Person: Govaerts, B.
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Govaerts
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Govaerts, B.
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0000-0002-6109-7286 5 results
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- Clasificación y evaluación edafológica de tres sitios experimentales en el altiplano central de México(Presses agronomiques de Gembloux, 2008) Govaerts, B.; Barrera-Franco, M.G.; Limon-Ortega, A,; Muñoz-Jiménez, P.; Sayre, K.D.; Deckers, J.
Publication - How to evaluate cropping management practices: the cook book(CIMMYT, 2008) Govaerts, B.Soil compaction is a form of physical soil degradation where an increase in soil bulk density, and a decline in percentage and stability of aggregates as well as porosity and pore continuity, is verified (Kooistra and Tovey, 1994). Possible problems associated with soil compaction are: decreased aeration (increased proportion of soil pores filled with water) (Stepniewski el aL, 1994), decreased water infiltration, increased surface runoff and erosion, as well as poor crop establishment (seed germination and early root growth) and root development (Lal and Shukla, 2004; Logsdon and Karlen, 2004). Compaction can occur when heavy farm machinery circulates over the field, especially under wet conditions (Hom el al., 2006). Tillage has also been found to cause soil compaction through plough pan formation. Because of its importance, soil bulk density (Blake and Hartge, 1986) is very frequently included in analysis of soil quality (e.g. Govaerts el al., 2005). There have even been attempts to establish soil bulk density (SBD) threshold values, to indicate when compaction is occurring (e.g. 1.55 Mg m3 in silt and silt loam soils). This is based on the rationale that if bulk density is higher than a critical level, considering variations caused by soil texture, compaction would be present (USDA-NRCS, 1996). However, increased SBD values are not necessarily related to compaction since this parameter is dependent on a wide array of factors such as type of parent material, the crop being grown, soil organic matter content and type of present and past management (Logsdon and Karlen, 2004). Management, for example, has an overarching effect on soil physical properties, including soil packing density. Under conservation agriculture (CA), soil is not tilled and a protective residue cover is left over the soil's surface. Recent studies (Logsdon and Karlen, 2004; Osunbitan el al., 2005; Mati and Kotorová, 2007) found that soil bulk density values were higher under CA when compared to conventional systems. Soils treated under CA are denser but characterized by stable macroporosity (formed by soil macrofauna and decayed plant roots) with significant effects on soil hydraulic conductivity. Greater total porosity in tilled soils is not related to greater water infiltration given their lack of connectivity, lower proportion of macropores and temporary character (Osunbitan et al., 2005). This illustrates how soil bulk density is not necessarily related to compaction and threshold values designed for conventional tillage (CI) are not necessarily applicable to CA. In conclusion, measures on aggregation, water infiltration and crop performance have to complement SBD values. But also temporal variations in soil bulk density values due to changing conditions, particularly at the topsoil where agricultural management and environmental conditions have their greatest impact, makes repeated measures throughout the season highly recommended. For example, Logsdon et al. (1999) and Logsdon and Cambardella (2000) showed significant temporal changes in near-surface incremental bulk density for tillage systems in a subhumid climate.
Publication - Conservation agriculture and soil carbon sequestration: between myth and farmer reality(CIMMYT, 2009) Verhulst, N.; Francois, I.; Govaerts, B.Human efforts to produce ever-greater amounts of food leave their mark on the environment. Persistent use of conventional farming practices based on extensive tillage, especially when combined with removal or in situ burning of crop residue, have magnified soil erosion losses and the soil resource base has been steadily degraded. Another direct consequence of farmers’ persistent use of traditional production practices is rapidly increasing production costs; the costs of inputs such as improved varieties and fertilizers continue to increase and farmers make inefficient use of them. Despite the availability of improved varieties with increased yield potential, the potential increase in production is not achieved because of poor crop management systems. Nowadays, people have come to understand that agriculture should not only be high yielding, but also sustainable. Conservation agriculture (CA) has been proposed as a widely adapted set of management principles that can assure more sustainable agricultural production. Conservation agriculture is a broader concept than conservation tillage, a system where at least 30% of the soil surface is covered with crop residues after seeding of the next crop. In CA, the emphasis not only lies on tillage components but on the combination of the following three principles: 1. Reduction in tillage: The objective is to achieve zero tillage (i.e., no tillage at all); however, the system may involve controlled tillage seeding systems that do not disturb more than 20–25% of the soil surface. 2. Retention of adequate levels of crop residues and soil surface cover: The objective is the retention of sufficient residue on the soil to: protect the soil from water and wind erosion; reduce water run-off and evaporation; improve water productivity; and enhance soil physical, chemical, and biological properties associated with long-term sustainable productivity. 3. Use of crop rotations: The objective is to employ diversified crop rotations to: help moderate/mitigate possible weed, disease and pest problems; utilize the beneficial effects of some crops on soil conditions and on the productivity of the next crop; and provide farmers with economically viable options that minimize risk. These CA principles are applicable to a wide range of crop production systems from low-yielding, dry, rain-fed conditions to high-yielding, irrigated conditions. However, applying the principles of CA will be very different in different situations. Specific and compatible management components such as pest and weed control tactics, nutrient management strategies, rotation crops, etc. will need to be identified through adaptive research with active farmer involvement. Conservation agriculture has been promoted as an agricultural practice that increases agricultural sustainability and is associated with the potential to lessen greenhouse gas emissions. There are, however, contrasting reports on the potential of CA practices for C sequestration (i.e., the process of removing carbon dioxide, CO2, from the atmosphere and depositing it in the soil).
Publication - Conservation agriculture toward sustainable and profitable farming(CIMMYT, 2005) Govaerts, B.; Sayre, K.D.Global agriculture faces major challenges. In large areas, soil erosion and the loss of fertility progressively reduce crop yields and can lead to land being abandoned and turning to desert. Households, industries, and growing urban areas compete with agriculture for increasingly scarce water supplies. Rising fuel and fertilizer prices hike up production costs. Conservation agriculture (CA) provides sustainable ways to address these and other challenges. CA crop management systems are based on three principles: (1) minimum soil movement (for example, no soil inversion by tillage), (2) a soil surface cover of crop residues and/or living plants, and (3) use of crop rotations to avoid build-ups of pests and diseases. The principles of CA appear to have wide adaptation, and CA systems are used for numerous crops in diverse soil types and environments. Nevertheless, the techniques to apply the principles depend heavily on local conditions: climate, soil characteristics, and farmer’s circumstances such as wealth, land size, the availability of labor or a tractor, to name several factors. Expected benefits from CA include: Reduced frequency/intensity of moisture stress: CA increases infiltration; cuts run-off and evaporation from the soil surface. Savings in irrigation water and energy for pumping. Reduced erosion. Higher, more stable crop yields. Reduced labor/tractor use for land preparation, saving fuel, cutting costs. Increased soil organic matter content, resulting in better soil structure, higher cation exchange capacity and nutrient availability, and greater water-holding capacity. Improved biological soil fertility and pest control.
Publication - Compendium of deliverables of the conservation agriculture course 2008(CIMMYT, 2008) Castellanos-Navarrete, A.; Govaerts, B.This book is the result of the hard work of 8 CIMMYT trainees who participated in the visiting scientist 2008 Conservation Agriculture Course: "Laying the groundwork for sustainable and productive cropping systems". During 5 weeks, the scientists received and intense training program that combined mentoring and problem solving approaches. Each participant had to define a clear research objective for the period of stay. The scientists participated actively in the ongoing cropping systems management activities of the CIMMYT Mexico-based Cropping Systems Management team at both the experimental stations, located near to Mexico City at El Batan and Toluca, and in nearby farmers' fields. Emphasis was given to conservation agriculture and resource conserving technologies: conventional and reduced till permanent bed planting for both irrigated and rain-fed conditions, using alternative crop residue management strategies. Wheat, maize, barley and dry beans were the crops under study. Strong focus was placed on the importance of interdisciplinary approaches. Breeders helped to provide a better understanding of the nature of crop management by genotype interactions. Similarly, plant pathologists were involved in order to better understand disease interactions with the new tillage and crop residue management practices. An economist shed light on the complex system interactions and market chain development related to conservation agriculture, just to mention some of the numerous interactions of several CIMMYT scientists. Upon completion of the program, the participants presented their plans to initiate activities in their home countries to do research on and to extend to farmers the new technologies encountered in the program. They developed the necessary skills for trial management and plant and soil monitoring as influenced by management practices. The main objectives of the program were: To enhance understanding of the use and application of the conservation agriculture planting technologies and relevant agriculture implements (with emphasis on planters/planter modifications) for irrigated and rain-fed wheat and maize production systems. To encourage and develop participants' ability to synthesize and use the information and knowledge related to conservation agriculture technologies (seeding methodologies in the different planting systems, irrigation water management, crop nutrient management, weed control strategies, and the importance of crop residue management). To increase participants' knowledge of (long-term) trial planning and management. To develop ski lls for monitoring soil and plant parameters as they relate to cropping management systems, as well as their influence on physical, chemical and biological soil quality, their effect on climate change adaptation and mitigation, and their impact on water and nutrient lise efficiency. To foster positive attitudinal changes, such as improved confidence, increased motivation, and heightened appreciation of the benefits of team work and interdisciplinary research. To create a minimum level of proficiency in order to generate scientifically-sound hypotheses, determine data collection strategies, and interpret data and summarize them into scientifically-sound conclusions and recommendations. In order to achieve the last objective each participant has chosen a clear deliverable to work on during the 5 week course. Some scientists analyzed and summarized data they brought from their home country, others reviewed a specific theme of interest related to conservation agriculture. Some of the papers, in collaboration with and with follow up from the CIMMYT scientists, will be presented to national and international scientific journals.
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