The effects of soil tillage techniques on weed flora in high input barley systems in northern Spain

In barley cropping systems of northern Spain, agronomic practices and weather conditions are key components of weed control efficacy. We compared the short-term effects of conventional tillage (CT) with minimum tillage (MT) and zero-tillage (ZT), in barley monoculture and barley rotation systems. Weed density and weed species number were measured at tillering and flowering barley stages. We found that tillage system can influence weed density and weed species establishment due to, in part, the available light for weed seeds. The results obtained led us to believe that MT system facilitate the prevalence of the grass weed Bromus diandrus Roth (50.37%) and the annuals dicots Galium aparine (L.) and Lithospermun arvense (L.) abundant were high in MT system too, 43.71% and 43.97% respectively. The germination of these species showed high dependence of light availability. We saw that barley-monoculture plots had a great infestation of Bromus (71.29%) and barley-rotated plots presented more infestation of Galium and Lithospermun (74.36% and 84.4%). After herbicide application, weed infestation in conservation systems was reduced in barley-rotated plots compared to barley-monoculture. If conservation systems avoided the presence of dominant weeds, the weight of each weed species was balanced within competitive relationships of the cropping systems. Our results confirmed that MT and ZT systems favour different weed species emergences in barley-rotated plots. The combination of MT and barley rotated cropping system resulted in terms of greater weed diversity and lower total weed density.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Integrating statistical and ecophysiological analyses of genotype by environment interaction for grain filling of barley I. Individual grain weight

In Mediterranean-type environments, grain weight of barley (Hordeum vulgare L.) is influenced by the presence of terminal abiotic stresses such as drought or elevated temperature. The relative importance of these climatic constraints acting together prior to and after anthesis, as well as the specificity of genotypic responses, have not been clearly documented. Field experiments were carried out in 12 rainfed environments of northern Spain involving five six-rowed and five two-rowed cultivars. A large variability in individual grain weight (IGW) among environments was recorded (34.8-59.3 mg). An analysis of variance for IGW revealed genotype by environment (G x E) interaction. Environments were characterized by climatic covariables (temperature, rainfall and potential evapotranspiration) measured during three consecutive periods of plant development: jointing, heading and grain filling. Genotypes were described by covariables related to differences in morphological (ear-type), development (anthesis date) and physiological (carbon isotope discrimination, response to chemical desiccation) traits. Possible factors underlying G x E were examined by additive main effects and multiplicative interaction (AMMI) and factorial regression models. Genotypic and environmental descriptors were used as concomitant variables at the levels of the genotypic and environmental factor to partition G x E. The factorial regression model confirmed that the incidences of drought and of high temperatures during grain filling were responsible for the differential genotypic responses found in IGW: some cultivars were affected by both constraints, others by a single one, and some proved to be insensitive. These responses could be partially ascribed to the contrast between two- and six-rowed barleys: six-rowed types were more prone to be negatively influenced by terminal abiotic stresses than two-rowed cultivars. For breeding purposes there are opportunities to exploit the apparent genetic variability for tolerance to drought and/or thermic stress.Peer Reviewe

Integrating statistical and ecophysiological analysis of genotype by environment interaction for grain filling of barley in Mediterranean areas. I. Individual grain weight

In Mediterranean-type environments, grain weight of barley (Hordeum vulgare L.) is influenced by the presence of terminal abiotic stresses such as drought or elevated temperature. The relative importance of these climatic constraints acting together prior to and after anthesis, as well as the specificity of genotypic responses, have not been clearly documented. Field experiments were carried out in 12 rainfed environments of northern Spain involving five six-rowed and five two-rowed cultivars. A large variability in individual grain weight (IGW) among environments was recorded (34.8¿59.3 mg). An analysis of variance for IGW revealed genotype by environment (G × E) interaction. Environments were characterized by climatic covariables (temperature, rainfall and potential evapotranspiration) measured during three consecutive periods of plant development: jointing, heading and grain filling. Genotypes were described by covariables related to differences in morphological (ear-type), development (anthesis date) and physiological (carbon isotope discrimination, response to chemical desiccation) traits. Possible factors underlying G × E were examined by additive main effects and multiplicative interaction (AMMI) and factorial regression models. Genotypic and environmental descriptors were used as concomitant variables at the levels of the genotypic and environmental factor to partition G × E. The factorial regression model confirmed that the incidences of drought and of high temperatures during grain filling were responsible for the differential genotypic responses found in IGW: some cultivars were affected by both constraints, others by a single one, and some proved to be insensitive. These responses could be partially ascribed to the contrast between two- and six-rowed barleys: six-rowed types were more prone to be negatively influenced by terminal abiotic stresses than two-rowed cultivars. For breeding purposes there are opportunities to exploit the apparent genetic variability for tolerance to drought and/or thermic stress

Conservation Agriculture Under Mediterranean Conditions in Spain

19 Pag., 2 Tabl., 2 Fot. The definitive version is available at: http://www.springerlink.com/Intensive agriculture with deep tillage and soil inversion causes rapid soil deterioration with loss of soil organic matter content. This practice leads to a decrease of soil biological activity, a damage of the physical properties and a reduction of crop yields. Conservation agriculture aims to achieve sustainable and profitable agriculture through the application of three basic principles: minimal soil disturbance by conservation tillage, permanent soil cover and crop rotations. Any practice of conservation agriculture must maintain on the soil enough surface residues throughout the year. Conservation tillage is thus any tillage and planting system that maintains at least 30% of the soil surface covered by residues after planting to reduce soil erosion by water. Here we review the main advances about the adoption of conservation agriculture under Mediterranean conditions in Spain. There are major cost savings, e.g. fuel and fertilizer costs, compared with conventional agriculture. Conservation tillage has been proven to be highly efficient for water storage, to increase moderately the organic matter in the soil top layer, and to improve soil physical properties and aggregation. However, no tillage may induce greater soil compaction in some cases. In this case, an occasional tillage is advised. Furthermore, conservation tillage can reduce soil CO2 emissions, mobility and persistence of herbicides. In general, conservation tillage enhances biodiversity compared to conventional tillage. Crop yields under conservation tillage are similar or even greater than yields of traditional tillage. All these benefits show that ­conservation agriculture in Spain is a more sustainable alternative than conventional agriculture. Nonetheless, we have found from the literature analysis some constraints for its adoption, mainly due to inadequate extension and technology transfer systems and lack of access to specific inputs.This work was carried out with the support of the projects GOCE-CT-2004–505582–KASSA (EU), AGL2004–07763–CO2–01–AGR, AGL2007–66320–CO2–01–AGR and AGL2008–00424 from the Spanish CICYT, and the Research Group AGR 151 (Junta de Andalucía).Peer reviewe