Conservation Tillage Systems Research Articles

Short Communication: A corn test crop confirms beneficial effects of crop rotation in three tillage systems

Légère, A. Stevenson, F. C. and Vanasse, A. 2011. Short Communication:A corn test crop confirms beneficial effects of crop rotation in three tillage systems. Can J. Plant Sci. 91: 943–946. Glyphosate-tolerant corn was planted with minimal fertilization in an 18-yr-old tillage and crop rotation experiment. Silage yields were 24% greater following a cereal-oilseed rotation than a cereal monoculture, regardless of tillage, and in spite of greater weed biomass in no-till. The diversified crop rotation proved beneficial, even in mature conservation tillage systems.

Glyphosate-resistant Palmer amaranth: A threat to conservation tillage

Conservation tillage reduces the physical movement of soil to the minimum required for crop establishment and production. When consistently practiced as a soil and crop management system, it greatly reduces soil erosion and is recognized for the potential to improve soil quality and water conservation and plant available water. Adoption of conservation tillage increased dramatically with the advent of transgenic, glyphosate-resistant crops that permitted in-season, over-the-top use of glyphosate (N-[phosphonomethyl] glycine), a broad-spectrum herbicide with very low mammalian toxicity and minimal potential for off-site movement in soil or water. Glyphosate-resistant crops are currently grown on approximately 70 million ha (173 million ac) worldwide. The United States has the most hectares (45 million ha [99 million ac]) of transgenic, glyphosate-resistant cultivars and the greatest number of hectares (46 million ha [114 million ac]) in conservation tillage. The practice of conservation tillage is now threatened by the emergence and rapid spread of glyphosate-resistant Palmer amaranth (<i>Amaranthus palmeri</i> [S.] Wats.), one of several amaranths commonly called pigweeds. First identified in Georgia, it now has been reported in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee. Another closely related dioecious amaranth, or pigweed, common waterhemp (<i>Amaranthus rudis</i> Sauer), has also developed resistance to glyphosate in Illinois, Iowa, Minnesota, and Missouri. Hundreds of thousands of conservation tillage hectares, some currently under USDA Natural Resources Conservation Service conservation program contracts, are at risk of being converted to higher-intensity tillage systems due to the inability to control these glyphosate-resistant <i>Amaranthus</i> species in conservation tillage systems using traditional technologies. The decline of conservation tillage is inevitable without the development and rapid adoption of integrated, effective weed control strategies. Traditional and alternative weed control strategies, such as the utilization of crop and herbicide rotation and integration of high residue cereal cover crops, are necessary in order to sustain conservation tillage practices.

Root Growth of Barley as Affected by Tillage Systems and Nitrogen Fertilization in a Semiarid Mediterranean Agroecosystem

Conservation tillage systems are being widely adopted in the Mediterranean region. A long‐term field experiment was established in 1996 comparing three N fertilization levels (zero, 0 kg ha−1; medium, 60 kg ha−1; and high, 120 kg ha−1), under three tillage systems (conventional tillage, CT; minimum tillage, MT; and no‐tillage, NT) in a semiarid Mediterranean agroecosystem annually cropped with winter barley (Hordeum vulgare, L., cultivar Hispanic), to study the response of root growth. During four consecutive growing seasons, from 2005 to 2009, root length density (RLD) and soil water content were evaluated. Penetration resistance (PR) and soil bulk density were only evaluated in the fourth and last year of this experiment. In dry years, root growth was similar under NT and MT systems but highly reduced under CT due to reduced water availability, which, in the surface 25 cm of soil was 7% and 18% lower than under MT and NT systems, respectively. However, in a wet year (i.e., 2009), RLD was double under CT than under NT due to reduced soil strength. PR at 5 to 15 cm soil depth under NT was 1MPa greater than under MT or CT. Root growth was not affected by N fertilization, in contrast to the response of grain yield that showed a significant interaction between N fertilization and tillage system. In spite of moderate soil compaction, which may reduce root growth in wet years, long‐term NT adoption does not reduce grain yields for monoculture of barley under semiarid Mediterranean conditions.

Tillage, Cover-Crop Residue Management, and Irrigation Incorporation Impact on Fomesafen Runoff

Intensive glyphosate use has contributed to the evolution and occurrence of glyphosate-resistant weeds that threaten production of many crops. Sustained use of this highly valued herbicide requires rotation and/or substitution of herbicides with different modes of action. Cotton growers have shown considerable interest in the protoporphyrinogen oxidase inhibitor, fomesafen. Following registration for cotton in 2008, use has increased rapidly. Environmental fate data in major use areas are needed to appropriately evaluate risks. Field-based rainfall simulation was used to evaluate fomesafen runoff potential with and without irrigation incorporation in a conventional tillage system (CT) and when conservation tillage (CsT) was practiced with and without cover crop residue rolling. Without irrigation incorporation, relatively high runoff, about 5% of applied, was measured from the CT system, indicating that this compound may present a runoff risk. Runoff was reduced by >50% when the herbicide was irrigation incorporated after application or when used with a CsT system. Data indicate that these practices should be implemented whenever possible to reduce fomesafen runoff risk. Results also raised concerns about leaching and potential groundwater contamination and crop injury due to rapid washoff from cover crop residues in CsT systems. Further work is needed to address these concerns.

Trend and uncertainty analysis of simulated climate change impacts with multiple GCMs and emission scenarios

Trends and uncertainty of the climate change impacts on hydrology, soil erosion, and wheat production during 2010–2039 at El Reno in central Oklahoma, USA, were evaluated for 12 climate change scenarios projected by four GCMs (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emissions scenarios (A2, B2, and GGa). Compared with the present climate, overall t-tests ( n = 12) show that it is almost certain that mean precipitation will decline by some 6% (>98.5% probability), daily precipitation variance increase by 12% (>99%), and maximum and minimum temperature increase by 1.46 and 1.26 °C (>99%), respectively. Compared with the present climate under the same tillage systems, it is very likely (>90%) that evapotranpiration and long-term soil water storage will decease, but runoff and soil loss will increase despite the projected declines in precipitation. There will be no significant changes in wheat grain yield. Paired t-tests show that daily precipitation variance projected under GGa is greater than those under A2 and B2 ( P = 0.1), resulting in greater runoff and soil loss under GGa ( P = 0.1). HadCM3 projected greater mean annual precipitation than CGCM2 and CSIRO ( P = 0.1). Consequently, greater runoff, grain yield, transpiration, soil evaporation, and soil water storage were simulated for HadCM3 ( P = 0.1). The inconsistency among GCMs and differential impact responses between emission scenarios underscore the necessity of using multi-GCMs and multi-emission scenarios for impact assessments. Overall results show that no-till and conservation tillage systems will need to be adopted for better soil and water conservation and environmental protection in the region during the next several decades.

Tillage and green manure effects on Bt transgenic cotton ( Gossypium hirsutum L.) hybrid grown on rainfed Vertisols of central India

Transgenic Bt cotton hybrids, in India, now constitute more than 90% of the cotton area. Conservation tillage systems such as reduced tillage (RT) improve soil health and crop productivity. Field experiments were conducted to study the response of Bt cotton hybrids to the tillage methods in a split plot design for three years (2005–2006 to 2007–2008) with tillage practices as main plots (conventional tillage {CT}, RT with two inter-row cultivations {RT 1} and RT with no inter-row cultivation {RT 2}). In the sub-plot, in situ green manure (GM) was included along with 100 (GM + N 100), 80 (GM + N 80) and 60 kg N ha −1 (GM + N 60) and were compared to N alone (N 100). Growth, yield and fibre quality of Bt transgenic cotton hybrid (RCH-2 Bt) were monitored during the study. In all seasons, weed density and biomass were significantly lower in the RT treatments than in the CT treatments. Taller plants with more main stem nodes were produced on the RT plots (63.6–75.8 cm) than on the CT plots (58.1–70.2 cm). Thus, plants of RT treatment retained more bolls (60.8–62.0 m −2) than those of the CT treatment (52.4 m −2). Averaged over seasons, RT treatment had seed cotton yield (1717–1740 kg ha −1) significantly higher than the CT treatment (1489 kg ha −1). The treatments N 100, GM + N 100 and GM + N 80 (1687–1734 kg ha −1) did not differ and were significantly better than the GM + N 60 (1303 kg ha −1). Tillage × GM interaction was significant in two of three years and data combined over years. The RT plots with GM had significantly greater yield than the CT plots. Compared to the CT treatment, the RT plots had significantly greater proportion of water stable aggregates (48.6% vs. 54.4–56.0%) and mean weight diameter (0.47 mm vs. 0.49–0.51 mm). The GM plots had significantly higher WSA and MWD than those without. Further, soil moisture content was greater in the GM mulched plots up to 0.60 m depth compared to without GM treatment (CT + N 100). Favourable soil physical properties may have contributed to improved seed cotton yield in the RT treatments with GM than in the CT treatment. Fibre quality was not affected by either the tillage systems or GM. This study indicates that Bt transgenic cotton can be grown under RT systems with an in situ legume GM.

Effects of Fluidized Gas Desulfurization (FGD) Gypsum on Non-Target Freshwater and Sediment Dwelling Organisms

Fluidized gas desulfurization gypsum is a popular agricultural soil amendment used to increase calcium and sulfur contents, and reduce aluminum toxicity. Due to its surface application in conservation tillage systems and high solubility, the soluble components of gypsum may be transferred with agricultural runoff into receiving waters. The current study measured toxicity of gypsum to Ceriodaphnia dubia, Pimephales promelas, Chironomus dilutus, and Hyalella azteca. Solutions at 2,400 mg gypsum/L (maximum solubility) produced no observable toxicity to C. dubia and P. promelas. Mixtures of a control sediment and gypsum indicated no observed toxicity effects for H. azteca, although effects were noted at 25% dilution for C. dilutus. Data suggest gypsum is not harmful to freshwater organisms at concentrations expected in the agricultural environment.

Qualidade física de um Latossolo Vermelho submetido a sistemas de manejo avaliado pelo Índice S

O monitoramento da qualidade do solo pelos atributos físicos é importante para a avaliação e manutenção da sustentabilidade dos sistemas agrícolas. Um atributo indicador da qualidade do solo deve ser sensível às variações do manejo ao qual está sendo submetido. Este estudo teve como objetivo avaliar o parâmetro S como indicador da qualidade física do solo e a agregação de um Latossolo Vermelho distrófico, submetido a sistemas de manejo sem ou com a inclusão de plantas de cobertura em pré-safra durante 11 anos. Os tratamentos foram: sistema convencional (SC) e sistemas conservacionistas compostos por plantas de cobertura, crotalária (SDC), milheto (SDM) e lablabe (SDL). O delineamento experimental foi o de blocos casualizados, com quatro tratamentos e seis repetições; as camadas constituíram-se nas parcelas subdivididas. Os sistemas conservacionistas SDC, SDM e SDL apresentaram maior teor de matéria orgânica em relação ao SC nas camadas de 0 a 0,05 m. Maiores valores de diâmetro médio ponderado e geométrico dos agregados foram observados nos sistemas conservacionistas. O solo apresentou boa qualidade física determinada pelo índice S, com valores todos superiores a 0,035.

Implementation of chiselling and mouldboard ploughing in soil after 8 years of no-till management in SW, Spain: Effect on soil quality

Long-term no-till practices (NT) have a positive effect on recovery and improving soil fertility and decreasing soil erosion. Nevertheless, long term no-till practices may also cause some inconveniences, such as soil compaction, water infiltration and problems in seed germination. Thus, in the present work we assess the effects of the implementation (October 2008) of a traditional tillage (mouldboard ploughing) (TT) and reduced tillage (chiselling) (RT) on soil quality in a dryland calcareous soil (Leptic Typic Xerorthent) after 8 years of soil no-till management (NT) in SW Spain. The results were compared to those found under no-till. We hypothesised that C fractions and biological properties would be adequate indicators of soil quality changes. To test the hypothesis soil samples were collected at three depths (0–5, 5–10 and 10–25 cm) and in three sampling periods, after tillage and sowing (January 2009) after harvesting (June 2009) a vetch crop ( Vicia sativa, L) and after tillage and sowing (January 2010) of a wheat crop ( Triticum aestivum, L). Total organic carbon (TOC) and carbon labile fractions (active carbon (AC) and water soluble carbon (WSC)) were determined. Biological status was evaluated by the analysis of soil microbial biomass carbon and nitrogen (MBC and MBN) and enzymatic activities [dehydrogenase activity (DHA), and β-glucosidase activity (Glu)]. The implementation of chiselling did not cause depletion in most of the studied soil properties compared to no-till in the first 5 cm of soil. However, the application of traditional tillage reduced 23% of TOC, 27% of WSC, 12% of AC, 19% of MBC, 44% of MBN, 37% of DHA and 51% of Glu in the upper layer of the soil (0–5 cm depth) with respect to no-till. Soil organic carbon and microbial parameter values decreased as depth increased, particularly in conservation tillage systems (RT and NT) in all sampling periods. Under our conditions, dryland Mediterranean areas, the mouldboard ploughing is not considered a suitable soil tillage system since it showed an early negative effect on soil organic fractions and biochemical quality. Although further studies would be necessary, the use of chiselling could be a solution in case of problems related to no-till.

Winter barley performance on two different soils under conservation tillage systems

Conservation tillage is becoming increasingly attractive to farmers due its potential to reduce production costs and allow a more sustainable land use as compared with conventional tillage. Field experiments were conducted over three consecutive growing seasons to study barley performance under three tillage systems (minimum, reduced, and conventional tillage) on two different soils (a sandy loam and a clay soil) of northern Greece. No significant differences in plant number, ear number, or grain yield were observed among tillage systems in any growing season in the sandy loam soil. By contrast, reduced plant number by 15 and 18% in the first growing season and by 18 and 21% in the third growing season was observed for the reduced and the minimum tillage system, respectively, in the clay soil as compared with conventional tillage. Reduced plant number in the clay soil was due to the unfavorable soil conditions during sowing and the uneven seedbed as a result of the presence of summer weeds which apparently prevented correct and uniform planting depth. However, no significant differences in ear number or barley grain yield were found among tillage systems in any growing season in the clay soil. Findings of this study showed that conservation tillage can affect the establishment of barley stands depending on soil type and weather conditions but this is not always expressed in grain-yield reduction due to the effect of compensation through increased tillering.

ECONOMIC AND STOCHASTIC EFFICIENCY COMPARISON OF EXPERIMENTAL TILLAGE SYSTEMS IN CORN AND SOYABEAN UNDER RISK

SUMMARYThere are many reasons why agricultural researchers carefully evaluate approaches to experimental data analysis. Agricultural experiments are typically highly complex, with many types of variables often collected at a wide range of temporal and spatial scales. Furthermore, research in the developing world is often conducted on-farm where simple and conventional experimental designs are often unsuitable. Recently, a variant of stochastic dominance called stochastic efficiency with respect to a function (SERF) has been developed and used to analyse long-term experimental data. Unlike traditional stochastic dominance approaches, SERF uses the concept of certainty equivalents (CEs) to rank a set of risk-efficient alternatives instead of finding a subset of dominated alternatives. This study evaluates the efficacy of the SERF methodology for analysing conventional and conservation tillage systems using 14 years (1990–2003) of economic budget data collected from 36 experimental plots at the Iowa State University Northeast Research Station near Nashua, IA, USA. Specifically, the SERF approach is used to examine which of two different tillage systems (chisel plough and no-till) on continuous corn (Zea mays) and corn/soyabean (Glycine max) rotation cropping systems are the most risk-efficient in terms of maximizing economic profitability (gross margin and net return) by crop across a range of risk aversion preferences. In addition to the SERF analysis, we also conduct an economic analysis of the tillage system alternatives using mean-standard deviation and coefficient of variation for ranking purposes. Decision criteria analysis of the economic measures alone provided somewhat contradictive and non-conclusive rankings, e.g. examination of the decision criteria results for gross margin and net return showed that different tillage system alternatives were the highest ranked depending on the criterion and the cropping system (e.g. individual or rotation). SERF analysis results for the tillage systems were also dependent on the cropping system (individual, rotation or whole-farm combined) and economic outcome of interest (gross margin or net return) but only marginally on the level of risk aversion. For the individual cropping systems (continuous corn, rotation corn and rotation soyabean), the no-till tillage and rotation soyabean system was the most preferred and the chisel plough tillage and continuous corn system the least preferred across the entire range of risk aversion for both gross margin and net return. The no-till tillage system was preferred to the chisel plough tillage system when ranking within the continuous corn and the corn-soyabean rotation cropping systems for both gross margin and net return. Finally, when analysing the tillage system alternatives on a whole-farm basis (i.e. combined continuous corn and corn-soybean rotation), the no-till tillage system was clearly preferred to the chisel plough tillage system for both gross margin and net return. This study indicates that the SERF method appears to be a useful and easily understood tool to assist farm managers, experimental researchers and, potentially, policy makers and advisers on problems involving agricultural risk.

The Biology of Canadian Weeds. 145. Muhlenbergia frondosa (Poir.) Fernald

Darbyshire, S. J., Francis, A., Crompton, C. W. and Swanton, C. J. 2011. The Biology of Canadian Weeds. 145. Muhlenbergia frondosa (Poir.) Fernald. Can. J. Plant Sci. 91: 205-219. Muhlenbergia frondosa is a perennial grass native to eastern North America, which naturally inhabits moist to wet forest margins and openings, freshwater littoral habitats, and grasslands. In Canada, its spread as a weed appears to have coincided with changes in cultivation practices during the past few decades. Infestations in such crops as maize and soya bean have been reported mainly from southern Ontario and Quebec, and the Midwest and northeastern areas of the United States, where it reduces yields and can be difficult to control. It is shade tolerant and able to compete under the closed canopy of crops. Although this weed can be controlled by herbicides, its ability to spread by regrowth from rhizomes, and its abundant seed production, cause ongoing problems in arable fields, particularly in conservation-tillage systems. As a warm-season C4 grass, growth begins relatively late in the season (early June in Canada), after most intensive weed control measures have already been taken. Timing herbicide application with active growth stages (10-30 cm) is most effective and the use of herbicide-tolerant crops provides additional control opportunities after crop planting.

The Biology of Canadian Weeds. 145.Muhlenbergia frondosa(Poir.) Fernald

Darbyshire, S. J., Francis, A., Crompton, C. W. and Swanton, C. J. 2011. The Biology of Canadian Weeds. 145. Muhlenbergia frondosa (Poir.) Fernald. Can. J. Plant Sci. 91: 205–219. Muhlenbergia frondosa is a perennial grass native to eastern North America, which naturally inhabits moist to wet forest margins and openings, freshwater littoral habitats, and grasslands. In Canada, its spread as a weed appears to have coincided with changes in cultivation practices during the past few decades. Infestations in such crops as maize and soya bean have been reported mainly from southern Ontario and Quebec, and the Midwest and northeastern areas of the United States, where it reduces yields and can be difficult to control. It is shade tolerant and able to compete under the closed canopy of crops. Although this weed can be controlled by herbicides, its ability to spread by regrowth from rhizomes, and its abundant seed production, cause ongoing problems in arable fields, particularly in conservation-tillage systems. As a warm-season C4grass, growth begins relatively late in the season (early June in Canada), after most intensive weed control measures have already been taken. Timing herbicide application with active growth stages (10–30 cm) is most effective and the use of herbicide-tolerant crops provides additional control opportunities after crop planting.

Soil quality alteration by mouldboard ploughing in a commercial farm devoted to no-tillage under Mediterranean conditions

In semi-arid Mediterranean areas, studies about conservation tillage (CT) systems have demonstrated advantages in crop yield, soil water storage and soil protection. However, the benefits observed with CT in trials with experimental plots (normally of small dimensions) might not be so clear in large commercial farms. In many areas of SW Spain, farmers often do an occasional tillage with mouldboard ploughing (MP) to avoid potential compaction problems and to encourage the emergence of seedlings. The present study deals with the effect of the application of MP on soil quality: total organic carbon, water soluble carbon, active carbon, microbial biomass carbon, dehydrogenase, β-glucosidase and o-diphenol oxidase activities and crop development (wheat) in a commercial farm devoted to no-tillage (NT) since 1995. In 2006, MP was applied on a band of the soil, while the rest was left under the strict conservation system. The direct and residual effects of MP in the two subsequent years were evaluated. In the first year MP caused a decrease in soil quality that persisted in the following two years. Emergence, nutrient accumulation, nutrient efficiency ratios and yield of wheat were slightly enhanced by MP in the first year. However, this trend was the opposite in the two subsequent years. Although in other scenarios traditional tillage has been applied to avoid soil compaction and to increase crop yield, under our experimental conditions the occasional mouldboard ploughing application was not justified.

Stochastic dominance analysis of returns to stocker grazing on conservation tillage winter wheat forage in Arkansas

Grazing cattle on winter wheat is a common income-generating practice in the Southern Great Plains, but few Arkansas cattle producers utilize this practice. Many areas in the state with potential to benefit from this practice are highly erodible, and conservation tillage may be needed to best ensure the existing natural resource base is not degraded over time. This study evaluates the profitability and return variability of grazing stocker steers on conservation tillage winter wheat pasture using simulation and stochastic dominance analysis. Average daily gains are simulated for steers grazed on conventional tillage, reduced tillage, and no-till winter wheat pasture using seven years of steer weight gain data from a conservation tillage winter wheat forage study near Batesville, Arkansas. Steer prices and prices for key forage production inputs such as diesel, fertilizer, and glyphosate are also simulated to account for their stochastic impacts on return variability. Steer net return distributions are generated for each tillage system, and first and second degree stochastic dominance are used to rank each tillage system according to specified producer preferences. The results indicate both conservation tillage systems are more profitable and less risky than the conventional tillage system. The conventional tillage system is dominated by no-till based on first degree stochastic dominance and by reduced tillage based on second degree stochastic dominance. Thus both conservation tillage systems would be preferred by risk-averse cattle producers to the conventional tillage system based on this analysis.

Conventional and glyphosate-resistant maize yields across plant densities in single- and twin-row configurations

Maize ( Zea mays L.) produced in narrow rows can increase yields and accelerate canopy closure. Costly equipment modifications make narrow rows impractical, but a twin-row configuration may boost production with fewer equipment modifications. Four field experiments were conducted to measure weed biomass, leaf area index (LAI), and yield for a conventional (CN) and a glyphosate-resistant (GR) hybrid across three plant densities (low 4.0–4.4 plants m −2; medium 5.9–6.4 plants m −2; and high 7.9–8.4 plants m −2) and two row configurations (single vs. twin) in a conservation tillage system during the 2005 growing season. The experimental design was a split–split plot with a RCB arrangement of whole plots where hybrids were assigned to main plots, row configurations to subplots, and plant density to sub-subplots with four replications. Row configuration had little effect on weed biomass compared to plant density and hybrid. Leaf area index increased with higher plant density at all locations. In general, LAI increased with the twin-row configuration, but LAI also varied with hybrid based on interactions between hybrid and plant density or row configuration. Row configuration had little impact on maize yields, while plant density had the most effect on yields. Plant density also interacted with hybrid or row configuration at multiple locations, although maize yields did not always increase with higher plant density. Conventional hybrids may also provide an alternative to GR hybrids, particularly at lower plant densities. Maize yield increases with twin rows were minimal and may not justify twin row conversion under dryland conditions, but growers that already utilize twin-row equipment will not suffer yield decreases by planting twin rows.

Procedures of soil farming allowing reduction of compaction

Evaluation of new technologies using guidance systems is very important and can help producers with choosing the right equipment for their applications. Without using satellite navigation during field operations, there is a tendency for passes to overlap. That results in waste of fuel and pesticides, longer working times and also environmental damage. When utilising satellite guidance for field operations, there is a close connection with controlled traffic farming (CTF) as well. CTF is currently a quite quickly developing farming system based on fixed layout of machinery passes across a field. Tracks precisely set out for a machine’s tyres in the field could be a tool for minimising soil compaction risk which is another threat to the environment. The purpose of this paper was to evaluate the accuracy of currently available guidance systems for agricultural machines. Real pass-to-pass errors (omissions and overlaps) in a field were measured. Consequently, comparison between observed guidance systems was made regarding final working accuracy. Further, intensity of machinery passes, percentage of wheeled area and repeated passes in fields were monitored. These measurements were made in fields under real operating conditions using a conventional tillage system with ploughing and also a conservation tillage system, both systems with randomly organized traffic. Finally, the same parameters were monitored in fields where fixed machinery tracks were used for all operations and passes but only under a conservation tillage system. Pass-to-pass accuracy was measured for the evaluation of different guidance systems. Size of missed areas or overlaps was evaluated statistically. Concerning intensity of machinery passes and total field area affected by machinery passes, the following facts were found out. The experiments with randomized traffic showed a significant difference of the parameters mentioned above between a conventional tillage system with ploughing and a conservation tillage system. Wheeled area was 86 and 64%, respectively which proves benefits of conservation tillage. The experiments with a fixed track system showed that the total run-over area by machinery tyres decreased even more (up to 31%) in comparison to randomized traffic in a field (only fields under conservation tillage system were monitored and evaluated). The following statements based on our results can be made. The navigation and therefore possibility for better accuracy of machinery passes in fields together with permanent machinery tracks utilization could help with soil condition improvement and also energy savings which would result from that. The CTF system will help with further development of a system for soil compaction protection which is currently a real necessity.

Soybean Growth and Soil Microbial Populations under Conventional and Conservational Tillage Systems

Tillage systems play an important role in crop growth and soil improvement. This study was conducted to determine the best tillage system for the dark-soil area of northeast China with darkclay soil type (Millisol) and to examine the influence of different tillage systems on soybean [Glycine max (L.) Merr.] growth and soil microbial populations. Three conventional tillage systems and two conservational tillage systems were tested. Plant height and biomass as reflected by dry shoot and dry root weight under the no-till system were significantly reduced as compared with other tillage systems. The bacterial, fungal, and actinomycete populations reached their highest levels at soybean R2 (blooming) stage. The disease severity of root rot and population dynamics of bacteria, fungi, and actinomycetes in conservational tillage appeared to be higher than those in conventional systems; the latter were associated with an increased populations of Fusarium spp. and Trichoderma spp. Based on these research findings, a conventional tillage with reduced plowing frequency and intensity and increased crop-residue coverage would be a reasonable recommendation for soybean production in the dark-soil area of northeast China.

Stalk Borer (Lepidoptera: Noctuidae) Ecology and Integrated Pest Management in Corn

The stalk borer, Papaipema nebris (Guenee), is a native North American insect with a broad host range. It frequently damages corn, especially in conservation-tillage systems, and occasionally soybean, in the Midwestern United States. A review is presented of crop injury, especially to corn, brief descriptions of the life stages, degree-day development, and larval host plants along with a discussion of control strategies including planting date, weed control, mowing oviposition sites, burning, insecticide and herbicide combinations, and transgenic corn. EILs and an IPM approach for managing stalk borers in corn are presented.

Fate and Efficacy of Metolachlor Granular and Emulsifiable Concentrate Formulations in a Conservation Tillage System

Use of genetically modified cultivars resistant to the herbicide glyphosate (N-phosphonomethylglycine) is strongly associated with conservation-tillage (CsT) management for maize ( Zea mays L.), soybean ( Glycine max L.), and cotton ( Gossypium hirsutum L.) cultivation. Due to the emergence of glyphosate-resistant weed biotypes, alternate weed management practices are needed to sustain CsT use. This work focused on metolachlor use (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide) in a CsT system. The fate and efficacy of granular and emulsifiable concentrate (EC) formulations or an EC surrogate were compared for CsT cotton production in the Atlantic Coastal Plain region of southern Georgia (USA). The granular formulation, a clay-alginate polymer, was produced in the authors' laboratory; EC was a commercial product. In field and laboratory dissipations the granular metolachlor exhibited 8-fold greater soil persistence. Rainfall simulation runoff assessments indicated that use of the granular formulation in a common CsT system, strip-tillage (ST), may reduce metolachlor runoff loss when compared to conventional tillage (CT) management or when EC formulations are used in the ST system. Metolachlor leaching assessments using field-deployed lysimeters showed some tillage (ST > CT) and formulation (EC > granular) differences. Overall leaching was generally small when compared to runoff loss. Finally, greenhouse bioassays showed control of two weed species with the granular was greater than or equal to that of the EC formulation; however, the granular formulation suppressed cotton growth to a greater extent. In sum, this metolachlor granular formulation has advantages for CsT cotton production; however, additional research is needed to assess impacts on crop injury.