applied to all the plots annually for 20 consecutive years. The experiment was established in 1997 at the Waterman Agricultural and Natural Resources Laboratory (WANRL), Ohio State University, Columbus, Ohio. Each treatment was replicated thrice. Soil samples were obtained in November 2016 to determine the effects of variations in the axle load and vehicular passages on carbon (C) and nitrogen (N) storage and selected soil properties of a Crosby silt loam soil under NT-based corn-soybean rotation with residue retention in Central Ohio, USA. Three locations were also randomly selected in an adjoining natural woodlot (WL) soil plot and sampled (30 m away from the compaction field) to compare the effects of vehicular traffic on soil under NT with WL soil. Results revealed that soil bulk density (ρb) and total porosity at 0–10 and 10–20 cm depths were not affected by the passages of vehicular traffic for 20 years under the NT system. The penetration resistance (PR) (1.86 and 2.03 MPa at 0–10 and 10–20 cm soil depths, respectively) was significantly higher under NT-4 compared with that under other treatments. Saturated hydraulic conductivity at 0–10 and 10–20 cm soil depths ranged from 19.7 to 31.4 and 18.5 to 29.5 mm d−1, respectively, across all the treatments. The proportion of macroaggregates (> 0.25 mm) and microaggregates (< 0.25 mm), mean weight diameter and geometric mean diameter of aggregates, pH, electrical conductivity, and C and N contents and storage did not differ significantly between the treatments at either of the sampling soil depths. The data indicated that 2 to 4 passages of vehicles with 2.5 Mg of axle load did not cause significant compaction of the Crosby silt loam under NT compared with that under natural WL. Therefore, the continuous cultivation of row crops with NT and residue retention is feasible with passages of vehicular traffic for well-drained soils in Central Ohio.

Long‐term effects of vehicular passages on soil carbon sequestration and carbon dioxide emission in a no‐till corn‐soybean rotation on a Crosby silt loam in Central Ohio, USA

AbstractResearch information from a systematic planned study on the effects of vehicular passages and axle load on soil carbon dioxide (CO2) fluxes and soil carbon (C) sequestration under long‐term NT farming is scanty. Therefore, the present study was conducted on an on‐going 20‐year experiment to assess the impacts of variable vehicular passages of a low axle load on soil CO2 emission and soil C sequestration from a no‐till (NT) managed corn (Zea mays L.)–soybean (Glycine max Linneo) rotation in comparison with that a soil under woodlots (soils under natural wooded plantation). The experimental treatment consisted of an empty wagon [0 Mg load for compaction (C‐0; control)] compared with 2 (C‐2) and 4 (C‐4) passages of 2.5 Mg water wagon axle load, applied to the entire plot every year during April/May for 20 consecutive years. Soil samples were obtained in November 2016 to determine the effects of various vehicular passages on C and nitrogen (N) contents and CO2 emissions. Soil CO2 fluxes were measured from November 16, 2016, to May 30, 2017, on the bi‐weekly (November to December and April to May) and monthly (January to March) basis by using high‐density polyvinyl chloride static gas chambers. The soil CO2 fluxes ranged from –1.05 to 9.03 g CO2 m−2 d−1. The lowest soil CO2 fluxes were observed in December coinciding with the minimum soil temperature. In general, daily soil CO2 fluxes were higher under C‐0 than those under other treatments. Vehicular traffic and axle load reduced the cumulative emission of CO2 by 22.6 and 29.8% under C‐2 and C‐4, respectively, compared with that under C‐0 (6.09 Mg ha−1). Soil and air temperatures had a significant positive correlation with the diurnal fluxes of soil CO2 in all the treatments except that under C‐4. Electrical conductivity, soil C and N contents and pools did not differ significantly among the treatments. Further, 2 to 4 passages of vehicles with 2.5 Mg of axle load decreased the soil CO2 emission on Crosby silt loam under NT as compared to that under the control. Therefore, continuous cultivation of row crops with moderate trafficking under NT and residue retention is recommended, and it also reduces the potential of soil CO2 emission while improving the soil organic C pools of well‐drained soils of Central Ohio.

Towards a standard technique for soil quality assessment

A soil quality index (SQI) that integrates key soil attribute information would be beneficial in minimizing spillover effects of indiscriminate soil management such as shortages in food, water, energy and abate adverse repercussions of climate change. In this study, a new SQI that synthesizes soil attributes is developed using partial least squares regression (PLSR), and compared with crop yields. The field data were acquired in the year 2013 from 5 different on-farm sites within Ohio, USA that were under Natural Vegetation (NV), No-Till (NT), and Conventional Till (CT) management. The data shows that Pw (Pewamo silty clay loam) soil under NV land use had a higher quality, than GWA (Glynwood silt loam), kbA (Kibbie fine sandy loam), CrA (Crosby silt loam), and CtA (Crosby Celina silt loams) soil; whereas CT managed soil had Pw>CrA>kbA>CtA>GWA. The soil bulk density (ρb), electrical conductivity (EC), available water capacity (AWC) and soil organic carbon (SOC) greatly influenced the SQI especially at the soil surface. The SQI and yield were highly correlated, with that for corn (Zea mays L.) being 64%; whereas soybean (Glycine max (L.) Merr.) was 100%. This finding is of special relevance because it explicates the interconnection between on-farm soil quality vis-à-vis crop yields by objectively blending soil attributes from different management scenarios and soil layers. Future research will investigate techniques for integrating this SQI with socio-economic indicators of agro-ecosystem sustainability.

A standardized soil quality index for diverse field conditions

Understanding the nexus between soil quality and productivity is constrained by data artifacts, compounded by limitations of the existing models. Here, we explore the potential of 4 regression methods (i.e., Reduced Regression (RR), SIMPLS, Principal Component Regression (PCR), and Partial Least Squares Regression (PLSR)), to synthesize 10 soil physical and chemical properties acquired from 3 major management practices and different soil layers, into an unbiased soil quality index (SQI) capable of evaluating soil functions (e.g., biomass production). The data was acquired from privately owned fields within the state of Ohio, USA, at the following land use and management sites: natural vegetation (NV) or woodlands, conventional till (CT), and no-till (NT). The soils were sampled at similar landscape positions (i.e., summit) at depth intervals of 0–10, 10–20, 20–40 and 40–60cm, and analyzed for bulk density (ρb), carbon/nitrogen (C/N) ratio, soil organic C (SOC), total N (TN), available water capacity (AWC), pH and electrical conductivity (EC). Preliminary analyses revealed the PLSR method as the most robust. The PLSR Variable Importance of Projection (VIP) was calculated, transformed into the SQI score and compared with yield data. SOC, ρb, C/N and EC were identified as the major variables influencing soil quality status. The data shows that the quality of Pewamo silty clay loam (Pw) soil was higher than Crosby Celina loams (CtA), Kibbie fine sandy loam (kbA), Glynwood silt loam (GWA) and Crosby silt loam (CrA), respectively. In 2012, the mean SQI was 42.9%, with corn and soybean yields of 7 and 2Mg/ha. The R2 of SQI versus yield was 0.74 for corn (Zea mays L.), and 0.89 for soybean (Glycine max (L.) Merr.). Future studies will investigate techniques for mapping this SQI.

Comparison of greenhouse gas emissions monitored with a photoacoustic infrared spectroscopy multi-gas monitor and a gas chromatograph from a Crosby silt loam

The photoacoustic infrared spectroscopy multi-gas monitor (PAS) method is a promising technique for in situ monitoring of gaseous emissions in agricultural soils. However, few studies have been done to evaluate its accuracy and precision under different management practices, soil and environmental conditions. Thus, the objectives of this study were to provide information regarding the PAS method, and compare it to the gas chromatograph (GC) method's results for GHG emission, and to discuss the PAS and GC methods in terms of operation simplicity and time, precision, cost and efficiency of gaseous flux measurements. Emissions of CO2 by PAS and GC methods were within 1.4 to 7.5% and 0.3 to 5.1% of each other in 2012 and 2013, respectively. Similarly emissions of N2O measured by PAS and GC methods for 2012 and 2013 were within 18.4 to 30.7%, and 3.4 to 10.6% of each other, respectively. The accuracy and precision of GHG emissions with the PAS and GC methods are similar and comparable. For field measurement of GHG emission, the PAS method is better than the GC method in terms of ease of operation, time required, cost and sample variation.

Soil quality index of a crosby silt loam in central Ohio

• We assessed soil quality index using the scoring function analysis. • The saturated hydraulic conductivity was the key soil physical indicator for SQI. • The soil organic carbon was the key soil chemical indicator for SQI. • The SQI was significantly correlated with corn yield. Soil quality index (SQI) assessment is an important tool for evaluating land use and soil management practices in agroecosystems. Thus, the objectives of this research were to assess SQI using the scoring function analysis for different agricultural management practices, and to evaluate the effects of tillage and drainage systems on SQI of a crosby silt loam in central Ohio. Treatments included two tillage: no-till (NT), chisel tillage (CT), and two drainage factors: drainage ( D ) and no-drainage (ND). Three main steps were followed for the SQI assessment: (1) identification of the minimum data set of indicators, (2) indicator interpretation, and (3) integration of all indicator scores into one SQI value. The data showed that saturated hydraulic conductivity ( K sat ) and soil organic carbon (SOC) concentration were the most discriminating and key indicator for SQI assessment. The SQI was not significantly affected by subsurface drainage treatment ( D = 0.69 and ND = 0.70, P = 0.763). The results imply that long-term NT and subsurface drainage may not significantly alter the SQI because of the effects of weather condition, crop rotation, and weed-control. The SQI was significantly correlated with corn yield ( R = 0.62, P < 0.05; n = 12), suggesting that the SQI is an effective and useful tool for assessing the agronomic productivity. The SQI computed by the method described is a useful tool to synthesize the soil and agronomic information.

Impacts of Biochar and Other Amendments on Soil-Carbon and Nitrogen Stability: A Laboratory Column Study

There have been a large number of recent soil incubation studies examining the potential of biochar as a soil amendment tool for enhancing soil fertility and C sequestration. However, direct comparisons of biochar’s effects to that of other nontraditional soil amendments are lacking. In addition, most soil incubation studies with biochar examined gaseous emissions in closed systems that do not allow for water flow through (i.e., leaching). Thus, three amendments—humic acid (HA), water treatment residual (WTR), and biochar produced from oak at 650°C were incubated with Crosby silt-loam (fine, mixed, active, mesic Aeric Epiaqualfs) soil at a rate of 1% (w/w) in triplicated soil-columns. Effects of biochar and the other amendments on gaseous (CH₄, CO₂, and N₂O) emissions and leaching of total organic C (TOC), NO₃⁻, and NO₂⁻ were simultaneously monitored over a 257-d incubation period. Biochar-amended soil had reduced mean cumulative leaching of TOC by 30%, nitrate by 33%, and nitrite by 34%, compared to the control (control: 93, 75, and 2 mg kg⁻¹ for TOC, nitrate, and nitrite, respectively), likely due to sorption by the biochar. The WTR-amended soil exhibited similar leaching trends; however, HA-amended soil leached significantly greater (p < 0.05) TOC than either WTR or biochar. No amendments had any significant impact on gaseous emissions due to the high variability within each treatment. We hypothesize that the labile C and N compounds, which otherwise become emitted by microbial activity and produced significant differences in treatments, were probably leached out from the system as both leaching and gaseous sampling events took place at the same time due to the experimental settings employed. Thus, it is probable that the labile C and N compounds most likely to be oxidized and emitted in gaseous forms in any closed system incubations were either protected via mineral sorption or lost as leachate in the open column system in the present experiment. Considering both leaching and gaseous losses, C and N mean residence times (MRT) of 50 and 15 yr were calculated for the biochar-amended soil compared to 28 and 12 yr for the control, and 518 and 1.5 million years considering only gaseous losses, respectively. These findings show that estimates of soil-C and N stability that do not take into account aqueous losses of these elements (leaching) may tremendously overestimate C and N-MRT. Comparison with a field study using the same soil and amendment types suggests that analyses from laboratory incubation may serve as reliable proxies for trends in field soil responses to amendments.

Tillage and drainage management effect on soil gas diffusivity

Subsurface drainage influences the gaseous exchange in soils and improves crop productivity. Thus, gas diffusivity were monitored on a long-term drainage/tillage experiment established in 1994 at the Waterman Farm of The Ohio State University, Columbus, OH, USA. Specific objectives of the present study were to compare the gas diffusion and physical properties (bulk density and water retention) of soils managed under no-till (NT) and chisel-tillage (CT) systems with subsurface drainage management. Soils of the experimental site are classified as Crosby silt loam (Fine, mixed, mesic, Aeric Ochraqualf; fine, mixed, mesic, Typic Argiaquall). Treatments included: NT with tile drainage (NT-D), NT with no-drainage (NT-ND), CT with drainage (CT-D), and CT with no-drainage (CT-ND). The research site has been under continuous corn (Zea mays L.) cropping system since the start of the experiment. Intact core samples (n=36) from 0–10, 10–20, and 20–30cm depths were collected during November 2011 in three replicated plots of NT and CT systems under D and ND treatments. Results from this study showed that drainage treatments significantly influencing the relative gas diffusion (Dp/D0), is defined as the ratio of the soil gas diffusion coefficient to that in free air. The Dp/D0 for NT soils (23.1×10−3) were 26% higher than those for CT (18.3×10−3). Similarly, the ratio was 22% higher for soils under D (25.0×10−3) compared with those under ND (20.5×10−3). The tillage by drainage interaction was also significant for the Dp/D0 at the 0–10cm depth. Corn yield was positively correlated with relative gas diffusion (R2=0.36). It can be concluded from this study that NT system under drainage management can improve the gas diffusivity, enhance the soil structure and increase crop yield.

Effects of long-term tillage and drainage treatments on greenhouse gas fluxes from a corn field during the fallow period

Advance tillage research suggests that tillage decreases soil fertility and adversely affects the environment. The objective of this research was to estimate the greenhouse gas (GHG) flux vis-à-vis GHG production potential at different soil depths (0–100cm) from tillage and drainage management treatments during the fallow period (October 2009 to April 2010) in a continuous (since 1994) corn (Zea mays) growing field at the Waterman farm in central Ohio. The Crosby silt loam (Aeric ochraqualf) soil of the experimental farm has been managed with the same practice since 1994 with two tillage sub-factors: no till (NT) and chisel tillage (T) and two drainage sub-factors: tile drainage (D) and no-drainage (ND). The fallow period was from the middle of October to the middle of April. The field was under snow cover during the middle of December to the first week of March. GHG fluxes (CO2, CH4 and N2O) were significantly lower during the snow cover period. This study suggests that the CO2 flux was significantly higher from T and D plots compared to NT and ND plots. Neither CH4 nor N2O fluxes were influenced by tillage or drainage. The CO2 flux from T+D treatments was significantly higher (25.98–398.65mgm−2h−1) throughout the fallow period. Significantly higher N2O flux (87.07–125.76μgm−2h−1) was recorded from all treatments during the thawing period in the first week of March. Considering that the total C flux involves only the loss from the SOC stock, as much as 3.05% of the total SOC stock (1.23MgCha−1) was lost during the fallow period from T–D plots as CO2 and CH4. Analysis of soil from different soil depths suggests that the CO2 and N2O emissions from soil were mostly dependent on production potential at 0–10cm and 0–30cm of soil depths, respectively. However, there was no such trend for CH4 emissions from soil.

Twenty two years of tillage and mulching impacts on soil physical characteristics and carbon sequestration in Central Ohio

Knowledge about the changes in carbon (C) concentration and mechanical and hydrological properties under different tillage and mulch treatments is necessary to assess the feasibility of adoption of conservation practices for sustaining productivity and protecting the environment. It is widely recognized that no-till (NT) farming conserves soil and water, saves energy, improves the environment and enhances soil quality. However, the magnitude and direction of tillage and mulch-induced changes are soil and site specific. Therefore, a field study was conducted on a long-term on-going experiment to evaluate the effects of three tillage {NT, ridge till (RT) and plow till (PT)} and three mulch rates (0, 8 and 16Mgha−1yr−1) on soil physical properties and total C concentrations in macro (250–2000μm) and micro (<250μm) aggregates. The experiment was initiated in 1989 on a Crosby Silt Loam (Stagnic Luvisol) in Central Ohio. The data show positive effects of mulch rate on soil physical attributes and total C concentration under NT. Significant (P<0.05) variations in bulk density (ρb) and penetration resistance (PR) along with their interactions were observed among tillage and mulch treatments. The water infiltration capacity (ic) ranged from 1.2cmh−1 (PT) to 4.6cmh−1 (NT). With increase in mulch rate from 0 to 16Mgha−1, saturated hydraulic conductivity (Ks) for 0–10cm depth increased from 1.78 to 3.37, 1.57 to 2.95 and 1.37 to 2.28 (×10−2cmh−1) under NT, RT and PT, respectively. Analyses of variance indicate significant interaction between tillage, mulch and soil depth for the Ks. Similarly, the mean weight diameter (MWD, mm) increased from 0.36 to 1.21, 0.29 to 0.84, 0.25 to 0.62 under NT, RT and PT, respectively, with increase in mulch rate from 0 to 16Mgha−1. Total C (%) increased from 1.26 to 1.50, 1.20 to 1.47 and 0.95 to 1.10 under NT, RT and PT, respectively, with increase in mulch rate from 0 to 16Mgha−1. Macro-aggregates (250–2000μm) contained 30% more total C and N concentrations than microaggregates (<250μm). Under NT, the soil showed a higher structural stability than PT with significantly lower compaction values. Further, with NT the soil showed a higher capacity to retain C than PT. Thus, long term use of NT along with mulch application enhances soil quality with respect to soil mechanical, hydrological properties along with carbon concentration in the soil.

Nitrous oxide and methane emissions from long-term tillage under a continuous corn cropping system in Ohio

Nitrous oxide (N 2O) and methane (CH 4) emitted by anthropogenic activities have been linked to the observed and predicted climate change. Conservation tillage practices such as no-tillage (NT) have potential to increase C sequestration in agricultural soils but patterns of N 2O and CH 4 emissions associated with NT practices are variable. Thus, the objective of this study was to evaluate the effects of tillage practices on N 2O and CH 4 emissions in long-term continuous corn ( Zea mays) plots. The study was conducted on continuous corn experimental plots established in 1962 on a Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf) in Ohio. The experimental design consisted of NT, chisel till (CT) and moldboard plow till (MT) treatments arranged in a randomized block design with four replications. The N 2O and CH 4 fluxes were measured for 1-year at 2-week intervals during growing season and at 4-week intervals during the off season. Long-term NT practice significantly decreased soil bulk density ( ρ b) and increased total N concentration of the 0–15 cm layer compared to MT and CT. Generally, NT treatment contained higher soil moisture contents and lower soil temperatures in the surface soil than CT and MT during summer, spring and autumn. Average daily fluxes and annual N 2O emissions were more in MT (0.67 mg m −2 d −1 and 1.82 kg N ha −1 year −1) and CT (0.74 mg m −2 d −1 and 1.96 kg N ha −1 year −1) than NT (0.29 mg m −2 d −1 and 0.94 kg N ha −1 year −1). On average, NT was a sink for CH 4, oxidizing 0.32 kg CH 4-C ha −1 year −1, while MT and CT were sources of CH 4 emitting 2.76 and 2.27 kg CH 4-C ha −1 year −1, respectively. Lower N 2O emission and increased CH 4 oxidation in the NT practice are attributed to decrease in surface ρ b, suggesting increased gaseous exchange. The N 2O flux was strongly correlated with precipitation, air and soil temperatures, but not with gravimetric moisture content. Data from this study suggested that adoption of long-term NT under continuous corn cropping system in the U.S. Corn Belt region may reduce GWP associated with N 2O and CH 4 emissions by approximately 50% compared to MT and CT management.

Long-term tillage effects on soil carbon storage and carbon dioxide emissions in continuous corn cropping system from an alfisol in Ohio

The experiment designed to quantify the effects of long-term tillage practices on soil organic carbon (SOC) storage and CO 2 emissions, was conducted on long-term tillage and continuous corn ( Zea mays L.). The experimental plots were established in 1962 on a Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf) in Ohio. It consisted of moldboard plow till (MT) chisel till (CT), and no-till (NT) laid out in a randomized block design with four replications. After 43 yrs of continuous corn, the pool of SOC in the top 30 cm depth was significantly greater under NT (80.0 ± 3.7 Mg C ha −1) than under CT (45.3 ± 1.7 Mg C ha −1) and MT (44.8 ± 3.7 Mg C ha −1). A large proportion (68–74%) of SOC, in the 0–30 cm depth originated from corn residues (C4-C). On average, MT, CT and NT treatments sequestered C4-C in the top 30 cm at a rate of 0.73, 0.71 and 1.37 Mg ha −1 yr −1. The average daily CO 2 fluxes (g CO 2-C m −2 d −1) were greater under MT (2.14) and CT (2.07) than under NT (1.61). In addition, the daily CO 2 fluxes were highest in summer (2.62–3.77 g CO 2-C m −2 d −1), the lowest in winter (0.75–0.87 g CO 2-C m −2 d −1), and were positively correlated with air ( R 2 = 0.78, P < 0.01) and soil temperatures in the top 20 cm ( R 2 = 0.76, P < 0.01) and negatively with soil water content ( R 2 = 0.57, P < 0.05). Tillage management had a significant influence on average daily CO 2 fluxes during summer and autumn but not during winter and spring. Annual CO 2 emissions calculated by extrapolating daily CO 2 fluxes were significantly higher under MT (6.6 ± 0.3 Mg CO 2-C ha −1 yr −1) and CT (6.2 ± 0.4 Mg CO 2-C ha −1 yr −1) than under NT (5.5 ± 0.5 Mg CO 2-C ha −1 yr −1; LSD = 0.25 Mg CO 2-C ha −1 yr −1). These results indicated that, during the growing season, NT reduced CO 2 emissions by an average of 0.7 and 0.6 Mg C ha −1 yr −1 compared to MT and CT, respectively.

Mulching effects on selected soil physical properties

The suitability of soil for sustaining plant growth and biological activity is a function of physical and chemical properties, many of which depend on the quantity and quality of soil organic matter. The equilibrium level of soil organic matter depends on the balance between input through plant residues and other biosolids and output through decomposition, erosion and leaching. However crop residues have numerous competing uses such as fodder, fuel and construction material. Similarly, costs are incurred in its application and these increase with mulch level. Therefore, it is necessary to establish optimum mulch application rates. Empirical data on soil organic matter in relation to input residue of residue are needed to understand management impact on soil quality. Long-term field plots were setup in 1989 to study the effects of mulching on soil physical properties of a Crosby silt loam (Aeric Ochraqualf or stagnic luvisol) soil in central Ohio. Treatments included mulch application at 0, 2, 4, 8 and 16 Mg ha −1 year −1 without crop cultivation. Soil samples from 0 to 10 cm depth were obtained in December 2000, 11 years after establishing the plots. The results demonstrated that mulch rates significantly increased available water capacity by 18–35%, total porosity by 35–46% and soil moisture retention at low suctions from 29 to 70%. At high suctions, no differences in soil moisture content were observed between mulch levels. Soil bulk density was not affected by mulch rate. High correlations were obtained between mulch rate and soil mean weight diameter ( R 2 = 0.87) and percent stable aggregates ( R 2 = 0.84). The study was able to determine optimum mulch rates of 4 Mg/ha for increased porosity and 8 Mg/ha for enhanced available water capacity, moisture retention and aggregate stability.

Impacts of Long‐Term Wheat Straw Management on Soil Hydraulic Properties under No‐Tillage

Crop residues left on the soil surface conserve soil and water, but residue impacts on near‐surface soil hydraulic properties have not been widely studied. Therefore, soil hydraulic properties were determined under uncropped no‐tillage (NT) plots receiving three levels of wheat (Triticum aestivumL.) straw mulch (0, 8, and 16 Mg ha−1yr−1) application for 10 consecutive yr on a Crosby silt loam (fine, mixed, active, mesic Aeric Epiaqualfs) in central Ohio. Water infiltration rates, earthworm population, saturated hydraulic conductivity (Ksat), soil water retention (SWR), total porosity, and pore‐size distribution were determined and unsaturated hydraulic conductivity was estimated from SWR andKsatdata. Mulching significantly impacted hydraulic properties in the 0‐ to 3‐cm soil depth (P&lt; 0.01), but water infiltration rate was unaffected. Earthworm counts were 0 m−2in the unmulched treatment, 158 ± 52 m−2(mean ± SD) in treatments with 8 Mg ha−1yr−1of straw, and 267 ± 58 m−2in those with 16 Mg ha−1yr−1of straw. Mulched treatments had aKsat123 times greater and retained 40 to 60% more water between 0 and −1500 kPa than the unmulched treatment. Soil porosity increased by 28% under 8 Mg ha−1yr−1of straw and by 44% under 16 Mg ha−1yr−1in the 0‐ to 3‐cm depth compared with the unmulched treatment. Pore volume of macro‐ and mesopores was greater in mulched treatments and that of fine mesopores was greater in the unmulched treatment in the 0‐ to 3‐cm depth. Straw mulching appears to be a viable practice to improve near‐surface hydraulic properties in long‐term NT soils, although residues may not increase water infiltration rates.

Soil structure and organic carbon relationships following 10 years of wheat straw management in no-till

Crop residue retention is important for sequestering soil organic carbon (SOC), controlling soil erosion, and improving soil quality. Magnitude of residue management impacts on soil structural properties and SOC sequestration is, however, site specific. This study assessed long-term (10 year) impacts of three levels (0, 8, and 16 Mg ha −1 on a dry matter basis) of wheat ( Triticum aestivum L.) straw applied annually on SOC concentration and physical properties of the bulk soil and individual 5- to 8-mm aggregates for the 0- to 50-cm soil depth under no-till (NT) on a Crosby silt loam (fine, mixed, active, mesic Aeric Epiaqualfs) in central Ohio. This study also quantified relationships between soil properties and straw-induced changes in SOC concentration. Changes in soil properties due to straw mulching were mostly confined to the upper 5 cm of the soil. Mulching increased SOC concentration, but it did not significantly change cone index (CI) and shear strength (SHEAR). Within the upper 0–5-cm soil depth, mulching decreased bulk density ( ρ b) by 40–50%, aggregate density ( ρ agg) by 30–40%, and particle density ( ρ s) by 10–15%, and increased tensile strength (TS) of aggregates by up to 14 times as compared to unmulched soil. At the same depth, soil with mulch retained >30% more water than soil without mulch from 0 to −1500 kPa potentials. The SOC amount was 16.0 Mg ha −1 under no straw, 25.3 Mg ha −1 under 8 Mg ha −1 straw, and 33.5 Mg ha −1 under 16 Mg ha −1 straw in the 0- to 10-cm depth. Below 10 cm, differences in SOC pool between mulched and unmulched soil were not significant. Overall, SOC from 0- to 50-cm depth was 82.5 Mg ha −1 for unmulched soil, 94.1 Mg ha −1 for 8 Mg ha −1 mulch, and 104.9 Mg ha −1 for 16 Mg ha −1. About 33% of C added with straw over the 10-year period was sequestered in soil. This means that 2/3 of the wheat straw applied was not converted to SOC and most probably was lost as emissions of CO 2 and CH 4. The annual rate of total C accrual was 1.2 Mg ha −1 in soil mulched with 8 Mg ha −1 and 2.2 Mg ha −1 in soil mulched with 16 Mg ha −1 of straw in the 0- to 50-cm depth. The percentage of macroaggregates (>5-mm) was six times higher under 8 Mg ha −1 of straw and 12 times higher under 16 Mg ha −1 compared to unmulched treatments. Macroaggregates contained greater SOC than microaggregates in mulched soil. The SOC concentration explained the variability in aggregate properties by as much as 96%. Overall, long-term straw mulching increased SOC concentration and improved near-surface aggregate properties.

COMPOST AND MULCH EFFECTS ON GASEOUS FLUX FROM AN ALFISOL IN OHIO

Accelerating soil erosion, leading to loss of the surface soil, is a common occurrence in croplands on undulating terrain. Yet the impact of erosion and reclamation measure on emission of greenhouse gases (GHG) is not known. Three predominant GHG emitted from cropland are as follows: carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). The most abundant GHG is CO2, but N2O and CH4 are also important, with global warming potentials (GWP) of 297 and 23, respectively. The objectives of this study were to evaluate the effect of imitated soil erosion on gaseous emission, to determine the effects of application of wheat (Triticum aestivum) residue mulch and swine manure and soybean (Glycine max) residue compost as soil-restorative measures on fluxes of CO2, N2O, and CH4 from uncropped, undisturbed, and desurfaced plots, and to determine relations between GHG fluxes and air and soil temperature, precipitation, and soil-moisture regimes. The microplot (2 × 2 m) experiment was established in 2002 on a Crosby silt loam (fine mixed Aeric Ochraqudalf) near South Charleston, Ohio. The experimental design included two soils: undisturbed and desurfaced soil in which the top 0-cm to 20-cm layer was mechanically removed to simulate severe soil erosion. There were three cover treatments: bare soil, wheat mulch at the rate of 8 Mg dry matter ha−1 y−1, and compost made from swine manure and soybean residues at the rate of 20 Mg drymatter ha−1 y−1. All plots received mineral fertilizer at the rate of 100kgN ha−1. Desurfacing decreased soil moisture, increased temperature, decreased daily and annual CO2 fluxes (1.05 vs. 1.59 g CO2-C m−2 d−1), and increased N2O fluxes (3.58 vs. 1.81 mg N2O-N m−2 d−1). Daily CO2 and annual fluxes were higher from compost than mulch plots. The lowest daily CO2 flux was measured from bare plots. The daily N2O fluxes significantly increased after compost application but were more significantly affected by rainfall events. CH4 fluxes were characterized by a high variability; however, more uptake was observed in compost (−0.41 kg ha−1 y−1) than in mulch (0.60 kg ha−1 y−1) and bare plots (2.75kgha−1 y−1). Daily CO2 fluxes were positively correlated with soil (r = 0.82) and air temperatures (r = 0.84) and negatively correlated with soil-moisture content (r = −0.53). Daily N2O fluxes were highly correlated with precipitation (r = 0.88). Fluxes of CO2 and N2O were mutually correlated (r = 0.56), but CH4 fluxes were not correlated with temperature, moisture, precipitation, or fluxes of other GHG. Computed GWP was higher in compost-covered plots than in mulched and bare plots. Estimation of fluxes of GHG indicates that N2O accounts for 13% to28% and CH4 for −0.5% to 5% of the total emission. Therefore, acompleted assessment of flux of GHG must be based on measurement ofall three gases (i.e., CO2, N2O, and CH4).

SOIL ORGANIC CARBON SEQUESTRATION RATES IN TWO LONG-TERM NO-TILL EXPERIMENTS IN OHIO

The effectiveness of no-till (NT) farming in reducing loss of soil organic matter (SOM) depends on climate and soil properties. Soil samples were obtained from two long-term experiments that were designed to study the impact of tillage systems on crop yields. However, the objectives of this experiment were to assess the impact of NT on soil organic carbon (SOC) sequestration rate and other soil properties and to estimate historic depletion of SOC under different soil management practices with reference to the undisturbed wooded control. The two long-term experiments in Ohio studied were those sited at South Charleston and Hoytville. The South Charleston (83° 30′ W and 39° 48′ N) experiment was established in 1962 on Crosby silt loam (fine mixed, mesic Aeric Ochraqualf). The site has long-term annual temperature and precipitation of 10.8 °C and 1043 mm, respectively. Tillage treatments for continuous corn (Zea mays) were NT, chisel plow (CP), and moldboard plow (MP). The Hoytville (84° 04′ W and 41° 03′ N) experiment was established in 1987 on Hoytville clay loam (fine, illitic mesic Mollic Epiaqualfs) soil. The site has long-term annual temperature and precipitation of 9.9 °C and 845 mm, respectively. There were two crop rotations: (i) 2-year corn-soybean (Glycine max) rotation with NT and subsoiling and (ii) 3-year corn-soybean-oat (Avena sativa) rotation with NT, CP, and rotational tillage soil management. The Hoytville clay site is poorly drained, has higher clay content, and higher and more even by distributed antecedent level of SOC in the soil profile than does the South Charleston silt loam soil. No-till increased SOC and N pools in the 0 to 5-cm layer in silt loam soil but had no effect in clay soil. The rate of SOC sequestration in the silt-loam soil under NT was 175 kg C ha−1 y−1. The silt loam soil had higher SOC and N stratification ratios in NT than in MP and CP treatments, whereas the stratification ratios were low and similar in all treatments in the clayey soil. For both soils, there were no differences between tillage treatments in several soil properties including texture, available water capacity, hydraulic conductivity (Ks), and cation exchange capacity. The NT decreased soil bulk density and pH in the 0 to 15-cm layer in the silt loam soil. The plow till treatments had a small impact on soil aggregation in clayey soil. The decline in water-stable aggregates with reference to NT was no more than one sixth. In the silt loam soil, however, the water-stable aggregates in plow till treatments were merely one third of that in the NT treatment. The historic loss of the SOC pool for 0 to 30-cm depth under agricultural land use was 25 to 35% in silt loam and 19 to 25% in the clayey soil.