Renato Ribeiro Passos

Carbono orgânico e Nitrogênio em agregados de um Latossolo Vermelho distrófico sob duas coberturas vegetais

Soil organic matter is constituted by a vast array of compounds that include active and more stable fractions, with different cycling rates. Management practices affect organic carbon and nitrogen contents, organic matter quality, and soil aggregation. The present study aimed to characterize organic carbon and nitrogen in aggregates of a Dystrophic Red Latosol of Minas Gerais State, Brazil, in an area of native vegetation (Cerradao) and another one that has been for 30 years under conventional corn cultivation. Soil samples were collected at depths of 5-10 and 15-20 cm at four different sites. The dried samples were fractioned in the following aggregate classes: diameter 4.75-2.0; 2.0-1.0; 1.0-0.5; 0.5-0.25; 0.25-0.105; and less than 0.105 mm. Total organic carbon (COT), water soluble organic carbon (COS), total nitrogen (NT) and anaerobically-mineralized nitrogen (NMA) were determined for each sample. On average, the COT contents of soil aggregates under conventional tillage were higher, while NT contents were greater in the aggregates of the Cerradao surface layer. The COS and NMA contents, that correspond to more active fractions of organic matter, were significantly higher in aggregates of Cerradao soil. Aggregates of smaller size tended to present higher contents of COT, NT and NMA. Ratios of C/N, COT/COS and NT/NMA were, on average, higher in aggregates of soils under corn. The NT/NMA ratio was significantly higher in the 15-20 cm layer. However, independent of the soil, the lowest NT/NMA ratios were observed in the smallest aggregate classes, indicating the presence of more labile nitrogen forms. Results showed that vegetation cover type and soil management influenced not only the organic carbon and nitrogen contents, but also organic matter quality. Smaller aggregates are not only responsible for a greater stock of organic matter in the soil but also represent important sites of mineralizable nitrogen. The COS, NMA and the ratios of COT/COS and NT/NMA represent valuable indicators to detect alterations in the lability of organic matter due to management.

SUBSTÂNCIAS HÚMICAS, ATIVIDADE MICROBIANA E CARBONO ORGÂNICO LÁBIL EM AGREGADOS DE UM LATOSSOLO VERMELHO DISTRÓFICO SOB DUAS COBERTURAS VEGETAIS

Organic matter is an indicator of the soil quality. Knowledge about its different components, explaining the influence of management practices on organic matter and soil aggregation, is essential for the sustainability of agricultural systems. In the present work, we evaluated humic substances, microbial activity and labile organic carbon in a Dystrophic Red Latosol from Minas Gerais state, Brazil, under natural vegetation (Cerradao) or under 30-years of conventional corn cultivation. Soil samples were collected from depths of 5-10 and 15-20 cm at four different sites. Then the samples were dried and fractioned in aggregate classes (diameter 4.75-2.0; 2.0-1.0; 1.0-0.5; 0.5-0.25; 0.25-0.105; and less than 0.105 mm). Furthermore, organic carbon of fulvic acid (AF), humic acids (AH) and humins (HUM) fractions, and labile organic carbon (COL) using KMnO4 15.6 and 33.0 mmol L-1 of the samples were determined. The material was further subjected to a respirometry test, in which CO2 production values were adjusted to logistic equations [Y = a/1 + e-(b + cx)] to estimate the time needed to achieve half of the maximum CO2 (t1/2), production. Results showed higher mean organic carbon contents in the AH fraction and COL with KMnO4 33.0 mmol L-1 of soil aggregates under conventional tillage. For AF and HUM fractions and COL with KMnO4 15.6 mmol L-1 this behavior was only observed in the 15-20 cm layer. The highest CO2 production was observed in the aggregates of the soil under Cerradao. The smaller aggregates tended to present higher organic carbon contents in the AF and AH fractions and COL. These were responsible for the highest CO2 production and constituted favorable sites of organic matter storage, due to the physical and chemical protection, as well as for mineralization, since microorganisms prefer these sites. The coefficients of the logistic equation (a, b, c) and the t1/2 can be considered important indicators of organic matter quality and lability under different managements.

Soil aggregation and organic carbon of Oxisols under coffee in agroforestry systems

Intensive land use can lead to a loss of soil physical quality with negative impacts on soil aggregates, resistance to root penetration, porosity, and bulk density. Organic and agroforestry management systems can represent sustainable, well-balanced alternatives in the agroecosystem for promoting a greater input of organic matter than the conventional system. Based on the hypothesis that an increased input of organic matter improves soil physical quality, this study aimed to evaluate the impact of coffee production systems on soil physical properties in two Red-Yellow Oxisols (Latossolos Vermelho-Amarelos) in the region of Caparao, Espirito Santo, Brazil. On Farm 1, we evaluated the following systems: primary forest (Pf1), organic coffee (Org1) and conventional coffee (Con1). On Farm 2, we evaluated: secondary forest (Sf2), organic coffee intercropped with inga (Org/In2), organic coffee intercropped with leucaena and inga (Org/In/Le2), organic coffee intercropped with cedar (Org/Ced2) and unshaded conventional coffee (Con2). Soil samples were collected under the tree canopy from the 0-10, 10-20 and 20-40 cm soil layers. Under organic and agroforestry coffee management, soil aggregation was higher than under conventional coffee. In the agroforestry system, the degree of soil flocculation was 24 % higher, soil moisture was 80 % higher, and soil resistance to penetration was lower than in soil under conventional coffee management. The macroaggregates in the organic systems, Org/In2, Org/In/Le2, and Org/Ced2 contained, on average, 29.1, 40.1 and 34.7 g kg-1 organic carbon, respectively. These levels are higher than those found in the unshaded conventional system (Con2), with 20.2 g kg-1.

Comparação entre métodos de amostragem do solo para recomendação de calagem e adubação do cafeeiro conilon

This study aimed to evaluate the soil sampling conventional methodology with spatial analysis for liming and fertilization with nitrogen, phosphorus and potassium on soil cultivated with conilon coffee. The trial was carried out during the 2004/2005 - 2005/2006 harvests in a 1.0 ha area with samples collected at 0-0.20 m depth. Fifteen sub samples in zigzag were collected for the conventional method forming a compound sample; as for the spatial method, 109 georeferenced points formed a sample grid. After the analysis results, the liming and fertilization needs were calculated based on the function of the element content in the soil and on the plant expected yield. Data were analyzed by both the classical statistics (descriptive and exploratory) and spatial analysis, using geostatistics techniques (modeling of the spatial variability structure and inferences) and geoprocessing (map algebra). Except for phosphorus in 2005 and potassium in 2006, every other recommendation showed spatial dependence. Data analysis by the spatial method provided the identification of zones with deficient or excessive liming and fertilization which could not be defined by the conventional sampling method (zigzag).

Propriedades físicas do solo em função de manejos em lavouras de cafeeiro conilon

Physical soil properties as a function of management in crops of conilon coffee Agricultural soils are subject to change in their properties, according to the type of use and management systems adopted. The objective of this study was to evaluate, in different sampling sites, the physical properties of soils cultivated with conilon coffee under different managements in the South of Espirito Santo State, Brazil. Samples were collected from the layers 0,00-0,20 m and 0,20-0,40 m in the upper part of the coffee plant canopy, in relation to the direction of the slope. Coffee crops, representative of the South of the Espirito Santo State, with the same soil class (dystrophic Red Yellow Latosol (Oxisol) hilly relief), were used for the study ,including the following managements: M1 – drip irrigation, liming every two years, fertilization, cleared and use of the straw of conilon; M2 - manuring, cleared and weedings; M3 - weedings and mowing. For each management, the following sampling sites were evaluated: UT upper third, MT - medium third; LT - lower third, along the slope. The physical soil properties evaluated were: bulk density, total porosity, macroporosity, microporosity and soil resistance penetration. For the experimental conditions, the soil resistance penetration, the macroporosity and microporosity important physical indicators of the quality of the soil were shown, influenced by the management, sampling site and evaluation depth.

Influência da capacidade de campo na taxa de crescimento do cafeeiro conilon

The objective of this work was to evaluate the influence of field capacity (FC) on the growth rate of the conilon coffee plant by using three tensions (0.006 MPa (FC1), 0.010 MPa (FC2) and 0.033 MPa (FC3)) in two soils (Red-Yellow Oxisol and Red-Yellow Ultisol). The experiment was carried out in a greenhouse at the Center of Studies and Technology Dissemination in Forestry, Water Resources and Sustainable Agriculture, in the municipality of JerBnimo Monteiro-ES. Plants of Coffea canephora Pierre ex A. Froehner, variety Robusta Tropical (EMCAPER 8151), were cultivated in 12 L containers for 255 days. Growth analyses were carried out 15 days after transplanting and at the end of the experiment total dry matter and leaf area were determined. The soil moisture level in the field capacity varied as a function of the tension chosen for its determination. The highest rates of relative and absolute growth of Conilon coffee plants were obtained when the soil moisture was kept close to the field capacity determined at 0.010 MPa in the Red-Yellow Oxisol and at 0.006 MPa in the Red-Yellow Ultisol. The lowest growth rates of the crop were found in the field capacity determined at 0.033 MPa, making it unfeasible to the use in the estimation of the irrigation sheet with the Richards pressure plate apparatus.

Substratos de origem orgânica para produção de mudas de teca ( Tectona grandis Linn. F.)

A utilizacao de residuos renovaveis como fonte de nutrientes para producao de mudas florestais pode ser uma solucao para problemas ambientais, principalmente relacionados a destinacao destes materiais. Neste contexto, este trabalho teve por objetivo avaliar a utilizacao de substratos renovaveis como componentes de substrato na producao de mudas de teca. As mudas foram produzidas em tubetes com capacidade volumetrica de 280 cm³, utilizando-se para a composicao dos tratamentos esterco bovino, cama de frango ou esterco de codorna associados a terra de subsolo e a uma fracao de 25% de substrato comercial florestal. Noventa dias apos a repicagem das plântulas, foram analisadas as seguintes caracteristicas morfologicas: altura da parte aerea (H), diâmetro do coleto (D), massa seca da parte aerea (MSPA), radicular (MSR) e total (MST) e o indice de qualidade de Dickson (IQD). Os resultados indicaram que as mudas produzidas com substratos formulados com a cama de frango apresentaram os maiores valores das caracteristicas analisadas, sendo que o tratamento com 35% deste material proporcionou os maiores indices em H, D, MSPA, MSR, MST e IQD. A utilizacao de substratos renovaveis pode ser indicada para producao de mudas de teca, contribuindo para a melhoria das propriedades quimicas dos substratos formados e, consequentemente, para a nutricao das plantas.

Phytomass production and nutrient accumulation by green manure species

Green manuring is recognized as a viable alternative to improve nutrient cycling in soils. The aim of this study was to evaluate the phytomass production and nutrient accumulation in shoots of the summer green manures jack bean [Canavalia ensiformis (L.) DC.], dwarf pigeon pea (Cajanus cajanvar var. Flavus DC.), dwarf mucuna [Mucuna deeringiana (Bort) Merr] and sunn hemp (Crotalaria juncea L.), under nitrogen fertilization and/or inoculation with N-fixing bacteria. A split plot design was arranged with the four Fabaceae species as main plots and nitrogen fertilization (with and without) and inoculation with diazotrophic bacteria (with and without) as the subplots, in a 2 2 factorial. The experiment was arranged as a randomized complete block design with four replications. In the conditions of this trial, the sunn hemp had the highest production of shoot phytomass (12.4 Mg ha -1 ) and nutrient accumulation, while the dwarf mucuna had the lowest production of shoot phytomass (3.9 Mg ha -1 ) and nutrient accumulation. The results showed no effect of nitrogen fertilization or inoculation with N-fixing bacteria on the production of shoot phytomass and nutrient accumulation, except for inoculation without nitrogen fertilization, resulting in greater P accumulation (p <0.05) in the sunn hemp and greater Zn and Mn accumulation in the dwarf mucuna. These findings indicate that N fertilization or inoculation with N2-fixing bacteria for Fabaceae are low efficiency practices in the edaphoclimatic conditions of this study.

Variabilidade espacial de atributos químicos do solo sob cafeeiro Conilon: relação com textura, matéria orgânica e relevo

Chemical properties are related to other soil attributes, including geomorphology, and constitute one of the factors that control spatial variability. The objective of this work was to evaluate the variability of soil chemistry and how it is interrelated with granulometric size fractions and organic soil components. Geostatistics and Principal Component Analysis (PCA) were used to describe the influence of topography. Spatial variability was more influenced by topography at lower depths. The PCA technique showed that attributes associated with soil reactions (pH, Ca, Mg, Al, V and m) contributed to the first prin cipal component (PC1) at the two studied depths. Only PC1 at the 0.0–0.1 m depth was, however, correlated to topography; higher altitudes and smaller slopes favored higher clay content and lower coarse sand proportion, thus resulting in increased retention of cations in the soil. The humic substances of organic matter have low influence on the variability of the chemical attributes, with the exception of Ca and Mg that are well related to humic acids in sites that are richer in sand. Homogeneous areas correlated with geomorphologic attributes was been describe for the K concentrations compared to other attributes at both depths. Thus, the use of spatial analysis for landscape stratification in homogeneous regions for the purpose of fertilizer management depends not only on topography, but on the chemical attributes evaluated and on sample depth.

Desempenho de sistemas de irrigação por aspersão convencional na cultura do milho (Zea mays L.)

In irrigated agriculture inadequate uniformity of water application in irrigation systems provides an excess of one part of the acreage and a deficit in another, reducing the availability of water to corn and increasing the cost of production. The objective of this study was to evaluate in the field the performance of systems for conventional sprinkler irrigation in the south of the state of Espirito Santo. Five irrigation projects with conventional sprinkler irrigation were chosen randomly. Each project was tested for uniformity of application of water by determining several coefficients of uniformity (Coefficient of Uniformity of Christiansen, Coefficient of Statistical Uniformity and Coefficient of Uniformity of Distribution), and for the efficiency of application of water. The results show that 60% of the irrigation projects with conventional sprinkler irrigation evaluated presented low uniformity of application of water; that the depth of water applied in the appraised period is superior to the required depth for the plant; and that the average of the application efficiency in the projects was 71.88%, below the 75% recommended in the literature as the acceptable minimum