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

Study of C, N, P and K Release from Residues of Newly Proposed Cover Crops in a Spanish Olive Grove

Cover crops (CC)s are increasingly employed by farmers in olive groves. Spontaneous soil cover is the most commonly used CC. Its continuous utilization changes ruderal flora. It is necessary to study new CCs. Living CCs provide C and nutrients to soil during decomposition. Information on this issue in olive groves is scarce. A 4-year field study involving grab sampling of Brachypodium distachyon, Sinapis alba and spontaneous CC residues was conducted to study C and nutrient release from cover crop residues. Throughout the decomposition cycles, C, N and P release accounted for 40 to 58% of the C, N and P amounts in the residues after mowing. Most K was released (80–90%). Expressed in kg per hectare, the release of C and N in Brachypodium (C: 4602, N: 181, P: 29, K: 231) and Sinapis (C: 4806, N: 152, P: 18, K: 195) was greater than that in spontaneous CC (C: 3115, N: 138, P: 21, K: 256). The opposite results were observed for K. The Rickman model, employed to estimate the amount of C, N and P in residues, yielded a good match between the simulated and measured values. In comparison to spontaneous CC, the newly proposed CCs have a higher potential to provide soil with C and N

Soil Management, Irrigation, and Fertilisation Strategies for N2O Emissions Mitigation in Mediterranean Agricultural Systems

Feeding a growing population, which will reach 10 billion in 2050, is a major challenge. Another major challenge is to increase crops’ productivity in a sustainable way, as the increase in agricultural inputs may lead to greenhouse gas emissions, including N2O fertiliser. Several factors can influence N2O emissions such as irrigation, the soil management system, or the type of fertiliser used. The aim of this research is to study the impact of each above-mentioned factor on N2O emissions during three growing seasons in a maize field, considering three nitrogen fertilisers: urea (U), ammonium nitrate (AN), and a fertiliser with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP); two irrigation strategies: on demand (100%) and deficit irrigation (75% of demand); and a comparison of two soil management systems: conventional tillage (T) systems and no-tillage (NT) system. The interactions among the three factors and their effects on emissions were analysed through a principal component analysis. Higher emissions were recorded in plots that received the highest irrigation dose. The most favourable management to reduce N2O emissions derived from agricultural activity for maize crops under a Mediterranean climate was the NT soil management, using a fertiliser with nitrification inhibitor and an irrigation dose of 75% of conventional irrigation

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