Junior Cesar Avanzi

Erosividade da chuva e erodibilidade de Cambissolo e Latossolo na região de Lavras, sul de Minas Gerais

Relatively few studies in Brazil have investigated soil erodibility, mainly for Cambisols (Inceptisols), due to the tediousness of data collection in natural rainfall experiments. Knowledge about erodibility and erosivity is important for conservation planning, which contributes to soil sustainability. This study aimed at evaluating the rainfall erosivity and erodibility of a typic dystrophic Tb Haplic Cambisol (Inceptisol) and a typic dystroferric Red Latosol (Oxisol) under natural rainfall, in Lavras, state of Minas Gerais, Brazil, between 1998 and 2002. Pluvial precipitation data were obtained from the main weather station of Lavras, of the Universidade Federal de Lavras, close to the soil loss experimental plots. Erosivity (EI30) was calculated as the product of the rain kinetic energy by the maximum intensity in 30 min. Based on these data, correlated with the soil losses, the soil erodibility could be computed. The mean annual total precipitation was 1,287 mm and the mean calculated erosivity 4,865 MJ mm ha-1 h-1 year-1. The erodibility of the Cambisol was 0.026 Mg h MJ-1 mm -1 and of the Latosol 0.004 Mg h MJ-1 mm -1, in agreement with their differential mineralogical, chemical, physical and morphological properties.No Brasil, ainda sao relativamente poucos os estudos envolvendo erodibilidade do solo, principalmente Cambissolos, dada a morosidade na obtencao dos resultados de experimentos com chuva natural. O conhecimento dos indices de erosividade e de erodibilidade e importante para o planejamento conservacionista, contribuindo para a sustentabilidade dos solos. Este estudo teve como objetivos determinar a erosividade da chuva e a erodibilidade de Cambissolo Haplico Tb distrofico tipico e Latossolo Vermelho distroferrico tipico, sob chuva natural, em Lavras (MG), no periodo de 1998 a 2002. Os dados de precipitacao pluviometrica foram obtidos na Estacao Climatologica Principal de Lavras, localizada no campus da Universidade Federal de Lavras, proxima das unidades experimentais de perdas de solo. A erosividade (EI30) foi determinada a partir do produto da energia cinetica da chuva pela sua intensidade maxima em 30 min. Estes dados, correlacionados com as perdas de solo, permitiram obter o indice de erodibilidade dos solos. A precipitacao total media anual foi 1.287 mm e a erosividade media foi de 4.865 MJ mm ha-1 h-1 ano-1. A erodibilidade foi 0,0355 Mg h MJ-1 mm-1 para o Cambissolo e 0,0032 Mg h MJ-1 mm-1 para o Latossolo, em consonância com seus atributos mineralogicos, quimicos, fisicos e morfologicos diferenciais.

Perdas de solo, água, nutrientes e carbono orgânico em Cambissolo e Latossolo sob chuva natural

Water erosion is responsible for considerable losses of nutrients and organic carbon from agricultural soils. The reduction of soil, water, nutrients and organic carbon losses constitutes an important aspect of the conservation planning. The objectives of this work were to evaluate the soil, water, nutrients and organic carbon losses from a Typic Dystrochept (TD) and a Rhodic Hapludox (RH). The samplings were performed after each considered erosive rain event. The mean annual soil losses were 205.65 Mg ha -1 for the TD and 14.90 Mg ha -1 for the RH. The mean annual water losses were 369 mm for the TD and 113 mm for the RH, representing 28.67% and 8.78% of the total precipitation, respectively. The mineralogical, chemical and physical attributes and the relief where these soils occur satisfactorily explain the obtained results. The TD presents higher nutrients and organic carbon losses than the RH. The organic carbon was the main component of the eroded sediment, evidenced by the selective character of erosion.

Erosão hídrica em latossolo vermelho sob diversos sistemas de manejo do cafeeiro no Sul de Minas Gerais

A erosao hidrica contribui para a reducao da sustentabilidade dos sistemas agricolas. O presente estudo avaliou, sob condicoes de chuva natural, as perdas de solo, agua, nutrientes e materia orgânica em um Latossolo Vermelho distroferrico tipico, com 12 % de declividade, localizado na regiao de Lavras (MG). O trabalho foi conduzido em parcelas experimentais de perdas de solo. Os sistemas de manejo estudados foram: cafe sob cultivo convencional, com capina manual (CCC); cultivo convencional, com rocado (CCR); cultivo convencional, com utilizacao de herbicida (CCH); cultivo orgânico, com capina manual (COC); cultivo orgânico, com rocado (COR); e como referencia parcela com solo descoberto (SD). Nos sistemas de manejo em que foi mantida a cobertura da vegetacao espontânea (rocado), obteve-se maior eficiencia de protecao do solo quando comparado aos sistemas onde houve exposicao do solo (capina). No sistema com utilizacao de herbicida, observou-se um comportamento intermediario. Todos os sistemas de manejo estudados se mostraram conservacionistas quanto a protecao do solo em relacao a erosao hidrica, onde o espacamento adensado merece ser enfatizado.

Plantas de cobertura no controle das perdas de solo, água e nutrientes por erosão hídrica

R ESU M O Plantas com alto indice de cobertura e elevada produtividade de fitomassa propiciam melhor protecao ao solo, amortecendo o impacto das gotas de chuva sobre a superficie do solo reduzindo, consequentemente, os processos erosivos. Objetivou-se avaliar a influencia das plantas de cobertura e dos espacamentos de plantio no controle das perdas de solo, agua e nutrientes por erosao hidrica, visando a conservacao do solo. O experimento foi conduzido em um Argissolo Vermelho-Amarelo, cujos tratamentos foram definidos por tres especies de plantas de cobertura: crotalaria juncea, feijao-deporco e milheto e com dois espacamentos entrelinhas (0,25 e 0,50 m). Para a quantificacao das perdas de solo, agua e nutrientes, utilizaram-se parcelas de 4 x 12 m em que a maior dimensao obedeceu ao sentido do declive. Nos meses de dezembro e janeiro ocorrem os maiores valores de erosividade requerendo, neste periodo, melhor cobertura da superficie do solo. O feijao-de-porco foi a especie que apresentou maior potencial no controle dos processos erosivos; quanto ao espacamento a melhor protecao do solo para todas as culturas foi obtida no espacamento de 0,25 m, propiciando menores perdas de solo, agua e nutrientes. Palavras-chave: crotalaria juncea, feijao-de-porco e milheto

Water erosion in soils under eucalyptus forest as affected by development stages and management systems

The constant increasing of eucalyptus forest areas in Brazil requires an accurate monitoring of water erosion. The present study aimed to evaluate soil, nutrients and organic carbon losses occasioned by water erosion in eucalyptus planted forests (EPF) at different development stages (2, 3 and 7 years old). Soil erosion sediments were measured and sampled from standard erosion plots installed on Red Argisol-RA (Ultisol) and Haplic Cambisol-HC (Inceptisol). Soil loss decreased as the age of plants increased; at the beginning of plant development, the canopy barely covered the soil surface, exposing the soil to higher erosion at young EPF plantations. Furrow planting system was used in the Red Argisol area and caused higher soil losses (1.1 to 6.2 Mg ha-1 year-1) as compared to pit planting system that was used in the Cambisol area (1.1 Mg ha-1 year-1). It is known that Cambisol is less resistant to erosion than Argisol. However, using pit system in this EPF, resulted in lower erosion and, therefore, nutrients and carbon losses than the traditional furrow system used in Argisol. Concerning the soil loss, this work points to the need of improving soil conservation practices to prevent soil erosion at the earlier stages of eucalyptus plantation. The amount of calcium and potassium were higher than magnesium in the soil sediment.The relatively high amount of carbon found in the erosion sediments raises additional concerns about the environmental sustainability and deserves future research.

Sistemas de manejo em plantios florestais de eucalipto e perdas de solo e água na região do Vale do Rio Doce, MG

Water erosion is the main responsible for decreasing the productive capacity of soils under forest plantations and it changes the amount and the quality of water in sub-basins. Thus, this work aimed to evaluate the influence of management systems adopted in Eucalyptus forest plantations (eucalyptus in contour planting - EN, eucalyptus up and downslope planting - ED, and eucalyptus up and downslope planting with burning - EDQ) on soil and water losses by water erosion and to compare them with losses in native forest (FN), pasture (PP) and bare soil (SD), in a Red Latosol (LV) and Red-Yellow Latosol (LVA), indicating which is the most critical period in relation to water erosion during the cycle of Eucalyptus forest plantation. The study was carried out in two places: Belo Oriente (LVA) and Guanhaes (LV), located in ‘Doce’ River Valley, central and eastern region of Minas Gerais State, Brazil. Except for the SD system in the LVA, the average soil losses were below the limit of soil loss tolerance, in such regions, which are 11.22 Mg ha -1 yr -1 for the LV and 7.17 Mg ha -1 yr -1 for the LVA. The water losses in the eucalyptus systems were lower in the contour planting, in the LVA. In the eucalyptus systems, the periods immediately after planting showed the greatest soil and water losses with reduction at the final period. On the other hand, in the LVA, the bare soil and native forest systems increased water losses with the advancing of the evaluation period, indicating adequacy of Eucalyptus systems.

Spatial distribution of water erosion risk in a watershed with eucalyptus and Atlantic Forest

The process of water erosion occurs in watersheds throughout the world and it is strongly affected by anthropogenic influences. Thus, the knowledge of these processes is extremely necessary for planning of conservation efforts. This study was performed in an experimental forested watershed in order to predict the average potential annual soil loss by water erosion using the Universal Soil Loss Equation (USLE) and a Geographic Information System (GIS), and then compared with soil loss tolerance. All the USLE factors were generated in a distributed approach employing a GIS tool. The layers were multiplied in the GIS framework in order to predict soil erosion rates. Results showed that the average soil loss was 6.2 Mg ha-1 yr-1. Relative to soil loss tolerance, 83% of the area had an erosion rate lesser than the tolerable value. According to soil loss classes, 49% of the watershed had erosion less than 2.5 Mg ha-1 yr-1. However, about 8.7% of the watershed had erosion rates greater than 15 Mg ha-1 yr-1, being mainly related to Plinthosol soil class and roads, thus requiring special attention for the improvement of sustainable management practices for such areas. Eucalyptus cultivation was found to have soil loss greater than Atlantic Forest. Thus, an effort should be made to bring the erosion rates closer to the native forest. Implementation of the USLE model in a GIS framework was found to be a simple and useful tool for predicting the spatial variation of soil erosion risk and identifying critical areas for conservation efforts.

Comparação de distribuições de probabilidade e estimativa da precipitação provável para região de Barbacena, MG

Probabilistic studies involving climatic variables are of extreme importance for farming activities, construction, tourism, among others. Seeking to contribute for the planning of irrigate agriculture, this work had as objectives to compare adjusted probability distribution models to the monthly and decennial historical series and to estimate the probable rainfall for the Barbacena County, Minas Gerais State, Brazil. Rainfall data of December, January and February, from 1942 to 2003, were studied, constituting historical series with 62 years of observations. Daily rainfall depths were added for 10 and 30 days, applying Gama, log-Normal 2 and log-Normal 3 parameters probability distribution models. Probability distributions models, were compared with Qui-square statistical test, at 5% significance level. Probable rainfall was estimated for each period, using the best distribution, which was evaluated based on the smallest Qui-square value, for the probability occurrence levels of 75, 90 and 98%. Gama probability distribution was the most adequate model.

Soil losses from typic cambisols and red latosol as related to three erosive rainfall patterns

SUMMARY Rainfall erosivity is one of the main factors related to water erosion in the tropics. This work focused on relating soil loss from a typic dystrophic Tb Haplic Cambisol (CXbd) and a typic dystrophic Red Latosol (LVdf) to different patterns of natural erosive rainfall. The experimental plots of approximately 26 m 2 (3 x 8.67 m) consisted of a CXbd area with a 0.15 m m-1 slope and a LVdf area with 0.12 m m -1 slope, both delimited by galvanized plates. Drainpipes were installed at the lower part of these plots to collect runoff, interconnected with a Geib or multislot divisor. To calculate erosivity (EI30), rainfall data, recorded continuously at a weather station in Lavras, were used. The data of erosive rainfall events were measured (10 mm precipitation intervals, accuracy 0.2 mm, 24 h period, 20 min intervals), characterized as rainfall events with more than 10 mm precipitation, maximum intensity > 24 mm h -1 within 15 min, or kinetic energy > 3.6 MJ, which were used in this study to calculate the rainfall erosivity parameter, were classified according to the moment of peak precipitation intensity in advanced, intermediate and delayed patterns. Among the 139 erosive rainfall events with CXbd soil loss, 60 % were attributed to the advanced pattern, with a loss of 415.9 Mg ha -1 , and total losses of 776.0 Mg ha -1 . As for the LVdf, of the 93 erosive rainfall events with soil loss, 58 % were listed in the advanced pattern, with 37.8 Mg ha -1 soil loss and 50.9 Mg ha -1 of total soil loss. The greatest soil losses were observed in the advanced rain pattern, especially for the CXbd. From the Cambisol, the soil loss per rainfall event was greatest for the advanced pattern, being influenced by the low soil permeability.

Índice de cobertura vegetal pela cultura do milho no período de chuvas intensas no sul de Minas Gerais

A cobertura vegetal e a defesa natural do solo contra a erosao hidrica. Nos modelos de estimativas de perdas de solo, o efeito da cobertura vegetal na interceptacao da energia cinetica da chuva e a variavel chave na modelagem do processo erosivo. Assim sendo, objetivou-se avaliar a eficiencia da cobertura vegetal, proporcionada pela cultura do milho, e suas relacoes com os atributos fitotecnicos desta cultura para alguns hibridos. O estudo foi realizado no campo demonstrativo de hibridos de milho da Universidade Federal de Lavras, localizada no municipio de Lavras, MG. Para determinacao da cobertura vegetal utilizou-se um aparato que consiste em uma estrutura horizontal, contendo orificios para visualizacao dos pontos com cobertura e sem cobertura vegetal, sendo as leituras feitas de forma aleatoria e transversalmente as linhas da cultura. Os atributos fitotecnicos avaliados foram altura da planta, estande, materia seca e producao de graos. Diante dos resultados pode-se concluir que o maior indice de cobertura vegetal foi observado para os hibridos de milho P 30F33, P 30F90, P 3021, STRIKE, FORT, VALENT, UFLA 2001, UFLA 2004, CO 32, D 8480, D 8420 DKB 333B, DKB 440, evidenciando boa qualidade como planta protetora do solo. No periodo de maior ocorrencia de chuvas, na regiao sul de Minas Gerais, a cultura do milho pode minimizar o efeito do processo erosivo. A producao de materia seca relacionou-se bem com o indice de cobertura vegetal, podendo ser um indicativo quanto a protecao do solo.