Cover crop effects on soils and subsequent crops in the pampas: A meta-analysis
Introduction
It has long been recognized that the replacement of a bare fallow period by a cover crop is a suitable tool for decreasing runoff and soil erosion in many agroecosystems (Reeves, 1994, Langdale et al., 1991). As cover crops reduce soil nitrate-N accumulation they can also substantially reduce nitrogen leaching (Constantin et al., 2015, Valkama et al., 2015). One unique application is the use of catch crops; a non-harvested cover crop with the primary function being control of leaching (Thorup-Kristensen et al., 2003). Another well known effect of cover crops is their function as green manure for the subsequent commercial crop in some cases through the introduction of nitrogen to the agroecosystem by atmospheric fixation (Fageria et al., 2005, Li et al., 2015) or by increasing the mineralization from cover crop residues during the grain crop growing cycle (Thorup-Kristensen et al., 2003). This results in a nitrogen credit for the commercial crop (Fageria et al., 2005, Ketterings et al., 2015) and a positive feedback on yield (Fageria et al., 2005, Miguez and Bollero, 2005, Sainju and Singh, 1997). Weed control is another possible benefit of cover crop use (Cherr et al., 2006, Harrwing and Ulrich Ammon, 2002). These positive environmental and agronomic effects of cover crops can offset the cost of its seeding (Reeves, 1994, Snapp et al., 2005).
The introduction of cover crops in rotations can bring along some other desired or undesired effects in agroecosystems. The soil physical status may be improved by cover crops but conflicting results have been reported in different experiments. Soil organic carbon commonly increases some years after the introduction of cover crops (Poeplau and Don, 2015) and this may be related to the improved structural condition of some soils under cover crop treatment (Fageria et al., 2005, Harrwing and Ulrich Ammon, 2002). In some experiments, however, no structural improvement was reported (Mendes et al., 1999). Bulk density was minimally impacted by cover crops (Hubbard et al., 2013, Zhu et al., 2012) or it did not differ significantly in comparison to soils with fallow periods (Chen et al., 2014, Hubbard et al., 2013). Soil penetration resistance may decrease (Folorunso et al., 1992) or not be affected (Chen et al., 2014) by cover crop cultivation. Similarly, controversial data were published on the impact of cover crops on infiltration, with increases in some situations (Lal et al., 1978) or no effects in others (Steele et al., 2012). In low rainfall areas (<800 mm annual rainfall) cover crops can lead to soil water depletion reducing commercial crop yield (Blanco-Canqui et al., 2015, Reeves, 1994). Consequently, cover crops are multifunctional crops with multiple impacts on ecosystem services (Blanco-Canqui et al., 2015) and their adoption must be decided based on an overall evaluation of their advantages and disadvantages.
Modern meta-analytic techniques were developed for averaging means across different studies with heterogeneous variation and to permit a sound statistical comparison (Hedges and Olkin, 1985). These techniques are currently replacing review papers from which average effect size cannot be summarized. Some meta-analysis on the impact of cover crops on soil carbon (Poeplau and Don, 2015), nitrates (Tonitto et al., 2006) and grain crop yield, mainly corn (Zea mays (L.)) (Miguez and Bollero, 2005) were performed. In these studies results generated mainly in experiments carried out in the Northern Hemisphere and under temperate climate conditions were used. Other effects of cover crops on the agroecosystems have not been assessed yet by meta-analysis.
The Argentine Pampa is a vast plain of ca. 60 Mha which has been considered one of the main grain crop production areas of the world because of its extension and yield potential (Satorre and Slafer, 1999). This region is distinct from other important agricultural areas because of its warm-temperate climate and extensive use of soybean in crop rotations. Winter cover crops are being adopted by farmers gradually and many experiments were performed by official institutions to evaluate their suitability as a common production practice. A first attempt to analyze part of the available information reported a great increase in soil organic carbon when a fallow was replaced by cover crops (>5 t C ha−1 equivalent to ca. 15% increase of carbon content in the 0–20 cm layer), with no clear effect on soil water content and no impact on summer crop yields (Rimski-Korsakov et al., 2015). Our aim was to perform a meta-analysis of available information on winter cover crop effects on physical and chemical soil properties, soil available water content and soybean and corn yield in order to generate possible management recommendations based on an overall evaluation of the impact of this type of crops on local agroecosystems.
Section snippets
Study area
The Argentine Pampa is located between 28°S and 40°S and 57°W and 68°W. Around 90% of the grain produced in the country originates in this region. The natural predominant vegetation is grassland and natural forests account for about 7% of the surface (INDEC, 2002). Climate is warm-temperate and humid with mean temperature ranging from 14 °C in the south to 23 °C in the north and mean annual rainfall ranging from 500 mm in the west to 1200 mm in the east. The relief is flat or slightly rolling with
Results
The weighting function used for the meta-analysis did not affected results, that were similar using an unweighted meta-analysis or a meta-analysis weighted by replication or by the inverse of the pooled variance.
Soil physical properties generally improved when replacing a fallow period by the inclusion of cover crops. Changes in bulk density were very small with decreases or increases not greater than 0.1 g ml−1. In the 0–5/0–6 cm soil layer, bulk density decreased in 63% of cases and did not
Discussion
The results from our meta-analysis were generally not affected by the weighting method used. When sample size is similar, no great variability between studies is to be expected (Gurevitch and Hedges, 1999) and consequently, different weighting functions can lead to the same conclusion. This was the case in our study. Previous comparisons of different weighting functions in soil science studies arrived to similar results (Hungate et al., 2009, van Groenigen et al., 2011).
Soil bulk density
Acknowledgements
This research was granted by the University of Buenos Aires (UBACYT 20020130100484) and CONICET (PIP 11220130100084CO).
References (145)
- et al.
Climate, organic matter and clay content relationships in the Pampa and Chaco soils, Argentina
Geoderma
(1998) - et al.
Carbon and nitrogen sequestration in soils under different management in the semi-arid Pampa (Argentina)
Soil Till. Res.
(2014) - et al.
A regional audit of nitrogen fluxes in pampean agroecosystems
Agric. Ecosys. Environ.
(2014) - et al.
Land use effects on soil carbon in the Argentine Pampas
Geoderma
(2013) - et al.
Effects of compaction and cover crops on soil least limiting water range and air permeability
Soil till. Res.
(2014) - et al.
Large-scale assessment of optimal emergence and destruction dates for cover crops to reduce leaching in temperate conditions using STICS soil-crop model
Eur. J. Agron.
(2015) - et al.
Soil surface strength and infiltration rate as affected by winter cover crops
Soil Technol.
(1992) - et al.
A review of the usefulness of relative bulk density values in studies of soil structure and compaction
Soil Till. Res.
(2000) - et al.
Soil compaction in cropping systems. A review of the nature: causes and possible solutions
Soil Till. Res
(2005) - et al.
Effects of winter cover crops and successive spring tillage on soil aggregation
Soil Till. Res.
(1997)
Effects of cover crop systems on soil physical properties and carbon/nitrogen relationships in the plain of southeastern USA
Soil till. Res.
Controls over soil microbial biomass responses to carbon amendments in agricultural systems: a meta-analysis
Agric. Ecosys. Environ.
How much nitrógeno do legumes fix?
Adv Agron
No-till framing alter various grasses and leguminous cover crops in tropical Alfisol. I: Crop performance
Field Crops Res.
Harvest impacts on soil carbon storage in temperate forest
For. Ecol. Manag.
Carbon sequestration in agricultural soils via cultivation of cover crops-A meta-analysis
Agric. Ecosys. Environ.
Resampling tests for meta-analysis of ecological data
Ecology
Vicia villosa como cultivo de cobertura en el sur de Santa Fe
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Introducción de cultivos de cobertura en agroecosistemas extensivos de la región central de Córdoba
Dosificación de la fertilización en maíz
Prediction of soil nitrate in depth using nitrate concentration in the upper layer
Comm. Soil Sci. Plant Anal.
Impacto del manejo de cereales de cobertura invernal sobre propiedades edáficas y producción de soja
Proceedings of XXI Congreso Argentino de la Ciencia del Suelo
Cultivos de cobertura: manejo y efectos sobre la nutrición de suelos y cultivos
Proceedings of Simposio Fertilidad 2013: Nutrición de cultivos para la intensificación productiva sustentable
Dinámica de agua en barbechos y cultivos de cobertura en la Región Pampeana
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Rangos de densidad aparente medidos en suelos pampeanos
Proceedings XXIV Congreso Argentino de la Ciencia del Suelo
Fertilizer use in pampean agroecosystems: impact on productivity and nutrient balance
El rol de los fertilizantes en la agricultura
Carbono orgánico
Mejora de propiedades edáficas con inclusión de cultivos de cobertura en agroecosistemas pampeanos
Proceedings of XXV Congreso Argentino de la Ciencia del Suelo
Physical tests for monitoring soil quality
Efecto del rolado de cultivos de cobertura sobre la dinámica de agua y malezas
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Secuencias agrícolas y su efecto en la productividad de soja y propiedades edáficas
Proceedings of XXV Congreso Argentino de la Ciencia del Suelo
Cultivos de cobertura en sistemas de agricultura continua en la región central de Córdoba
Efecto del centeno sobre los niveles de carbono y nitrógeno del suelo
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Efecto de la Fertilización sobre la eficiencia del uso del agua de especies invernales utilizadas como cultivos de cobertura
Bulk density
Cover crops and ecosystems services: insights from studies in temperate soils
Agron. J.
Cultivos de cobertura y fertilización nitrogenada en maíz
Proceedings of Simposio Fertilidad 2013: Nutrición de cultivos para la intensificación productiva sustentable
Estimación del uso consuntivo de trigo, maíz y girasol en la Región Semiárida-Subhúmeda Pampeana
Actas XXV Congreso Argentino de la Ciencia del Suelo
Intake rate: cylinder infiltrometer
Penetrability
Cultivos de cobertura: impacto sobre la materia orgánica del suelo
Proceedings of XXIII Congreso Argentino de la Ciencia del Suelo
Cultivos de cobertura en el Sur de la provincia de Santa Fe
Recarga del perfil hídrico en barbechos de distinta duración con diferentes niveles de cobertura
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Cultivos de cobertura: efecto sobre la porosidad y el rendimiento de soja
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Balance de carbono en sistemas agrícolas continuos de la región sudeste de la Provincia de Córdoba
Proceedings of XXII Congreso Argentino de la Ciencia del Suelo
Green manure approaches to crop production: a synthesis
Agron. J.
Rendimiento de maíz: Efecto de cultivos de cobertura/abonos verdes en el sudeste bonaerense
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Cultivos de cobertura: Longitud de barbecho y disponibilidad hídrica
Proceedings of XXIV Congreso Argentino de la Ciencia del Suelo
Bases funcionales para el manejo del agua en los sistemas de producción de los cultivos de granos
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