Conventional Tillage Plots Research Articles

Maize-based conservation agriculture systems in Malawi: Long-term trends in productivity

In Malawi and throughout much of Africa, maize yields have declined over the past several decades due to continuous cultivation, often in monocropping with little or no inputs. As a result, soil degradation has been aggravated by the loss of valuable top soil caused by rainwater runoff due to the absence of effective conservation practices. To combat this trend, Conservation Agriculture (CA) systems were introduced using a pointed stick or hand hoe to plant directly into untilled soil with crop residues as surface mulch. The objective of this study was to compare the effects of different cropping systems (CA and conventional) on soil physical and chemical parameters and long-term maize productivity in target communities of the southern and central regions of Malawi. This study analysed the effects of CA on soil parameters and maize yield over eight cropping seasons. The biophysical variability of the communities was explored through principal component analysis. Results showed that maize yields in CA systems were strongly affected by rainfall infiltration, which was 24–40% greater compared with the conventional ridge and furrow system. In some cases, maize yields in CA plots were double that of conventional tillage plots. The larger water infiltration observed in CA plots relative to conventional tillage indicated that CA systems may increase access to soil water by the crop and offset the negative effects of seasonal dry spells. Yield benefits of CA over conventional tillage systems were greater especially from the 5th season although, in some instances, greater yields on CA were recorded almost immediately. CA can be practiced in diverse environments from sandy to clay soils, nutrient rich to infertile soils and from low to high rainfall areas as long as adequate inputs (fertilizer, herbicides and labour) are available with good extension support to farmers, especially in the initial years.

Relationships between winter wheat yields and soil carbon under various tillage systems

 Soil quality and fertility are associated with its productivity, and this in turn is connected to the soil biological activity. To study these effects, well designed long-term field experiments that provide comprehensive data sets are the most applicable. Four treatments (tillage methods) were set up: (1) conventional tillage (CT); (2) no tillage (NT); (3) minimum tillage + straw (MTS), and (4) no tillage + mulch (NTM). Our objective was to assess the relationships between soil microbial characteristics and winter wheat yields under these different techniques of conservation tillage within a field experiment, originally established in 1995. The differences in average grain yields over time period 2002–2009 between the variants were not statistically significant. Organic carbon in the topsoil was higher in plots with conservation tillage (NT, MTS, and NTM), than in the conventional tillage plots. There was a statistically significant correlation (P ≤ 0.01) between the grain yields and organic C content in topsoil.  

Evaluating the effects of tillage techniques on soil hydro-physical properties in Guinea Savanna of Nigeria

This study aimed at evaluating the effect of four tillage techniques: no-till (NT), minimum tillage (MT), contour tillage (CoT) and conventional tillage (CT) on soil hydraulic properties and physical quality using RETC (retention curve) computer model. Particle size distribution, bulk density and water retention at various soil matric potentials were determined using standard methods and the data were fitted into RETC computer programme for prediction of water retention curve and their analysis. Findings are: (1) the highest amount of water retained at all soil matric potential ranges and soil depths in the NT plot. (2) Pore-size classes varied inconsistently with depth and matric potential ranges in the tillage treatments, but predominantly greater equivalent pore diameter was observed in CT plots at most of the potential ranges. (3) In soil physical quality index 7.9, 11.5 and 18.3% reduction at 0–5cm depth and 0.1, 1.6 and 4.2% at 5–15cm depth were observed in MT, CoT and CT treatments respectively compared to NT. (4) The RETC model described the measured and predicted related hydraulic properties of the tillage techniques used in soybean cultivation.

Soil Carbon Dioxide Fluxes in Conventional and Conservation Tillage Corn Production Systems Receiving Poultry Litter and Inorganic Fertilizer

Soil management practices can alter the natural balance at the soil-plant-atmosphere ecosystem interface, which can significantly affect the environment. This study compared CO2 fluxes in conventional tillage (CT) and no-tillage (NT) corn (Zea mays L.) production systems receiving poultry litter (PL) and ammonium nitrate (AN) fertilizers on a Decatur silt loam soil in the Tennessee Valley region of North Alabama from Spring 2008 to Fall 2009. Soil CO2 flux in CT plots (9.5 kg CO2 ha−1 day−1) was significantly greater than that in NT plots (4.9 kg CO2 ha−1 day−1 in summer. Soil CO2 fluxes were lowest in fall where CT plots had a mean soil CO2 emission of 0.8 kg CO2 ha−1 day−1, while plots under NT and grass fallow system were sinks of CO2 with fluxes −0.6 and −1.0 kg CO2 ha−1 day−1, respectively. Mean soil CO2 flux averaged over seasons in NT plots was 36% lower than that in CT plots. Grass fallow plots were net sinks of CO2 with a mean CO2 flux of −0.4 kg CO2 ha−1 day−1. Our study showed that application of PL or AN fertilizer in NT systems can significantly reduce soil CO2 emissions compared to CT systems in corn production.

A comparison of the effects of minimum-till and conventional-till methods, with and without straw incorporation, on slugs, slug damage, earthworms and carabid beetles in autumn-sown cereals

SUMMARYThe present study compared slug, earthworm and carabid beetle abundance and slug damage to plants in minimum tillage (MT) and conventional tillage (CT) autumn-sown cereals. Winter barley was sown by CT and MT for 3 years followed by winter wheat for 6 years on a light-textured soil (Trial 1). Each cultivation was split so that straw was incorporated into the soil during cultivation in one split while the other did not receive straw. A similar investigation with winter wheat, over the same period, was undertaken on a nearby heavy-textured soil (Trial 2). The effects of method of cultivation and soil incorporation of straw on slug abundance and damage, and on earthworm populations were measured. Additionally, at Trial 1, the effects of cultivation and straw treatments on carabid beetle occurrence were measured in years 5–9. Over the 9 years, the method of cultivation had a significant effect on slug numbers in each trial. Slugs were more numerous in MT than CT plots, significantly so in 3 of the 9 years in Trial 1 and in 5 years in Trial 2. In Trial 1, slug numbers were significantly greater on no-straw than straw plots in 3 years as well as for the 9 years combined. Slug numbers did not differ between straw and no-straw plots in Trial 2. Slug numbers varied significantly between years and were influenced by factors other than the method of cultivation and straw application. Slug damage to seed and seedlings was quite low in each year (1–2%). Slug damage to cereal leaves at GS 23 was widespread in both trials, and severe in some years. MT had more leaf damage than CT in 5 of the 9 years in each trial, significantly so in 3 years in Trial 1 and in 4 years in Trial 2. Straw did not affect leaf damage in either MT or CT. Slug damage was not related to, nor did it affect either ear density or grain yield. The dominant slug species wasDeroceras reticulatum.Earthworm numbers were significantly greater in MT than CT, for combined years, in each trial. Annually, these differences were significant for 5 years in Trial 1 and 2 years in Trial 2. Straw plots had significantly more earthworms than no-straw, for combined years, in each trial. The latter differences were significant for 5 years in Trial 1 and 3 years in Trial 2. In MT, the positive effect of straw on earthworm numbers was significant in Trial 2 but not in Trial 1. In CT, the latter effect was significant in each trial.Lumbricusspecies were more numerous in MT than CT and in straw than no-straw treatments. The impact of cultivation on numbers of carabid beetles was species-specific. The large beetle,Pterostichus melanarius, was significantly more numerous in MT than CT in 2 of the 5 years and for the aggregate of 5 years. Small carabids (Bembidionspecies andTrechus quadristriatus) were significantly more abundant in CT than MT in 3 of the 5 years as well as for the aggregate of 5 years. Straw did not affect the number of any or all carabid species either for combined cultivations (MT + CT) or within either MT or CT. It is concluded that MT increases slug numbers, slug damage and earthworm numbers relative to CT cultivations. MT favours large carabid beetles and CT favours small beetles. Straw incorporation increases earthworm numbers but not slugs, slug damage or carabid beetles. Slug damage to cereal leaves does not affect ear density or grain yield in either MT or CT crops when sown to a depth of 40 mm and before 18 September.

Impact of tillage on runoff in long term no-till wheat systems

Adoption of no-till cropping systems continues to increase worldwide due to enhanced soil and water conservation, reduced inputs and maintained crop production. Soil compaction, particularly in grazed systems, can become a concern within no-till cropping systems and occasional tillage may be a method to relieve these concerns. However, there is no data within the US Southern Great Plains examining the impact of tilling long-term no-till wheat cropping systems and the potential subsequent impacts on runoff characteristics. The objective of this study was to evaluate the impact of tilling long term no-till wheat systems on runoff water quantity and quality. The study was conducted within a field that had been in no-till wheat with occasional grazing for seven years. Seven tillage treatments were evaluated, including: no-till, conventional till, and soil aeration using roller angles of 0°, 2.5°, 5°, 7.5°, and 10°. Rainfall simulation studies providing a 7cmh−1 storm event were conducted approximately three months after tillage. Results showed that conversion from no-till to conventional tillage increased runoff volume by 38%. Total sediment losses were at least 2.8 times greater from conventional till plots than no-till and aerated treatments. Nutrient concentrations were similar among tillage treatments. However, total P and ammonium-N loads in runoff water were significantly higher from conventional till plots compared with other tillage treatments. Aeration did not provide a consistent trend and generally provided no significant improvement in runoff characteristics compared with no-till. Initial results indicate no advantage of tilling long term no-till wheat systems in regard to runoff quality and quantity three months after tilling.

Soil carbon dynamics as influenced by tillage and crop residue management in loamy sand and sandy loam soils under smallholder farmers’ conditions in Malawi

Conservation agriculture (CA) characterised by minimal soil disturbance, permanent soil surface cover by dead or living plants and crop rotations is one way of achieving higher soil organic carbon (C) in agricultural fields. Sandy loam and loamy soil samples from zero tillage (ZT) and conventional tillage (CT) plots were taken from farmers’ fields during the dry season in August 2006. Soil organic carbon (SOC) and soil organic nitrogen (SON), microbial biomass carbon (MB-C) and microbial biomass nitrogen (MB-N), C mineralization and SOC distribution in particle size fractions in 0–20 cm layer were evaluated. Forty eight farmers’ fields were randomly sampled at four different locations in Central and Northern Malawi, representing ZT plots maintained for a different number of years, and ten fields under CT with similar soil type and crop grown were selected. SOC and SON in ZT fields were 44 and 41 % (4 years ZT) and 75 and 77 % (5 years ZT) higher, respectively, than CT plots. MB-C and MB-N in ZT fields were 16 and 44 % (4 years ZT) and 20 and 38 % (5 years ZT) higher, respectively, than CT plots. However, MB-C and MB-N in ZT fields were 27 and 25 % (2 years ZT) and 17 and 9 % (3 years ZT) lower than in CT plots. The proportion of the total organic C as microbial biomass C was relatively higher under CT than ZT treatments. The higher SOC and MB-C content in the ZT fields resulted in 10, 62, 57 % higher C mineralization rate in ZT plots of 3, 4 and 5 years of loamy sand soils and 35 % higher C mineralization rate in ZT plot of 2 years than CT of sandy loam soils in undisturbed soils in the laboratory. Simulating plough from the undisturbed soils that were used for C mineralization experiment resulted in linear curves indicating that all organic C was already depleted during the first incubation period. The relative distribution of soil organic matter (SOM) in silt and clay size fractions was strongly correlated (r = 0.907 and P ≤ 0.01) with silt percentages. Easily degradable carbon pool (CA,f) was correlated (r = 0.867 and P ≤ 0.05) with organic carbon in sand size fraction. In developing viable conservation agriculture practices to optimize SOC content and long-term sustainability of maize production systems, priority should be given to the maintenance of C inputs, crop rotations and associations and also to reduced soil disturbance by tillage.

Integrated Foliar Disease Management to Prevent Yield Loss in Argentinian Wheat Production

Zero tillage often leads to wheat (Triticum aestivum L.) yield losses from diseases caused by necrotrophic foliar pathogens. The aim of this work was to evaluate the combined effect of tillage, N fertilization, fungicides, and resistant cultivars in reducing foliar disease severity to prevent significant yield losses. A 2‐yr study including combinations of (i) conventional and zero tillage; (ii) N fertilization rates 0, 80, or 160 kg ha−1 N; (iii) two fungicide treatments (with and without a fungicide (1 L of metconazole, 9%) at growth stages (GS) 32 and 39; and (iv) three wheat cultivars was conducted in the Rolling Pampas region in Argentina. The most common foliar disease in the trial was tan spot [Pyrenophora tritici‐repentis (Died.) Drechs.]. Conventional tillage reduced foliar disease severity at GS 23 by 46 and 56% and the area under disease progress curve (AUDPC) by 20 and 14% for each season, respectively compared with zero tillage. The cultivar Buck Bigua had significantly lower AUDPC values than the others. Fungicide and N application reduced disease severity at GS 23 by 35 and 34% respectively, on average over both years. Disease was less severe in zero tillage plots which received a fungicide compared to conventional tillage plots that were not treated with fungicide. In 2002 yields were greater in conventional tillage plots with 160 kg ha−1 N and fungicide application than in all other treatments. In 2003 yields were greatest in zero tillage plots with 160 kg ha−1 N and fungicide. The results of this study indicate that in spite of the increase of necrotrophic diseases, developing no‐till systems in wheat monoculture is possible without significant yield losses if effective disease management practices are applied.

Effects of Harvest Residue and Tillage on Lesser Cornstalk Borer (Lepidoptera: Pyralidae) Damage to Sugarcane

Lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) is an important pest of sugarcane (a complex hybrid of Saccharum spp.) in southern Florida. Cultural controls for E. lignosellus were evaluated in preparation for the potential loss of effective insecticides. Field studies conducted in 2006 compared the effects of harvest residues from green-harvested sugarcane (no preharvest burning to remove leaf matter) on E. lignosellus stalk damage and yield. Damage by E. lignosellus was significantly lower in plant cane plots that were covered with harvest residues collected from a green-harvested field before shoot emergence compared with plots without harvest residue. There were no yield differences between plots with and without harvest residues in plant or ratoon sugarcane fields in the 2006 study. The effects of three postharvest tillage levels (conventional, intermediate, and no tillage) were evaluated in preharvest burned and green-harvested fields in 2008 and 2009. Significantly less E. lignosellus damage was observed in the green- versus preharvest burned fields in both years. Intermediate and no-tillage plots had very little damage in green-harvested field. Conventional tillage plots had the greatest damage in the green-harvested field and the lowest damage in the preharvest burned field. In 2008, biomass yield was greater in the intermediate than conventional tillage in the green-harvested field, but it was greater in the conventional than in other tillage levels in the preharvest burned field. These studies demonstrated that cultural controls could greatly reduce E. lignosellus damage in sugarcane without the use of insecticides.

IMPACT OF LOW RATES OF NITROGEN APPLIED AT PLANTING ON SOYBEAN NITROGEN FIXATION

Environmental conditions in the northern Great Plains can delay emergence, nitrogen (N) fixation and growth of soybean due to cool and wet soil conditions at planting. The objective was to evaluate the impact of low rates of N applied at planting on soybean N fixation and crop growth. A field experiment was established within corn soybean rotation using a split-plot design with four replications. Whole plots were no-tillage and conventional tillage and split plots were starter fertilizer. Nitrogen sources were ammonium nitrate or urea applied at four rates. The amount of plant N fixation increased with growth stage reaching a maximum fixation at the R5 growth stages. Plant ureide content decrease with increase N applied for all growth stages except R7. The increase in plant biomass contributed to an overall increase in yield indicating that in unfavorable environments application of N at planting can have a positive impact on soybean growth.

Sesame Hill Dropping Performance of a Vacuum Seeder for Different Tillage Practices

The purpose of this research was to examine the performance of a modified vacuum seeder for hill drop sowing of sesame (Sesamum indicum L.) following wheat (Triticum aestivum) for no-till and reduced tillage farming. Tests were conducted during the growing seasons of 2008 and 2009 in the Bati Akdeniz Agricultural Research Institute's fields in Antalya, Turkey. A fluted coulter and double disc-type furrow opener were mounted on each unit of a common vacuum seeder. A seed plate modified to achieve hill-dropping of seeds was used in the metering mechanism of the seeder. Mean plant number per hill, coefficient of variation of plant number per hill, mean hill distance, coefficient of variation of hill distance, scattering distance ratio along the length of the row, sowing depth uniformity, and percent emergence of seeds and of hills were determined. Uniformity of hill spacing obtained from no-till plots was lower than from reduced and conventional tillage plots. Treatment effects were compared for three sesame seed varieties. No-till decreased the percent emergence of both seeds and hills for all varieties.

Field‐Scale Soil Moisture Pattern Mapping using Electromagnetic Induction

Soil apparent electrical conductivity (ECa) responds to time‐variable soil properties, such as soil water content (θ), and can therefore be used to characterize the spatial and temporal dynamics of θ at the field scale. When clay content is high and uniform and the θ range small, however, it is not clear whether ECa maps can be used for this purpose. A soil management experiment established in a Vertisol in 1982 was surveyed for ECa on 13 occasions to capture changing soil conditions and to determine the sources of this variability. Less variation with time was found in subsoil than in topsoil ECa patterns, especially within the conventional tillage (CT) plots, in areas with shallow soil, and along the drainage network. Using the 13 ECa relative difference data sets as variables, principal component (PC) analysis showed that the first three PCs explained 90% of their total variance. The time‐stable or mean ECa pattern was significantly correlated with PC1 and could also be associated with topography, soil depth, and soil structure but could not be related to a single survey. Topography and soil management could be associated with PC2 and PC3, respectively. Time‐stable θ patterns, inferred from 26 surveys, revealed topographical and management characteristics and showed significant relationships (P < 0.001) with ECa–derived patterns like soil porosity and infiltration caused by soil management, topography, and rainfall. Electromagnetic induction sensors were useful for mapping soil spatial variability and changing soil conditions due to management effects and external forcing in uniform clay soils.

Effect of Tillage and Planting Date on Seasonal Abundance and Diversity of Predacious Ground Beetles in Cotton

A 2-year field study was conducted in the southern High Plains region of Texas to evaluate the effect of tillage system and cotton planting date window on seasonal abundance and activity patterns of predacious ground beetles. The experiment was deployed in a split-plot randomized block design with tillage as the main-plot factor and planting date as the subplot factor. There were two levels for each factor. The two tillage systems were conservation tillage (30% or more of the soil surface is covered with crop residue) and conventional tillage. The two cotton planting date window treatments were early May (normal planting) and early June (late planting). Five prevailing predacious ground beetles, Cicindela sexguttata F., Calosoma scrutator Drees, Pasimachus spp., Pterostichus spp., and Megacephala Carolina L. (Coleoptera: Carabidae), were monitored using pitfall traps at 2-week intervals from June 2002 to October 2003. The highest total number of ground beetles (6/trap) was observed on 9 July 2003. Cicindela sexguttata was the dominant ground dwelling predacious beetle among the five species. A significant difference between the two tillage systems was observed in the abundances of Pterostichus spp. and C. sexguttata. In 2002. significantly more Pterostichus spp. were recorded from conventional plots (0.27/trap) than were recorded from conservation tillage plots (0.05/trap). Significantly more C. sexguttata were recorded in 2003 from conservation plots (3.77/trap) than were recorded from conventional tillage plots (1.04/trap). There was a significant interaction between year and tillage treatments. However, there was no significant difference in the abundances of M. Carolina and Pasimachus spp. between the two tillage practices in either of the two years. M. Carolina numbers were significantly higher in late-planted cotton compared with those observed in normal-planted cotton. However, planting date window had no significant influence on the activity patterns of the other species. Ground beetle species abundance, diversity, and species richness were significantly higher in conservation tillage plots. This suggests that field conditions arising from the practice of conservation tillage may support higher predacious ground beetle activity than might be observed under field conditions arising from conventional tillage practices.

Tillage and fertilizer effects on some soil properties, leaf nutrient concentrations, growth and sweet potato yield on an Alfisol in southwestern Nigeria

Tillage and fertilizer influenced soil characteristics through their effects on soil properties which in turn affect crop performance. Field experiments were conducted during 2006 and 2007 cropping seasons on an Alfisol (Oxic Tropuldalf) at Owo in the forest-savanna transition zone of Nigeria to evaluate the effect of tillage and fertilizer types on soil properties and sweet potato yield ( Ipomoea batatas L.). Two tillage treatments namely: zero tillage (ZT) and conventional tillage (CT) were combined with each of NPK-15-15-15 fertilizer at 250 kg ha −1, poultry manure (PM) at 10 t ha −1, combined application of 125 kg ha −1 NPK 15-15-15 fertilizer + 5 t ha −1 poultry manure and a control (no fertilizer/manure). The experiment was laid out on a randomized complete block design in a factorial combination of eight treatments that were replicated three times. The surface soil (0–15 cm depth) was chemically analysed before and after crop harvest and some selected soil physical properties, leaf nutrient concentrations, growth and sweet potato yield were determined. Conventional tillage plots had significantly lower soil bulk density (1.30 Mg m −3) than zero tillage plots and resulted in higher leaf N, P, K, Ca and Mg and tuber yield of sweet potato compared with zero tillage. Soil water content was higher, whereas temperature was lower, in zero tillage than conventional tillage. Zero tillage had significantly higher concentrations of soil pH, organic C, N, P, K, Ca and Mg for surface soil (0–15 cm depth). Conventional tillage increased mean tuber yield of sweet potato by 30% compared with planting on untilled zero soil. Application of poultry manure alone and complementary application of NPK fertilizer and poultry manure reduced bulk density and temperature and increased soil water content and porosity, whereas NPK fertilizer did not improve soil physical properties. Compared with control, poultry manure alone, NPK fertilizer alone and complementary application of NPK fertilizer and poultry manure increased soil total N, available P, and exchangeable K, Ca and Mg concentrations as well as leaf N, P, K, Ca and Mg concentrations. Poultry manure tended to improve soil pH, SOC, N, Ca and Mg compared with NPK fertilizer. Combined application of sub-optimal rates of NPK fertilizer and poultry manure gave higher soil and leaf N, P and K concentrations, vine length, vine girth, leaf area and tuber yield compared with NPK fertilizer or poultry manure alone. Compared with control, NPK fertilizer, poultry manure and NPK fertilizer plus poultry manure increased tuber yield by 39, 45 and 83%, respectively. Conventional tillage in combination with NPK fertilizer plus poultry manure gave the highest tuber yield of sweet potato.

Nitrous oxide emissions and controls as influenced by tillage and crop residue management strategy

Abstract Mixed responses of soil nitrous oxide (N2O) fluxes to reduced tillage/no-till are widely reported across soil types and regions. In a field experiment on a Danish sandy loam soil we compared N2O emissions during winter barley growth following five years of direct drilling (DD), reduced tillage (RT) or conventional tillage (CT). Each of these tillage treatments further varied in respect to whether the resulting plot crop residues were retained (+Res) or removed (−Res). Sampling took place from autumn 2007 to the end of spring 2008. Overall N2O emissions were 27 and 26% lower in DD and RT, respectively, relative to N2O emissions from CT plots (P

Influence of tillage on adult and immature pea leaf weevil (Coleoptera: Curculionidae) densities in pea.

The pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), has been a major pest of pea, Pisum sativum L., in eastern Washington and northern Idaho since its introduction to the region in the early 1970s. Eggs are deposited in the spring on the soil surface and first instars hatch and move to pea root nodules, where larvae feed before they pupate and adults emerge in mid- to late summer. No-tillage practices are known to reduce pea leaf weevil colonization in pea, but the effects of tillage on larval densities and subsequent adult emergence have not been examined. During 2005, 2006, and 2007, we compared densities of colonizing adult and immature pea leaf weevils on pea plots grown using conventional tillage and no-tillage. In 2005 and 2006, emergence of adult pea leaf weevil was monitored in the same plots. Densities of colonizing adult and immature pea leaf weevil were significantly higher in conventional tillage plots. Larvae in conventional tillage were further along in development than larvae in no-tillage plots during June and July. Densities of emerging adult pea leaf weevil were significantly greater from conventional tillage than no-tillage plots. Based on densities of colonizing and subsequent emerging adults, survival of weevils from egg through adult was greater in conventional tillage plots. Soils under no-tillage are cooler, resulting in later emergence of the pea crop and delayed root nodule development, possibly affecting the ability of first-instar pea leaf weevil to locate host plant roots. Our results indicate no-tillage fields are less suitable for pea leaf weevil colonization and survival than conventional tillage fields.

A comparison of the occurrence of aphids and barley yellow dwarf virus in minimum-till and conventional-till autumn-sown cereals

SUMMARYWinter barley was sown by conventional-tillage (CT) and minimum-tillage (MT) cultivation over three seasons. Each cultivation treatment was split so that straw was incorporated into the soil during cultivation in one split, while the other did not receive straw. Aphid occurrences in autumn and incidence of barley yellow dwarf virus (BYDV) in spring were compared. Similar investigations on winter wheat were made over a further three seasons. The method of cultivation affected the number of aphids on barley and wheat plants in autumn and on wheat heads in summer; MT had fewest aphids. Soil incorporation of straw during cultivation had a similar effect. Method of cultivation affected the incidence of BYDV disease, with MT having least infection. Straw-treated cereal plots had fewer aphids and less BYDV than no-straw plots. Aphids and virus reached damaging levels only in the first barley crop. In this season, MT barley had significantly fewer aphids (48% fewer) and significantly less BYDV (71% less) than CT. Straw-treated plots within the CT system had rather similar aphid infestation and BYDV incidence as no-straw plots. Barley grown in the MT system with straw added had significantly fewer aphids (68%) than in the case when no straw was added. Overall, aphids in autumn were significantly fewer on MT relative to CT cereals in three of the six seasons and significantly fewer on straw relative to no-straw plots in two seasons. Aphids on wheat heads in summer were significantly fewer in MT relative to CT plots in one of the three seasons. Aphids on heads were also significantly fewer on straw-treated plots within each system of cultivation in two seasons, while MT wheat with straw had significantly fewer aphids/head than those without straw in one season. BYDV was lower each season in MT barley and wheat when compared with CT crops. These differences were significant for two of the three seasons in which each crop was grown. There was a lower incidence of virus in straw-treated plots than in no-straw plots. This effect was significant for one of the three seasons in which barley and wheat were grown. Plant and tiller density did not differ significantly between MT and CT barley either with or without straw incorporation. Plant density of wheat in autumn was significantly lower for straw-treated plots relative to no-straw plots in one season. Wheat head density was lower for MT relative to CT in one season, while MT with straw had significantly fewer heads than CT plots with straw in two seasons. BYDV significantly reduced grain yield only in 2001/02 when incidence of the disease was high. Grain yield in 2001/02 was 0·95 t/ha (16%) greater for MT barley, due to less BYDV, than for CT. Straw-treated CT barley outyielded no-straw plots by 0·45 t/ha, while the comparable value for the MT system was 0·3 t/ha. The combined effect of MT plus straw had a 1·24 t/ha (21%) yield advantage over CT without straw.It is concluded that MT cereals sown at the same time as CT crops in autumn have a lower risk of aphid infestation and BYDV infection than CT crops. The soil incorporation of straw further enhances the beneficial impact of MT in reducing aphids and virus.

Dynamics and recovery of fertilizer 15N in soil and winter wheat crop under minimum versus conventional tillage

The development of reduced tillage in cropping systems raises the question of adaptation of N fertilization of crops in response to changes in the chemical, physical and biological soil caused by the cessation of ploughing. The purpose of the work was to investigate the fate of fertilizer 15N applied in spring to a winter wheat crop ( Triticum aestivum L.) under minimum tillage (MT) and conventional tillage (CT) and to examine the hypothesis that in MT systems plants face stronger microbial competition for N. The experiment was conducted in Northern France on a silt loam in two different rotations [sugar beet ( Beta vulgaris L.)–winter wheat–maize ( Zea mays L.)–winter wheat and seed flax ( Linum usitatissimum L.)–winter wheat–pea ( Pisum sativum L.)–winter wheat] from which we selected two crop sequences, pea–wheat and maize–wheat. At the beginning of stem elongation, 15N labelled fertilizer was applied at the rates of 100 kg N ha −1 for wheat after pea and 120 kg N ha −1 for wheat after maize. The dynamics of fertilizer 15N in soil and plant was assessed at six dates between N application and wheat harvest. In addition, soil respiration was monitored continuously on the maize–wheat CT and MT plots as a way of assessing heterotrophic microbial activity. The type of tillage (MT vs CT) had little effect on fertilizer N dynamics in the soil. The amount of labelled N immobilized was low with values ranging from 3.5 to 11.9% of applied 15N. Plant 15N recovery (above ground biomass + roots) amounted to 59–63% at flowering and harvest. The 15N balance at harvest time (i.e. the sum of 15N recovered from all plant and soil compartments) indicates that approximately 29% of the fertilizer N applied was lost whichever the tillage considered. The type of rotation (i.e. the nature of the preceding crop) had more influence on wheat N uptake than the type of tillage. The lack of observed effect of tillage on the dynamics of nitrogen fertilizer and plant recovery is in agreement with most published results obtained in other soil and climate conditions.

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

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

Herbicide sorption, degradation, and leaching in three Swedish soils under long-term conventional and reduced tillage

Soil tillage has the potential to influence water flow and solute transport through the soil by cutting continuous macropores which connect the soil surface to the subsoil. Tillage also affects soil organic carbon sequestration which may lead to different sorption and degradation properties depending on the long-term tillage practices. The objective of this study was to quantify the differences in sorption, degradation and leaching of the herbicides bentazone and isoproturon between conventional tillage ( CT) and reduced tillage ( RT) under Swedish conditions. Three sites, Ultuna (silty clay), Säby (loam), and Lönnstorp (sandy loam moraine till), where replicate plots had been under either CT or RT for at least 9 years, were included in the study. A higher organic carbon content had developed in the top 5 cm of RT plots compared to the 10–20 cm depth and CT plots since the establishment of the experimental treatments. Adsorption and degradation were studied in laboratory experiments and solute transport was studied in undisturbed column experiments using non-reactive tracers and herbicides. The results from the column experiments were not significantly different between tillage treatments for Säby and Lönnstorp. For Ultuna, RT resulted in a more pronounced preferential tracer transport pattern and isoproturon leaching was twelve times larger compared to CT columns. This indicates that the tillage treatment had affected the macropore connectivity only at Ultuna. Freundlich adsorption coefficients for both bentazone and isoproturon were larger (though not always significantly) in the top 5 cm of RT soil compared to the 10–20 cm depth and to CT, reflecting the higher organic carbon content. The degradation rate was also generally larger (though not always significantly) in the top 5 cm of RT soil. These results show that RT has the potential to reduce pesticide leaching. However, any such reduction may be counter-balanced by enhanced preferential flow for soils where RT results in improved macropore connectivity.