Effects Of Tillage Intensity Research Articles

Effects of tillage intensity and pesticide treated seeds on epigeal arthropod communities and weed seed predation in a maize-soybean rotation

Tillage practices and the use of pesticide seed treatments (PST) both have the potential to influence epigeal arthropod communities and the ecosystem services they provide, yet few studies have examined both factors in conjunction. A three-year field study (2017–2019) was conducted to assess the independent and interactive effects of tillage and pesticide seed treatments on epigeal arthropod communities and weed seed predation in a long-term row crop tillage intensity experiment located in southeastern New Hampshire, USA. Throughout the study, maize and soybean were planted in rotation with and without pesticide seed treatments (seed coatings containing a mixture of systemic and contact fungicides and neonicotinoid insecticides) under three tillage systems (full-, strip-, and no-till) in a randomized complete block design with four replications. Epigeal arthropod communities were sampled with pitfall traps from September to October 2018–2019 and weed seed predation was assessed over the same period each year from 2017–2019. A total of 1669 individual arthropods, representing 47 taxonomic groups, were observed over the course of the study. In 2018, epigeal arthropod communities differed based only on pesticide seed treatment. The opposite response was observed in 2019, as epigeal arthropod communities differed based only on tillage. Activity densities of Pterostichus melanarius (Illiger) were higher in the strip-till compared to full-till treatment in 2018. Annual levels of post-dispersal weed seed predation by invertebrates (% total seeds removed) varied based on tillage treatment in 2017 and 2019, but not in 2018, and ranged from as low as 6.1 % to as much as 27.2 % depending on year and treatment. These data provide evidence that both pesticide seed treatments and tillage systems can influence the communities of epigeal arthropods that inhabit annual row crop agroecosystems relatively late in the growing season, when the majority of pesticide residues have likely dissipated, and that the weed seed predation services provided by members of this community can be strongly negatively impacted by intensive tillage.

Ammonia volatilization measured with the IHF method in a rainfed arable crop: Evaluation of tillage intensity and the number of experimental replicates

Ammonia (NH3) volatilization losses have severe impacts on human health, climate change and natural environments, but the effect of tillage intensity on these emissions has been barely evaluated in field conditions, particularly using micrometeorological methods, which require large surfaces. In this context, a field experiment in a barley (Hordeum vulgare L.) crop was set up in central Spain, in which NH3 volatilization losses from non-tilled plots (NT) were compared with those from conventionally tilled (T) plots, using the integrated horizontal flux (IHF) technique with three replicates. Ancillary soil and meteorological measurements were taken to explain NH3 fluxes, and the effect of the number of replicates on the results was statistically addressed. The highest NH3 emissions were obtained in NT plots after both basal (40 kg N ha−1 applied as urea) and top-dressing (120 kg N ha−1 applied as urea) fertilization events, while NH3 emission factors were higher after basal fertilization, in comparison with top-dressing application. Considering the sum of both periods, NT significantly increased NH3 emissions by 63 % with respect to T. We observed a notable influence of the number of replicates, since only two of the nine combinations of two replicates led to rejecting the null hypotheses. No tillage requires the optimized management of N (timing, rate and particularly source) to abate the potential side effects regarding NH3 volatilization, while the use of robust measurement methods (e.g. IHF) should be implemented with enough replicates to increase the precision in estimating differences.

Effects of Tillage Intensity, Cover Crop Species and Cover Crop Biomass on N-Fluxes, Weeds and Oat Yields in an Organic Field Experiment in Germany

The non-turning or only superficial turning of soil is considered to be a gentle tillage method. Nevertheless, conventional ploughs are widely used in organic farming for crop production reasons. For the further development of reduced tillage, and up to no tillage, the effects of three cover crop species and their incorporation with different tillage intensities on nitrogen (N) dynamics, weed emergence and the yield of the subsequent main crop, oats, were examined in a repeated organic one-year trial. Sinapis alba, Trifolium resupinatum, Vicia sativa and bare fallow were tested and incorporated using (1) a plough (PL), (2) reduced tillage (RT), (3) mulching + drilling (MD) and (4) direct drilling (DD). V. sativa was the most promising cover crop in combination with RT, MD and DD. In Trial 1, the soil mineral N content and oat yields after the introduction of V. sativa were on a similar level as those in the PL treatments, and weeds were not yield-limiting there. In Trial 2, the biomass production of V. sativa was only about half of that of Trial 1 and did not offer sufficient weed control, but V. sativa was still successful in the RT treatments. In both trials, the yield differences were more pronounced between the cover crop treatments after RT than after PL. RT, therefore, was more dependent on an adequate cover crop species than PL. The no-till method was not only dependent on an adequate cover crop species but also on its proper biomass production for sufficient weed control.

Soil Bacterial Community Diversity and Composition as Affected by Tillage Intensity Treatments in Corn-Soybean Production Systems

Our understanding on the effects of tillage intensity on the soil microbial community structure and composition in crop production systems are limited. This study evaluated the soil microbial community composition and diversity under different tillage management systems in an effort to identify management practices that effectively support sustainable agriculture. We report results from a three-year study to determine the effects on changes in soil microbial diversity and composition from four tillage intensity treatments and two residue management treatments in a corn-soybean production system using Illumina high-throughput sequencing of 16S rRNA genes. Soil samples were collected from tillage treatments at locations in the Southern Coastal Plain (Verona, MS, USA) and Southern Mississippi River Alluvium (Stoneville, MS, USA) for soil analysis and bacterial community characterization. Our results indicated that different tillage intensity treatments differentially changed the relative abundances of bacterial phyla. The Mantel test of correlations indicated that differences among bacterial community composition were significantly influenced by tillage regime (rM = 0.39, p ≤ 0.0001). Simpson’s reciprocal diversity index indicated greater bacterial diversity with reduction in tillage intensity for each year and study location. For both study sites, differences in tillage intensity had significant influence on the abundance of Proteobacteria. The shift in the soil bacterial community composition under different tillage systems was strongly correlated to changes in labile carbon pool in the system and how it affected the microbial metabolism. This study indicates that soil management through tillage intensity regime had a profound influence on diversity and composition of soil bacterial communities in a corn-soybean production system.

On-farm assessment of cassava root yield response to tillage, plant density, weed control and fertilizer application in southwestern Nigeria

Abstract Cassava is growing in importance in Nigeria as a food and industrial crop. Current yields are low due to poor soil fertility and because farmers do not use improved germplasm, clean planting material, or improved crop management in Nigeria. To provide feasible agronomic recommendations targeting increased root yield, the effects of tillage intensity, fertilizer application, plant density and weed control were tested in 230 farmers’ fields in southwestern Nigeria over two years. In 2016, tillage treatments were zero, single and double passage with a disc plough, followed by ridging (soil shaping) versus leaving the soil flat. Fertilizer application at 75:20:90 kg ha−1 NPK was tested against a control and two plant densities (10,000 versus 12,500 ha−1) were compared. In 2017, plant density at 10,000 ha−1 and double plough were excluded, while pre- and post-emergence herbicide application versus farmer’s choice of weed control (i.e. manual weeding using hand hoe) was introduced. Cassava was harvested at 12 months after planting, and yields were recorded as fresh root mass. In 2016, double plough (15.9 Mg ha−1) had a minor advantage over single plough (14.3 Mg ha−1), while zero plough produced 12.9 Mg ha−1 (P

Tillage Intensity Effects on Soil Structure Indicators—A US Meta-Analysis

Tillage intensity affects soil structure in many ways but the magnitude and type (+/−) of change depends on site-specific (e.g., soil type) and experimental details (crop rotation, study length, sampling depth, etc.). This meta-analysis examines published effects of chisel plowing (CP), no-tillage (NT) and perennial cropping systems (PER) relative to moldboard plowing (MP) on three soil structure indicators: wet aggregate stability (AS), bulk density (BD) and soil penetration resistance (PR). The data represents four depth increments (from 0 to >40-cm) in 295 studies from throughout the continental U.S. Overall, converting from MP to CP did not affect those soil structure indicators but reducing tillage intensity from MP to NT increased AS in the surface (<15-cm) and slightly decreased BD and PR below 25-cm. The largest positive effect of NT on AS was observed within Inceptisols and Entisols after a minimum of three years. Compared to MP, NT had a minimal effect on soil compaction indicators (BD and PR) but as expected, converting from MP to PER systems improved soil structure at all soil depths (0 to >40-cm). Among those three soil structure indicators, AS was the most sensitive to management practices; thus, it should be used as a physical indicator for overall soil health assessment. In addition, based on this national meta-analysis, we conclude that reducing tillage intensity improves soil structure, thus offering producers assurance those practices are feasible for crop production and that they will also help sustain soil resources.

Effects of tillage intensity on pore system and physical quality of silt-textured soils detected by multiple methods

Understanding the effects of agricultural management practices on soil functionality is an ongoing challenge in environmental science and agricultural practice. In the present study we quantified the effects of changes in tillage intensity on soil physical quality and pore size distribution after 6, 10 and 23 years. At three long-term tillage experimental sites in central Europe we analysed soils under four different soil management systems: conventional mouldboard tillage; chiselling + rotary harrow; rotary harrow; and no till. These treatments differed in mechanical intensity and depth. Pore size distributions were calculated from soil water retention curves based on high-resolution measurements. Subsequently, fractions of functional pore size classes and indicators of soil physical quality were determined and compared between the treatments. In addition, we evaluated the performance of two calculation approaches for pore size distribution: (1) fitting of a smoothing cubic spline; and (2) a bimodal van Genuchten function. The parametric function yielded a higher proportion of storage pores by approximately 3–5%. The combination of multiple measurement and evaluation methods enabled detailed comparison of soil physical characteristics between different tillage treatments. No-till soils showed a distinct lack of transmissive pores and higher bulk density, but similar plant-available water capacity, compared with the other treatments. Under all soil management systems, aeration deficits were observed, emphasising the high vulnerability for compaction of silt-dominated arable soils with a low organic matter content. Hence, the design of agricultural soil management strategies on such soils needs to consider the risks of compaction as thoroughly as erosion or chemical degradation.

Soil carbon and nitrogen dynamics under zone tillage of varying intensities in a kura clover living mulch system

Zone tillage is a reduced-tillage approach that attempts to capture both the environmental advantages of year-round ground cover and the agronomic benefits of in-row tillage. This study was conducted to determine the effect of differing levels of zone tillage intensity on soil carbon and nitrogen cycling in a corn-kura clover cropping system (Zea maize-Trifolium ambiguum). Research took place in Rosemount, MN in 2015 and 2016 in an established kura clover stand. Soils and kura clover biomass were each sampled three times in crop rows per year in four treatments that varied by intensity: NT (spray-down no-till), ST (shank-till, traditional strip till unit), RZT (zone-till, PTO-driven rotary zone tiller), and DT (double-till, ST + RZT). Samples were analyzed for microbial biomass (MB), soil inorganic nitrogen, and permanganate oxidizable carbon (POXC). Additionally, potentially mineralizable nitrogen (PMN) was measured for 2016 post-spring tillage soils. Greater spring kura clover biomass in 2016 (2449 kg ha−1) relative to 2015 (187 kg ha−1) influenced overall differences in soil quality between years. The double-till (DT) treatment had greater post-till soil inorganic N than the no-till (NT) treatment in 2016, and by corn harvest, both zone-till (RZT) and double-till (DT) had higher soil inorganic N than NT, indicating that the addition of kura clover biomass contributed to in-row, plant-available nitrogen. Double-till was also more effective in reducing kura clover encroachment into crop rows than NT. No effect of tillage intensity on PMN, MB, or POXC was observed at any sampling time, although trends of decreasing POXC paired with increasing MB over the 2016 growing season suggest that the quantity of incorporated kura clover biomass may have governed belowground nutrient cycling and soil fertility.

Conventional tillage decreases the abundance and biomass of earthworms and alters their community structure in a global meta-analysis.

The adoption of less intensive soil cultivation practices is expected to increase earthworm populations and their contributions to ecosystem functioning. However, conflicting results have been reported on the effects of tillage intensity on earthworm populations, attributed in narrative reviews to site-dependent differences in soil properties, climatic conditions and agronomic operations (e.g. fertilization, residue management and chemical crop protection). We present a quantitative review based on a global meta-analysis, using paired observations from 165 publications performed over 65years (1950-2016) across 40 countries on five continents, to elucidate this long-standing unresolved issue. Results showed that disturbing the soil less (e.g. no-tillage and conservation agriculture [CA]) significantly increased earthworm abundance (mean increase of 137% and 127%, respectively) and biomass (196% and 101%, respectively) compared to when the soil is inverted by conventional ploughing. Earthworm population responses were more pronounced when the soil had been under reduced tillage (RT) for a long time (>10years), in warm temperate zones with fine-textured soils, and in soils with higher clay contents (>35%) and low pH (<5.5). Furthermore, retaining organic harvest residues amplified this positive response to RT, whereas the use of the herbicide glyphosate did not significantly affect earthworm population responses to RT. Additional meta-analyses confirmed that epigeic and, more importantly, the bigger-sized anecic earthworms were the most sensitive ecological groups to conventional tillage. In particular, the deep burrower Lumbricus terrestris exhibited the strongest positive response to RT, increasing in abundance by 124% more than the overall mean of all 13 species analysed individually. The restoration of these two important ecological groups of earthworms and their burrowing, feeding and casting activities under various forms of RT will ensure the provision of ecosystem functions such as soil structure maintenance and nutrient cycling by "nature's plough."

Effect of ten years of reduced tillage and recycling of organic matter on crop yields, soil organic carbon and its fractions in Alfisols of semi arid tropics of southern India

Reducing tillage intensity and retaining residues are important components of conservation agriculture but in small holder systems in developing countries where crop residues have alternate uses such as fodder and fuelwood, recycling or external additions of organic matter may be a possible option. Information on impacts of long term reduced tillage on soil carbon, labile organic carbon fractions and their depth distribution is scant in drylands of semi arid regions. The effect of tillage intensity (CT—conventional tillage; RT—reduced tillage and MT—minimum tillage) and sources of nitrogen (100% OS: 100% of recommended N through organic source; 50% OS +50%IOS: 50% N through organic source and 50% N through inorganic source and 100% IOS: 100% N through inorganic source) on crop yields, soil organic carbon and C fractions in an Alfisol was assessed at the end of a 10 year long term experiment. Finger millet yields decreased significantly with reduction in tillage intensity (29%). Among N sources, highest yields were recorded with substitution of 50% of the N through organic source. After 10 years, the soil organic carbon (SOC) in 0–20cm soil layer with MT was 11% higher than with CT. The labile fractions of carbon, viz. particulate organic carbon (POC), microbial biomass carbon (MBC) and permanganate oxidizable carbon (KMnO4-C) under MT were 47%, 16% and 43% higher, respectively, in comparison to CT in the 0–20cm soil layer. The total carbon (TC) and total organic carbon (TOC) with MT were higher by 28% and 27% over CT and higher by 20% and 20% with 100%OS over 100% IOS. Labile carbon fractions revealed differential sensitivity and POC, MBC and KMnO4-C are sensitive indicators to detect short term management effects. Reducing tillage intensity and applying various N sources enhanced SOC marginally and the C sequestration rate varied from 62 to 186kgha−1yr−1. Based on the study it can be recommended for substitution of 50% of the recommended N with organic source as it increases crop yields and soil carbon and could be a potential alternative for residue retention for crops which have fodder value. Reducing the tillage intensity can enhance the SOC in semi arid rainfed systems but lower crop yields under MT is a concern which needs to be addressed in order to make these systems acceptable to the farming community.

Effect of tillage intensity, fertilizer and cowdung on soil water conservation, yield and protein content of wheat

Effect of tillage intensity, fertilizer and cowdung on soil water conservation, yield and protein content of wheat

Effects of tillage intensities on spatial soil variability and site-specific management in early growth of Eucalyptus grandis

Soil tillage is one of the most common and important site preparation managements in forestry. However, in highly variable soils, uniform management practices might not be the best alternative. Site-specific management on the other hand, allows an optimal resource management as well as decreased environmental impact. However, the choice of a suitable strategy to manage areas with high soil variability is still a challenge. Our goal was to compare strategies that use soil characteristics to improve the comparison of tillage managements on Eucalyptus grandis growth. Specifically, we aimed to: compare strategies that incorporate soil characteristics into the models to compare tillage treatments; to determine the most useful soil characteristics for zone management delineation; and to compare tillage methods for site-specific management. We compared tillage intensities in contrasting soil types in a randomized complete block design with four and five replications. Tillage treatments included pit-planting, disc harrowing, and subsoiler. Experimental units consisted of three rows of fifteen trees each. Soil characteristics as well as plant height and diameter were evaluated periodically during the first 30month after implantation. Intra-plot variability was described with multivariate geostatistical models. Using soil properties as covariates in the model to compare tillage treatments improved model fit. When root development is limited by soil conditions and electroconductivity is high, tillage intensity makes a difference in plant growth; subsoiler is the best treatment when electroconductivity is high, while disc harrowing is the best when electroconductivity is low. However, when root development is not limited by soil conditions, no differences were found between subsoiler and disc harrowing. We show how the use of soil characterization is a tool that provides better comparisons among treatments when high intra-plot variability is present. Additionally, the use of soil characterization either directly into the model or to determine zones provides useful information for site-specific management. Site-specific management could therefore easily be implemented to decrease the environmental impact of soil tillage as well as to increase wood production in forestry.

Influence of tillage on some soil chemical properties and Eucalyptus grandis growth

Afforestation has increased rapidly in Uruguay since the Congress in1989 passed a law that promotes commercial forestation. This has raised public questions about the long term effects of forestation on soil quality and tillage requirements. The objective of this work was to evaluate the effect of tillage intensity on some soil chemical properties and wood production. The experiment was carried out in a Mollic Hapludalf , and planted with Eucalyptus grandis in 1992. A randomized complete block design with three replicates was established. Tillage treatments included: pitplanting (PP), intensive tillage of the whole surface (IT), reduced tillage (RT) that corresponds to 1/3 of the surface, and unplanted soil (US). Soil organic carbon (SOC), pH(H20), pH(KCl), and exchangeable Al was measured in the planting row from 0-2.5, 2-5, 5-10, and 10-15 cm depth after remove all soil surface litter, 8 and 19 years after plantation. Diameter breath height (DBH), tree height (Ht), and wood volume (WV) was determined. Soil pH (H20) was higher in PP than the mean between IT and RT 8 years after plantation; however soil pH (H20) was higher in US than the mean of all tillage systems from 10-25 cm depth. Tillage systems did not affect soil pH (H20) 19 year after plantation. Soil pH (KCl) was higher in PP than IT and RT mean from 0-0.025, 0-025-0.05, and 0.10-0.15 m depth 8 years after plantation. Pit planting had more SOC from 0-2.5 than the other tillage systems in both evaluations. DBH, Ht, and WV were not affected by tillage systems. This research indicates that tillage systems effects on soil pH detected 8 years after plantation tends to disappear when the plantation was 19 years-old. Pit-planting had more SOC than intensive tillage systems while maintaining the same wood production than more intensive tillage systems.

Effects of tillage intensity and anionic polyacrylamide on sediment and nitrogen losses in irrigated wheat field

Degradation of agricultural soils and nutrient losses affected by intensive agriculture and tillage is of environmental and agricultural concerns. These concerns lead to emergence and development of conservative technologies such as conservation tillage systems [reduced tillage (RT) and no-till (NT)] and anionic polyacrylamide (PAM). A study was done in order to investigate the interactive effects of three tillage systems and three PAM concentration on sediment loss, runoff nitrate concentration, nitrogen losses from the soil-plant system and nitrogen recovery. The experimental design was a randomized complete block with split-plot arranged in three replications. The anionic polyacrylamide (PAM) were in three levels of zero (P0), 10 (P10) and 20 (P20) mg L-1 as the main plot and different tillage intensities as the subplot including moldboard plowing plus two disk harrow passes (CT1), one stubble cultivator pass (RT) and moldboard plowing plus one power harrow pass (CT2). The RT treatment relative to CT2 led to soil loss reduction by 23.56% during the first irrigation. The P10 and P20 treatments relative to P0, caused sediment concentration reduction by 98.1 and 98.09% and soil loss reduction by 98.7% and 98.8%, respectively. The RT × P20 treatment had a greater impact in reduction runoff nitrate losses than CT1 × P20 and CT2 × P20 treatments. Losses of N in the fertilized plots and recovery of applied N (RAN) was influenced by both tillage system and PAM application. Key words: Tillage, polyacrylamide, polyacrylamide, soil losses, nitrate.

Efecto del laboreo sobre la eficacia de herbicidas y el crecimiento de crecimiento de Eucalyptus spp.

La eliminación de la competencia de malezas en el cultivo de Eucalyptus es fundamental en las etapas iniciales de crecimiento hasta el cierre de copa. En el Uruguay, el control de malezas en el surco de plantación se realiza básicamente con herbicidas premergentes, los cuales se asocian a una preparación de suelo muy estricta en relación al afinado para mejorar así la efectividad de los herbicidas, con el consecuente incremento de los costos de producción y de los riesgos de erosión. Se estudió el efecto del tipo de laboreo en la fila (una pasada de excéntrica; dos pasadas de excéntrica, la última con una rastra de dientes; igual al anterior, seguido de acamellonado) sobre la efectividad de los herbicidas premergentes y sobre el crecimiento del clon Eucalyptus grandis x Eucalyptus globulus. Los tratamientos herbicidas fueron oxifluorfen 240 g/ha, oxifluorfen 480 g/ha, isoxaflutole 150 g/ha, sulfentrazona 300 g/ha, sulfentrazona 400 g/ha, diclosulam 42 g/ha + acetoclor 1800 g/ha, acetoclor 1800 g/ha, oxifluorfen 240 g/ha+ acetoclor 1800 g/ha. La mayor intensidad en el laboreo disminuyó la infestación inicial de malezas. La eficiencia de los herbicida premergentes sobre la cobertura total de malezas no interaccionó con el tipo de laboreo. Los tratamientos selectivos de mayor control de malezas fueron isoxaflutole y oxifluorfen + acetoclor.

Effect of tillage intensity on weed infestation in organic farming

Conservation tillage is not yet widely accepted by organic farmers because inversion tillage is considered to be necessary for weed control. Three long-term experiments were established with combinations of reduced and conventional plough tillage and stubble tillage to determine weed infestation levels in organic farming, i.e. herbicide application being excluded. Experiment 1 (with very low stocking density of perennial weeds) showed that in presence of primary tillage by mouldboard ploughing the number of annual weeds was nearly unaffected by the mode of stubble tillage. In experiment 2, however, with Canada thistle ( Cirsium arvense) being artificially established, thistle density was significantly affected by stubble tillage and by a perennial grass–clover forage crop. Experiment 3 combined two levels of stubble tillage (skimmer plough, no stubble tillage = control) with four implements of primary tillage in the order of decreasing operation depth (deep mouldboard plough, double-layer plough, shallow mouldboard plough or chisel plough). Primary tillage by chisel plough resulted in significantly highest annual weed density compared to all other treatments. The natural C. arvense infestation in experiment 3 showed highest shoot density in the “skimmer plough/chisel plough” treatment compared to the lowest infestation in the “skimmer plough/double-layer plough” treatment. The poor capacity of the chisel plough for weed control was also reflected by the soil seed bank (5500 m −2 C. arvense seeds for chisel plough, <300 seeds for all other primary tillage). A reduced operation depth of the mouldboard plough (“shallow mouldboard plough”) seemed to have an insufficient effect in controlling C. arvense infestation as well. Stubble tillage by the skimmer plough in addition to nearly any primary tillage operation largely reduced both annual weeds and thistle shoots. Most effective in controlling C. arvense was also a biennial grass–clover mixture as part of the crop rotation.Double-layer ploughing is a compromise between soil inversion and soil loosening/cutting and can be regarded as a step towards conservation tillage. In terms of controlling annual weeds and C. arvense, the double-layer plough was not inferior to a deep mouldboard plough and seems to be suitable for weed control in organic farming. Tilling the stubble shallowly after harvest can support weed control in organic farming remarkably, particularly in reducing C. arvense. If no noxious, perennial weeds occur and primary tillage is done by soil inversion, an omission of stubble tillage can be taken into consideration.

Effect of tillage intensity on population densities of Heterodera glycines in intensive soybean production systems

The effects of tillage on Heterodera glycines, the most important yield-reducing pathogen of soybean in the U.S., were examined in a long-term tillage and crop sequence study initiated in 1975 on a mollisol at Purdue University. Population densities of H. glycines were monitored under corn–soybean rotation and soybean monoculture in 2003 and 2004. Tillage treatments included: (A) fall moldboard plow + spring secondary tillage; (B) fall chisel plow + spring secondary tillage; (C) ridge tillage; and (D) no-tillage. In both years in the rotational plots, final population densities of H. glycines were proportional to tillage intensity. Under both soybean and corn rotation crops, highest population densities were observed with plowing + secondary tillage and lowest population densities were detected under no-tillage. In 2004, population densities in monoculture soybean soil declined with depth intervals in layers of 0–10, 10–20, and 20–30-cm depth under no-till, but not in plowed plots. Multiple regression analysis determined that the stratification of nematode population densities was strongly correlated to penetrometer resistance and potassium concentration of the soil. Tillage seemed to affect population densities of H. glycines by modification of the soil physical parameters in corn–soybean rotation plots. Reducing tillage intensity was beneficial in reducing population densities of H. glycines in rotational soils. Thus, the choice of tillage system can reduce the risk for damage by this widely distributed pathogen.

Suitability of enzyme activities for the monitoring of soil quality improvement in organic agricultural systems

There is growing interest in the applications of soil enzymes as early indicators of soil quality change under contrasting agricultural management practices. However, despite there being an abundant literature on this subject, most comparative assessments have been based on a limited number of experimental farms and, therefore, conclusions are not as robust as desired. In this study, we compare 18 pairs of organic and neighbouring conventional olive orchards in southern Spain. These sites were selected to allow the definition of the relative contributions of site-landscape features, soil type, and time since organic accreditation and tillage intensity, on the soil quality. Soils were analysed for physico-chemical properties, the activities of dehydrogenase, β-glucosidase, arylsulphatase, acid and alkaline phosphatase, and potential nitrification. The geometric mean of the assayed enzymes (GMea) was validated with an independently performed Principal Component Analysis (PCA), and used as a combined soil quality index. The effects of tillage intensity and time since organic accreditation on the improvement of soil quality were also evaluated within the subset of organic farms. Overall for the 18 sites, contrasted management practices did not differ in their impact on basic soil physico-chemical properties, except for loss of on ignition and available inorganic N which were higher and lower in organic farms, respectively. Organic management resulted in significantly higher soil enzyme activities. However, differences were not significant in some of the paired comparisons when considered individually. This highlights the need for extensive comparative assessment, as in this study, to draw clear conclusions concerning the changes to soil quality under sustainable management practices. The GMea was significantly correlated with the first axis of the PCA and shown to be appropriate for condensing the set of soil enzyme values to a sole numerical value. Soil quality changes in organic versus conventional farms, as measured by the GMea, ranged from −23% to 97%, and was highly dependent on time since organic accreditation ( r = 0.88; P < 0.01). On the other hand, tillage intensity clearly tended to delay any progress in soil quality in the organic farms.

Growth, yield, and yield components of winter wheat and the effects of tillage intensity, preceding crops, and N fertilisation

Conservation tillage is widely practiced in semi-arid climates, mostly in small grain crop rotations. It is implemented to a much lesser extent in cool and humid climates of Europe, mainly due to a lack of knowledge about agronomic and ecological impacts. This study was conducted in light- to medium-textured soils in the Swiss midlands from 1995 to 2000. The aim was to determine whether tillage intensity impacted wheat yield and measure the effects of the preceding crop and the level of N fertilisation. Conventional tillage (CT) with ploughing, minimum tillage (MT) with a chisel, and no-tillage (NT) were studied in the following crop rotation: winter wheat ( Triticum aestivum L.)–oilseed rape ( Brassica napus L.)–winter wheat–maize ( Zea mays L.). Winter wheat was grown at either 0 kg N ha −1 (N0) or at the recommended N supply (N1). Harvest residues of all the crops were left on the field. In the early stages wheat development under NT was slightly slower than under CT and MT, but at maturity the shoot biomass was 2% higher under NT than under the other tillages. The grain yield decreased by 3% under NT compared to CT and MT, mainly due to fewer ears per area and a significantly lower thousand-kernel weight. Wheat planted after oilseed rape had significantly higher shoot biomass and grain yield than wheat planted after maize. At the beginning of the vegetation season there were small but significant differences in the soil mineral N content among the tillage treatments. Accordingly, the level of N fertiliser applied was adjusted to ensure similar N availability in all tillage systems. The relative reduction in grain yield under NT compared to CT and MT was similar with and without N fertilisation. Thus, N availability was not a limiting factor for the yield of NT wheat in this study.

Effect of tillage intensity and herbicide programs on changes in weed species density and composition in the southeastern coastal plains of the United States

An experiment was conducted from spring 2001 to 2005 at Blackville, SC, to determine the impact of no-till and glyphosate-resistant crops on changes in the weed community. Glycine max (L.) Merr. (soybean) was grown in 2001 and 2003, and Zea mays L. (corn) was grown in 2002 and 2004. Tillage each year included no-tillage and conventional tillage (disking and field cultivation prior to crop sowing). Glyphosate-only and nonglyphosate programs were evaluated within each tillage system. Soil cores were collected at 0–5 and 5–10 cm depths prior to spring to estimate the seedbank. Weed biomass by species was determined in mid-summer each year, except in 2003. Twenty-seven species were found in soil collected from the test site throughout the study. Digitaria sanguinalis (L.) Scop. (large crabgrass), Amaranthus palmeri S. Wats. (Palmer amaranth), and Mollugo verticillata L. (carpetweed) were the dominant weeds in soil at initiation of the experiment. Summer annual grasses comprised more than 20% of total weed biomass in 2001, but less than 1% of total biomass in 2002 and 2004. D. sanguinalis seed density in soil was reduced rapidly in all management systems and was replaced by Dactyloctenium aegyptium (L.) Willd (crowfootgrass) as the dominant summer annual grass. There was an 80–99% reduction in the A. palmeri seed density (0–5 cm depth) during the first year of the study and M. verticillata became the dominant summer annual broad-leaved weed. Perennial weeds comprised <10% of the total weed biomass in 2001, but by 2004, >99% of the total weed biomass was made up of perennial weeds in nonglyphosate systems regardless of tillage treatment. These perennial weeds consisted of Cynodon dactylon (L.) Pers. (bermudagrass), Cyperus rotundus L. (purple nutsedge), and Solanum carolinense L. (Carolina horsenettle). The seed density in soil of most species declined over the four cropping seasons.