Plow Tillage Research Articles

Precision control of soil nitrogen cycling via soil functional zone management

Managing the soil nitrogen (N) cycle is a major component of agricultural sustainability. Soil functional zone management (zonal management) is a novel agroecological strategy for managing row-crop agroecosystems. It may improve the efficiency of soil N cycling compared with conventional and no-tillage approaches, by managing the timing and location (crop row vs inter-row) of key soil N cycling processes. We compared N mineralization and availability during the period of maize peak N demand in crop rows and inter-rows in zonal management and conventional chisel plow tillage systems at four sites across the US Corn Belt over three growing seasons. Under zonal management, potential N mineralization and N availability during crop peak N demand were significantly greater in crop rows, where the majority of crop roots are found, compared with inter-rows. Averaged across all site-years, plant-available N in zonal management crop rows was 46mgkg−1 compared with 21mgkg−1 in inter-rows. In contrast, in conventional tillage, potential N mineralization and N availability were greater in inter-rows compared with crop rows; averaged across all site-years, plant-available N in conventional tillage crop rows was 24mgkg−1 compared with 51mgkg−1 in inter-rows. The results demonstrate that the active management of crop residues under zonal management can enhance the spatiotemporal efficiency of soil N cycling processes, by concentrating N mineralization and availability close to crop roots in synchrony with crop developmental needs. Zonal management therefore has potential to increase crop N-use efficiency compared with conventional tillage, and thereby reduce the impacts of row-crop agricultural production on water resources and greenhouse gas emissions that result from N leaching and denitrification.

Cover crops prevent the deleterious effect of nitrogen fertilisation on bacterial diversity by maintaining the carbon content of ploughed soil

Synthetic nitrogen (N) fertilisers are widely used for enhancing agrosystem productivity and are thus thought to increase organic inputs from crop residues. However, many crop rotations have a low amount of organic residue returned to the soil since the whole aboveground crop biomass is harvested and exported. To compensate for such organic outputs and to improve soil quality, the introduction of winter cover crops in rotations has been suggested. A 4-year controlled field experiment was conducted to quantify the respective and combined effects of chemical N fertilisation and winter cover crops on plant productivity, organic carbon (C) and N inputs from crop residues and cover crops, changes in soil C and N concentrations, C:N ratio, soil mineral N, pH, soil moisture and soil bacterial biodiversity. A ploughing tillage system with low organic input was assessed, for which the main crops were spring wheat, green pea, forage maize, along with cover crops of different legume and non-legume species.N fertilisation did not have an impact on the aboveground biomass except following forage maize. Cover crops increased the total amount of C and N inputs, irrespective of N fertilisation which had no significant effect. The soil N concentration decreased in all treatments, particularly when N fertilisers were applied under bare fallow conditions. The latter treatment also caused decreased soil C concentrations (slightly increased in the other treatments) and decreased bacterial biodiversity (no change in the other treatments). Bacteria from the Proteobacteria and Bacterioidetes phyla were highly correlated with soil from fertilised bare fallow conditions. While Verrucomicrobia was characteristic of non-fertilised bare fallow soils, Acidobacteria and Cyanobacteria were associated with the high C and N concentrations present in soils following cover crop treatments.Taken together, these results demonstrate that in ploughing systems, under low organic restitution regimes, intensive N fertilisation decreases the diversity of the bacterial soil community and reduces soil C and N concentrations, but only in bare fallow conditions. There is a protective effect of winter cover crops against the deleterious effect of chemical N fertilisation on soil biodiversity and nutrient cycling, since they can maintain soil C and N concentrations. The use of winter cover crops containing legumes is thus a practice that is able to meet the criteria of a sustainable agriculture.

Transformation of soil organic matter in leached chernozems under minimized treatment in the forest-steppe of West Siberia

Changes in the contents of total organic carbon and the carbon of easily mineralizable fractions of organic matter (labile humus, detritus, and mortmass) in the layers of 0–10, 10–25, and 0–25 cm were studied in leached chernozems ((Luvic Chernozems (Loamic, Aric)) subjected to deep plowing and surface tillage for nine years. In the layer of 0–25 cm, the content of Corg did not show significant difference between these two treatments and comprised 3.68–3.92% in the case of deep plowing and 3.63–4.08% in the case of surface tillage. Tillage practices greatly affected the distribution of easily mineralizable fractions of organic matter in the layers of 0–10 and 10–25 cm, though the difference between two treatments for the entire layer (0–25 cm) was insignificant. Surface tillage resulted in the increase in the contents of mortmass (by 59%), detritus (by 32%), and labile humus (by 8%) in the layer of 0–10 cm in comparison with deep plowing. At the same time, the contents of these fractions in the layer of 10–25 cm in the surface tillage treatment decreased by 67, 46, and 3%, respectively. The estimate of the nitrogen-mineralizing capacity made according to the data on the uptake of soil nitrogen by oat plants in a special greenhouse experiment confirmed the observed regularities of the redistribution of easily mineralizable organic matter fractions by the soil layers. In case of surface tillage, it increased by 23% in the layer of 0–10 cm; for the layer of 0–25 cm, no significant differences in the uptake of nitrogen by oat plants were found for the two studied treatments.

Soil Organic Carbon and Nitrogen Fractions under Different Land Uses and Tillage Practices

ABSTRACTMany questions have surfaced regarding long-term impacts of land-use and cultivation system on soil carbon (C) sequestration. The experiment was conducted at Ohio Agricultural Research and Development Center. Only minor variations of soil organic carbon (SOC) and nitrogen (N) fractions with depth under plow tillage (PT). The SOC, total nitrogen (TN), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) concentrations were higher under grassland and forestland in the top 0–15 cm depth than arable soils. No-tillage (NT) also increased SOC and N fractions concentrations in the surface soils than PT. Compared to arable, grass and forest could significantly improve proportions of MBC and MBN, and reduce proportions of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). NT and forest also increased the ratio of SOC/TN, MBC/MBN, and DOC/DON. Overall, grass and forest provided more labile C and improved C sequestration than arable. So did NT under arable land-use.

Mulching Affects Soil Properties and Greenhouse Gas Emissions Under Long‐Term No‐Till and Plough‐Till Systems in Alfisol of Central Ohio

AbstractAgricultural activities emit greenhouse gases (GHGs) and contribute to global warming. Intensive plough tillage (PT), use of agricultural chemicals and the burning of crop residues are major farm activities emitting GHGs. Intensive PT also degrades soil properties by reducing soil organic carbon (SOC) pool. In this scenario, adoption of no‐till (NT) systems offers a pragmatic option to improve soil properties and reduce GHG emission. We evaluated the impacts of tillage systems (NT and PT) and wheat residue mulch on soil properties and GHG emission. This experiment was started in 1989 on a Crosby silt loam soil at Waterman Farm, The Ohio State University, Columbus, Ohio, USA. Mulching reduced soil bulk density and improved total soil porosity. More total carbon (16.16 g kg−1), SOC (8.36 mg L−1) and soil microbial biomass carbon (152 µg g−1) were recorded in soil under NT than PT. Mulch application also decreased soil temperature (0–5 cm) and penetration resistance (0–60 cm). Adoption of long‐term NT reduced the GHG emission. Average fluxes of GHGs under NT were 1.84 g CO2‐C m−2 day−1 for carbon dioxide, 0.07 mg CH4‐C m−2 day−1 for methane and 0.73 mg N2O‐N m−2 day−1 for nitrous oxide compared with 2.05 g CO2‐C m−2 day−1, 0.74 mg CH4‐C m−2 day−1 and 1.41 mg N2O‐N m−2 day−1, respectively, for PT. Emission of nitrous oxide was substantially increased by mulch application. In conclusion, long‐term NT reduced the GHG emission by improving the soil properties. Copyright © 2016 John Wiley & Sons, Ltd.

Application of plow-tillage as an innovative technique for eliminating overwintering cyanobacteria in eutrophic lake sediments

Surface sediment in eutrophic lakes is both a destination and a habitat for overwintering cyanobacteria. The resuspension and recovery of viable, overwintering cyanobacteria from the surface sediment during warm spring weather is usually the primary stage of cyanobacterial blooms (CBs) in shallow eutrophic lakes. Therefore, the elimination of overwintering cyanobacteria in sediment is vital to control CBs. In the present study, sediment plow-tillage (PT) was introduced as an innovative technique for eliminating overwintering cyanobacteria in sediments from Lake Chaohu. Four depths of PT (2, 5, 10, and 15 cm) were tested during the 42-day experiment. The results showed that rapid cell death during the first 0–7 d after PT was accompanied by high oxygen uptake rates. The viable cells in deeper sediment died more quickly and at a higher rate after PT. A PT depth of >10 cm effectively eliminated viable cyanobacteria (with a removal rate of 82.8%) from the sediment and prevented their resuspension. The activity of the viable cyanobacteria also decreased quickly as cyanobacteria were eliminated. It appears that the dark, anoxic environment of the deeper sediment after PT was responsible for the elimination of viable cells. Although high release rates of nitrogen and phosphorus were found to accompany the dying and decomposition of cyanobacteria during days 0–7 of the experiment, greater depth of PT was found to decrease nutrient concentrations in the overlying water. In conclusion, we recommend sediment PT as a new technique for eliminating overwintering algae in sediments. However, the release of nutrients from the sediment and the in situ control of CBs in lakes after PT should be further studied.

Tillage effects on carbon footprint and ecosystem services of climate regulation in a winter wheat–summer maize cropping system of the North China Plain

Inappropriate farm practices can increase greenhouse gases (GHGs) emissions and reduce soil organic carbon (SOC) sequestration, thereby increasing carbon footprints (CFs), jeopardizing ecosystem services, and affecting climate change. Therefore, the objectives of this study were to assess the effects of different tillage systems on CFs, GHGs emissions, and ecosystem service (ES) values of climate regulation and to identify climate-resilient tillage practices for a winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) cropping system in the North China Plain (NCP). The experiment was established in 2008 involving no-till with residue retention (NT), rotary tillage with residue incorporation (RT), sub-soiling with residue incorporation (ST), and plow tillage with residue incorporation (PT). The results showed that GHGs emissions from agricultural inputs were 6432.3–6527.3kgCO2-eqha−1yr−1 during the entire growing season, respectively. The GHGs emission from chemical fertilizers and irrigation accounted for >80% of that from agricultural inputs during the entire growing season. The GHGs emission from agricultural inputs were >2.3 times larger in winter wheat than that in the summer maize season. The CFs at yield-scale during the entire growing season were 0.431, 0.425, 0.427, and 0.427 without and 0.286, 0.364, 0.360, and 0.334kgCO2-eqkg−1yr−1 with SOC sequestration under NT, RT, ST, and PT, respectively. Regardless of SOC sequestration, the CFs of winter wheat was larger than that of summer maize. Agricultural inputs and SOC change contributed mainly to the component of CFs of winter wheat and summer maize. The ES value of climate regulation under NT was ¥159.2, 515.6, and 478.1ha−1yr−1 higher than that under RT, ST, and PT during the entire growing season. Therefore, NT could be a preferred “Climate-resilient” technology for lowering CFs and enhancing ecosystem services of climate regulation for the winter wheat–summer maize system in the NCP.

Development of a Plow Tillage Cycle for an Agricultural Tractor

<abstract> <b><sc>Abstract.</sc></b> Various field tests are needed to improve agricultural tractor performance; however, field tests require expenditures for constructing an experiment system and time for conducting the tests repeatedly. In addition, it is difficult to acquire reliable data because field tests depend on environmental conditions. For this reason, indoor tests using dynamometers have been used in the automotive industry instead of field tests. To ensure the reliability of indoor tests, standardized driving cycles are needed as input data for the dynamometer. Therefore, this study aimed to develop a standardized plow tillage cycle for agricultural tractors using real field data. A load measurement system was installed on a tractor to collect real field data from loads acting on the four driving axles and the hydraulic pumps. Plow tillage was conducted on ten farmlands of similar size (3000 m²; 100 m x 30 m) at three sites (A, B, and C). The plow tillage cycles for each site were developed using the driving cycle construction method for conventional vehicles with the measured load data. At one site, the entire dataset from the ten farmlands was first classified into micro-trips, which were the minimum patterns of plow tillage including plowing, three-point hitch ascending, and tractor turning. The arbitrary working cycles were generated by combining micro-trips, and less than 5% absolute percentage error was achieved between the entire dataset and the generated arbitrary working cycle. Second, the plow tillage cycle was determined considering the sum square difference (SSD) with a torque and torque variation probability distribution. The selected working cycle with the lowest SSD was determined as the plow tillage cycle. Third, the performance values (PVs) of the plow tillage cycles of agricultural tractors and the driving cycles of conventional vehicles were compared to evaluate the performance of the plow tillage cycle. The results showed that the ranges of absolute percentage error relative to the entire dataset were 1.0% to 4.9% for all sites. The SSDs of the plow tillage cycles were 1195.96, 958.77, and 1202.50, and the PVs of the plow tillage cycles were 99.60, 77.90, and 84.15 for sites A, B, and C, respectively. The PVs of the commonly used driving cycles were low, at 60% to 125% of the plow tillage cycles. The plow tillage cycles had especially higher performance than some of the international standard driving cycles by 104% to 125% for site B. The results showed that the developed plow tillage cycles can be applied to indoor tests for performance evaluation of agricultural tractors.

Fate of 15N-fertilizers in the soil-plant system of a forage rotation under conservation and plough tillage

For agriculture sustainability and biosphere conservation in the 21st century, to improve N use efficiency and to reduce the fertilization rates is fundamental. The N dynamics in the soil-plant system can be altered after the adoption of conservation practices, making necessary to evaluate the fertilizer efficiency and, if needed, to adapt N fertilization. Accordingly, during two years, we assess the effect of conventional plough tillage (PT) and conservation minimum tillage (MT) on the N dynamics in a 14-year-old ryegrass-maize forage rotation. We used a 15N-tracing approach to evaluate the recovery efficiency of N (REN) taking into account both the N immobilized in soil (0–5, 5–15, 15–30, 30–45 and 45–60cm) and that exported at harvest. Adjacent PT (n=9) and MT (n=9) plots were randomly assigned in triplicate to three treatments to which 15NH415NO3 (10 atom% 15N) was applied in one of the three first fertilizations (15NOctober-, 15NMarch- and 15NMay-fertilizer), the others being done with unlabelled N. Plant N concentration (% N) was affected (p<0.001; n=18) by the crop [80% of variance explained: ryegrass-1 (2.6±0.9%)>ryegrass-2 (1.9±0.4%)>maize-2 (1.4±0.1%)>maize-1 (1.1±0.2%)] and the crop-tillage interaction (22% of variance explained). Jointly considering all data, more 15N-fertilizer was recovered in the MT (25±4%) than in the PT soil profile (19±6%) at the end of the experiment whereas the N exported with the crops was unaffected by the tillage system and varied from 5–6% (15NOctober-fertilizer) to 45–49% (15NMarch-fertilizer) and 52–53% (15NMay-fertilizer; despite only three instead of four subsequent crops were studied).The 15N unaccounted for in the case of 15NOctober-fertilizer (72±5%) was more than twice that in 15NMarch- (34±7%) and 15NMay-fertilizer (25±14%). Considering soil, site and weather conditions, denitrification and nitrate leaching during the ryegrass-1 crop were the most likely processes explaining the high losses of the 15NOctober-fertilizer. Results suggested a higher initial immobilization of the applied 15N in the soil organic matter (SOM) of MT, that reduces 15N availability to the first crop, followed by an increase of the residual availability of the fertilizer 15N to the subsequent 2–3 crops.

Conservation tillage vs. conventional tillage: long-term effects on yields in continental, sub-humid Central Europe, Hungary

The present study reports novel data concerning Conservation Tillage (CT) in the continental sub-humid climate zone in Central Europe (Hungary), an area which has been mostly neglected in the course of previous CT studies. The results of a 10-year (2003–2013) comparative study of mouldboard ploughing tillage (PT) and CT (no inversion, using a reduced number of tillage operations and leaving min. 30% crop residues on the soil surface) types are reported. Our extensive monitoring system has provided new and detailed information concerning technologies and yields both from the first, transitional period and, over the following years, of adapted technology. Our results suggest that tillage type was a more important factor in the question of yields than either the highly variable climate of the studied years, or the diverse slope conditions of the plots. During the first three years of technological changeover to CT (2003–2006), a decrease of 8.7% was measured, respective to PT. However, the next seven years (2007–2013) brought a 12.7% increase of CT yields. Our study revealed key factors in the initial reduction of crops during the technological change, and may accordingly serve as a guideline for the shortening or avoidance of decline in the transitional period.

Influence of tillage systems and nitrogen management on grain yield, grain protein and nitrogen-use efficiency in UK spring wheat

SUMMARYEffects of soil tillage systems and nitrogen (N) fertilizer management on spring wheat yield components, grain yield and N-use efficiency (NUE) were evaluated in contrasting weather of 2013 and 2014 on a clay soil at the Royal Agricultural University's Harnhill Manor Farm, Cirencester, UK. Three tillage systems – conventional plough tillage (CT), high intensity non-inversion tillage (HINiT) and low intensity non-inversion tillage (LINiT) for seedbed preparation – were compared at four rates of N fertilizer (0, 70, 140 and 210 kg N/ha). Responses to the effects of the management practices were strongly influenced by weather conditions and varied across seasons. Grain yields were similar between LINiT and CT in 2013, while CT produced higher yields in 2014. Nitrogen fertilization effects also varied across the years with no significant effects observed on grain yield in 2013, while in 2014 applications up to 140 kg N/ha increased yield. Grain protein ranged from 10·1 to 14·5% and increased with N rate in both years. Nitrogen-use efficiency ranged from 12·6 to 49·1 kg grain per kg N fertilizer and decreased as N fertilization rate increased in both years. There was no tillage effect on NUE in 2013, while in 2014 NUE under CT was similar to LINiT and higher than HINiT. The effect of tillage and N fertilization on soil moisture and soil mineral N (SMN) fluctuated across years. In 2013, LINiT showed significantly higher soil moisture than CT, while soil moisture did not differ between tillage systems in 2014. Conventional tillage had significantly higher SMN at harvest time in 2014, while no significant differences on SMN were observed between tillage systems in 2013. These results indicate that LINiT can be used to produce similar spring wheat yield to CT on this particular soil type, if a dry cropping season is expected. Crop response to N fertilization is limited when soil residual N is higher, while in conditions of lower residual SMN, a higher N supply is needed to increase yield and improve grain protein content.

Responses of soil fungi to 5-year conservation tillage treatments in the drylands of northern China

Soil fungi have many important ecological functions such as decomposition of soil organic matter and facilitation of nutrient turnover and availability in agricultural soils, which can be influenced by tillage treatments. Conservation tillage is widely used in the dryland regions of northern China. However, insights into the effect of conservation tillage on soil fungal community compositions and structures are considerably limited. This study aimed to investigate the effect of 5-year conservation tillage treatments, including chisel plow tillage (CPT), zero tillage (ZT), and plow tillage (PT) as convention tillage treatment, on soil fungal communities by using high-throughput sequencing technology and quantitative polymerase chain reaction. Conservation tillage significantly influenced soil fungal diversity and phylogenetic composition by altering soil organic carbon content and texture. The fungal diversity and composition structure were similar for treatments causing higher soil perturbation, i.e., CPT and PT; ZT, a less disruptive agriculture practice, preserved soil biological integrity. The most abundant phyla across all samples were Ascomycota and Basidiomycota, which are considered to be the main classical fungal decomposers in soils. These results suggested that conservation tillage can affect crop residue decomposition and the soil organic carbon content, leading to changes in soil fungal community distribution patterns. Our findings might form the basis for the application of conservation tillage to produce more stable and sustainable soil ecosystems in the drylands of northern China.

Methane and nitrous oxide emissions under no-till farming in China: a meta-analysis.

No-till (NT) practices are among promising options toward adaptation and mitigation of climate change. However, the mitigation effectiveness of NT depends not only on its carbon sequestration potential but also on soil-derived CH4 and N2O emissions. A meta-analysis was conducted, using a dataset involving 136 comparisons from 39 studies in China, to identify site-specific factors which influence CH4 emission, CH4 uptake, and N2O emission under NT. Comparative treatments involved NT without residue retention (NT0), NT with residue retention (NTR), compared to plow tillage (PT) with residue removed (PT0). Overall, NT0 significantly decreased CH4 emission by ~30% (P < 0.05) compared to PT0 with an average emission 218.8 kg ha(-1) for rice paddies. However, the increase in N2O emission could partly offset the benefits of the decrease in CH4 emission under NT compared to PT0. NTR significantly enhanced N2O emission by 82.1%, 25.5%, and 20.8% (P < 0.05) compared to PT0 for rice paddies, acid soils, and the first 5 years of the experiments, respectively. The results from categorical meta-analysis indicated that the higher N2O emission could be mitigated by adopting NT within alkaline soils, for long-term duration, and with less N fertilization input when compared to PT0. In addition, the natural log (lnR) of response ratio of CH4 and N2O emissions under NT correlated positively (enhancing emission) with climate factors (temperature and precipitation) and negatively (reducing emission) with experimental duration, suggesting that avoiding excess soil wetness and using NT for a long term could enhance the benefits of NT. Therefore, a thorough understanding of the conditions favoring greenhouse gas(es) reductions is essential to achieving climate change mitigation and advancing food security in China.

Analysis of the axle load of an agricultural tractor during plow tillage and harrowing

Analysis of the axle load of an agricultural tractor during plow tillage and harrowing

Effects of tillage management on soil CO2 emission and wheat yield under rain-fed conditions

Tillage disturbance can affect carbon dynamics in soil and plant production through several mechanisms. There are few integrated studies that have dealt with the effect of tillage management on soil CO2 emission and yield of wheat grain (Triticum aestivum L.) in the Loess Plateau in China. A 3-year (2010–12 and 2013–14) field experiment with two types of tillage was established to investigate CO2 emission, its related soil properties, crop yields and yield-scaled CO2 emissions (CO2 emissions per unit crop production) under rain-fed field conditions. Some land was planted with winter wheat without using tillage (‘no tillage’; NT), whereas some used mouldboard plough tillage (‘conventional tillage’; CT). The results indicate that CO2 was significantly and positively related to total nitrogen (P &lt; 0.01), soil organic matter (P &lt; 0.01), soil enzymes (P &lt; 0.01; urease, invertase, and catalase), soil temperature (P &lt; 0.01) and total pore space (P &lt; 0.05). Multiple linear regression analysis in the NT plot included soil temperature and air filled pore space, explaining 85% (P &lt; 0.05) of the CO2 variability, whereas in the CT plot the multiple linear regression model included soil temperature, urease, bulk density and pH, explaining 80% (P &lt; 0.001) of the CO2 variability. Compared with the CT treatment, NT reduced the 3-year average yield-scaled CO2 emissions by 41% because of a 40% reduction in total CO2 emissions with no reduction in wheat yield. Thus, the results indicate that NT could be used to reduce the contribution of agriculture to CO2 emissions while simultaneously maintaining wheat crop production in this area.

Long-term tillage impacts on soil organic matter components and related properties on a Typic Argiudoll

Soil organic matter affects a number of soil processes and properties. A better understanding of soil-profile distribution of organic matter components and related soil properties under long-term tillage systems is thus needed. The objective of this study was to evaluate the impacts of 33 years no-till (NT), double disk (DD), chisel (CH), and plow tillage (PT) under corn (Zea mays L.)–soybean (Glycine max L.) rotation on soil organic C (SOC), particulate organic matter (POM), pH, and wet aggregate stability to 100cm soil depth on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) in eastern NE. After 33 years, NT and DD management increased SOC by 1.2 times and mean weight diameter (MWD) of aggregates by 2 times compared with CH and PT at the 0–10cm depth. At the 0–20cm, NT had 1.1 times higher SOC concentration than CH and PT. When compared with data collected 24 years prior to this study, SOC at the 0–20cm increased by 12.5% across NT, DD, and CH and by 2.7% for PT. No-till had 5 times higher total POM concentration than PT, 4.7 times higher than CH, and 2.4 times higher than DD at the 0–10cm depth. However, at the 10–20cm, PT had higher POM than other tillage systems, which is most probably due to mixing and burial of residues at the bottom of the plow layer. Soil pH did not differ among tillage treatments at the 0–10cm, but it differed in this order: PT>CH>DD>NT at the 10–20cm and PT=CH=DD>NT at the 20–40cm depth. The lower pH under NT, DD, and CH in deeper soil depths may be due to the limited or no lime mixing in these systems compared with PT. When compared with data (pH 5) collected 33 years prior to this study, soil pH increased by 0.9 in NT, 1.4 in DD, 1.5 in CH, and 1.9 units in PT at 0–20cm depth, probably due to surface application and incorporation of lime. Overall, 33 years of NT increased near-surface soil organic matter components and soil aggregation compared with the PT.

Cover crop and tillage intensities alter ground-dwelling arthropod communities during the transition to organic production

AbstractWe conducted a cropping systems experiment in central Pennsylvania, USA, to determine the effects of initial cover crop species and soil management on the abundance and composition of the ground-dwelling arthropod community. We hypothesized that we would detect legacy effects of the cover crops planted in year 1 of a 3-yr crop sequence on the arthropod community in the subsequent 2 yrs, and that these effects would be influenced by the intensity of tillage. We compared four systems in a factorial combination of perennial sod and legumes or annual cereal grain and legume as initial cover crops and moldboard or chisel plow tillage implemented in soybeans followed by maize in the subsequent 2 yrs. The entire experiment was initiated twice in adjacent locations, starting in 2003 (Start 1) and 2004 (Start 2). We quantified soil arthropod activity-density and community composition and identified all arthropods to order or family, and the ground and tiger beetles (Coleoptera: Carabidae) to species. In Start 1, but not Start 2, arthropod activity-density increased with each year following implementation of organic management. We observed few legacy effects of cover crop or tillage intensity on arthropod activity-density. The composition of the soil arthropod community was primarily defined by the initial cover crop in the first year, and by the interaction between cover crop and tillage intensity in the second and third year. A legacy effect associated with a yr-1 cover crop of cereal rye was observed for Scarabaeidae beetles and Formicidae (ants) in yr 2 and Carabidae beetles in yr 3 of Start 1, but not Start 2. Weed indicators contributed significantly to the variation in the soil arthropod community that was explained by the environment in yr 2 in Start 1, and in yr 3 in both Starts. Our observations support the concept that both immediate and legacy effects of management shape arthropod communities during the organic transition period, suggesting that transitioning systems could be managed in ways that conserve or enhance natural enemy populations.

Soil carbon storage and stratification under different tillage/residue-management practices in double rice cropping system

The importance of soil organic carbon (SOC) sequestration in agricultural soils as climate-change-mitigating strategy has become an area of focus by the scientific community in relation to soil management. This study was conducted to determine the temporal effect of different tillage systems and residue management on distribution, storage and stratification of SOC, and the yield of rice under double rice (Oryza sativa L.) cropping system in the southern China. A tillage experiment was conducted in the southern China during 2005–2011, including plow tillage with residue removed (PT0), plow tillage with residue retention (PT), rotary tillage with residue retention (RT), and no-till with residue retention on the surface (NT). The soil samples were obtained at the harvesting of late rice in October of 2005, 2007 and 2011. Multiple-year residue return application significantly increased rice yields for the two rice-cropping systems; yields of early and late rice were higher under RT than those under other tillage systems in both years in 2011. Compared with PT0, SOC stocks were increased in soil under NT at 0–5, 5–10, 10–20, and 20–30 cm depths by 33.8, 4.1, 6.6, and 53.3%, respectively, in 2011. SOC stocks under RT were higher than these under other tillage treatments at 0–30 cm depth. SOC stocks in soil under PT were higher than those under PT0 in the 0–5 and 20–30 cm soil layers. Therefore, crop residues played an important role in SOC management, and improvement of soil quality. In the 0–20 cm layer, the stratification ratio (SR) of SOC followed the order NT>RT>PT>PT0; when the 0–30 cm layer was considered, NT also had the highest SR of SOC, but the SR of SOC under PT was higher than that under RT with a multiple-year tillage practice. Therefore, the notion that conservation tillage lead to higher SOC stocks and soil quality than plowed systems requires cautious scrutiny. Nevertheless, some benefits associated with RT system present a greater potential for its adoption in view of the multiple-year environmental sustainability under double rice cropping system in the southern China.

Stover Harvest and Tillage System Effects on Corn Response to Fertilizer Nitrogen

Demand for corn (Zea mays L.) stover is increasing for livestock and bioenergy production. Excessive stover harvest (SH) could impact crop productivity and soil N cycling. A 3-yr study was conducted at two Iowa sites with continuous corn to determine the effect of SH level and tillage system on grain yield, response to N fertilization, and optimal N rate. Treatments were none, partial, and complete SH, chisel plow tillage and recently implemented no-till, and six N rates from 0 to 280 kg N ha⁻¹. Profile soil NO₃–N concentration (with no fertilizer N) increased slightly from spring preplant to early June only with no SH but were the same with all SH levels after corn harvest. Corn canopy normalized difference vegetative index (NDVI) values were greatest with both SH levels and chisel plow. Increases in NDVI due to SH was less with chisel plow than no-till. Corn grain yield was 9% (0.84 Mg ha⁻¹) greater with chisel plow than with no-till. At the economic optimum N rate (EONR), grain yield was not influenced by SH with chisel plow but was 6% greater with each SH level under no-till. The EONR was the same with both tillage systems but was 22 and 45 kg N ha⁻¹ lower with partial and complete SH, respectively, than no SH. Results of this study indicate the potential for increased corn yield with SH in a no-till system and a reduced fertilizer N rate requirement with SH regardless of tillage system.

Effects of tillage systems on soil organic carbon and total nitrogen in a double paddy cropping system in Southern China

Soil organic carbon (SOC) and total nitrogen (TN) stocks in cropland soils play important roles in soil quality and climate change mitigation. Farming management have great impacts on SOC and TN dynamics, and thus affecting soil quality. The objective of this study was to assess the effect of tillage systems on the changes in SOC and TN pools under a double rice (Oryza sativa L.) cropping system in Southern China. A field experiment was conducted during 2005 in Ningxiang, Hunan Province. It comprised of four tillage treatments including no-till with residue retention (NT), rotary tillage with residue incorporation (RT), plow tillage with residue incorporation (PT), and plow tillage with residue removed (PT0). The results showed that NT increased soil bulk density (ρb) in the 0–20cm soil layer. Adoption of NT increased the concentrations of SOC and TN at 0–5cm depth but decreased the concentrations in deeper soil. The greatest SOC and TN concentrations were observed under RT at 5–10cm depth and under PT at 10–20cm depth. Tillage practice had small effect on the soil C:N ratio in the soil profile. Adoption of NT farming enhanced the SOC and TN stocks in the 0–10cm layer, whereas PT increased SOC and TN stocks in the 0–50cm profile. The stratification ratio (SR) of the SOC and TN concentrations were larger under NT compared with RT and PT. Thus, the adoption of short-term (7–8 years) NT practices is beneficial for the enhancement of SOC and TN stocks in the 0–10cm soil profile, and rotational tillage may be an appropriate farming practice for paddy rice system.