Spatial and temporal variability of CO2 emisions in soils under conventional tillage and no-till farming

Agricultural soils can act as a carbon sink depending on the soil management practices employed. As a result of this functional duality, soil management systems are present in international documents relating to climate change mitigation. Agricultural practices are responsible for 14% of total greenhouse gas emissions (GHG’s) (MMA, 2009)(1). Conservation agriculture (CA) is one of the most effective agricultural systems for reducing CO2 emissions, as it increases the sequestration of atmospheric carbon in the soil. In order to assess the performance of CA in terms of CO2 emissions, a field trial was conducted comparing soil derived CO2 fluxes under No-till (NT) farming and under conventional tillage. Three pilot farms were selected in the cereal-growing area of southern Spain, located in Las Cabezas de San Juan (Seville), Carmona (Seville) and Cordoba. Each pilot farm comprises six experimental plots with an approximate area of five hectares; three of the six plots implement CA practices, while the other three use conventional tillage techniques. The subdivision of each tillage system into 3 plots allowed the simultaneous cropping of the three crops of the wheat-sunflower-legume rotation each year. Results showed that carbon dioxide emissions were 31 to 91% higher in tilled soils than in untilled soils, and that there was a great seasonal variability of CO2 emissions, as weather conditions also differed considerably for the different sampling periods. In all cases, the CO2 fluxes emitted into the atmosphere were always higher when soil was subject to conventional tillage

Effect of agronomic and environmental factors on CO2 emissions on a dryland rotation

Agriculture is a substantial source of greenhouse gas emissions (GHG) in many countries. Conservation agriculture includes soil management systems that help to reduce CO2 emission levels. However, there are many factors involved in the production of these emissions such as soil management type and time at which the agriculture operations are performed, crop phenological state, the weather, and handling of the residue amongst others. In the long term, the relationships that exist between these factors seem to determine the balance of these emissions. In this study, we analyzed the influence of the soil management system as well as the climatology of the different seasons studied and the phenological state of the different crops implanted. For this purpose a field trial was conducted in Las Cabezas de San Juán (Seville). This pilot farm consisted of six experimental plots with an approximate area of 5 ha; conservation agriculture practices were employed in three of the six plots while traditional tillage management was used in the other three. Within these plots the three crops of the wheat-sunflower-legume rotation were tested simultaneously. The study was conducted over four agricultural seasons - 2009/10, 2010/11, 2011/12 and 2012/13. Each of these cropping seasons were characterised by very different rainfall amounts, registering a total of 814.4, 721.6, 268.2 and 676.4 l/m2, respectively. When we studied the evolution of emissions over four seasons, an increase could be observed for both management systems during the time in which the crops were established due to the roots respiration processes. These increases were heavily influenced by the rainfall recorded during the time in which the crop was in place. In the case of wheat, higher emissions were produced during the cultivation time of the first and fourth season during which 84% and 60% of the total rainfall of each season was recorded. These emissions were 9 and 5 kg CO2/ha for conventional tillage and no tillage, respectively for the 2009/10 season and 11.7 and 6.8 kg CO2/ha, respectively in the 2012/13 season. Conversely during the 2011/12 season, a season in which lower precipitation was registered, the higher emissions were comparatively minor with respect to the previous values, specifically 3.7 and 1.9 kg CO2/ha for non-tillage and conventional tillage

The Effect of Conservation Agriculture and Environmental Factors on CO2 Emissions in a Rainfed Crop Rotation

There are many factors involved in the release of CO2 emissions from the soil, such as the type of soil management, the soil organic matter, the soil temperature and moisture conditions, crop phenological stage, weather conditions, residue management, among others. This study aimed to analyse the influence of these factors and their interactions to determine the emissions by evaluating the environmental cost expressed as the kg of CO2 emitted per kg of production in each of the crops and seasons studied. For this purpose, a field trial was conducted on a farm in Seville (Spain). The study compared Conservation Agriculture, including its three principles (no-tillage, permanent soil cover, and crop rotations), with conventional tillage. Carbon dioxide emissions measured across the four seasons of the experiment showed an increase strongly influenced by rainfall during the vegetative period, in both soil management systems. The results of this study confirm that extreme events of precipitation away from the normal means, result in episodes of high CO2 emissions into the atmosphere. This is very important because one of the consequences for future scenarios of climate change is precisely the increase of extreme episodes of precipitation and periods extremely dry, depending on the area considered. The total of emission values of the different plots of the study show how the soils under the conventional system (tillage) have been emitting 67% more than soils under the conventional agriculture system during the 2010/11 campaign and 25% for the last campaign where the most appreciable differences are observed

Making Climate Change Mitigation and Adaptability Real in Africa with Conservation Agriculture

In this report, the authors have gathered essential information on how the agricultural sector can respond to climate change through Conservation Agriculture (CA). This document aims to serve as a basis for decision-making based on science and agricultural experimentation in Africa

Potencial de secuestro de carbono de residuos de diferentes tipos de cubiertas en olivar bajo clima mediterráneo

The maintenance of plant cover between olive grove lanes until the beginning of spring is a soil management alternative that is gradually being adopted by olive growers. As well as protecting the soil from erosion, plant covers have other advantages such as improving the physicochemical properties of the soil, favouring its biodiversity and contributing towards the capturing of atmospheric carbon and its fixation in the soil. A trial was conducted over three growing seasons in an olive plantation situated in southern Spain. It was designed to evaluate the C fixation potential of the residues of the cover species Brachypodium distachyon, Eruca vesicaria, Sinapis alba and of spontaneous weeds; and also to study the decomposition dynamics of plant residues after mowing cover. After 156 and 171 days of decomposition, the species that released the largest amount of C was Brachypodium with values of 2,157 and 1,666 kg ha-1 respectively, while the lowest values of 461 and 509 kg ha-1 were obtained by spontaneous weeds. During the third season (163 days of decomposition) and due to the weather conditions restricting the emergence and growth of cover, spontaneous weeds released the most C with a value of 1,494 kg ha-1. With respect to the fixation of C, Sinapis records the best results with an increase in soil organic C (SOC) concentration of 7,690 kg ha-1. Considering the three seasons and a depth of 20 cm, the behaviour sequence of the different species in favouring the fixation of soil organic C was Sinapis>Brachypodium>spontaneous weeds>Eruca.El mantenimiento de una cubierta vegetal entre líneas de olivo hasta el comienzo de la primavera es una alternativa de manejo de suelo que está siendo gradualmente adoptada por los olivareros. Así como la protección del suelo contra la erosión, las cubiertas vegetales tienen otras ventajas como la mejora de las propiedades físico-químicas del suelo, favorecer su biodiversidad y contribuir a la captura de carbono atmosférico y su fijación en el suelo. Se ha realizado un ensayo durante tres campañas en una plantación de olivos situada en el sur de España. Éste fue diseñado para evaluar el potencial de fijación de C en residuos de cubiertas de las especies Brachypodium distachyon, Eruca vesicaria, Sinapis alba y de hierba espontánea; y también para estudiar la dinámica de descomposición del residuo tras el desbroce de la cubierta. Después de 156 y 171 días de descomposición, la especie que más cantidad de C liberó fue el Brachypodium con un valor de 2157 y 1666 kg ha-1 respectivamente, mientras que los valores más bajos fueron 461 y 509 kg ha-1 y se obtuvieron por la hierba espontánea. Durante la 3ª campaña (163 días de descomposición), debido a las condiciones climáticas, se vio restringida la emergencia y el crecimiento de la cubierta. La hierba espontánea liberó la mayor cantidad de C con un valor de 1494 kg ha-1. Con respecto a la fijación de C, Sinapis registró los mejores resultados con un incremento de la concentración de C orgánico en suelo de 7690 kg ha-1. Considerando las 3 campañas y una profundidad de 20 cm, la secuencia de especies que favorecen la fijación de C orgánico fue Sinapis>Brachypodium>hierba espontánea>Eruca

Soil organic carbon fractions under conventional and no-till management in a long-term study in southern Spain

In dryland farming systems under a Mediterranean climate, soil quality and productivity can be enhanced by increasing the content of soil organic carbon (SOC) through alternative soil management systems. Some fractions of C are directly involved in increasing total SOC and therefore in enhancing any benefits in terms of soil properties. This study compares the viability of no-till farming (NT) with conventional (traditional) tillage (TT) for improving SOC levels. The influence of management practices was investigated for different fractions of C (particulate OC, active OC, humic acids, fulvic acids) and CO2 emissions in clayey soils in the south of Spain. The experiment was conducted over three farming seasons (2006–07, 2007–08 and 2008–09) covering a crop rotation of peas (Pisum sativum L.), wheat (Triticum aestivum L.) and sunflowers (Helianthus annuus L.). The NT system improved the levels of the different fractions of C in the surface soil and reduced the amount of CO2 released into the atmosphere compared with the TT system. Generally, the relationship between CO2 and SOC content was greater in soils under NT for the farming seasons sampled

. Climate change adaptability and mitigation with Conservation Agriculture

The status quo of agriculture based on soil tillage is unacceptable from a climate point of view. To reverse agriculture’s field performance from that of a net GHG emitter to a GHG mitigator requires a new paradigm. CA is a holistic agricultural system that is able to mitigate and adapt to climate change. The three interlinked principles of CA enable the system to deliver many benefits in terms of carbon sequestration and climate adaptation, especially with regards to soil, water, nutrient, and energy management

LIFE+ AGRICARBON: Sustainable agriculture in carbon arithmetics

This project is an EU funded project in partnership with AEAC.SV, ECAF, UCO and IFAPA (www.agricarbon.eu). The objective of this project is to promote sustainable agriculture (conservation agriculture, CA; precision agriculture, PA), to mitigate climate change due to reducing GHG emissions, increase resilience and adapt to the new climate conditions foreseen within the global warming. The study is implemented in 3 farms of 30 hectares each, distributed along Andalusia, in South Spain. Not only field work performed has been useful to obtain supportive data for publications, but also technology transfer activities, such as field days, courses, or even the final Green Carbon Conference, have been a relevant strand within the project. The joint use of CA&PA, captured up to 35% more CO2 compared to tillage. Moreover, the absence of tillage made CA and PA reduce soil’s emissions between 56% -218%. Regarding energy use, the implementation of CA&PA in the testing farms, where the current crop rotation is wheat-sunflower-legume, resulted in cuts by 13.8% in wheat, 21.6% in sunflower and 24.4% in the legume when compared to tillage. These savings caused lower CO2 emissions, corresponding to 199.1 kgha-1 for wheat, 63.6 kgha-1 for sunflower and 107.1 kgha-1 for legume. In the mentioned rotation, yields show no major differences between sustainable agriculture and tillage. Dissemination has been successful as well: over 1,100 farmers trained in 10 field days and over 40 publications released