Suchergebnisse

The aim of this study was to assess the effect on soil quality of a governmental program whose objective is restoring the fertility of degraded acidic volcanic ash soils. The program consisted of (i) liming, (ii) correction of the P status, and (iii) sowing forage plants. We measured soil fertility of fields after 1 to 4 years since start of the program, and compared these fields against fields under old permanent natural grasslands, used to estimate the baseline soil test values for the properties considered in this study. The survey was conducted in five localities (Lonquimay, Curacautín, Vilcún, Cunco and Villarrica) in the temperate southern part of Chile (Araucania region). The impacts of the program on acidity (pH and exchangeable aluminum) were different among localities. At Cunco, exchangeable aluminum was not affected, while pH increased initially but decreased to its initial value within four years. Instead, at Lonquimay exchangeable aluminum decreased significantly, and pH remained slightly higher than the control values through the first four years. At Lonquimay P-Olsen was initially increased, showing a positive short-term effect of the program, but gradually decreased after the first year, until it returned to the initial level. At Vilcún, an increase with time was observed during the whole period. In Curacautín, Villarrica and Cunco, the P-Olsen content increased during the first years of the experiment but began to decline at the end of the period. This study provided important results for the improvement of the program. ; El objetivo de este estudio, realizado en el sur de Chile, fue evaluar los efectos sobre el suelo de un programa gubernamental cuyo objetivo es la restauración y mantenimiento de la fertilidad de suelos degradados. Éste consiste en encalado, corrección de fósforo, y establecimiento de praderas. En este estudio se midió la fertilidad del suelo de praderas con 1 a 4 años desde el inicio del programa y sin fertilización de mantención, y se comparó con praderas naturalizadas de más de 4 años, estas se consideraron representantes de suelos en estado natural de baja fertilidad, y fueron la línea base en los parámetros considerados en este estudio. La investigación se realizó en Lonquimay, Curacautín, Vilcún, Cunco y Villarrica. El impacto del programa sobre la acidez (pH y aluminio intercambiable) y disponibilidad de P fue diferente entre localidades. En Cunco, el aluminio intercambiable no se vio afectado, el pH aumentó inicialmente, reduciéndose a su valor inicial en el plazo de cuatro años, el contenido de P-Olsen aumentó al inicio y comenzó a decaer a finales del período, al igual que en Curacautín y Villarrica. En Lonquimay, el aluminio intercambiable disminuyó significativamente, el pH se mantuvo ligeramente superior al control durante los primeros cuatro años y el P-Olsen se incrementó en un principio pero disminuyó después del primer año al nivel inicial. En Vilcún, se observó un aumento durante todo el periodo. Este estudio proporcionó resultados importantes para mejorar el programa apoyando la necesidad de repetir las aplicaciones de fósforo y cal.

Recent literature on no-till is reviewed with particular emphasis on research on commercial uptake and environmental concerns in northern, western and south-western Europe. Increased interest in no-till, and minimum or reduced tillage, results from changes in the economic circumstances of crop production, the opportunity to increase the area of more profitable autumn-sown crops and increased concern about environmental damage associated with soil inversion by ploughing. Highly contrasting soil and climate types within and between these regions exert a strong influence on the success of no-till. While no-till may often result in crop yields which equal or exceed those obtained after ploughing, modest reductions in yield may be tolerated if production costs are lower than with ploughing. The relative costs of fuel and herbicides have changed appreciably in recent years making no-till more attractive commercially. While effective weed control is an essential aspect of no-till, current herbicide technology may not yet fully achieve this. In northern regions no-till usually allows earlier drilling of winter-sown crops but will give lower soil temperature and higher moisture content in spring, causing delayed drilling of spring-sown crops. No-till soils have greater bulk density and bearing capacity than ploughed soils with a pronounced vertical orientation of macroporosity allowing penetration of roots and water, especially in view of the increased population of deep-burrowing earthworms. Particular care must be taken with no-till to minimise soil damage at harvest and to ensure the even distribution of crop residues prior to drilling. Reduced erosion and runoff after adoption of no-till are widely observed and are of particular importance in southwestern Europe. No-till reduces losses of phosphorus in runoff and, in some cases, reduces the loss of nitrate through leaching. Emissions of greenhouse gases CO2 and N2O from no-till soils are highly variable and depend on complex interactions of soil properties. Emission of CO2 from fuel during machinery usage is always appreciably reduced with no-till. Increased soil organic carbon in surface layers of no-till soils is widely found but may not be associated with increased carbon sequestration throughout the profile. The evaluation of the relative carbon balance for no-till and ploughing depends upon complex inter-relationships between soil and climate factors which are as yet poorly understood. Adoption of no-till could be encouraged by government financial assistance in recognition of environmental benefits, although future restrictions on the use of herbicides may be a deterrent. Opportunities for further research on no-till are outlined. 2 2

Recent literature on no-till is reviewed with particular emphasis on research on commercial uptake and environmental concerns in northern, western and south-western Europe. Increased interest in no-till, and minimum or reduced tillage, results from changes in the economic circumstances of crop production, the opportunity to increase the area of more profitable autumn-sown crops and increased concern about environmental damage associated with soil inversion by ploughing. Highly contrasting soil and climate types within and between these regions exert a strong influence on the success of no-till. While no-till may often result in crop yields which equal or exceed those obtained after ploughing, modest reductions in yield may be tolerated if production costs are lower than with ploughing. The relative costs of fuel and herbicides have changed appreciably in recent years making no-till more attractive commercially. While effective weed control is an essential aspect of no-till, current herbicide technology may not yet fully achieve this. In northern regions no-till usually allows earlier drilling of winter-sown crops but will give lower soil temperature and higher moisture content in spring, causing delayed drilling of spring-sown crops. Notill soils have greater bulk density and bearing capacity than ploughed soils with a pronounced vertical orientation of macroporosity allowing penetration of roots and water, especially in view of the increased population of deep-burrowing earthworms. Particular care must be taken with no-till to minimise soil damage at harvest and to ensure the even distribution of crop residues prior to drilling. Reduced erosion and runoff after adoption of no-till are widely observed and are of particular importance in southwestern Europe. No-till reduces losses of phosphorus in runoff and, in some cases, reduces the loss of nitrate through leaching. Emissions of greenhouse gases CO2 and N2O from no-till soils are highly variable and depend on complex interactions of soil properties. Emission of CO2 from fuel during machinery usage is always appreciably reduced with no-till. Increased soil organic carbon in surface layers of no-till soils is widely found but may not be associated with increased carbon sequestration throughout the profile. The evaluation of the relative carbon balance for no-till and ploughing depends upon complex inter-relationships between soil and climate factors which are as yet poorly understood. Adoption of no-till could be encouraged by government financial assistance in recognition of environmental benefits, although future restrictions on the use of herbicides may be a deterrent. Opportunities for further research on no-till are outlined. 2011 Elsevier B.V. All rights reserved.