Abstract The objective of this work was to evaluate different pastures types on carbon footprint (CF). The cattle in the Piedmont zone, Cumaral, Meta, Colombia are principally Brahman, the pastures are formed with the tropical forage grasses Brachiaria decumbens for improved pastures (IP) and degraded pastures of B. brizantha (DP), also, various silvopastoral systems (SPSs) depending of planting trees on pasture at the same time and in the same space were evaluated. GHG emissions per kg of live weight (LW) were estimated to be reduced from 9.14, and 7.17 to 4.4 kgCO2eq.kgLW-1 in SPSs, and IP to DP, respectively. In all systems the largest GHG emission were enteric fermentation CH4, manure management N2O, feed animal management CO2. Soil C sequestration rates ranged from 2.46 to -1.72 tCO2.ha-1.yr-1 in DP to SPSs, respectively, IP account for -1.35tCO2eq.ha-1yr-1. CF were neutralized from 8.12 to -11.6 kg CO2eq.kg LW-1 in DP to IP. The beef production system with the lowest CF studied were that based on SPSs, mainly B. decumbens associated with Acacia mangium, accounting -60 kg CO2eq.kgLW-1. In our study, all other SPSs had a very large impact on negative CF, due to differences in C stored in biomass that would account for GHG neutralization of -15.3, -21.8, -24.31, -20.42 kg CO2eq.kgLW-1 in SPSs of B. decumbens + Gliricidia sepium, B. decumbens + Mangifera indica, B. decumbens + G. angustifolia and B. decumbens + citrus cinensis, respectively. It is possible to neutralize CF in beef cattle production through several SPSs in Piedmont’s case study.

ABSTRACT Actinobacteria of the genus Streptomyces are part of the soil microbiota from rice-growing areas and along with other microorganisms, such as Trichoderma spp., combine to act as natural enemies against the destructive soil-borne pathogen Rhizoctonia solani, causal agent of rice sheath blight disease. In this study, seven actinobacteria of the genus Streptomyces and three fungi of the genera Trichoderma and Purpureocillium were isolated from soils cultivated with rice using the serial dilution method. Streptomyces spp. M2A2 was selected for its ability to significantly reduce the in vitro growth of R. solani by 52% after 96 h by antibiosis in dual culture, while in the control treatment the mycelial growth was 100%. Furthermore, biocontrol efficacy of treated plants of the susceptible cultivar Fedearroz 68 with actinobacteria was confirmed and the onset of symptoms were delayed up to 14 days, compared to the control treatment. Rice plants treated with Streptomyces spp. M2A2 showed lesions of R. solani reaching 0.7% of the plant height, the effectiveness of this treatment was similar to the difenoconazole treatment, whereas in the control treatment, the lesions covered 34% of the plant height. When compared to the antagonist fungus Trichoderma spp. M2H1, Streptomyces spp. M2A2 presented a better performance of biological control. The results clearly demonstrated that Streptomyces spp. M2A2 isolate from soils of rice growing areas has biocontrol efficiency against R. solani and therefore can be a promising biocontrol agent.

HIGHLIGHTS Brachiaria decumbens pasture associated with kudzu Pueraria phaseloides legume represents an alternative for higher arbuscular mycorrhizal fungi (AMF). Higher lime doses presented high rates of AMF and improved soil chemical properties (SCP). Higher lime doses were the most influential technological factor than the type of pasture and the N, P, K fertilizer sources on AMF.

RESUMEN El presente estudio fue realizado en Villanueva, departamento del Casanare, Oriente de Colombia. Se evaluó el impacto de tres sistemas de labranza: T1: Labranza reducida (desbrozadora, un pase de cincel vibratorio, un pase de rastra y siembra), T2: siembra directa y T3: labranza de conservación (desbrozadora, un pase de cincel vibratorio, siembra con 30% de cobertura) sobre algunas variables físicas, químicas y biológicas del suelo, como la densidad aparente (Da), porosidad (ɲ), porcentaje de materia orgánica del suelo (%MOS) y unidades formadoras de colonias de hongos y bacterias UFCs. Se utilizó un Diseño de Bloques Completamente al Azar con tres tratamientos y cinco repeticiones para 15 unidades experimentales, evaluados en dos épocas: uno antes de la preparación y el otro después de dos meses de siembra de maíz. Se realizó Análisis de Varianza y la Prueba De Comparación de Medias de Tukey (p≤0,05). La Da fue más alta en T1 (1,52g/cm3) en el primer muestreo. Con el T3 se alcanzó una Da más baja en ambas épocas (1,27g/cm3). La porosidad fue mayor con el T3 sin diferencias entre muestreos. La siembra directa ocasionó un mayor porcentaje de MOS durante el último muestreo. La labranza de conservación presentó mayores UFCs de hongos y bacterias con respecto a los otros dos sistemas de labranza.

ABSTRACT Based on the negative effects of conventional tillage in Inceptisoil at Villanueva, department of Casanare, Oriente of Colombia, the present investigation evaluated the impact of three tillage systems: T1: Reduced tillage (brushcutter, vibratory chisel, harrowing and sowing), T2: direct sowing and T3: conservation tillage (brushcutter, vibratory chisel, sowing with 30% crop residues) on some physical, chemical and biological soil variables, such as bulk density (Da), porosity (ɲ), percentage of soil organic matter (%SOM) and colony forming units of fungi and bacteria CFUs. A completely randomized block design was used with three treatments and five repetitions for 15 experimental units, evaluated in two periods: M1: before preparation and M2: after two months of corn sowing. Analysis of variance and Tukey's mean comparison test (p≤0.05) was performed. The Da was higher in T1 (1.52g/cm3) in M1. The T3 got the lower Da in both seasons (1.27g/cm3) and a greater porosity without differences between samplings. The T2 produced the higher percentage of SOM in M2. T3 showed higher CFUs of fungi and bacteria with respect to T1 and T2. Conservation tillage must be taken into account for a better soils management.