C, N AND P STOCKS AND FLUX THROUGH THE MICROBIAL BIOMASS UNDER DIFFERENT SOIL MANAGEMENT

Abstract - The objective of this study was to determine the effects of different crop systems on soil microbial properties and C, N and P stock after 22 years of cropping on an Oxisol (Typic Haplorthox) at Londrina, Brazil. Soil samples were taken at 0-5, 5-10 and 10-20 cm depths and evaluated for microbial biomass C, N and P. The cultivated sites presented lower microbial biomass and C and N stock than Forest site. While the total P stock presented under crop sites were higher than Forest site. The annual N and P flux through the soil microbial biomass means respectively about 65% and 45% for Coffee, about 50% and 70% for maize and 65% and 60% for wheat of the annual N e P needs. Those results evidence that the microbial biomass represents a substantial reserve of nutrients in the soil and may contribute substantially to the nutrients requirements of crops

Soil carbon and nitrogen mineralization caused by pig slurry application under different soil tillage systems

O objetivo deste trabalho foi avaliar as alterações na mineralização de C e N do solo resultantes da aplicação de dejetos líquidos de suínos (DLS) em sistemas de preparo do solo convencional (CT) e plantio direto (NT). O experimento foi conduzido em um Latossolo Vermelho eutrófico, de textura argilosa, em Palotina, PR, Brasil. Doses crescentes de DLS (0, 30, 60 e 120 m3 ha-1 por ano) foram aplicadas nos dois sistemas de preparo do solo, com três repetições. Metade das dosagens de DLS foi aplicada antes do preparo do solo da cultura de verão e a outra metade antes do da cultura de inverno. As áreas foram cultivadas com soja (Glycine max L.) e milho (Zea mays L.) nos verões de 1998 e 1999, respectivamente, e trigo (Triticum sativum Lam.) nos invernos de ambos os anos. As amostras de solos foram coletadas nas profundidades de 0–5, 5–10 e 10–20 cm. A aplicação de DLS aumentou a mineralização de C e de N, tanto no sistema CT como no NT. Contudo, o aumento da dose de DLS diminuiu a razão de mineralização entre C e N. No sistema de NT, a mineralização de C e de N foi maior que no CT.The objective of this work was to evaluate the change in soil C and N mineralization due to successive pig slurry application under conventional tillage (CT) and no tillage (NT) systems. The experiment was carried out in a clayey Latossolo Vermelho eutrófico (Rhodic Eutrudox) in Palotina, PR, Brazil. Increasing doses of pig slurry (0, 30, 60 and 120 m3 ha-1 per year) were applied in both tillage systems, with three replicates. Half of the pig slurry was applied before summer soil preparation, and the other half before the winter crop season. The areas were cultivated with soybean (Glycine max L.) and maize (Zea mays L.) in the summers of 1998 and 1999, respectively, and with wheat (Triticum sativum Lam.) in the winters of both years. Soil samples were collected at 0–5, 5–10, and 10–20 cm depths. Under both CT and NT systems, pig slurry application increased C and N mineralization. However, increasing pig slurry additions decreased the C to N mineralization ratio. Under the NT system, C and N mineralization was greater than in CT system

Ocorrência de bactérias diazotróficas e fungos micorrízicos arbusculares na cultura da mandioca

This study was performed to evaluate the occurrence and to isolate and identify diazotrophic bacteria and arbuscular mycorrhizal fungi associated with the cassava (Manihot esculenta) crop. Samples from rhizospherical soil, roots, tubers, stems and leaves from several localities of the States of Rio de Janeiro, São Paulo and Paraná, in Brazil, were inoculated in three media specific for diazotrophic associative bacteria, LGI-P, NFb-malate and NFb-GOC, evaluating the most probable number of cells and the acetylene-reducing activity. Diazotrophic bacteria were detected in all plant parts except for the leaves, and were identified as Klebsiella sp., Azospirillum lipoferum and a bacterium called "E", probably belonging to the Burkholderia genus. Bacterium E was able to accumulate, in the N-free semi-solid media, from 7.63 to 14.84 mg of N/g of C and to maintain N fixation capacity after ten consecutive transferences. Mycorrhizal root colonization varied from 31% to 69% and spore density from 10 to 384 spores/100 mL of soil, predominating the species Entrophospora colombiana and Acaulospora scrobiculata in Rio de Janeiro, A. scrobiculata and Scutellospora heterogama in Paraná and in Piracicaba (São Paulo), and A. appendicula and S. pellucida in Campinas (São Paulo).Este trabalho teve como objetivo avaliar a ocorrência, isolar e identificar fungos micorrízicos arbusculares associados à cultura da mandioca (Manihot esculenta). Amostras de solo rizosférico e de várias partes da planta (raízes, tubérculos, manivas e folhas) de locais nos Estados do Rio de Janeiro, São Paulo e Paraná, foram inoculadas nos meios LGI-P, NFb-malato e NFb-GOC, avaliando-se o número mais provável de células e a atividade de redução de acetileno. Bactérias diazotróficas foram isoladas de todas as partes da planta, com exceção das folhas, sendo identificadas como Klebsiella sp., Azospirillum lipoferum e uma bactéria denominada "E", provavelmente pertencente ao gênero Burkholderia. A Bactéria E acumulou de 7,63 mg a 14,84 mg de N/g de C em meio semi-sólido, isento de N, e conseguiu manter a capacidade de fixação biológica de N, mesmo após uma dezena de repicagens consecutivas. A colonização micorrízica variou de 31% a 69%, e a densidade de esporos de 10 a 384 esporos/100 mL de solo, predominando as espécies Entrophospora colombiana e Acaulospora scrobiculata no Rio de Janeiro, A. scrobiculata e Scutellospora heterogama no Paraná e em Piracicaba (São Paulo) e A. appendicula e S. pellucida em Campinas (São Paulo)

Soil Quality in Relation to Forest Conversion to Perennial or Annual Cropping in Southern Brazil

Many forested areas have been converted to intensive agricultural use to satisfy food, fiber, and forage production for a growing world population. There is great interest in evaluating forest conversion to cultivated land because this conversion adversely affects several soil properties. We examined soil microbial, physical, and chemical properties in an Oxisol (Latossolo Vermelho distrófico) of southern Brazil 24 years after forest conversion to a perennial crop with coffee or annual grain crops (maize and soybeans) in conventional tillage or no-tillage. One goal was to determine which soil quality parameters seemed most sensitive to change. A second goal was to test the hypothesis that no-tillage optimized preservation of soil quality indicators in annual cropping systems on converted land. Land use significantly affected microbial biomass and its activity, C and N mineralization, and aggregate stability by depth. Cultivated sites had lower microbial biomass and mineralizable C and N than a forest used as control. The forest and no-tillage sites had higher microbial biomass and mineralizable C and N than the conventional tillage site, and the metabolic quotient was 65 and 43 % lower, respectively. Multivariate analysis of soil microbial properties showed a clear separation among treatments, displaying a gradient from conventional tillage to forest. Although the soil at the coffee site was less disturbed and had a high organic C content, the microbial activity was low, probably due to greater soil acidity and Al toxicity. Under annual cropping, microbial activity in no-tillage was double that of the conventional tillage management. The greater microbial activity in forest and no-tillage sites may be attributed, at least partially, to lower soil disturbance. Reducing soil disturbance is important for soil C sequestration and microbial activity, although control of soil pH and Al toxicity are also essential to maintain the soil microbial activity high

High coffee population density to improve fertility of an oxisol

O objetivo deste trabalho foi verificar os efeitos de diferentes densidades de população de cafeeiros (Coffea arabica L.) nas propriedades químicas, físicas e microbiológicas do solo. Amostras de um Latossolo foram coletadas na profundidade 0-20 cm em um experimento de campo onde estavam sendo avaliadas diferentes populações de cafeeiros. Os tratamentos foram 7.143, 3.571, 2.381, 1.786, 1.429, 1.190, 1.020 e 893 covas/ha. Os resultados demonstraram que o aumento da população de plantas por unidade de área aumentou o pH, o Ca, o Mg e o K trocáveis, o P disponível, o carbono orgânico, o teor de umidade e a colonização radicular por micorrizas, e diminuiu o Al trocável e a biomassa microbiana. Foram considerados como causas da melhoria da fertilidade do solo, sob cafeeiros adensados, o adequado controle da erosão, o correto manejo dos resíduos vegetais e a baixa lixiviação dos íons. O manejo da população de cafeeiros pode constituir uma estratégia importante para a recuperação da fertilidade dos solos ácidos do Paraná.The objective of this work was to evaluate the effect of coffee (Coffea arabica L.) population densities on the chemical and microbiological properties of an Oxisol. The work was carried out on soil samples of 0-20 cm depth originated from an experimental site which had been used for coffee tree spacing studies during 15 years, in Paraná State, Brazil. Eight coffee tree populations were evaluated: 7143, 3571, 2381, 1786, 1429, 1190, 1020, and 893 trees/ha. Increasing plant population increased soil pH, exchangeable Ca, Mg, K, extractable P, organic carbon, moisture content and coffee root colonization by vesicular arbuscular mycorrhizal fungi, and decreased exchangeable Al and microbial biomass. Such results were attributed to better erosion control, improved plant residue management and nutrient cycling, and decreased leaching losses. Increasing coffee tree population per unit of area has shown to be an important reclamation recuperation strategy for improving fertility of the acid soils in Paraná, Brazil

SOIL QUALITY IN RELATION TO FOREST CONVERSION TO PERENNIAL OR ANNUAL CROPPING IN SOUTHERN BRAZIL

Many forested areas have been converted to intensive agricultural use to satisfy food, fiber, and forage production for a growing world population. There is great interest in evaluating forest conversion to cultivated land because this conversion adversely affects several soil properties. We examined soil microbial, physical, and chemical properties in an Oxisol (Latossolo Vermelho distrófico) of southern Brazil 24 years after forest conversion to a perennial crop with coffee or annual grain crops (maize and soybeans) in conventional tillage or no-tillage. One goal was to determine which soil quality parameters seemed most sensitive to change. A second goal was to test the hypothesis that no-tillage optimized preservation of soil quality indicators in annual cropping systems on converted land. Land use significantly affected microbial biomass and its activity, C and N mineralization, and aggregate stability by depth. Cultivated sites had lower microbial biomass and mineralizable C and N than a forest used as control. The forest and no-tillage sites had higher microbial biomass and mineralizable C and N than the conventional tillage site, and the metabolic quotient was 65 and 43 % lower, respectively. Multivariate analysis of soil microbial properties showed a clear separation among treatments, displaying a gradient from conventional tillage to forest. Although the soil at the coffee site was less disturbed and had a high organic C content, the microbial activity was low, probably due to greater soil acidity and Al toxicity. Under annual cropping, microbial activity in no-tillage was double that of the conventional tillage management. The greater microbial activity in forest and no-tillage sites may be attributed, at least partially, to lower soil disturbance. Reducing soil disturbance is important for soil C sequestration and microbial activity, although control of soil pH and Al toxicity are also essential to maintain the soil microbial activity high

Seasonal fluctuations of vesicular-arbuscular mycorrhiza in coffee (Coffea Arabica L.)

Foi feito um estudo de flutuaçãoo sazonal de fungos micorrízicos vesículo-arbusculares (FMVA) no cafeeiro, em um experimento de campo instalado no Centro Experimental do Instituto Agronômico, Campinas. Para tanto, utilizou-se plantas com cinco anos de idade, formadas a partir de mudas não colonizadas e colonizadas com o fungo Gigasporã margarita. Esse experimento havia sido instalado num esquema de parcelas subdivididas, em blocos causalizados, sendo que as amostras foram coletadas de sub-parcelas de tratamentos com 25 ou 100g de superfosfato triplo, com 152g de fostato Alvorada por cova, aplicados no plantio, e do controle sem fósforo, em parcelas inoculadas e não-inoculadas. Preliminarmente foi feita uma amostragem de solo e de raízes a diferentes distâncias do tronco e posição sob a copa do cafeeiro, para determinar a região com maior quantidade de raízes finas, colonização e esporulação de fungo MVA. Nesse estudo não foram observadas diferenças significativas entre médias da quantidade de esporos e da percentagem de colanização micorrízica para diferentes distâncias e profundidades de coleta das amostras. A maior densidade de raízes finas foi observada nas amostras à distância de 0-50 cm do tronco e 0-10 cm de profundidade. Em base a esses resultados as amostras foram retiradas numa distância de 30 cm do tronco, na profundidade de 0-10 cm. Foi coletado um volume constante de 0,10 x 0,10 x 0,10 m. Elas foram retiradas bimestralmente de março de 1987 a fevereiro de 1988. As raízes com diâmetro iguais ou menores de 1 mm foram separadas da amostra e nelas determinados o peso de matéria seca e a percentagem do comprimento de raízes colonizadas. O solo restante foi homogeneizado e uma alíquota foi separada para peneiramento úmido, separando-se os esporos para caracterização das espécies e contagens dos esporos. O menor peso da matéria seca de raízes foi observado no inverno e o maior no verão. A percentagem do comprimento de raízes colonizadas teve pouca variaçio durante o perfodo de amostragem. Foram verificadas seis espicies nativas de fungos MVAs e tambim a espicie introduzida. Gigaspora margarita. De modo geral, todas as espécies apresentaram número crescente de esporos a partir de março/abril, atingindo o máximo em setembro/outubro, logo após o período de menor temperatura e precipitação pluvial. Apesar do baixo número de esporos de Gigaspora margarita, a maioria deles foi verificada nas parcelas inoculadas. A introdução de G. margarita estimulou a esporulação das espécies nativas, com exceção de Acaulospora apendicula.A study of the vesicular-arbuscular mycorrhizal (VAM) fungi seasonal fluctuations was made on coffee trees of an experiment, located at the Central Experiment Station of Instituto Agronômico, Campinas, SP, Brazil. Plants with five years from field transplanting, originated from no colonized and Gigaspora margarita colonized seedlings were sampled. This experiment used a randomized block design ln split-plot blocks. Samples were collected from non-inoculated and inoculated plots in sub plot treatments with no phosphorus and with 25 or 100 g of triple superphosphate or with 152 of Alvorada rock phosphate per tree. Before iniciating the seasonal sampling a preliminary study was carried out in trees bordering the experimental area in order to find out the position under canopy with highest root density, colonization and sporulation of VAM fungi. No significative differences were found among means for number of spores or percentage of root length colonized with VAM fungi. Highest fine roots density was observed in samples from 0-50 cm from the stem v at 0-10 cm depth. Based on this preliminary study, samples for the seasonal study were composed of two sub samples, collected bimonthly as a regular soil volume of 10 x 10 x10 cm, located at the distance of 30 cm from the stem, in different positions and sistematically rotated around the stem during March 87 to February 88. Roots with 1 mm diameter, or thiner, were handled separed thy for dry matter and for VAM colonization study. Then the soil was homogenized, and a sample was wet sieved for determination of spores numbers and VAM fungi species identification. Six VAM species besides G. margarita, which had been previously introduded, were identified. In generalp the spore number increased from March/April to September/October, when they reached the maximum, right after the lower temperature and drier period. Despite the general low number of spores of G. margarita recovered p they were higher in samples collected from the inoculated plots. Introduction of G. margarita seems to have stimulated the sporulation by native VAM fungi, with exception of Acaulospora appendicula. Spores of two species of Acaulospora (A. dilatata e A. trappei) were the most abundantly recovered from the experimental area

Soil carbon and nitrogen mineralization under different tillage systems and Permanent Groundcover cultivation between Orange trees

The objective of this work was to evaluate the alterations in carbon and nitrogen mineralization due to different soil tillage systems and groundcover species for intercropped orange trees. The experiment was established in an Ultisol soil (Typic Paleudults) originated from Caiuá sandstone in northwestern of the state of Paraná, Brazil, in an area previously cultivated with pasture (Brachiaria humidicola). Two soil tillage systems were evaluated: conventional tillage (CT) in the entire area and strip tillage (ST) with a 2-m width, each with different groundcover vegetation management systems. The citrus cultivar utilized was the 'Pera' orange (Citrus sinensis) grafted onto a 'Rangpur' lime rootstock. The soil samples were collected at a 0-15-cm depth after five years of experiment development. Samples were collected from under the tree canopy and from the inter-row space after the following treatments: (1) CT and annual cover crop with the leguminous Calopogonium mucunoides; (2) CT and perennial cover crop with the leguminous peanut Arachis pintoi; (3) CT and evergreen cover crop with Bahiagrass Paspalum notatum; (4) CT and cover crop with spontaneous B. humidicola grass vegetation; and (5) ST and maintenance of the remaining grass (pasture) of B. humidicola. The soil tillage systems and different groundcover vegetation influenced the C and N mineralization, both under the tree canopy and in the inter-row space. The cultivation of B. humidicola under strip tillage provided higher potential mineralization than the other treatments in the inter-row space. Strip tillage increased the C and N mineralization compared to conventional tillage. The grass cultivation increased the C and N mineralization when compared to the others treatments cultivated in the inter-row space