Impact Of Tillage Research Articles

Short-term impact of an occasional tillage on microbial communities in a Vertosol after 43 years of no-tillage or conventional tillage

Occasional strategic tillage (ST) has been suggested as a possible solution to manage herbicide-resistant weeds and control crop diseases in Australia's northern grain-growing regions. We evaluated the impact of ST on microbial communities as indicators of soil quality for two distinct tillage systems that have been applied to a Vertosol for 43 years (no-tillage – NT or conventional tillage – CT) and two stubble management practices (retention – SR or burning – SB). Soil samples were collected 15 weeks after ST and analysed for total enzymatic activity (fluorescein diacetate assay), metabolic diversity (Ecoplates Biolog®) and bacterial community structure (terminal restriction fragment length polymorphism). There was no significant effect of ST on the measured biological attributes. However, total enzymatic activity for treatments under CTSR and CTSR-ST were significantly higher compared with NTSR-ST (+0.8 fluorescein μg ml−1 g−1 soil h−1, P < 0.01). Differences may be attributed to a significant increase in bulk density for CTSR treatment (P < 0.05) and an increment in bulk density on CTSR-ST plots. The lack of changes may be attributed to a high resistance and/or resilience of soil microbial communities after 15 weeks of tillage. More studies on the long-term effect of ST are required to assess the impact on soil biological properties.

Soil carbon and nitrogen changes after 28 years of no-tillage management under Mediterranean conditions

Abstract Mouldboard ploughing is known to accelerate soil organic matter (SOM) mineralization rate in Mediterranean regions. Long-term reduced tillage intensity potentially diminishes soil organic carbon (SOC) and total nitrogen (STN) depletions. Here, we compared long-term no-tillage (NT) and conventional tillage (CT) impact on SOC and STN sequestration rates at different depths ranging from 0 to 30 cm. The long-term experiment started in 1986 on a Typic Xerofluvent soil in Central Italy using a randomized complete block design with four replications. Ten years after the experiment began, SOC and STN concentrations in the 0–30 cm soil layer were already higher under NT compared to CT. The shallow layer (0–10 cm) showed the highest SOC and STN concentration increments. However, no differences between tillage systems were observed in the deeper layers. After 28 years, continuous NT increased SOC and STN content in the 30 cm soil depth by 22% compared to initial values. In the same period, continuous CT decreased SOC and STN content by 3% and 5%, respectively. On average, the total SOC and STN gains under NT may be attributed to the shallow layer increments. In the 10–20 and 20–30 cm soil layers, SOC accumulation over time was negligible also under NT. In the whole profile (0–30 cm), the mean annual SOC variation was +0.40 Mg ha −1 yr −1 and −0.06 Mg ha −1 yr −1 under NT and CT, respectively. Under NT, SOC content increased rapidly in the first ten years (+0.75 Mg ha −1 yr −1 ); later on, SOC increments were slower indicating the reaching of a new equilibrium. Data show that NT is a useful alternative management practice increasing carbon sequestration and soil health in Mediterranean conditions.

Aggregate size distribution and associated organic C and N under different tillage systems and Ca-amendment in a degraded Ultisol

The physical protection and stabilization of soil organic carbon in soil aggregates are important processes for the mitigation of greenhouse gas emissions through carbon sequestration. Compared with temperate soils, the relationships between management practices, soil aggregation and soil organic matter (SOM) are not well understood in subtropical and tropical soils. The objectives of this study were to assess the influence of tillage system and Ca-amendment on the size distribution of soil aggregates and aggregate-associated organic C and N, as well as to contribute to the understanding of the role of soil organic matter in the aggregation process in a soil with tropical mineralogical characteristics. Our study was conducted on an annual forage agrosystem with a degraded Palexerult soil in SW Spain with mineralogical and morphological characteristics inherited from a pre-Quaternary humid-subtropical climate. The experiment had a split-plot design with tillage (no-tillage vs. traditional tillage) as the main factor and with or without Ca-amendment as the second factor. Aggregate size distribution was dominated by microaggregates (0.053–0.250mm). Compared with tilled plots, after six years, no-tillage increased the macroaggregates (>0.250mm) to a depth of 10cm by about 40%. The relatively low clay content of the surface soil may explain the strong impact of tillage on macroaggregation and the relatively slow recovery after the adoption of no-tillage. In contrast to the tillage system, the Ca-amendment barely influenced aggregation parameters. No-tillage also favored accumulation of organic C and N in all aggregate fractions but no size preference between macro- and microaggregates was observed while Ca-amendment enhanced accumulation only in large macroaggregates. Our results indicate an aggregation hierarchy in these kaolinitic soils, as well as an important role of SOM in enhancing soil aggregation.

Impact of Conservation Tillage on Soil Organic Carbon and Physical Properties –a Review

Impact of Conservation Tillage on Soil Organic Carbon and Physical Properties –a Review

Structural disruption of arable soils under laboratory conditions causes minor respiration increases

AbstractPrevious field studies in N Europe have shown that the impact of soil tillage on soil respiration is mostly indirect, caused by altered distribution of plant residues in soil affecting decomposition of residues. Tillage operations alter soil moisture and temperature conditions in soil, which control decomposition dynamics. Experiments under laboratory conditions allow indirect effects of altered residue decomposition to be distinguished from direct effects of mechanical disruption, i.e., the increased exposure of substrates within aggregates and micropores upon tillage. This study examined the effects of physical disruption of soils with different soil texture, land‐use history, and soil organic C content on soil respiration under controlled abiotic conditions. Undisturbed soil samples from 7 sites (arable land and grassland) were incubated at 20°C and three different water potentials (–1, –10, and –30 kPa). Soil respiration was measured before and after physical disruption with laboratory homogenizer, using an automated respiration apparatus. Soil organic C, water content, and bulk density explained 67% of the variation in base respiration. In half of the disrupted samples, bulk density was re‐adjusted by re‐compaction to conditions prevailing before disruption. Disruption and re‐compaction generally resulted in higher respiration flushes than disruption alone. Respiration peaks increased with water content. However, total C losses were small and corresponded to &lt; 0.1 Mg C ha−1. Overall, physical soil disruption increased decomposition of soil organic matter only marginally and temporarily. It would be difficult to detect an effect of tillage on soil organic matter decomposition under field conditions.

Stable isotope technique in the evaluation of tillage and fertilizer effects on soil carbon and nitrogen sequestration and water use efficiency

Abstract Agricultural soil could be made to serve as a sink rather than a source of greenhouse gases by suitable soil management. This study was, therefore, conducted to assess the impact of tillage and fertilizer application on soil and plant carbon and nitrogen fractionation and intrinsic water use efficiency (iWUE). The experiment was a split–split-plot factorial design with three replications. The main plot consisted of two tillage treatments: zero tillage (ZT) and conventional tillage (CT). The sub-plot contained four NPK fertilizer treatments (0, 90, 120 and 150 kg N ha−1), while the sub–sub-plot comprised three poultry manure (PM) treatments (0, 10 and 20 Mg ha−1). Soil carbon and nitrogen sequestration were evaluated using stable isotope of carbon (δ13C) and nitrogen (δ15N). The δ13C in maize plant was used to obtain iWUE. It was observed that soil δ13C and δ15N were more depleted under ZT than CT and in plots treated with 20 Mg ha−1 PM (PM20) implying carbon and nitrogen sequestration under ZT and by PM20. Relative to the control, application of PM20 raised soil δ15N enrichment by 82% and 96% under CT and ZT, respectively. Higher iWUE of 25.7% was obtained under CT and was significantly higher than the iWUE values under ZT in the second year of the study while the iWUE was significantly lower with PM20 application than other fertilizer treatments. The significant δ13C depletion and hence lower iWUE with combination of NPK fertilizer and PM under CT than the control implied that soil disturbance under tilled plots was mediated by combined nutrient management thereby limiting soil C available for fractionation resulting in lower iWUE. This suggests that conservation tillage such as zero tillage and integrated application of organic and inorganic fertilizers are good strategies for reducing soil carbon and nitrogen emission.

Impact of Tillage and Irrigation Management on Bell Pepper (Capsicum annuum L.) Grown in Organic and Conventional Production Systems

Trials were conducted in 2011 and 2012 with ‘Aristotle’ bell pepper (Capsicum annuum L.) grown under different tillage methods and irrigation regimes in organically and conventionally managed production systems. Treatments consisted of strip tillage or plastic mulch in well-watered or water-restricted irrigation regimes. Within organic and conventional production systems, the study was arranged as a split-plot randomized block design with strip tillage or plastic mulch as the main plot and irrigation regime as subplot. Leaf water potential (ΨL), soil penetration resistance (compaction), volumetric water content (VWC), soil temperature, and pepper yield were measured. Soil VWC was greater in strip-tillage plots compared with plastic mulch plots under both well-watered and water-restricted conditions for plots in the organic system in 2011 and conventional system in 2012. In addition, soil VWC was numerically lower, if not always statistically different, in water-restricted plots compared with well-watered plots. The trend of soil temperatures within each production system were similar in 2011 and 2012, with plastic mulch plots having slightly higher soil temperatures than strip tillage, despite using white-on-black plastic mulch. Midday ΨL was affected by water regime, with well-watered plants having a significantly lower ΨL than water-restricted plants; however, there were no effects of irrigation on predawn ΨL. Tillage method and sampling location (between row and within row) significantly interacted to affect soil penetration resistance in 2011 and 2012. There was a significant interaction of tillage by irrigation regime on yield within conventional systems in both years, but not in organically managed plots. In 2011, yield data also indicated that the date at which 50% of marketable fruit were harvested (yield_mid) were later for strip–tillage-grown plants than plastic mulch–treated plants within conventional and organic production systems, respectively.

Impact of crop residue retention and tillage on water infiltration into a water-repellent soil

AbstractWater repellence is a condition in which soils become hydrophobic and do not readily absorb water. The condition causes problems in agricultural production relating to water availability for seed germination and plant growth. In this research we assess the impact of disturbing the soil by a single annual soil tillage (compared with no-till) and crop residue retention (compared with residue removal by burning) on the severity of water repellency, and on water infiltration during and immediately after rainfall, for 5 discrete rainfall events over an 18-month period covering two crop growing seasons. Soil tillage and crop residue removal were associated with decreased severity of water repellency. Despite this, soil tillage resulted in less infiltration of rain water, especially in the crop inter-row spaces, one hour after the commencement of rainfall, and 6 hours after the conclusion of rainfall. Where a single soil tillage was performed, soil in the inter-row spaces absorbed 19-30% of incident rainfall, compared with 58-78% in undisturbed soils. This was observed for a rainfall event 11 months after soil tillage, indicating that soil tillage has a long-lasting impact on pathways of water entry into the soil.

Impact of land management system on crop yields and soil fertility in Cameroon

Abstract. The impact of direct-seeding mulch-based cropping systems (DMC), direct seeding (DS) and tillage seeding (TS) on Sorghum yields, soil fertility and the rehabilitation of degraded soils was evaluated in northern Cameroon. Field work consisted of visual examination, soil sampling, yield and rainfall data collection. Three fertilization rates (F1: 100 kg ha−1 NPK + 25 kg ha−1 of urea in DMC, F2: 200 kg ha−1 NPK + 50 kg ha−1 of urea in DMC and F3: 300 kg ha−1 NPK + 100 kg ha−1 of urea in DMC) were applied to each cropping system (DS, TS and DMC), resulting in nine experimental plots. Two types of chemical fertilizer were used (NPK 22.10.15 and urea) and applied each year from 2002 to 2012. Average Sorghum yields were 1239, 863 and 960 kg ha−1 in DMC, DS and TS, respectively, at F1, 1658, 1139 and 1192 kg ha−1 in DMC, DS and TS, respectively, at F2, and 2270, 2138 and 1780 kg ha−1 in DMC, DS and TS, respectively, at F3. pH values were 5.2–5.7 under DMC, 4.9–5.3 under DS and TS and 5.6 in the control sample. High values of cation exchange capacity were recorded in the control sample, TS system and F1 of DMC. Base saturation rates, total nitrogen and organic matter contents were higher in the control sample and DMC than in the other systems. All studied soils were permanently not suitable for Sorghum due to the high percentage of nodules. F1 and F2 of the DS were currently not suitable, while F1 and F3 of DMC, F3 of DS and F1, F2 and F3 of TS were marginally suitable for Sorghum due to low pH values.

Impact of tillage and fertility management options on selected soil physical properties and sorghum yield

Water and soil fertility are the most limiting biophysical factors affecting crop production in semi-arid West Africa. . This study was conducted in Nadion (south Sudan zone of Burkina Faso) to assess the impact of tillage practices (no-till, tied ridging; ripping and conventional tillage) combined with soil fertility management options (compost, NPK + Urea, crop residues, Compost+ NPK + Urea and a control) on soil moisture content and sorghum yield. The soil moisture was monitored weekly using the Time Domain Reflectometer (TDR) method and the soil bulk density was evaluated 30 days after planting. Zero tillage increased the soil water storage capacity compared to the other tillage practices at 0-30 cm depth. Sorghum straw residues application improved soil water content by 20%. Conventional tillage decreased surface soil (0-10 cm) bulk density. Compost + NPK + Urea application increased sorghum yield by 74% over the control while, NPK + urea and compost increased sorghum grain yield by 50% and 29%, respectively relative to the control (no soil amendment). Conventional tillage led to decrease in yield compared to zero tillage after two years of experimentation. The zero tillage combined with compost, NPK and urea increased sorghum yield by 28% compared to tied-ridging regardless of the fertility management options. Zero tillage is a promising option for sorghum production in the South Sudan agro-ecological zone of Burkina Faso. Keywords : Bulk density, fertility management, sorghum yield, South Sudan zone, tillage, water conservation.

Observed and predicted changes in soil carbon stocks under export and diversified agriculture in the Caribbean. The case study of Guadeloupe

Export agriculture in the Caribbean is often blamed for pollution of soils and water resources. At the same time, the reduction of preferences in the international markets for major agricultural exports from the Caribbean induced a partial reorientation of the agriculture towards the local markets, which included crop diversification. This study was carried out to assess the sustainability of that agricultural switch with respect to maintaining, increasing or decreasing soil organic carbon (SOC) stocks. We analysed the impact of export crops (sugarcane and banana monocultures) and diversified agriculture (as monoculture or in rotation with export crops) on SOC stocks using the case study of Guadeloupe (Lesser Antilles). Agriculture in Guadeloupe involves a mosaic of soils, climates, crops and farming practices, which well represent the tropical conditions of export and diversified agriculture in the region. The study was based on: (i) a soil database including information on the SOC stocks of numerous cropping system—agro-ecological region (AER) situations, (ii) a survey of farming practices performed on a network of 382 farmers (e.g. crop rotations and yields, management of residues and organic amendments), and (iii) the development of a simple model of annual C inputs and outputs to assess SOC dynamics at the AER scale. The model was calibrated and evaluated using 253 plots and included 827 SOC measurements selected from the soil database. The model produced satisfactory estimates of changes in SOC stocks and provided an explanation for differences between cropping systems and AERs in terms of the C inputs and outputs. While sugarcane and banana monocultures were able to preserve or increase SOC, diversification was likely to reduce it. These differences were due to higher C inputs from crop residues together with lower C outputs for export agriculture. Lower SOC outputs by mineralization were mainly associated with the longer cycle of these pluriannual crops (5yr), which decreased the impact of soil tillage at planting. Banana monoculture in the most humid AERs was the only cropping system that displayed a clear pattern of C sequestration (+0.5MgCha−1yr−1). The highest SOC losses were observed with vegetable crops in the same AERs (e.g. −2.0MgCha−1yr−1). Calculations made using the model indicated that the sustainability of diversified agriculture in the Caribbean might be reinforced by adopting reduced soil tillage, organic amendments and the liming of the more acid soils to increase yields and crop residues. The results of this study suggest that the implementation of new agricultural policies to reduce the negative environmental impacts of export crops should involve measures to preserve their positive effect on SOC storage.

Consequences of minimum soil tillage on abiotic soil properties and composition of microbial communities in a shallow Cambisol originated from fluvioglacial deposits

A long-term field experiment was run for 12 years to evaluate the impact of minimum tillage (MT) compared to conventional mouldboard ploughing (CT) on soil chemical, physical and microbial properties in a shallow Cambisol formed over fluvioglacial deposits of Drava river in Slovenia. Significant differences between MT and CT were found in vertical distribution of soil organic C (SOC) and nutrients (total N and plant available potassium); under MT, concentrations decreased from the soil surface to the lower layers, as opposed to CT which maintained rather uniform distribution down to the ploughing depth. MT in comparison with CT also increased the proportion of water-stable 2–4-mm-sized aggregates (80.9 and 61.3 %, respectively), water holding capacity (24.8 and 22.2 %, respectively) and plant available water (13.4 and 10.3 %, respectively) in the upper 0–10-cm soil layer. Bulk density, porosity, the proportion of water-stable 1–2-mm-sized aggregates and infiltration rate showed no significant differences between the tillage treatments. SOC content in the upper 0–10-cm soil layer was not significantly different between MT and CT (1.60 ± 0.07 and 1.45 ± 0.05 %, respectively), as well as the overall stock in the investigated soil profile (0–60 cm) remained unaffected (57.4 ± 0.8 and 59.1 ± 2.2 t ha−1, respectively). Microbial biomass, estimated by the total soil DNA, was higher in MT than CT in the 0–10-cm layer. Furthermore, a positive linear dependence of microbial biomass on SOC content was observed. Fingerprinting of bacterial, fungal and archaeal communities indicated that microbial community composition changed by long-term MT, whereas changes in microbial diversity were not detected for any domain. The most pronounced shifts in the composition were found for bacterial communities in the 10–20-cm layer, while the composition of fungal communities slightly changed in the upper 0–10 cm of MT soil. The composition of archaeal communities was not affected by the tillage or by the soil depth. Our results indicate that MT generates modest changes in soil structure and soil water retention properties and could support measures against erosion, drought and nutrient leaching. Considering increased microbial biomass in the topsoil of MT and shifts in microbial diversity, the impacts of MT on soil microbiome are also evident and need to be further investigated to identify the affected functional traits.

Tillage impact on herbicide loss by surface runoff and lateral subsurface flow

There is worldwide interest in conservation tillage practices because they can reduce surface runoff, and agrichemical and sediment losses from farm fields. Since these practices typically increase infiltration, their use may increase subsurface transport of water-soluble contaminants. Thus, to assess long-term environmental benefits of conservation tillage data may be needed that quantify both surface and subsurface contaminant fluxes. This study focused on the herbicide fluometuron (N,N-dimethyl-N′-[3-(trifluoromethyl)phenyl]-urea) and its soil degradate DMF (N-methyl-N′-[3-(trifluoromethyl) phenyl]-urea). Both compounds are classed as “leachable”. They were measured for 10years in surface runoff and lateral subsurface flow from paired fields located on a hill slope in the Atlantic Coastal Plain region of the southeastern USA. One group of fields was conventionally tilled incorporating all crop residues into soil prior to planting. The second was strip tilled, a common conservation tillage practice. Seven fluometuron applications were made to cotton (Gossypium hirsutum) produced in rotation with peanut (Arachis hypogea). Combined fluometuron and DMF surface and subsurface losses from the conventionally tilled fields were equivalent to 1.2% and 0.13% of fluometuron applied and 0.31% and 0.32% from the strip tilled fields. Annual surface runoff losses were significantly greater from the conventionally tilled fields while the strip tilled fields had significantly greater annual subsurface losses. Results demonstrated that shifting from conventional to conservation tillage management of farm fields in this landscape will reduce surface runoff losses of herbicides like fluometuron but subsurface losses will likely increase. The same trends can be expected in landscapes with similar soil and hydrologic properties. This should be considered when planning implementation of programs that promote conservation tillage use.

Impact of Location, Cropping History, Tillage, and Chlorpyrifos on Soil Arthropods in Peanut.

Demand for agricultural production systems that are both economically viable and environmentally conscious continues to increase. In recent years, reduced tillage systems, and grass and pasture rotations have been investigated to help maintain or improve soil quality, increase crop yield, and decrease labor requirements for production. However, documentation of the effects of reduced tillage, fescue rotation systems as well as other management practices, including pesticides, on pest damage and soil arthropod activity in peanut production for the Mid-Atlantic US region is still limited. Therefore, this project was implemented to assess impacts of fescue-based rotation systems on pests and other soil organisms when compared with cash crop rotation systems over four locations in eastern North Carolina. In addition, the effects of tillage (strip vs. conventional) and soil chlorpyrifos application on pod damage and soil-dwelling organisms were also evaluated. Soil arthropod populations were assessed by deploying pitfall traps containing 50% ethanol in each of the sampled plots. Results from the present study provide evidence that location significantly impacts pest damage and soil arthropod diversity in peanut fields. Cropping history also influenced arthropod diversity, with higher diversity in fescue compared with cash crop fields. Corn rootworm damage to pods was higher at one of our locations (Rocky Mount) compared with all others. Cropping history (fescue vs. cash crop) did not have an effect on rootworm damage, but increased numbers of hymenopterans, acarina, heteropterans, and collembolans in fescue compared with cash crop fields. Interestingly, there was an overall tendency for higher number of soil arthropods in traps placed in chlorpyrifos-treated plots compared with nontreated controls.

Long-term impact of tillage and crop rotation on soil health at four temperate agroecosystems

Long-term agricultural production with different tillage systems and crop rotations affect soil health, and thereby influence agricultural sustainability. However, quantifying and integrating the numerous soil health attributes is complex. One method of measuring overall soil health is the Cornell Soil Health Assessment (CSHA) used in New York; however, its applicability for other regions should be evaluated. Soil samples were collected from the 0–15cm depth in 2009 and 2010 at four temperate, rainfed long-term experimental sites in Ontario (Ridgetown, Delhi, Elora, and Ottawa) and we evaluated the impact of tillage systems and crop rotations on 15 soil attributes. Based on a principal component analysis (PCA), the first two components accounted for 62% of the cumulative variability. The PCA eigenvectors were used to weight individual CSHA scores and develop the new Ontario Soil Health Assessment (OSHA) overall score. The OSHA scoring system was 2–10 times more sensitive than the CSHA in showing numerical differences for soil health among different tillage systems and crop rotations, which may help growers to more clearly see differences in soil health under different management practices. No-till (NT) compared to conventional tillage (CT) had significantly greater OSHA scores at Ridgetown, Delhi, and Elora, but there was no difference at Ottawa. At Ridgetown and Elora, crop rotations which included winter wheat or alfalfa tended to have higher OSHA scores, while lowest scores were with monoculture corn (monoC) or soybean–corn (S–C or S–S–C–C). This study provides the first soil health assessment for Ontario and a framework for improving overall soil health testing elsewhere.

Effects of tillage, cultivar and fungicide on Phomopsis longicolla and Cercospora kukuchii in soybean

It has become a standard practice for farmers to use a no-till production system where crop residues are left on the soil surface rather than incorporated into the soil. This practice helps reduce soil erosion, conserve energy, increase soil moisture, and reduce erosion. However, many plant pathogens survive in the previous year's crop residue, increasing disease risk in reduced-tillage systems. The effect of tillage on seed borne diseases has not been objectively evaluated in side by side comparisons of till and no-till culture. We evaluated the impact of tillage and foliar fungicide on percent seed infection by Phomopsis Seed Decay (PSD) and Purple Seed Stain (PSS) over 4 years at the Milan Research and Education Center, Milan, TN. Analysis of variance indicated there was no significant difference (P≤0.05) in PSD and PSS infection due to tillage. However, there was a significant interaction between fungicide and tillage where fungicide significantly reduced PSD in tilled but not in no-till plots. On the contrary, PSS increased in both tilled and no-till plots with fungicide application. These results suggest that fungicide programs under both till and no-till systems may alter the level of severity of these two seed borne diseases and may require further research to minimize the risk.

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.

Impact of conservation tillage and organic farming on the diversity of arbuscular mycorrhizal fungi

Communities of arbuscular mycorrhizal fungi (AMF) are strongly affected by land use intensity and soil type. The impact of tillage practices on AMF communities is still poorly understood, especially in organic farming systems. Our objective was to investigate the impact of soil cultivation on AMF communities in organically managed clay soils of a long-term field experiment located in the Sissle valley (Frick, Switzerland) where two different tillage (reduced and conventional mouldboard plough tillage) and two different types of fertilization (farmyard manure & slurry, or slurry only) have been applied since 2002. In addition, a permanent grassland and two conventionally managed croplands situated in the neighborhood of the experiment were analyzed as controls. Four different soil depths were studied including top-soils (0–10 and 10–20 cm) of different cultivation regimes and undisturbed sub-soils (20–30 and 30–40 cm). The fungi were directly isolated from field soil samples, and additionally spores were periodically collected from long-term trap culture (microcosm) systems. In total, >50,000 AMF spores were identified on the species level, and 53 AMF species were found, with 38 species in the permanent grassland, 33 each in the two reduced till organic farming systems, 28–33 in the regularly plowed organic farming systems, and 28–33 in the non-organic conventional farming systems. AMF spore density and species richness increased in the top-soils under reduced tillage as compared to the ploughed plots. In 10–20 cm also the Shannon–Weaver AMF diversity index was higher under reduced tillage than in the ploughed plots. Our study demonstrates that AMF communities in clay soils were affected by land use type, farming system, tillage as well as fertilization strategy and varying with soil depth. Several AMF indicator species especially for different land use types and tillage strategies were identified from the large data set.

Surface organic carbon enrichment to explain greater CO2 emissions from short-term no-tilled soils

The impact of agricultural practices on CO2 emissions from soils needs to be understood and quantified to enhance ecosystem functions, especially the ability of soils to sequester atmospheric carbon (C), while enhancing food and biomass production. The objective of this study was to assess CO2 emissions in the soil surface following tillage abandonment and to investigate some of the underlying soil physical, chemical and biological controls. Maize (Zea mays) was planted under conventional tillage (T) and no-tillage (NT), both without crop residues under smallholder farming conditions in Potshini, South Africa. Intact top-soil (0–0.05m) core samples (N=54) from three 5×15m2 plots per treatment were collected two years after conversion of T to NT to evaluate the short-term CO2 emissions. Depending on the treatment, cores were left intact, compacted by 5 and 10%, or had surface crusts removed. They were incubated for 20 days with measurements of CO2 fluxes twice a day during the first three days and once a day thereafter. Soil organic C (SOC) content, soil bulk density (ρb), aggregate stability, soil organic matter quality, and microbial biomass and its activity were evaluated at the onset of the incubation. CO2 emissions were 22% lower under NT compared with T with CO2 emissions of 0.9±0.10 vs 1.1±0.10mg C–CO2gC−1 day−1 under NT and T, respectively, suggesting greater SOC protection under NT. However, there were greater total CO2 emissions per unit of surface by 9% under NT compared to T (1.15±0.03 vs 1.05±0.04g C–CO2m−2 day−1). SOC protection significantly increased with the increase in soil bulk density (r=0.89) and aggregate stability (from 1.7±0.25mm to 2.3±0.31, r=0.50), and to the decrease in microbial biomass and its activity (r=−0.59 and −0.57, respectively). In contrast, the greater NT CO2 emissions per m2 were explained by top-soil enrichment in SOC by 48% (from 12.4±0.2 to 19.1±0.4gkg−1, r=0.59). These results on the soil controls of tillage impact on CO2 emissions are expected to inform on the required shifts in agricultural practices for enhancing C sequestration in soils. In the context of the study, any mechanism favoring aggregate stability and promoting SOC allocation deep in the soil profile rather than in the top-soil would greatly diminish soil CO2 outputs and thus stimulate C sequestration.

Influence of sequential tillage and residue management practices on soil and root parameters in soybean (Glycine max) - wheat (Triticum aestivum) cropping system

A field study was conducted in 2009-10 and 2010-11 at Indian Agricultural Research Institute, New Delhi to assess the effect of sequential tillage and crop establishment and residue management practices on soil health and root parameters in soybean [Glycine max (L.) Merr.] - wheat (Triticum aestivum L.) cropping system. The results pertaining to the experiments at the end of the two year study revealed that most of the soil properties except infiltration rate and microbial biomass carbon (MBC); and root parameters of both crops except root length density (RLD) and average root diameter of wheat were non-significant by the sequential tillage and crop establishment treatments. Unlike sequential tillage and crop establishment techniques, all soil properties except bulk density, pH, EC and root parameters of both soybean and wheat responded significantly to the residue management practices. The infiltration rate was significantly higher with skipping the sequence of CT-Flat by ZT-Flat. Skipping the sequence of CT-Flat and bed with ZT-Flat and bed recorded higher soil mean weight diameter (MWD) and grand mean diameter (GMD) at 0- 10 cm soil depth than the counterpart by skipping of ZT-Flat and bed with CT-Flat and bed. The percentage of soil macro-aggregate was high by skipping ZT-Flat and bed with CT-flat and bed at all depths while the reverse was exhibited in case of percentage soil micro-aggregates by skipping CT-Flat and bed with ZT-Flat and bed. By skipping CT-flat and bed with ZT-flat and bed significantly higher soil MBC was recorded than the counterpart skipping tillage treatments. The same significant trend was also exhibited for soil MBC with residue management treatments, where the wheat + soybean residue application recorded 20.90 % higher than the control. Root parameters like RLD, root surface area (RSA), root volume density (RVD), average root diameter (ARD) in soybean while these were partly non-significant (RSD and RVD) in wheat with the sequential tillage and crop establishment treatments, whereas the residue management practices significantly influenced the root parameters of both the crops. Among the residue management practices, wheat + soybean residue obtained higher RLD (2.57 and 1.03 cm/cm3); RSA (0.79 and 0.32 cm2/cm3); RVD (18.11 and 7.46 × 10-3 cm3/cm3) and average root diameter (1.04 and 0.85 mm) both in soybean and wheat crops than rest of the treatments. Thus, impact of short-term zero tillage is short lived for favourable soil health and root parameters when skipping with conventional tillage.