Soybean response to starter nitrogen and Bradyrhizobium inoculation on a Cerrado oxisol under no-tillage and conventional tillage systems

In Brazil, Bradyrhizobium inoculation has successfully replaced the use of N fertilizer on soybean [Glycine max (L) Merr.] crops. However, with the expansion of no-tillage cropping systems in the Cerrados region, the idea that it is necessary to use small N rates at the sowing to overcome problems related with N immobilization has become widespread, mainly when soybean is cultivated after a non-legume crop. In this study we examined soybean response to small rates of N fertilizer under no-tillage (NT) and conventional tillage (CT) systems. Four experiments (a completely randomized block with five replicates) were carried out in a red yellow oxisol, during the periods of 1998/1999 and 1999/ 2000, under NT and CT. The treatments consisted of four urea rates (0, 20, 30 and 40 kg ha-1 N). All treatments were inoculated with Bradyrhizobium japonicum strains SEMIA 5080 and SEMIA 5079, in the proportion 1 kg of peat inoculant (1,5 x 10(9) cells g-1) per 50 kg of seeds. In both experiments, soybean was cultivated after corn and the N fertilizer was band applied at sowing. In all experiments, N rates promoted reductions of up to 50 % in the nodule number at 15 days after the emergence. Regardless of the management system, these reductions disappeared at the flowering stage and there was no effect of N rates on either the number and dry weight of nodules or on soybean yields. Therefore, in the Brazilian Cerrados, when an efficient symbiosis is established, it is not necessary to apply starter N rates on soybean, even when cultivated under notillage systems.

Suprimento de potássio em função da adubação potássica residual em um Latossolo Vermelho do Cerrado

Em alguns solos com baixos teores de potássio trocável, formas não trocáveis participam do suprimento às plantas. Há evidências de que a disponibilização do K não trocável depende mais da demanda das plantas pelo nutriente do que das propriedades do solo. O objetivo deste trabalho foi avaliar o suprimento e a exaustão de formas de K em um Latossolo Vermelho do Cerrado em decorrência da adubação potássica residual e do cultivo de Brachiaria ruziziensis (Syn. Urochloa ruziziensis). Amostras de solos foram coletadas na camada de 0-20 cm, em parcelas de um experimento de campo em que a soja vinha sendo adubada anualmente, por 10 anos, com 0, 60, 120 e 180 kg ha-1 de K2O. em casa de vegetação, as amostras de solo receberam a aplicação de 0, 150 e 300 mg dm-3 de K e foram cultivadas com B. ruziziensis, com cinco cortes sucessivos. O suprimento de K às plantas dependeu mais do fertilizante recém-adicionado do que do efeito residual de adubações anteriores. O K não trocável foi responsável, ao longo do tempo, pela manutenção dos teores de K trocáveis e, na ausência de adubação potássica, constituiu a principal fonte de K para as plantas de B. ruziziensis. As plantas de B. ruziziensis possuem capacidade de extrair quantidade considerável de K do solo, confirmando sua importância como cultura de cobertura, na ciclagem do nutriente no solo.

Resposta do cafeeiro à inoculação de fungos micorrízicos arbusculares, em latossolo vermelho, do cerrado

The aim of this study was evaluate the response of two coffee cultivars (tolerant and sensitive to aluminum - Al), inoculated or not by two arbuscular mycorriza fungi (AMF), Gigaspora margarita and Glomus etunicatum, in cerrado Oxisol, with different base saturation. This experiment was conducted under greenhouse conditions, with a complete randomized design, in a 2x3x2 factorial scheme, consisting of 2 cultivars (tolerante and sensitive to Al), 3 treatments with mycorrhizal (inoculated with two species of AMF and without inoculation) and 3 levels of soil base saturation (30, 45 and 53 V%), with five replicates per treatment. The variables were: plant height, stem diameter, leaf area, shoot dry weight, root fresh weight, nitrate reductase activity, chlorophyll concentration, root colonization and number of AMF spores. Mycorrhizae isolates promoted greater response of coffee plants, in acid soil with high concentration of Al, but this response was observed for both cultivars when plants were colonized by G. margarita. The cultivars evaluated showed no differences in Al tolerance when non inoculated.

Changes in soil organic carbon storage under different agricultural management systems in the Southwest Amazon Region of Brazil

The Cerrado and Amazon regions of Brazil are probably the largest agricultural frontier of the world, and Could be a sink or source for C depending on the net effect of land use change and subsequent management on soil organic C pools. We evaluated the effects of agricultural management systems on soil organic C (SOC) stocks in the Brazilian states of Rondonia and Mato Grosso, and derived regional specific factors for soil C stock change associated with different management systems. We used 50 observations (data points) in this study, including 42 dealing with annual cropping practices and 8 dealing with perennial cropping, and analyzed the data in linear mixed-effect models. No tillage (NT) systems in Cerrado areas increased SOC Storage by 1.08 +/- 0.06 relative to SOC stocks under native conditions, while SOC storage increased by a modest factor of 1.01 +/- 0.17 in Cerradao and Amazon Forest conditions. Full tillage (FT) had negative effect on SOC storage relative to NT, decreasing SOC stocks by a factor of 0.94 +/- 0.04. but did not significantly reduce SOC stocks relative to native levels when adopted in the Cerrado region. Perennial cropping had a minimal impact on SOC stocks, estimated at a factor Value of 0.98 +/- 0.14, suggesting these systems maintain about 98% of the SOC stock found under native vegetation. The results Suggest that NT adoption may be increasing SOC with land use change from native vegetation to cropland management in the Cerrado region of Brazil. (C) 2009 Elsevier B.V. All rights reserved.

Plant-available soil water capacity: estimation methods and implications

The plant-available water capacity of the soil is defined as the water content between field capacity and wilting point, and has wide practical application in planning the land use. In a representative profile of the Cerrado Oxisol, methods for estimating the wilting point were studied and compared, using a WP4-T psychrometer and Richards chamber for undisturbed and disturbed samples. In addition, the field capacity was estimated by the water content at 6, 10, 33 kPa and by the inflection point of the water retention curve, calculated by the van Genuchten and cubic polynomial models. We found that the field capacity moisture determined at the inflection point was higher than by the other methods, and that even at the inflection point the estimates differed, according to the model used. By the WP4-T psychrometer, the water content was significantly lower found the estimate of the permanent wilting point. We concluded that the estimation of the available water holding capacity is markedly influenced by the estimation methods, which has to be taken into consideration because of the practical importance of this parameter.

Multiplicação do nematoide Meloidogyne paranaensis e velocidade de enraizamento de estacas caulinares em sete espécies de plantas medicinais

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Agronomia e Medicina Veterinária, Programa de Pós-Graduação em Agronomia, 2016.

Physical quality of an Oxisol under an integrated crop-livestock-forest system in the Brazilian Cerrado

Soil physical quality is an important factor for the sustainability of agricultural systems. Thus, the aim of this study was to evaluate soil physical properties and soil organic carbon in a Typic Acrudox under an integrated crop-livestock-forest system. The experiment was carried out in Mato Grosso do Sul, Brazil. Treatments consisted of seven systems: integrated crop-livestock-forest, with 357 trees ha-1 and pasture height of 30 cm (CLF357-30); integrated crop-livestock-forest with 357 trees ha-1 and pasture height of 45 cm (CLF357-45); integrated crop-livestock-forest with 227 trees ha-1 and pasture height of 30 cm (CLF227-30); integrated crop-livestock-forest with 227 trees ha-1 and pasture height of 45 cm (CLF227-45); integrated crop-livestock with pasture height of 30 cm (CL30); integrated crop-livestock with pasture height of 45 cm (CL45) and native vegetation (NV). Soil properties were evaluated for the depths of 0-10 and 10-20 cm. All grazing treatments increased bulk density (r b) and penetration resistance (PR), and decreased total porosity (¦t) and macroporosity (¦ma), compared to NV. The values of r b (1.18-1.47 Mg m-3), ¦ma (0.14-0.17 m³ m-3) and PR (0.62-0.81 MPa) at the 0-10 cm depth were not restrictive to plant growth. The change in land use from NV to CL or CLF decreased soil organic carbon (SOC) and the soil organic carbon pool (SOCpool). All grazing treatments had a similar SOCpool at the 0-10 cm depth and were lower than that for NV (17.58 Mg ha-1).

Cover plants and mineral nitrogen: effects on organic matter fractions in an oxisol under no-tillage in the cerrado

Cover plants are essential for the sustainability of no-tillage systems in tropical regions. However, information on the effects of these plants and N fertilization on soil organic matter fractions is still scarce. This study evaluated the effect of cover crops with different chemical composition and of N topdressing on the labile and humified organic matter fractions of an Oxisol of the Cerrado (savanna-like vegetation). The study in a randomized complete block design was arranged in split-plots with three replications. Four cover species were tested in the plots and the presence or absence of N topdressing in the subplot. The following cover species were planted in succession to corn for eight years: Urochloa ruziziensis; Canavalia brasiliensis M. ex Benth; Cajanus cajan (L.) Millsp; and Sorghum bicolor (L.) Moench. In general, the cultivation of U. ruziziensis increased soil C levels, particularly of C in the humic acid and particulate organic C fractions, which are quality indicators of soil organic matter. The C in humic substances and mineral organic C accounted for the highest proportions of total organic C, demonstrating the strong interaction between organic matter, Fe and Al oxides and kaolinite, which are predominant in these weathered soils of the Cerrado.

Water Erosion on an Oxisol under Integrated Crop-Forest Systems in a Transitional Area between the Amazon and Cerrado Biomes

ABSTRACT Water erosion is one of the main factors driving soil degradation, which has large economic and environmental impacts. Agricultural production systems that are able to provide soil and water conservation are of crucial importance in achieving more sustainable use of natural resources, such as soil and water. The aim of this study was to evaluate soil and water losses in different integrated production systems under natural rainfall. Experimental plots under six different land use and cover systems were established in an experimental field of Embrapa Agrossilvipastoril in Sinop, state of Mato Grosso, Brazil, in a Latossolo Vermelho-Amarelo Distrófico (Udox) with clayey texture. The treatments consisted of perennial pasture (PAS), crop-forest integration (CFI), eucalyptus plantation (EUC), soybean and corn crop succession (CRP), no ground cover (NGC), and forest (FRS). Soil losses in the treatments studied were below the soil loss limits (11.1 Mg ha-1 yr-1), with the exception of the plot under bare soil (NGC), which exhibited soil losses 30 % over the tolerance limit. Water losses on NGC, EUC, CRP, PAS, CFI and FRS were 33.8, 2.9, 2.4, 1.7, 2.4, and 0.5 % of the total rainfall during the period of study, respectively.

Effect of pH on the development of acidic sites in clayey and sandy loam Oxisol from the Cerrado Region, Brazil

Titration curves were determined for soil from horizon samples of a clayey and a sandy loam Oxisol by (a) adding NaOH to soil suspensions and (b) incubating moist soils with Ca(OH)(2). The organic fraction was primarily responsible for buffering in both soils. Humic acids were more important than fulvic acids in buffering against NaOH additions. With Ca(OH)(2), greater buffer capacities were found due to carboxyl sites, primarily on fulvic acids, becoming complexed with Ca2+ so that in the clay soil humic and fulvic acids were equally important as buffering components while fulvic acids were more important in the sandy loam soil. The buffer capacity of organic matter against Ca(OH)(2) additions was 1.1 mol(c) kg(-1) pH(-1). In the incubated soils, exchangeable cations were also determined and changes in the amounts of exchangeable and non-exchangeable Ca2+ acidity and effective cation exchange capacity were calculated. Up to half the added Ca2+ became complexed and was nonexchangeable. Aluminum complexed by organic matter appears to be an important buffering component, together with non exchangeable H+. With the increase of pH the dissociated sites from the carboxyl groups could complex Ca2+. (c) 2005 Elsevier B.V. All rights reserved.

Physical quality of an Oxisol under an integrated crop-livestock-forest system in the Brazilian Cerrado

Soil physical quality is an important factor for the sustainability of agricultural systems. Thus, the aim of this study was to evaluate soil physical properties and soil organic carbon in a Typic Acrudox under an integrated crop-livestock-forest system. The experiment was carried out in Mato Grosso do Sul, Brazil. Treatments consisted of seven systems: integrated crop-livestock-forest, with 357 trees ha-1 and pasture height of 30 cm (CLF357-30); integrated crop-livestock-forest with 357 trees ha-1 and pasture height of 45 cm (CLF357-45); integrated crop-livestock-forest with 227 trees ha-1 and pasture height of 30 cm (CLF227-30); integrated crop-livestock-forest with 227 trees ha-1 and pasture height of 45 cm (CLF227-45); integrated crop-livestock with pasture height of 30 cm (CL30); integrated crop-livestock with pasture height of 45 cm (CL45) and native vegetation (NV). Soil properties were evaluated for the depths of 0-10 and 10-20 cm. All grazing treatments increased bulk density (r b) and penetration resistance (PR), and decreased total porosity (¦t) and macroporosity (¦ma), compared to NV. The values of r b (1.18-1.47 Mg m-3), ¦ma (0.14-0.17 m³ m-3) and PR (0.62-0.81 MPa) at the 0-10 cm depth were not restrictive to plant growth. The change in land use from NV to CL or CLF decreased soil organic carbon (SOC) and the soil organic carbon pool (SOCpool). All grazing treatments had a similar SOCpool at the 0-10 cm depth and were lower than that for NV (17.58 Mg ha-1).

Use of nitrogen from fertilizer and cover crops by upland rice in an Oxisol under no-tillage in the Cerrado.

O objetivo deste trabalho foi avaliar os efeitos do uso de plantas de cobertura sobre a produtividade do arroz (Oryza sativa) de terras altas cultivado em sistema plantio direto, na presença e na ausência de adubação nitrogenada, bem como quantificar, em campo, o aproveitamento de N da ureia e de plantas de cobertura pelo arroz, com emprego da técnica de diluição isotópica de 15N. O experimento de campo foi realizado em Selvíria, MS, em um Latossolo Vermelho distroférrico, na região do Cerrado. O delineamento experimental foi o de blocos ao acaso com 15 tratamentos e quatro repetições, em arranjo fatorial 5x3. Os tratamentos foram quatro espécies de plantas de cobertura (Crotalaria juncea, Cajanus cajan, Mucuna pruriens e Pennisetum glaucum) + vegetação espontânea (pousio), combinados com três formas de adubação nitrogenada: controle, sem aplicação de N; 20 kg ha‑1 de N em semeadura; e 20 kg ha‑1 de N em semeadura mais 60 kg ha‑1 de N em cobertura. O arroz não responde à aplicação de N em cobertura, quando leguminosas são usadas como plantas de cobertura. O uso de leguminosas como planta de cobertura resulta em maior produtividade de grãos e aproveitamento do N do fertilizante pelo arroz do que o uso de milheto ou pousio. As leguminosas proporcionam efeito equivalente à aplicação de 60 kg ha‑1 de N na forma de ureia sobre a produtividade de grãos de arroz.

Effect of nitrogen fertilization on soil microbial biomass in an Oxisol cultivated with irrigated barley in the Brazilian Cerrado.

Abstract:The aim of this study was to evaluate the effect of different nitrogen doses and five period of sample collection, on soil microbial biomass - nitrogen (SMB-N), total nitrogen (total N) and percentual ratio of the microbial biomass and total N (SMB-N/total N) in a Oxisol cultivated with barley (Hordeum vulgare L.). The experiment was installed in June, 2005, in an area located at Embrapa Cerrados, Federal District. The experimental design was a randomized block, with three replicates. The plots received doses of nitrogen: 20 - 40 - 80 kg ha-1 N and a control without it and the subplots were period of soil sample. Three applications of N were realized: 10 kg ha-1 on the 5th day (06/14) after sowing; the rest of N was parceled in two applications with fertigation, on tillage, on the 27th (07/08) DAP, e no 43rd (07/22) DAP. Soil samples layer (0 - 10 cm deep) were collected for (SMB-N) determination and total N in six periods: 02 days before of the first fertigation; 02 days after of the first fertigation; 04 days before of the last fertigation and 04 days after of the last fertigation; on flowering stage and after harvesting. There was effect of the doses of N and the period of soil collection on the SMB-N, total N and in the ratio SMB-N/total N. The average values of total N revealed steadier in short-term (cycle of the culture) and this was not a good parameter to evaluate the behavior and N transformations in the soil-plant system. Resumen: El objetivo de este estudio fue evaluar el efecto de diferentes dosis de nitrógeno y cinco período de muestreo en la biomasa microbiana del complejo suelo - nitrogeno (BMS-N), nitrógeno total (N total) y la relación porcentual de la biomasa microbiana y N total (BMS-N/N total) en un Oxisol cultivado con cebada (Hordeum vulgare L.). El estudio se inició en junio de 2005 en la estación experimental de la Empresa de Pesquisa Agropecuaria (Embrapa-Cerrados), Distrito Federal, Brazil. El experimento se dispuso en bloques al azar con tres repeticiones. Las parcelas recibieron dosis de nitrógeno: 20 - 40 - 80 kg/ha de N más un control sin N, y las subparcelas fueron el periodo de muestro. Las aplicaciones de N se realizaron de la forma siguiente: cinco días después de la siembra (dds) se aplicaron 10 kg/ha y el resto de la dosis se aplicó con fertirrigación en dos dosis 27 y 43 dds. Las muestras de suelo (0-10 cm de profundidad) para determinar BMS-N y N total fueron tomadas, 2 días antes e igual número de días después de la primera fertirrigación y 4 días antes y después de la última, en floración y después de la cosecha. No se encontró efecto de las dosis de N y el período de muestreo en el BMS-N, N total y en la relación BMS-N/N total. Los valores medios de N total fueron más estable en el corto plazo (ciclo de la cultivo) lo que indica que éste no es un buen parámetro para evaluar la dinámica del N y sus transformaciones en el sistema suelo-planta.

Soil carbon stocks under no-tillage mulch-based cropping systems in the Brazilian Cerrado: An on-farm synchronic assessment

No-tillage mulch-based (NTM) cropping systems have been widely adopted by farmers in the Brazilian savanna region (Cerrado biome). We hypothesized that this new type of management should have a profound impact on soil organic carbon (SOC) at regional scale and consequently on climate change mitigation. The objective of this study was thus to quantify the SOC storage potential of NTM in the oxisols of the Cerrado using a synchronic approach that is based on a chronosequence of fields of different years under NTM. The study consisted of three phases: (1) a farm/cropping system survey to identify the main types of NTM systems to be chosen for the chronosequence; (2) a field survey to identify a homogeneous set of situations for the chronosequence and (3) the characterization of the chronosequence to assess the SOC storage potential. The main NTM system practiced by farmers is an annual succession of soybean (Glycine max)or maize (Zea mays) with another cereal crop. This cropping system covers 54% of the total cultivated area in the region. At the regional level, soil organic C concentrations from NTM fields were closely correlated with clay + silt content of the soil (r(2) = 0.64). No significant correlation was observed (r(2) = 0.07), however, between these two variables when we only considered the fields with a clay + silt content in the 500-700 g kg(-1) range. The final chronosequence of NTM fields was therefore based on a subsample of eight fields, within this textural range. The SOC stocks in the 0-30 cm topsoil layer of these selected fields varied between 4.2 and 6.7 kg C m(-2) and increased on average (r(2) = 0.97) with 0.19 kg C m(-2) year(-1). After 12 years of NTM management, SOC stocks were no longer significantly different from the stocks under natural Cerrado vegetation (p < 0.05), whereas a 23-year-old conventionally tilled and cropped field showed SOC stocks that were about 30% below this level. Confirming our hypotheses, this study clearly illustrated the high potential of NTM systems in increasing SOC storage under tropical conditions, and how a synchronic approach may be used to assess efficiently such modification on farmers` fields, identifying and excluding non desirable sources of heterogeneity (management, soils and climate). (C) 2010 Elsevier B.V. All rights reserved.

Soil organic carbon and fertility interactions affected by a tillage chronosequence in a Brazilian Oxisol

No-till (NT) adoption is an essential tool for development of sustainable agricultural systems, and how NT affects the soil organic C (SOC) dynamics is a key component of these systems. The effect of a plow tillage (PT) and NT age chronosequence on SOC concentration and interactions with soil fertility were assessed in a variable charge Oxisol, located in the South Center quadrant of Parana State, Brazil (50 degrees 23`W and 24 degrees 36`S). The chronosequence consisted of the following six sites: (i) native field (NF); (ii) PT of the native field (PNF-1) involving conversion of natural vegetation to cropland; (iii) NT for 10 years (NT-10); (iv) NT for 20 years (NT-20); (v) NT for 22 years (NT-22); and (vi) conventional tillage for 22 years (CT-22) involving PT with one disking after summer harvest and one after winter harvest to 20 cm depth plus two harrow disking. Soil samples were collected from five depths (0-2.5; 2.5-5; 5-10; 10-20; and 20-40 cm) and SOC, pH (in H(2)O and KCl), Delta pH, potential acidity, exchangeable bases, and cation exchangeable capacity (CEC) were measured. An increase in SOC concentration positively affected the pH, the negative charge and the CEC and negatively impacted potential acidity. Regression analyses indicated a close relationship between the SOC concentration and other parameters measured in this study. The regression fitted between SOC concentration and CEC showed a close relationship. There was an increase in negative charge and CEC with increase in SOC concentration: CEC increased by 0.37 cmol(c) kg(-1) for every g of C kg(-1) soil. The ratio of ECEC:SOC was 0.23 cmol(c) kg(-1) for NF and increased to 0.49 cmol(c) kg(-1) for NT-22. The rates of P and K for 0-10 cm depth increased by 9.66 kg ha(-1) yr(-1) and 17.93 kg ha(-1) yr(-1), respectively, with NF as a base line. The data presented support the conclusion that long-term NT is a useful strategy for improving fertility of soils with variable charge. (C) 2008 Elsevier B.V. All rights reserved.