No-till Practices Research Articles

Tillage effects on soil organic carbon storage and dynamics in Corn Belt of Ohio USA

Abstract No-till (NT) agriculture reduces soil disturbance, conserves soil and water, and lowers the cost of agricultural production. However, its role in soil organic carbon (SOC) sequestration can be soil and site specific. The applicability of the results from long-term tillage experiments (LTTEs) showing positive rate of carbon (C) sequestration is being questioned under large scale farmers’ field conditions. Therefore, this study assessed the soil C dynamics under conventional till (CT) and NT practices using three LTTEs and three farmer's field sites in Ohio, USA with diverse soil types, and environmental and management conditions. The hypothesis tested was that reduced soil disturbance in NT management system enhances soil C sequestration in comparison to CT management. Soils were sampled (0–40 cm) from adjacent CT, NT and woodlot (WL) plots at each site. Total C and nitrogen (N) pools were calculated based on equivalent soil mass basis. The SOC was fractioned into old C and new (corn C) using δ13C natural abundance. The CT soils had 26–55% lower SOC and 7–34% lower N pool compared to forest soils. Most of the historic SOC and N losses in cultivated soils occurred within the plow (0–25 cm) layer. The SOC pool in the top 40 cm was significantly greater under NT than CT at LTTEs and Coshocton farm. There were no significant differences in SOC pool of the top 40 cm among CT and NT at Delaware and Hoytville farms. Old C accounted for 69% and 66% of SOC under CT and NT, respectively at Northwestern Agricultural Research Station. However, at Western Agricultural Research Station, corn-derived C dominated CT and NT soils, accounting for 55% and 66% of SOC in the top 40 cm, respectively. At North Appalachian Experimental watersheds, corn-derived C dominated NT soils (64%), while old C dominated CT soils (64%). Result of this study indicated that a decrease in SOC and N pools occurs when forest soil is cultivated. Conversion of CT to NT restores some of the depleted SOC and N pools. This supports our hypothesis that the reduced soil disturbance in NT system slows the decomposition of SOC which increases soil C sequestration. The quantity and rate of loss or sequestration depends on several factors including soil type, texture and drainage, tillage intensity, and duration of NT practice.

Soil quality indicator response to tillage and residue management on semi-arid Mediterranean cropland

No-tillage (NT) practices for rainfed cereal production in semi-arid Mediterranean soils can conserve water and increase crop productivity, but producers are reluctant to adopt NT because of potential increases in penetration resistance and bulk density. We hypothesized that understanding soil quality could encourage NT adoption, but methods for selecting and assessing soil quality indicators needed to be developed for this region. Our objectives were to (1) identify the most sensitive indicators for evaluating long-term tillage and residue management within this region using factor analysis, and (2) compare soil quality assessment using those indicators with traditional evaluations using changes in water retention, earthworm activity and organic matter stratification ratio. Several soil physical, chemical, and biological indicators were measured within conventional tillage, minimum tillage, and NT (with and without stubble burning) treatments that represent a wide agro-climatic area in NE Spain. Sampling depth and management treatments significantly affected several indicators when evaluated individually and collectively. Principal component analysis identified three factors that accounted for 75 and 85% of the variation in soil measurements for 0–5- and 5–15-cm depth increments. Only two factors per depth showed significant differences among the four treatments. For both depth increments, one factor grouped soil physical attributes, and the other organic matter and biological properties. The indicators with the greatest loadings were identified as the most sensitive in each factor. These were penetration resistance, particulate organic matter (POM) and total organic matter within the 0–5 cm layer, and aggregate stability and POM within the 5–15-cm increment. Factor scores were positively correlated to soil water retention, earthworm activity and organic matter stratification, which were all greater in NT, regardless of stubble management. We conclude that (1) multivariate analyses are useful for selecting appropriate soil quality indicators, and (2) that adopting NT on Mediterranean semi-arid cropland can have several positive effects on soil quality within this region.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Short-Term Impacts of No Tillage on Aggregate-Associated C in Black Soil of Northeast China

In order to get a good indicator to evaluate the impacts of no tillage (NT) on soil structure and soil quality, we studied the dynamics of total soil organic carbon (SOC) and aggregate-associated SOC, and their relationships in the plow layer (30 cm) in black soil of Northeast China under NT practice. The tillage experiment was established in Dehui County, Jilin Province, China, in 2001. The total SOC and aggregate-associated SOC under 5-yr tillage treatments were measured. NT practices did not lead to the increase of average SOC content at 0-30 cm depth, but it did significantly increase SOC at the top soil (0-5 cm). In NT plots, the change of SOC in > 1 000 μm aggregate was the same with that of total SOC, but the effect of NT on SOC in > 1 000 μm aggregate was greater than the effect on total SOC, suggesting that > 1 000 μm aggregate had more sensitive response to the impact of tillage practices. Also, significant positive correlation occurred between total SOC and SOC in > 1 000 μm aggregate in black soil. Consequently, in the short term soil macroaggregate >1 000 μm could be used as an indicator to evaluate the impacts of tillage practices on soil structure in black soil of Northeast China.

Soil carbon sequestration rates and associated economic costs for farming systems of south-eastern Australia

Soil organic carbon (C) sequestration rates based on the Intergovernmental Panel for Climate Change (IPCC) methodology were combined with local economic data to simulate the economic potential for C sequestration in response to conservation tillage in the six agro-ecological zones within the Southern Region of the Australian grains industry. The net C sequestration rate over 20 years for the Southern Region (which includes discounting for associated greenhouse gases) is estimated to be 3.6 or 6.3 Mg C/ha after converting to either minimum or no-tillage practices, respectively, with no-till practices estimated to return 75% more carbon on average than minimum tillage. The highest net gains in C per ha are realised when converting from conventional to no-tillage practices in the high-activity clay soils of the High Rainfall and Wimmera agro-ecological zones. On the basis of total area available for change, the Slopes agro-ecological zone offers the highest net returns, potentially sequestering an additional 7.1 Mt C under no-tillage scenario over 20 years. The economic analysis was summarised as C supply curves for each of the 6 zones expressing the total additional C accumulated over 20 years for a price per t C sequestered ranging from zero to AU$200. For a price of $50/Mg C, a total of 427 000 Mg C would be sequestered over 20 years across the Southern Region, <5% of the simulated C sequestration potential of 9.1 Mt for the region. The Wimmera and Mid-North offer the largest gains in C under minimum tillage over 20 years of all zones for all C prices. For the no-tillage scenario, for a price of $50/Mg C, 1.74 Mt C would be sequestered over 20 years across the Southern Region, <10% of the simulated C sequestration potential of 18.6 Mt for the region over 20 years. The Slopes agro-ecological zone offers the best return in C over 20 years under no-tillage for all C prices. The Mallee offers the least return for both minimum and no-tillage scenarios. At a price of $200/Mg C, the transition from conventional tillage to minimum or no-tillage practices will only realise 19% and 33%, respectively, of the total biogeochemical sequestration potential of crop and pasture systems of the Southern Region over a 20-year period.

Farmers Experience and Practice of No-tillage System: Towards the Adoption of Conservation Agricultural Production in Atwima-Nwabiagya District of Ashanti Region, Ghana

Slash-and-burn farming in the Atwima-Nwabiagya district of Ghana has contributed to more fragile farmland and low soil fertility, resulting in very low crop yields. No-tillage is an agricultural practice whereby a crop is established without any prior tillage or burning of the land. and it was introduced to Ghanaian farmers by the Ministry of Food and Agriculture in 1995. In this study, factors affecting the promotion, adoption, and impacts of no-tillage farming were assessed. Questionnaires were administered to 50 farmers categorized as: adopter (practicing no-tillage farming), deserter (abandoned the practice), or never (never practiced no­ tillage). Slash-and-burn farmers used 16 man-days/ha for land preparation, whereas no-tillage farmers required 14 man-days/ha for land preparation. In-crop weed control required 12 man-days for slash-and-burn farming and 8 man-days under no-tillage. Slash-and-burn farmers employed 18 man-days/ha for harvesting maize, whereas no-tillage farmers used 24 man-days/ha. No-tillage farmers listed the following benelHs of using this system: increased yield (18% of respondents), reduced labor (17%), conserved soil moisture (16%), improved soil nutrients (15%), increased farm size (13%), reduced soil erosion (11 %), and reduced production costs (10%). Information on no-tillage practices was diffused by farmer-to-farmer information transfer. Most farmers practiced a mixed cropping system instead of a crop rotation system, and male farmers were seen to be more innovative and likely to adopt new technologies than their female counterparts. The reported challenges associated with no-tillage included poor society recognition of no-tillage practices, difficulties in planting through residues and application of herbicide, and pest invasion. The lack of no-tillage planters makes it rather difficult for large-scale farmers to switch from conventional farming to no-tillage. More effort is needed to investigate multipurpose conservation farming approaches suitable for fruit and crop production. Agricultural engineers and other experts must collaborate to develop suitable conservation agricultural tools and equipment for small-scale farmers to enhance agriculture production.

Gynumella flava gen. nov., sp. nov., isolated from the rhizosphere of rice (Oryza sativa L.) managed under no-tillage practice

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Assessment of the Effects of Poultry Litter on Surface Runoff Water Quality from Agricultural Lands

The use of pelletized poultry litter (PPL) as a substitute for inorganic fertilizers is increasingly being en-couraged in states like Delaware which have a considerable surplus of poultry litter. However, we know very little about the impacts of PPL on runoff water quality and whether it is an environmentally-sound and sus-tainable alternative to inorganic fertilizer. To address these questions we compared the exports of nutrients (NH4-N, NO3-N and PO4-P) and trace elements (As, Cu, and Zn) in surface runoff from agricultural plots receiving PPL, raw poultry litter (RPL), urea and no-fertilizer (control) treatments. The study was conducted on agricultural land located in Middletown, Delaware with corn as the cover crop. The experimental plots were 5 m wide and 12 m long with reduced tillage and no-tillage management practices. Sampling was con-ducted for six natural rainfall events from April through August 2008. Nutrient (NH4-N, NO3-N and PO4-P) exports from plots receiving PPL were less than those with urea or raw litter applications. While exports of trace elements from the PPL treatment exceeded those from urea, they were much lower than the corre-sponding exports from the RPL treatments. Mass exports of nutrients and trace elements were correlated with event size (rainfall amount) but were not correlated with timing of event (days since litter application). Results from this study suggest that the use of PPL in combination with no-tillage may provide an environ-mentally safe alternative to synthetic fertilizers.

No-tillage improvement of soil physical quality in calcareous, degradation-prone, semiarid soils

Many soils in the semiarid Mediterranean Ebro Valley of Spain are prone to physical and chemical degradation due to their silty texture, low organic matter content, and presence of carbonates, gypsum or other soluble salts. Rainfed agriculture on these soils is also hindered by the scarcity of water. No-tillage can increase plant-available water and soil organic matter, thus helping overcome most factors limiting crop production in this area. Our objective was to determine how conventional- and no-tillage practices affected soil physical quality indicators and water availability in an on-farm study in the Ebro Valley. Soil samples were collected from 0 to 5-, 5 to 15-, and 15 to 30-cm depth increments within adjacent farmer-managed conventional- and no-tillage fields in 2007 and 2008. Both fields were managed for continuous barley (Hordeum vulgare L.) production. The soil at both sites is a silt loam (Haplic Calcisol). Aggregate-size distribution and stability, soil water retention characteristics, organic carbon, and total carbonates were determined in 2007. Pore-size distribution was estimated from the water retention curve. Penetration resistance, soil bulk density and field water content during the entire crop growing season were measured for both fields in 2008. Aggregate dry mean weight diameter and stability in water were 1.2 and 2.2 times greater, respectively, under no-tillage than conventional tillage due to reduced mechanical disturbance and increased soil organic carbon content. Bulk density was 1.12 times greater (P < 0.1) under no-tillage only in the 0–5-cm depth. Two times greater penetration resistance to a depth of 15 cm in this treatment was related to bulk density and aggregates stability. Field water content was greater with no-tillage than conventional tillage during the driest months in 2008. The volume of equivalent diameter pores (0.2–9 μm) was 1.5 times higher under no-tillage. This increased plant-available water content and doubled barley production under no-tillage in 2008, which was a very dry year. We conclude that despite the greater penetration resistance under no-tillage, increased water availability as a result of improved structure characteristics was more important for crop yield. This suggests that producers should seriously consider adopting no-tillage practices for soil conservation in semiarid degraded areas like the one studied.

Soil Properties, Soybean Response, and Economic Return as Affected by Residue and Water Management Practices

Soil, water, and air quality can be positively impacted by alternative crop residue management practices that return residue to the soil. Double-crop production systems, particularly those with a grass included in the rotation, rely on successful residue management practices. Soil quality and overall soil tilth are often low in regions with a long history of intensely cultivated, row-crop production, such as in the Mississippi River Delta region of the mid-South. Therefore, the objective of this study was to evaluate the effects of alternative residue (i.e., tillage, residue burning, and residue level) and water management practices on soil properties, soybean [ Glycine max (L.) Merr.] production, and net economic returns, over two consecutive rotations in a wheat (Triticum aestivum L.)–soybean double-crop system in the Mississippi River Delta region of eastern Arkansas. Initiated in 2001, this study reports results from years 4 and 5 of the experiment. Residue management effects were inconsistent among soil properties and years, and differences were generally agronomically non-significant. Averaged across irrigation treatments, soybean yield was unaffected by tillage, burning, and residue level either year. Within the non-irrigated treatment, conventionally tilled (CT) soybean yield was 38 % greater (p < .05) than no-tillage (NT) in 2005, but similar in 2006. In 2005 and 2006, irrigated soybean yield was 34 and 26 % greater (p < .05), respectively, in the burned than non-burned treatment. In 2006, the estimated net return from the high residue/burned/NT/irrigated treatment combination was 51 % greater than the traditional combination of high residue/burned/CT/irrigated soybean. By years four and five following conversion from CT to NT, the more environmentally sustainable practice of NT appears to be a viable, and potentially more profitable, alternative to the traditional and common practice of CT.

White lupine as a beneficial crop in Southern Europe: I. Potential for N mineralization in lupine amended soil and yield and N 2 fixation by white lupine

Two experiments were carried out at Pegões (central Portugal) to determine the potential N mineralization in a pulse amended disturbed and undisturbed soil incubated at several temperatures, and to evaluate for 2 years the yield and N 2 fixation capacity of sweet lupine ( Lupinus albus L. cv. Estoril) inoculated with a mixture of rhizobia strains or nodulated by indigenous soil bacteria and submitted to conventional tillage or no-till practices. A completely randomized block design for soil mobilization with three replicates was used for the laboratory study, and completely randomized blocks for inoculation and tillage treatments with four replicates were used for the lupine yield and N 2 fixation experiment. Residue N immobilization occurred immediately after mature residue return to the soil independent of temperature, and was greater at 7 °C especially in the disturbed topsoil. Greater immobilization was also observed by doubling the amount of mature residue incorporated in the soil. This was expected since soil microorganisms would be in direct contact with the fresh organic matter and would be provided with more organic carbon under these circumstances. Nitrogen mineralization proceeded after 5 days of amendment. Potential N mineralization was higher at 25 °C than at 18 or 7 °C, for both conventional and no-till practices. At 25 °C, 42% of buried residue- 15N was released over 210 days, at a smaller rate than 18 °C (49%) over 81 days. Lupine yield and N 2 fixation capacity were similar in plots that were not inoculated and those receiving the mixture of three rhizobia strains. White lupine had an efficient symbiosis with indigenous soil rhizobia at pod-filling (>99%, >100 kg N ha −1 year −1) which was not affected by tillage. At this stage, plant residue including visible roots and nodules accounted for a soil N input of +96 kg ha −1 year −1 (91% of crop N), showing the large soil N benefit by the crop at this stage. The lupine residue at pod-filling stage can be used as a green manure under the conditions of organic farming systems. The apparent N “harvest” index of the pulse at pod-filling was only 9% though at maturity phase it should result in a higher value and the legume will show a lower fertilizer N value.

Regional variations in greenhouse gas emissions of biobased products in the United States—corn-based ethanol and soybean oil

Regional variations in the environmental impacts of plant biomass production are significant, and the environmental impacts associated with feedstock supply also contribute substantially to the environmental performance of biobased products. Thus, the regional variations in the environmental performance of biobased products are also significant. This study scrutinizes greenhouse gas (GHG) emissions associated with two biobased products (i.e., ethanol and soybean oil) whose feedstocks (i.e., corn and soybean) are produced in different farming locations. We chose 40 counties in Corn Belt States in the United States as biorefinery locations (i.e., corn dry milling, soybean crushing) and farming sites, and estimated cradle-to-gate GHG emissions of ethanol and of soybean oil, respectively. The estimates are based on 1 kg of each biobased product (i.e., ethanol or soybean oil). The system boundary includes biomass production, the biorefinery, and upstream processes. Effects of direct land use change are included in the greenhouse gas analysis and measured as changes in soil organic carbon level, while the effects of indirect land use change are not considered in the baseline calculations. Those indirect effects however are scrutinized in a sensitivity analysis. GHG emissions of corn-based ethanol range from 1.1 to 2.0 kg of CO2 equivalent per kilogram of ethanol, while GHG emissions of soybean oil are 0.4–2.5 kg of CO2 equivalent per kilogram of soybean oil. Thus, the regional variations due to farming locations are significant (by factors of 2–7). The largest GHG emission sources in ethanol production are N2O emissions from soil during corn cultivation and carbon dioxide from burning the natural gas used in corn dry milling. The second largest GHG emission source groups in the ethanol production system are nitrogen fertilizer (8–12%), carbon sequestration by soil (−15–2%), and electricity used in corn dry milling (7–16%). The largest GHG emission sources in soybean oil production are N2O emissions from soil during soybean cultivation (13–57%) and carbon dioxide from burning the natural gas used in soybean crushing (21–47%). The second largest GHG emission source groups in soybean oil production are carbon sequestration by soil (−29–24%), diesel used in soybean cultivation (4–24%), and electricity used in the soybean crushing process (10–21%). The indirect land use changes increase GHG emissions of ethanol by 7–38%, depending on the fraction of forest converted when newly converted croplands maintain crop cultivation for 100 years. Farming sites with higher biomass yields, lower nitrogen fertilizer application rates, and less tillage are favorable to future biorefinery locations in terms of global warming. For existing biorefineries, farmers are encouraged to apply a site-specific optimal nitrogen fertilizer application rate, to convert to no-tillage practices and also to adopt winter cover practices whenever possible to reduce the GHG emissions of their biobased products. Current practices for estimating the effects of indirect land use changes suffer from large uncertainties. More research and consensus about system boundaries and allocation issues are needed to reduce uncertainties related to the effects of indirect land use changes.

Monitoring of cropland practices for carbon sequestration purposes in north central Montana by Landsat remote sensing

We used an object-oriented approach in conjunction with the Random Forest algorithm to classify agricultural practices, including tillage (till or no-till (NT)), crop intensity, and grassland-based conservation reserve (CR). The object-oriented approach allowed for per-field classifications and the incorporation of contextual elements in addition to spectral features. Random Forest is a classification tree-based advanced classifier that avoids data over-fitting associated with many tree-based models and incorporates an unbiased internal classification accuracy assessment. Landsat satellite imagery was chosen for its continuous coverage, cost effectiveness, and image accessibility. Classification results for 2007 included producer's accuracies of 91% for NT and 31% for tillage when applying Random Forest to image objects generated from a May Landsat image. Low classification accuracies likely were attributed to the misclassification of conservation-based tillage practices as NT. Results showed that the binary separation of tillage from NT management is likely not appropriate due to surface spectral and textural similarities between NT and conservation-type tillage practices. Crop and CR lands resulted in producer's accuracies of 100% and 90%, respectively. Crop and fallow producer's accuracies were 95% and 82% in the 2007 classification, despite post-senesced vegetation; misclassification within the fallow class was attributed to pixel-mixing problems in areas of narrow (< 100 m) strip management. A between-date normalized difference vegetation index approach was successfully used to detect areas having “changed” in vegetation status between the 2007 and prior image dates; classified “changed” objects were then merged with “unchanged” objects to produce crop status maps. Field crop intensity was then determined from the multi-year analysis of generated crop status maps.

Traditional Tillage Systems as Drought Adaptation Strategies of Smallholder Farmers: The Case of Semi-Arid Central Tanzania

This article presents local knowledge on ecosystem management by analyzing and discussing traditional tillage practices applied by smallholder farmers as a response to drought risks in dryland areas of Mpwapwa District, central Tanzania. Farming activities in the area wholly depend on rain-fed systems. Information from key informants and in-depth household interviews indicate that farmers in this area use three different traditional tillage practices—no-till (sesa), shallow tillage (kutifua), and ridges (matuta). Available information suggests that selection of a particular practice depends on affordability (in terms of costs and labor requirements), perceived ability to retain nutrient and soil-water, and improvement of control of erosion and crop yield. In this area, smallholder farmers perceive no-till practice to contribute to more weed species, hence more weeding time and labor are needed than in the other two practices. The no-till practice also contributes to low soil fertility, low soil moisture retention, and poor crop yield. No plans have been made to introduce irrigation farming in these marginal areas of central Tanzania. Thus, improving the ability of the tillage practices to conserve soil moisture and maintain soil fertility nutrients using locally available materials are important tasks to be carried out. This will ensure the selection of practices that will have positive influence on improved crop yields in the area.

On farm assessment of tillage impact on soil carbon and associated soil quality parameters

No-tillage (NT) farming offers innumerable benefits to soil and water conservation, however, its potential to sequester soil organic carbon (SOC) and related soil properties varies widely. Thus, the impact of long-term (>4 yr) NT-based cropping systems on SOC sequestration and selected soil physical and chemical parameters were assessed across soils within five Major land Resource Areas (MLRAs: 99 and 111 in Michigan; 124 and 139 in Ohio; and 127 in Pennsylvania) in eastern U.S.A. Soil samples were collected from paired fields of NT and plow tillage (PT) based cropping systems and an adjacent woodlot (WL). The SOC concentration, bulk density (ρ b), texture, pH, electrical conductivity (EC), soil N, coarse particulate organic matter (CPOM) C and N, and nitrate N (NO 3-N) concentrations were determined. Conversion from NT to PT practice increased surface soil pH from 5.97, 6.56 and 6.02 to 6.62, 6.91 and 7.09 under MLRAs 127, 111 and 99, respectively. NT soils had higher SOC concentration soils by 30, 50 and 67% over PT soils at 0–5 cm depth under MLRAs 99, 111 and 127, respectively. Considering the whole soil profile SOC, WL had higher SOC pool than NT and PT practices under MLRAs 99, 111 and 124, however, there was no significant difference ( P < 0.05) between NT and PT practices across five soils. Almost the same trend was observed in the case of depthwise soil N content. NT soil had higher N content than PT soils by 27, 44 and 54% under MLRAs 99, 127 and 111, respectively. However, whole soil profile N content of NT soil was significantly higher by 12% than PT soil under MLRA 99. Concentrations of CPOM associated C and N of NT soil was higher than PT soil under MLRAs 99, 111 and 127 at 0–5 soil depth. These results indicated that impact of tillage on soil C and associated soil quality parameters is confined within specific soil types.

Micromorphological analysis of soil structure under no tillage management in the black soil zone of Northeast China

The structure of the “black soil” in Northeast China has been greatly deteriorated by long-term intensive conventional mouldboard plow tillage (CT) practices. In this study, micromorphological observation and image analysis of soil thin sections were conducted to evaluate the impacts of 21 years (1986–2007) of no tillage (NT) on soil structure as compared to CT in an experiment near Gongzhuling City, Jilin Province. Soil organic matter (SOM), wet aggregate stability and saturated hydraulic conductivity (Ks) were also analyzed. Total SOM was not significantly affected by tillage systems, but fresher SOM was observed in the surface layer under NT. The aggregates under NT showed different hierarchies in the form of crumbs, and the mean weight diameter (MWD) of NT was significant higher than that of CT in the surface layer. Platy and blocky aggregates were frequently observed in the lower layers under CT practice. The compound pore structure with intertwined intra- and inter- aggregates pores under NT was well developed in a layer from 0–5 cm to 20–25 cm. While under CT system, more inter-aggregate pores and fewer intraaggregate pores were observed, and planes and channels were frequently found in the 20–25 cm layer, where macroporosity decreased significantly and a plow pan was evident. The Ks values of NT were significantly lower at 0–5 cm but significantly higher at 20–25 cm compared with CT, which showed the same trend with macroporosity. These results confirmed that long-term CT practice fragmented the tillage layer soil and compacted the lower layer soil and formed a plow pan. While long-term NT practice in the black soil region favored soil aggregation and a stable porous soil structure was formed, which are important to the water infiltration and prevent soil erosion.

Effects of ants on water and soil losses from organically-managed citrus orchards in eastern Spain

Ants can play a key role in the erosion processes on agriculture land by modifying soil properties and increasing macropore flow. Ants are abundant in organically-managed orchards in the Mediterranean region due to climate conditions, no-till practices, no pesticide use, and the resulting vegetation cover. In order to determine the effect of ants on soil and water losses from these orchards growing on moderately-sloped land (4–8%), forty 1.0 m2 plots (20 with ants mounts and 20 without ants — controls) were established during the summer of 2007. A rainfall simulator was used to apply 78 mm of water to each plot over a one-hour period, equivalent to a 20-year return-period thunderstorm. Runoff was collected at 1-minute intervals and sediment concentration measured every 10 minutes. Sediment concentrations were 300% higher on plots with ant mounds, but runoff rates were similar to the plots without ants. Average soil erosion rates averaged 41 kg ha−1 h−1 on the ant plots and 13 kg ha−1 h−1 on the control plots. The low erosion rates are due to the effect of the vegetation and litter cover in this organically-managed soil, which were little impacted by ant activity at the pedon scale.

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.

Lysobacter oryzae sp. nov., isolated from the rhizosphere of rice (Oryza sativa L.)

The taxonomic position of a novel bacterial strain, YC6269(T), isolated from the rhizosphere of rice (Oryza sativa L.) managed under no-tillage practice in Jinju, South Korea, was studied using polyphasic approach. Cells of the strain were Gram-negative, rod-shaped and facultatively anaerobic. The novel strain grew at a temperature of 15-42 degrees C (optimum at 28 degrees C). Growth of the strain occurred between pH 5.5 and 11.0, with an optimum at pH 7.0-8.0. The G+C content of the total DNA was 67.4 mol%. The 16S rRNA gene sequence of the strain was most closely related to species of the genus Lysobacter, Lysobacter yangpyeongensis DSM 17635(T) (98.6 %), Lysobacter niabensis GH34-4(T) (97.2 %), Lysobacter enzymogenes DSM 2043(T) (96.9 %), Lysobacter daejeonensis DSM 17634(T) (96.3 %) and Lysobacter niastensis GH41-7(T) (96.2 %). The novel strain showed <96.0 % similarity with other species of the genus Lysobacter. Chemotaxonomic data (major quinone, Q-8; major polar lipids, phosphatidylethanolamine, phosphatidylglycerol and phosphatidyl-N-methylethanolamine, and major fatty acids, C(15 : 0) iso, C(16 : 0) iso, C(17 : 0) iso and C(17 : 1) iso omega9c) supported the affiliation of strain YC6269(T) to the genus Lysobacter. Phylogenetic analysis based on the 16S rRNA gene sequences, DNA-DNA hybridization data and biochemical and physiological characteristics strongly supported the genotypic and phenotypic differentiation of strain YC6269(T) from recognized species of the genus Lysobacter. Strain YC6269(T), therefore, represents a novel member of the genus Lysobacter, for which the name Lysobacter oryzae sp. nov. is proposed. The type strain is YC6269(T) (=KCTC 22249(T)=DSM 21044(T)).

Long-term Effect of Conventional and No-Tillage Production Systems on Nitrous Oxide Fluxes from Corn (Zea mays L.) Field in Southwestern Quebec

Problem statement: There is a growing trend in the adoption of conservation tillage as an alternative to conventional tillage farming system. Implications of this agricultural management shift with respect to nitrous oxide (N2O) emission, which has been a topic of intense research for the past few decades, is not yet completely understood. Approach: This study was conducted on a 2.4 ha field located at Macdonald research farm of McGill university, Montreal, to investigate the relative impact of long-term Conventional Tillage (CT) and No-Tillage (NT) practices on soil N2O fluxes (FN2O) under grain and silage corn (Zea mays L.) during the 2003 and 2004 growing seasons (May-Sept). Nitrous oxide fluxes were measured using static closed chamber by taking gas samples at 0, 10, 20 and 30 min. Results: In both years, the N2O fluxes were generally similar between the two tillage systems, with the exception of few sampling dates at the beginning of the growing season when N2O emissions measured under CT were significantly (p≤0.05) greater than NT. Despite our efforts to reduce experimental error by deploying six chambers per treatment plots, spatial and temporal variations were high which might had obscured the treatment differences to be detected. Conclusion: An important implication of present findings was that, contrary to many reports in the literature, the adoption of NT may not add to concerns over global atmospheric N2O concentrations. This might be due to a greater rate of N2O reduction to N2 in soils under NT than CT during diffusion up the soil profile because of the higher moisture content under NT system than CT.