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Bram Govaerts - One of the best experts on this subject based on the ideXlab platform.
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Conservation Agriculture increased organic carbon in the top soil macro aggregates and reduced soil co2 emissions
Plant and Soil, 2012Co-Authors: Mariela Fuentes, Nele Verhulst, Claudia Hidalgo, Jorge D Etchevers, Fernando De Leon, Armando Guerrero, Luc Dendooven, Bram GovaertsAbstract:Background and aims Conservation Agriculture, the combination of minimal soil movement (zero or reduced tillage), crop residue retention and crop rotation, might have the potential to increase soil organic C content and reduce emissions of CO2.
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Conservation Agriculture improving soil quality for sustainable production systems
2012Co-Authors: Nele Verhulst, Jozef Deckers, Bram Govaerts, Els Verachtert, A Castellanosnavarrete, Monica Mezzalama, Patrick C Wall, A Chocobar, Ken D SayreAbstract:Conservation Agriculture has been proposed as a widely adapted set of management principles that can assure more sustainable agricultural production. Conservation Agriculture removes the emphasis from the tillage component alone and addresses a more enhanced concept of the complete agricultural system. Applying Conservation Agriculture essentially means altering literally generations of traditional farming practices and implement use. Within the framework of agricultural production, high soil quality equates to the ability of the soil to maintain a high productivity without significant soil or environmental degradation. A comparative soil quality evaluation is one in which the performance of the system is determined in relation to alternatives. Inconsistent effects of a reduction in tillage on the variation in total porosity with depth may be related to differences in traffic on different sites, or on soil quality at the time tillage was reduced or stopped.
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Conservation Agriculture as a means to mitigate and adapt to climate change a case study from mexico
2012Co-Authors: Nele Verhulst, Bram Govaerts, Monica Mezzalama, K D Sayre, Kai Sonder, R Romeroperezgrovas, Luc DendoovenAbstract:Conservation Agriculture (CA) has been proposed as an adapted set of management principles that assures a more sustainable agricultural production. It combines the following basic principles: (1) reduction in tillage, (2) retention of adequate levels of crop residues and soil surface cover, (3) use of crop rotations. These CA principles are applicable to a wide range of crop production systems. However, the application of CA will be different in different situations. Specific and compatible management components (pest and weed control tactics, nutrient management strategies, rotation crops, appropriately-scaled implements, etc.) will need to be identified through adaptive research with active farmer involvement. In this chapter, climate change predictions for Mexico will be discussed. Then the potential of CA as a means to mitigate and adapt to climate change will be examined for two contrasting agro-ecological environments, using research results of long-term trials. Finally, the economic potential of CA for climate change mitigation and adaption will be examined and an extension strategy will be outlined.
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short term effects of Conservation Agriculture on vertisols under tef eragrostis tef zucc trotter in the northern ethiopian highlands
Soil & Tillage Research, 2010Co-Authors: Tigist Oicha, Wim Cornelis, Hubert Verplancke, Jan Nyssen, Bram Govaerts, Mintesinot Behailu, Mitiku Haile, Jozef DeckersAbstract:Abstract Soil erosion and declining soil quality are the major constraints for crop production and sustainable land management in Ethiopia. A Conservation Agriculture (CA) experiment was conducted in 2006 at Gumselasa, Northern Ethiopia, on experimental plots established in 2005 on a farmer's field. The objectives of this experiment were to evaluate the short-term changes in soil quality of a Vertisol due to the implementation of Conservation Agriculture practices and to assess their effect on soil erosion, crop yield and yield components of tef ( Eragrostis tef (Zucc.) Trotter). The treatments were permanent bed (PB), terwah (TERW) and conventional tillage (TRAD). Soil organic matter (SOM) was significantly higher in PB (2.49%) compared to TRAD (2.33%) and TERW (2.36%). Although aggregate stability of PB (0.94) was higher than TRAD (0.83), the difference was not significant. PB had larger macroporosity (0.07 m 3 m −3 ) compared to the other treatments. PB reduced runoff volume by 50% and TERW by 16% compared to TRAD. PB also reduced soil loss by 86% and TERW by 53% in comparison to TRAD. Despite the above soil physical quality improvements and effectiveness in runoff and soil loss reduction, biomass and plant height of tef were significantly higher in TRAD than PB. The significantly high weed dry matter at first weeding, the types of weeds and their water uptake behavior might have caused the lower tef yield on the PB. We therefore recommend that appropriate rate of herbicides must be used while growing tef using CA practices.
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Conservation Agriculture as a sustainable option for the central mexican highlands
Soil & Tillage Research, 2009Co-Authors: Bram Govaerts, Ken D Sayre, Luc Dendooven, Bart Goudeseune, Pieter De Corte, Kelly Lichter, Jozef DeckersAbstract:Tropical highlands of the world are densely populated and intensively cropped. Agricultural sustainability problems resulting from soil erosion and fertility decline have arisen all over this agro-ecological zone. Based on selected soil quality indicators, i.e. time-to-pond, aggregate distribution and stability (expressed as the mean weight diameter (MWD) for dry and wet sieving, respectively) and soil moisture, from a representative long-term sustainability trial initiated in 1991 in Central Mexico (2240 masl; 19.31°N, 98.50°W; Cumulic Phaeozem), some insights into the feasibility of Conservation Agriculture (CA) as part of a sustainable production system in the tropical highlands are given. Zero tillage plots with crop residue removal showed low aggregate distribution (average MWD = 1.34 mm) and stability (average MWD = 0.99 mm) resulting in top layer slaking, increased erosion and low time-to-pond values. Retaining the residue in the field with zero tillage avoided the above-mentioned negative evolution for both aggregate distribution as stability (average MWD = 2.77 and 1.51 mm, respectively) and even improved the physical conditions of the soil as compared to conventional practice. Throughout the growing season the lowest soil moisture content was found in zero tillage without residue (average over the entire growing season = 20.5% volumetric moisture content), the highest in zero tillage with residue retention (average = 29.7%) while conventional tillage had intermediate soil moisture values (average = 27.4%). Zero tillage without residue retention had most days of soil moisture values under permanent wilting point, while zero tillage with residue retention had the least. Taking into account these results, zero tillage with residue retention can clearly be a part of an integrated watershed management scheme towards sustainable Agriculture in the tropical highlands. It is clear that to develop new management practices to improve water use, reduce erosion and enhance human labor/animal power focus must be on the use of Conservation Agriculture both for rainfed as well as irrigated production systems and be fine tuned for each system.
Luc Dendooven - One of the best experts on this subject based on the ideXlab platform.
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Conservation Agriculture increased organic carbon in the top soil macro aggregates and reduced soil co2 emissions
Plant and Soil, 2012Co-Authors: Mariela Fuentes, Nele Verhulst, Claudia Hidalgo, Jorge D Etchevers, Fernando De Leon, Armando Guerrero, Luc Dendooven, Bram GovaertsAbstract:Background and aims Conservation Agriculture, the combination of minimal soil movement (zero or reduced tillage), crop residue retention and crop rotation, might have the potential to increase soil organic C content and reduce emissions of CO2.
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Conservation Agriculture as a means to mitigate and adapt to climate change a case study from mexico
2012Co-Authors: Nele Verhulst, Bram Govaerts, Monica Mezzalama, K D Sayre, Kai Sonder, R Romeroperezgrovas, Luc DendoovenAbstract:Conservation Agriculture (CA) has been proposed as an adapted set of management principles that assures a more sustainable agricultural production. It combines the following basic principles: (1) reduction in tillage, (2) retention of adequate levels of crop residues and soil surface cover, (3) use of crop rotations. These CA principles are applicable to a wide range of crop production systems. However, the application of CA will be different in different situations. Specific and compatible management components (pest and weed control tactics, nutrient management strategies, rotation crops, appropriately-scaled implements, etc.) will need to be identified through adaptive research with active farmer involvement. In this chapter, climate change predictions for Mexico will be discussed. Then the potential of CA as a means to mitigate and adapt to climate change will be examined for two contrasting agro-ecological environments, using research results of long-term trials. Finally, the economic potential of CA for climate change mitigation and adaption will be examined and an extension strategy will be outlined.
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Conservation Agriculture as a sustainable option for the central mexican highlands
Soil & Tillage Research, 2009Co-Authors: Bram Govaerts, Ken D Sayre, Luc Dendooven, Bart Goudeseune, Pieter De Corte, Kelly Lichter, Jozef DeckersAbstract:Tropical highlands of the world are densely populated and intensively cropped. Agricultural sustainability problems resulting from soil erosion and fertility decline have arisen all over this agro-ecological zone. Based on selected soil quality indicators, i.e. time-to-pond, aggregate distribution and stability (expressed as the mean weight diameter (MWD) for dry and wet sieving, respectively) and soil moisture, from a representative long-term sustainability trial initiated in 1991 in Central Mexico (2240 masl; 19.31°N, 98.50°W; Cumulic Phaeozem), some insights into the feasibility of Conservation Agriculture (CA) as part of a sustainable production system in the tropical highlands are given. Zero tillage plots with crop residue removal showed low aggregate distribution (average MWD = 1.34 mm) and stability (average MWD = 0.99 mm) resulting in top layer slaking, increased erosion and low time-to-pond values. Retaining the residue in the field with zero tillage avoided the above-mentioned negative evolution for both aggregate distribution as stability (average MWD = 2.77 and 1.51 mm, respectively) and even improved the physical conditions of the soil as compared to conventional practice. Throughout the growing season the lowest soil moisture content was found in zero tillage without residue (average over the entire growing season = 20.5% volumetric moisture content), the highest in zero tillage with residue retention (average = 29.7%) while conventional tillage had intermediate soil moisture values (average = 27.4%). Zero tillage without residue retention had most days of soil moisture values under permanent wilting point, while zero tillage with residue retention had the least. Taking into account these results, zero tillage with residue retention can clearly be a part of an integrated watershed management scheme towards sustainable Agriculture in the tropical highlands. It is clear that to develop new management practices to improve water use, reduce erosion and enhance human labor/animal power focus must be on the use of Conservation Agriculture both for rainfed as well as irrigated production systems and be fine tuned for each system.
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Conservation Agriculture and soil carbon sequestration between myth and farmer reality
Critical Reviews in Plant Sciences, 2009Co-Authors: Bram Govaerts, Nele Verhulst, A Castellanosnavarrete, Ken D Sayre, John Dixon, Luc DendoovenAbstract:Improving food security, environmental preservation and enhancing livelihood should be the main targets of the innovators of today's farming systems. Conservation Agriculture (CA), based on minimum tillage, crop residue retention, and crop rotations, has been proposed as an alternative system combining benefits for the farmer with advantages for the society. This paper reviews the potential impact of CA on C sequestration by synthesizing the knowledge of carbon and nitrogen cycling in Agriculture; summarizing the influence of tillage, residue management, and crop rotation on soil organic carbon stocks; and compiling the existing case study information. To evaluate the C sequestration capacity of farming practices, their influence on emissions from farming activities should be considered together with their influence on soil C stocks. The largest contribution of CA to reducing emissions from farming activities is made by the reduction of tillage operations. The soil C case study results are not conclusive....
Valérie Pot - One of the best experts on this subject based on the ideXlab platform.
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Adsorption and degradation of the herbicide nicosulfuron in a stagnic Luvisol and Vermic Umbrisol cultivated under conventional or Conservation Agriculture
Environmental Science and Pollution Research, 2020Co-Authors: Sixtine Cueff, Lionel Alletto, Valérie Dumény, Pierre Benoit, Valérie PotAbstract:The main goals of Conservation Agriculture are to enhance soil fertility and reduce soil degradation, especially through erosion. However, Conservation Agriculture practices can increase the risk of contamination by pesticides, mainly through vertical transfer via water flow. Better understanding of their sorption and degradation processes is thus needed in Conservation Agriculture as they control the amount of pesticide available for vertical transfer. The purpose of our study was to investigate the sorption and degradation processes of nicosulfuron in soil profiles (up to 90 cm deep) of a Vermic Umbrisol and a Stagnic Luvisol managed either in conventional or in Conservation Agriculture. Two laboratory sorption and incubation experiments were performed. Low sorption was observed regardless of the soil type, agricultural management or depth, with a maximum value of 1.3 ± 2.0 L kg^−1. By the end of the experiment (91 days), nicosulfuron mineralisation in the Vermic Umbrisol was similar for the two types of agricultural management and rather depended on soil depth (29.0 ± 2.3% in the 0–60-cm layers against 7.5 ± 1.4% in the 60–90 cm). In the Stagnic Luvisol, nicosulfuron mineralisation reached similar value in every layer of the Conservation Agriculture plot (26.5% ± 0.7%). On the conventional tillage plot, mineralisation decreased in the deepest layer (25–60 cm) reaching only 18.4 ± 6.9% of the applied nicosulfuron. Regardless of the soil type or agricultural management, non-extractable residue formation was identified as the main dissipation process of nicosulfuron (45.1 ± 8.5% and 50.2 ± 7.0% under conventional and Conservation Agriculture respectively after 91 days). In our study, nicosulfuron behaved similarly in the Vermic Umbrisol regardless of the agricultural management, whereas the risk of transfer to groundwater seemed lower in the Stagnic Luvisol under Conservation Agriculture.
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water and pesticide transfers in undisturbed soil columns sampled from a stagnic luvisol and a vermic umbrisol both cultivated under conventional and Conservation Agriculture
Geoderma, 2020Co-Authors: Marjolaine Bourdatdeschamps, Sixtine Cueff, Lionel Alletto, Pierre Benoit, Valérie PotAbstract:Abstract The main goals of Conservation Agriculture are to enhance soil fertility and to reduce soil degradation especially through erosion. However, Conservation Agriculture practices can exhibit a higher risk of contamination through vertical flows. The objectives of this study were to (i) characterise water and pesticide transfers in two different soils both managed under conventional and Conservation Agriculture and (ii) assess the effects of pesticide properties, soil type and agricultural system on pesticide fate. We studied the behaviour of two herbicides (nicosulfuron and mesotrione) and a molluscicide (metaldehyde) in percolation experiments in undisturbed soil columns. A series of two rain events (one with a high, the other with a low intensity) separated by a two-day flow interruption was applied three days after the pesticides and bromide application. Batch sorption coefficients, Kd, were also measured. While the Pesticides Properties Data Base (2020) indicated a decrease of sorption in the order mesotrione > metaldehyde > nicosulfuron, the measured Kd, decreased in the order mesotrione (2.3 ± 1.4 L.kg−1) > nicosulfuron (0.7 ± 0.4 L.kg−1) > metaldehyde (0.1 ± 0.1 L.kg−1). We highlighted distinct behaviour of pesticide leaching depending mainly on soil type, agricultural practices and pesticide properties. For low degree of preferential flow, pesticide leaching can be related to the sorption properties of pesticides. Nicosulfuron and mesotrione delays are more pronounced under Conservation management while metaldehyde always arrived with no delay. During the high intensity rain event, on one soil type, high degree of preferential flow masked sorption effect on leaching since every pesticide arrived at the same time as the tracer and amounted to up to 21% of pesticide recovery compared to 4% on the other soil type. Conservation Agriculture was found to improve the vertical transfers of water and pesticides while, on one of the studied soil type, the presence of a low conductive plough pan significantly limits water drainage.
Christian Thierfelder - One of the best experts on this subject based on the ideXlab platform.
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Complementary practices supporting Conservation Agriculture in southern Africa. A review
Agronomy for Sustainable Development, 2018Co-Authors: Christian Thierfelder, Peter Setimela, Isaiah Nyagumbo, Blessing Mhlanga, Nicole Lee, Walter Mupangwa, Frédéric Baudron, Bruno GerardAbstract:Conservation Agriculture (CA)—the simultaneous application of minimum soil disturbance, crop residue retention, and crop diversification—is a key approach to address declining soil fertility and the adverse effects of climate change in southern Africa. Applying the three defining principles of CA alone, however, is often not enough, and complementary practices and enablers are required to make CA systems more functional for smallholder farmers in the short and longer term. Here, we review 11 complementary practices and enablers grouped under six topical areas to highlight their critical need for functional CA systems, namely: (1) appropriate nutrient management to increase productivity and biomass; (2) improved stress-tolerant varieties to overcome biotic and abiotic stresses; (3) judicious use of crop chemicals to surmount pest, diseases, and weed pressure; (4) enhanced groundcover with alternative organic resources or diversification with green manures and agroforestry; (5) increased efficiency of planting and mechanization to reduce labor, facilitate timely planting, and to provide farm power for seeding; and (6) an enabling political environment and more harmonized and innovative extension approaches to streamline and foster CA promotional efforts. We found that (1) all 11 complementary practices and enablers substantially enhance the functioning of CA systems and some (e.g., appropriate nutrient management) are critically needed to close yield gaps; (2) practices and enablers must be tailored to the local farmer contexts; and (3) CA systems should either be implemented in a sequential approach, or initially at a small scale and grow from there, in order to increase feasibility for smallholder farmers. This review provides a comprehensive overview of practices and enablers that are required to improve the productivity, profitability, and feasibility of CA systems. Addressing these in southern Africa is expected to stimulate the adoption of CA by smallholders, with positive outcomes for soil health and resilience to climate change.
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The adaptive capacity of maize-based Conservation Agriculture systems to climate stress in tropical and subtropical environments: A meta-regression of yields
Agriculture Ecosystems and Environment, 2018Co-Authors: Peter R. Steward, Cameron M. Pittelkow, Maxwell Kudzala, Christian Thierfelder, Andrew J Dougill, Lindsay C. Stringer, Gorm E ShackelfordAbstract:Conservation Agriculture is widely promoted across sub-Saharan Africa as a sustainable farming practice that enhances adaptive capacity to climate change. The interactions between climate stress, management, and soil are critical to understanding the adaptive capacity of Conservation Agriculture. Yet Conservation Agriculture syntheses to date have largely neglected climate, especially the effects of extreme heat. For the sub-tropics and tropics, we use meta-regression, in combination with global soil and climate datasets, to test four hypotheses: (1) that relative yield performance of Conservation Agriculture improves with increasing drought and temperature stress; (2) that the effects of moisture and temperature stress exposure interact; (3) that the effects of moisture and temperature stress are modified by soil texture; and (4) that crop diversification, fertilizer application rate, or the time since no-till implementation will enhance Conservation Agriculture performance under climate stress. Our results support the hypothesis that the relative maize yield performance of Conservation Agriculture improves with increasing drought severity or exposure to high temperatures. Further, there is an interaction of moisture and heat stress on Conservation Agriculture performance and their combined effect is both non-additive and modified by soil clay content, supporting our second and third hypotheses. Finally, we found only limited support for our fourth hypothesis as (1) increasing nitrogen application rates did not improve the relative performance of Conservation Agriculture under high heat stress; (2) crop diversification did not notably improve Conservation Agriculture performance, but did increase its stability with heat stress; and (3) a statistically robust effect of the time since no-till implementation was not evident. Our meta-regression supports the narrative that Conservation Agriculture enhances the adaptive capacity of maize production in sub-Saharan Africa under drought and/or heat stress. However, in very wet seasons and on clay-rich soils, Conservation Agriculture yields less compared to conventional practices.
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intensification of Conservation Agriculture systems for increased livestock feed and maize production in zimbabwe
International Journal of Agricultural Sustainability, 2014Co-Authors: W Mupangwa, Christian ThierfelderAbstract:Livestock and crops are key components of mixed farming systems and are a source of household food and income. However, mixed farming systems face livestock feed shortages and low soil productivity challenges. Conservation Agriculture (CA) systems based on minimum soil disturbance, crop residue retention and crop rotations offer an opportunity to grow both fodder and food crops on the available land to improve productivity and crop output per-unit area. A four-year experiment involving maize monocropping as control treatment and four relay or intercropping treatments with different legume and fodder crops was set up on contrasting soils in Zimbabwe. Lablab was superior in biomass production compared with radish on both soil types. On the clay soil, continuous maize, sole lablab, sole radish, maize/lablab relay and radish/common beans relay treatments produced similar biomass when soil moisture was adequate. When soil moisture was limiting, lablab produced more biomass than continuous maize, radish, maize/...
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Conservation Agriculture for small holder rainfed farming opportunities and constraints of new mechanized seeding systems
Field Crops Research, 2012Co-Authors: C Johansen, Christian Thierfelder, M E Haque, R W Bell, R J EsdaileAbstract:Small holder farmers in rainfed Agriculture believe that soil tillage is needed to maximize crop yields. However, as cropping intensity, and hence tillage intensity, increases there may be a decline in particular physical, chemical and biological properties of the soil which limit crop yield. This is primarily caused by declining soil organic matter, its oxidation being accelerated by tillage, particularly in warmer climates, and exacerbated by the limited return of above-ground biomass to the soil due to its competing use for other purposes. In large-scale commercial Agriculture declining soil quality has been effectively addressed by Conservation Agriculture—cropping systems based on minimum tillage, crop residue retention and appropriate crop rotations and associations, preferably including legumes. This has required development of minimum tillage planting equipment along with herbicide technology to achieve weed control that is traditionally achieved through tillage. However, a shortage of mechanized options suitable for small holder farmers is creating an impediment to the adoption of Conservation Agriculture practices that would arrest the decline in soil quality in their fields. In South Asia, two-wheel tractors are replacing animal-drawn ploughing in small holder plots. This speeds the tillage operation and hence the turnaround time between crops, which may increase opportunities for crop intensification, but the problems associated with full tillage remain. Over the previous decade planter attachments to two-wheel tractors have been developed which permit seed and fertilizer placement with minimum to zero tillage in a single-pass. Recent tests have demonstrated that use of these implements can produce crop yields equal to or better than conventional tillage involving hand broadcasting of seed and fertilizer. Further, fuel and labour costs, seed and fertilizer inputs and turnaround time between crops can be reduced. In Africa, the introduction of animal-drawn rippers and direct seeders, originally developed for small-scale farmers in Brazil, is considered as a major breakthrough to small-scale farmer mechanization. It significantly reduces labour required for planting and benefits may be even greater if herbicides can be effectively used for weed control. Nevertheless, movement towards minimum tillage with two-wheel tractor mounted planters and animal-drawn direct seeding equipment is constrained by weed management issues. There are problems of availability and of safe and effective use of herbicides by resource-poor farmers and there is a need to develop more integrated weed management strategies that can be combined with small-scale planters. There is also a need to optimize the performance of small-scale planters to suit farmers’ needs in different agro-ecological environments. Tools and concepts are now available to implement Conservation Agriculture for small holders and thereby increase profitability of their cropping practices and at the same time improve soil quality and sustainability of their livelihoods. However, much more adaptive research and on-farm evaluation is needed across a diverse range of soils, cropping systems and agro-ecological regions to bring Conservation Agriculture to more small holders.
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effects of Conservation Agriculture on soil quality and productivity in contrasting agro ecological environments of zimbabwe
Soil Use and Management, 2012Co-Authors: Christian Thierfelder, Patrick C WallAbstract:Experimentation by farmers with Conservation Agriculture (CA) is increasing in southern Africa, but local longer term data on these new production systems are scarce. This study focuses on CA research at two contrasting on-farm sites and one on-station long-term trial in Zimbabwe. The on-farm trials were conducted at Chikato village on a sandy soil at Zimuto Communal Area with low rainfall and at Hereford farm near Bindura on a clay-rich soil in a high rainfall area. The on-station trial was at Henderson Research Station near Mazowe where more in-depth soil studies were possible. Results of CA systems from the on-station site show on average 38 and 65% greater water infiltration on riplineseeded (RS) and direct-seeded CA treatments compared with conventionally ploughed control treatments. Results from on-farm sites show a 123 and 168% greater aggregate stability at Hereford and 11 and 24% lower dispersion ratio at Chikato on the two CA compared with the conventionally ploughed control treatments. Soil carbon increased by 46% in the first 20 cm on the sandy soils at Chikato in RS and by 104% in direct-seeded CA treatments in four cropping seasons from 2004 to 2008, while it stayed at low levels on the conventionally tilled control treatment. Yields on CA plots were higher on the sandy soils in dry seasons, but lower in very wet seasons because of waterlogging. Yields on clay soils were less affected by the rainfall season. Crop productivity from CA systems increased at all sites over time owing to better management although significant differences between CA and conventional treatments on the three sites were apparent only after several cropping seasons. Conservation Agriculture offers practical solutions to small-scale farmers threatened by future soil degradation and fertility loss, but its successful use will depend on weed control and adequate application of fertilizers. The results indicate that there is no immediate increase in maize (Zea mays L.) yield when changing from a tilled to a CA system, but there is gradual improvement in some soil quality indicators over time.
Sixtine Cueff - One of the best experts on this subject based on the ideXlab platform.
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Adsorption and degradation of the herbicide nicosulfuron in a stagnic Luvisol and Vermic Umbrisol cultivated under conventional or Conservation Agriculture
Environmental Science and Pollution Research, 2020Co-Authors: Sixtine Cueff, Lionel Alletto, Valérie Dumény, Pierre Benoit, Valérie PotAbstract:The main goals of Conservation Agriculture are to enhance soil fertility and reduce soil degradation, especially through erosion. However, Conservation Agriculture practices can increase the risk of contamination by pesticides, mainly through vertical transfer via water flow. Better understanding of their sorption and degradation processes is thus needed in Conservation Agriculture as they control the amount of pesticide available for vertical transfer. The purpose of our study was to investigate the sorption and degradation processes of nicosulfuron in soil profiles (up to 90 cm deep) of a Vermic Umbrisol and a Stagnic Luvisol managed either in conventional or in Conservation Agriculture. Two laboratory sorption and incubation experiments were performed. Low sorption was observed regardless of the soil type, agricultural management or depth, with a maximum value of 1.3 ± 2.0 L kg^−1. By the end of the experiment (91 days), nicosulfuron mineralisation in the Vermic Umbrisol was similar for the two types of agricultural management and rather depended on soil depth (29.0 ± 2.3% in the 0–60-cm layers against 7.5 ± 1.4% in the 60–90 cm). In the Stagnic Luvisol, nicosulfuron mineralisation reached similar value in every layer of the Conservation Agriculture plot (26.5% ± 0.7%). On the conventional tillage plot, mineralisation decreased in the deepest layer (25–60 cm) reaching only 18.4 ± 6.9% of the applied nicosulfuron. Regardless of the soil type or agricultural management, non-extractable residue formation was identified as the main dissipation process of nicosulfuron (45.1 ± 8.5% and 50.2 ± 7.0% under conventional and Conservation Agriculture respectively after 91 days). In our study, nicosulfuron behaved similarly in the Vermic Umbrisol regardless of the agricultural management, whereas the risk of transfer to groundwater seemed lower in the Stagnic Luvisol under Conservation Agriculture.
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water and pesticide transfers in undisturbed soil columns sampled from a stagnic luvisol and a vermic umbrisol both cultivated under conventional and Conservation Agriculture
Geoderma, 2020Co-Authors: Marjolaine Bourdatdeschamps, Sixtine Cueff, Lionel Alletto, Pierre Benoit, Valérie PotAbstract:Abstract The main goals of Conservation Agriculture are to enhance soil fertility and to reduce soil degradation especially through erosion. However, Conservation Agriculture practices can exhibit a higher risk of contamination through vertical flows. The objectives of this study were to (i) characterise water and pesticide transfers in two different soils both managed under conventional and Conservation Agriculture and (ii) assess the effects of pesticide properties, soil type and agricultural system on pesticide fate. We studied the behaviour of two herbicides (nicosulfuron and mesotrione) and a molluscicide (metaldehyde) in percolation experiments in undisturbed soil columns. A series of two rain events (one with a high, the other with a low intensity) separated by a two-day flow interruption was applied three days after the pesticides and bromide application. Batch sorption coefficients, Kd, were also measured. While the Pesticides Properties Data Base (2020) indicated a decrease of sorption in the order mesotrione > metaldehyde > nicosulfuron, the measured Kd, decreased in the order mesotrione (2.3 ± 1.4 L.kg−1) > nicosulfuron (0.7 ± 0.4 L.kg−1) > metaldehyde (0.1 ± 0.1 L.kg−1). We highlighted distinct behaviour of pesticide leaching depending mainly on soil type, agricultural practices and pesticide properties. For low degree of preferential flow, pesticide leaching can be related to the sorption properties of pesticides. Nicosulfuron and mesotrione delays are more pronounced under Conservation management while metaldehyde always arrived with no delay. During the high intensity rain event, on one soil type, high degree of preferential flow masked sorption effect on leaching since every pesticide arrived at the same time as the tracer and amounted to up to 21% of pesticide recovery compared to 4% on the other soil type. Conservation Agriculture was found to improve the vertical transfers of water and pesticides while, on one of the studied soil type, the presence of a low conductive plough pan significantly limits water drainage.