The effect of crop sequences on soil microbial, chemical and physical indicators and its relationship with soybean sudden death syndrome (complex of Fusarium species)

The effect of crop sequences on soil quality indicators and its relationship with sudden death syndrome (SDS, a complex of Fusarium species) was evaluated by physical, chemical, biochemical and molecular techniques. Regarding physical aspects, soybean/maize and maize monoculture exhibited the highest stable aggregate level, with values 41% and 43% higher than in soybean monoculture, respectively, and 133% higher than in bean monoculture. Bulk density (BD) was higher in soybean monoculture, being 4% higher than in bean monoculture. The chemical parameters organic matter, total N, P, K, Mg, Ca, and water holding capacity also indicated that soybean/maize and maize monoculture improved soil quality. Fungal and bacterial community fingerprints generated using Terminal Restriction Fragment Length Polymorphism analysis of intergenic transcribed spacer regions of rRNA genes and 16S rRNA genes, respectively, indicated a clear separation between the rotations. Fatty acid profiles evaluated by FAME showed that bean monoculture had higher biomass of Gram (+) bacteria and stress indicators than maize monoculture, while the soybean/maize system showed a significant increase in total microbial biomass (total FAMEs content) in comparison with soybean and bean monoculture. The incidence of SDS (Fusarium crassistipitatum) was markedly higher (15%) under soybean monoculture than when soybean was grown in rotation with maize. In the present work, soil microbial properties were improved under soybean/maize relative to continuous soybean. The improvement of soil health was one of the main causes for the reduction of disease pressure and crop yield improvement due to the benefits that crop rotation produces for soil quality.EEA SaltaFil: Perez Brandan, Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; ArgentinaFil: Arzeno, Jose Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; ArgentinaFil: Huidobro, Dina Jorgelina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; ArgentinaFil: Conforto, Erica Cinthia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Grumberg, Betiana Clarisa. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Hilton, Sally. University of Warwick. School of Life Sciences; Reino UnidoFil: Bending, Gary D. University of Warwick. School of Life Sciences; Reino UnidoFil: Meriles, Jose Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Vargas Gil, Silvina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentin

Long-term effect of tillage systems on soil microbiological, chemical and physical parameters and the incidence of charcoal rot by Macrophomina phaseolina (Tassi) Goid in soybean

A 20-year field experiment was employed with the aim of evaluating the effect of tillage systems on biological, chemical and physical aspects of the soil, and to establish whether there was a correlation of these parameters with the incidence of charcoal rot (Macrophomina phaseolina) of soybean and crop yield. The tillage systems evaluated were direct seeding (DS), DS + scarifier (DS + S), minimum tillage (MT) and conventional tillage (CT). DS presented higher values than CT in culturable total fungi (26.33 × 105 vs. 2.33 × 105 CFU g−1 dry soil), total bacteria (182 × 107 vs. 64 × 107 CFU g−1 dry soil), microbial respiration (0.77 mg CO2 g−1 week−1 vs. 0.45 mg CO2 g−1 week−1) and fluorescein diacetate (FDA) hydrolysis (4.17 ug fluorescein g−1 h−1 vs. 1.70 ug fluorescein g−1 h−1 in CT. Fungal and bacterial community fingerprints, by terminal restriction fragment length polymorphism (T-RFLP) analysis, of Intergenic spacer regions of rRNA and 16S rRNA genes, respectively, were influenced by the tillage system. Also FAME (fatty acid methyl ester) profiles showed that microbial community structure in DS and CT was clearly different. DS samples contained significantly higher total microbial biomass than the other tillage treatments, but there were no significant differences in fungal biomass or any consistent trend with respect to stress index. Our results showed that microbial communities were more abundant and active in DS than in CT in response to high nutrient content in soil. Indeed, DS systems presented higher soil OM, total N, K and Ca than CT. Electrical conductivity and aggregate stability (AS) were also improved by DS. Soybean grown in high-quality soil was not affected by charcoal rot, however, under CT, disease incidence in soybean was 54%. These differences were correlated to the higher microbial abundance and activity under DS, the biological component being a key factor determining soil capacity to suppress the soilborne pathogen.EEA SaltaFil: Perez Brandan, Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; ArgentinaFil: Arzeno, Jose Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; ArgentinaFil: Huidobro, Dina Jorgelina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; ArgentinaFil: Grumberg, Betiana Clarisa. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; ArgentinaFil: Conforto, Erica Cinthia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Hilton, Sally. University of Warwick. School of Life Sciences; Reino UnidoFil: Bending, Gary D. University of Warwick. School of Life Sciences; Reino UnidoFil: Meriles, Jose Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Vargas Gil, Silvina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentin

Incorporación de trigo en la rotación agrícola : una herramienta para potenciar el funcionamiento del agroecosistema

Argentina es uno de los principales productores y exportadores de granos a nivel mundial. En particular, la región Pampeana es el área de mayor actividad agrícola centrando su producción en el cultivo de soja, seguido del maíz y trigo en menor proporción. En los últimos años, el sistema basado en la producción continua de un cultivo ha generado un impacto negativo sobre las propiedades del suelo. Históricamente, prácticas conservacionistas como la rotación de cultivos y labranza cero, se han propuesto como alternativas al monocultivo y remoción de residuos de cosecha. De esta manera, la diversificación del sistema (inclusión de gramíneas y/o cultivos de invierno), es una de las herramientas más importantes y válidas para potenciar el funcionamiento de los agroecosistemas. El propósito de este trabajo fue identificar la secuencia agrícola que contribuya a incrementar la actividad microbiana del suelo, en sintonía con las variables químicas edáficas. El estudio se llevó a cabo en un ensayo de larga duración iniciado en 1975 bajo siembra directa. De los tratamientos que conforman el ensayo sólo se seleccionaron cuatro secuencias de cultivos agrícolas: soja-soja (S-S), soja-trigo/soja (S-T/S), maíz-soja (M-S) y maíz-trigo/soja (M-T/S). Sobre las muestras de suelo se determinaron parámetros biológicos, como respiración microbiana y actividades enzimáticas, y parámetros químicos como contenido de materia orgánica y macronutrientes. El análisis conjunto de los parámetros dio como resultado una diferenciación entre las secuencias que incluyeron al cultivo invernal (S-T/S y M-T/S) de las secuencias basadas únicamente en cultivos de verano (S-S y M-S). De esta manera las funciones microbianas junto a la materia orgánica y los nutrientes del suelo, demostraron la importancia de la inclusión de trigo como cultivo de invierno en la rotación agrícola.Argentina is one of the main worldwide grains producers and exporters. In particular, the Pampas region is the area with the highest agricultural activity, focusing its production on soybean cultivation, followed by maize and wheat in a smaller proportion. In recent years, continuous cropping based systems have had a negative impact on soil properties. Historically, conservation practices such as crop rotation and zero tillage have been proposed as an alternative to monoculture and crop residue removal. In this way, the diversification of the system (including grasses and/or winter crops) is one of the most important and valid tools for enhancing the functioning of agroecosystems. The purpose of this work was to identify the agricultural sequences that contribute to increase the microbial activity of the soil, in relation with soil chemical variables. The study was carried out in a long-term trial under zero system. The treatments consisted of four agricultural crop sequences: soybean-soybean (S-S), soybean-wheat / soybean (S-T/S), maize-soybean (M-S) and maize-wheat /soybean (M-T/S). Biological parameters, such as microbial respiration and enzymatic activities, and chemical parameters such as organic matter content and macronutrients were determined from soil samples. Joint parameter analysis resulted in a differentiation between sequences that included the winter crop (S-T/S and M-T/S) from the sequences based only on summer crops (S-S and M-S). In this way, the microbial functions along with organic matter and soil nutrients, demonstrated the importance of the inclusion of wheat as winter crop in the agricultural rotationInstituto de Patología VegetalFil: Serri, Dannae Lilia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Meriles, Jose Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Conforto, Erica Cinthia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Perez Brandan, Carolina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta; ArgentinaFil: Pastor, Silvina Estela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Grumberg, Betiana Clarisa. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; ArgentinaFil: Luna, Celina Mercedes. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; ArgentinaFil: Lorenzon, Claudio Antonio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Arce, Juan Mateo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Marelli, Hugo Juan. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Vargas Gil, Silvina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentin