Substitution Of Native Vegetation Research Articles

CHANGES IN LAND COVER AND RELATIONS WITH THE EQUATION UNIVERSAL SOIL LOSSES IN BASIN OF THE WESTERN PLATEAU OF SAO PAULO IN BRAZIL

The soil loss has become a problem of environmental degradation in Southeastern Brazil. In a region of tropical climate, with precipitations concentrated in summer and sandy soils, the substitution of native vegetation by pasture and cultivation of sugarcane caused changes in the hydrological regime of the hydrographic basins. Soil degradation conditions, with marks present in the landscape, need to be quantified by empirical methods. In the estimates of water erosion, the most used method is the Universal Equation of Soil Losses. The method of estimating soil losses by generating geographic information and spatial data. The Confusion Stream’s basin is located in a region with replacement of pasture areas planted by sugarcane crop for fuel production. This research aims to estimate soil losses in a basin from comparative data from 2009 and 2018, derived from analysis of CBERS satellite images, with spatial resolution of 20 meters, in the mapping of land cover, through the classification of images in the IDRISI geographic information system. Rainfall erosivity factors and soil erodibility were obtained from secondary sources. The topographic factor was obtained from the processing of data from the Shuttle Radar Topography Mission. The areas of the land cover classes were related to factor C of the USLE and data estimates of secondary sources of erosivity factor (R), erodibility factor (K) and topographic factor with the data of slope (LS). From these parameters, an estimate of soil loss was presented for the basin of Confusion’s Stream. The soil loss in the basin of Confusion’s Stream was estimated by 2018 data at 2,484 t/ha/y.

Irrigated sugarcane crops improve the quality of soil organic carbon over time

The substitution of native vegetation in agricultural systems can cause several changes in the chemical and physical soil attributes, and in the dynamics of soil organic carbon. This study aimed to evaluate changes in soil physical attributes and carbon stock in soil organic matter fractions in irrigated sugarcane crops, as a function of land use and straw management practices over time, in the North of Minas Gerais State, Brazil. Four sugarcane fields with different ages and management systems were studied: Cane 6, Cane 7, Cane 8, and Cane 10. The data obtained were compared with a native vegetation area located near the sugarcane fields, and used as reference for unmanaged soil. In each system, soil samples were collected in the 0-10, 10-20, and 20-30 cm depth layers, to determine the physical attributes, the total organic carbon, and the physical fractions of the soil organic matter. We found that the sugarcane management with the maintenance of a part of the straw on the soil surface contributes to the preservation of the soil structure and the most stable fractions of organic carbon over time. However, in the regions with high annual mean temperature and in the irrigated systems, the soil tillage for the renewal of the sugarcane fields significantly decreases the total soil organic carbon.

Soil Organic Matter Quality in Jatropha spp. Plantations in Different Edaphoclimatic Conditions

The substitution of native vegetation by agricultural ecosystems can change the quantity and quality of soil organic matter (SOM), and the intensity of these changes depends on the soil type, climate, and land use. The objective of this study was to evaluate the quality of organic matter in chronosequences of Jatropha cultivation in contrasting soil and climatic conditions. Soil samples were evaluated at depths of 0.00-0.10, 0.20-0.30, and 0.80-1.00 m in chronosequences located in Planaltina, Distrito Federal (Cerrado-Pasture-Jatropha), Dourados, Mato Grosso do Sul (Atlantic Forest-Corn-Jatropha), and Araripina, Pernambuco (Caatinga-Jatropha). To assess SOM quality, we determined C contents in the SOM fractions, C stocks, the carbon management index (CMI), the SOM humification index (HLIF), and the C and N concentrations in the microbial biomass. The conversion of native vegetation to agropastoral systems changed the composition of SOM in the biomes evaluated, especially in the surface layers. The CMI and the C and N contents in the microbial biomass were the most responsive to land use changes in all the biomes studied. The pasture improved SOM quality by increasing the CMI (116) and the C content by 8, 21, and 6 % in the organic, mineral, and organomineral fractions, respectively, while maintaining the SOM humification index and the C and N contents in the microbial biomass in the 0-0.10 m layer. The lowest values of C in the SOM fractions, the CMI (52), and C microbial biomass (136 mg kg-1) were observed for annual crops. Jatropha cultivation increased C contents in the SOM fractions, C stocks, the CMI, and C and N in the microbial biomass with an increase in cultivation time, which demonstrates the potential of this long-term system for improving SOM quality.

ATRIBUTOS MICROBIOLÓGICOS, QUÍMICOS E FÍSICOS DE SOLO SOB DIFERENTES SISTEMAS DE MANEJO E CONDIÇÕES DE CERRADO

The aim of this research was to evaluate the effect of soil use and management on its chemical, physical and microbiological attributes. The research was carried out from the winter (2007) to the summer (2008), in Dourados, Mato Grosso do Sul State, Brazil, in a Distroferric Red Latossol. Data were analyzed as a complete randomized experimental design, with 5 collected samples that established 5 replications per management system. The management systems were: Area 1: area alloted to reforestation; Area 2: conventional soil tillage; Area 3: no-tillage; Area 4: degraded forage; and Area 5: natural system (native forest). The evaluation of a management system in its first year of implementation was not sufficient to evaluate the impacts on soil physical and microbiological attributes. The substitution of native vegetation by cultivation systems can cause important alterations on soil chemical attributes from the first year of implementation. Microbiological attributes were efficient indicators of alterations in physical attributes according to the soil use and management. KEY-WORDS: Soil quality; microbial biomass carbon; management practices.

Biomassa microbiana e matéria orgânica leve em solos sob sistemas agrícolas orgânico e convencional na Chapada da Ibiapaba - CE

Em muitos casos, a substituição da vegetação nativa por sistemas agrícolas resulta em decréscimo nos conteúdos de C e N nos diferentes compartimentos da matéria orgânica do solo. Para testar se as práticas de manejo que priorizam o aporte de resíduos orgânicos promovem aumento dos compartimentos da matéria orgânica mais sensíveis ao manejo, este estudo se propôs estudar áreas de uma propriedade que utiliza um sistema de produção de acerola em larga escala, sob manejo orgânico, e uma área sob cultivo convencional de cenoura e beterraba em rotação com milho, pertencentes à Fazenda Amway Nutrilite do Brasil e à Associação de Horticultores do Pivot Central, respectivamente, ambas localizadas na região da Chapada da Ibiapaba, Ceará. Selecionou-se, também, uma área de pastagem localizada no interior da primeira propriedade amostrada, bem como áreas sob mata nativa, próximas às áreas de cultivo. Amostras de um Neossolo Quartzarênico foram coletadas nas profundidades de 0-5 e 5-15 cm e foram determinados os teores de C orgânico total, de C e N microbiano (Cmic e Nmic) e da matéria orgânica leve (Cmol e Nmol), além do C mineralizável obtido por respirometria. O acúmulo médio nos estoques de Nmic nas áreas sob manejo orgânico em relação à mata nativa foi de 11,7 kg ha-1, o que representou um incremento de 585 % de Nmic nas áreas de cultivo. Já na pastagem, ocorreu acúmulo de 211 kg ha-1 no estoque de Cmic em relação à mata nativa em subsuperfície, representando um incremento de 514,6 %. Por outro lado, os estoques de Cmic no cultivo convencional sofreram reduções de 59 e 53 %, nas camadas de 0-5 e de 5-15 cm, respectivamente, em relação à mata nativa. Os estoques de Cmol obtidos nas linhas de cultivo nos sistemas orgânicos apresentaram incremento de 106 %, na camada de 0-5 cm, em relação à mata; no sistema convencional, porém, constatou-se uma redução em 31 % no estoque de Cmol na camada superficial. Os resultados indicaram que o manejo realizado nas áreas sob cultivo orgânico com acerola e pastagem contribuiu para a manutenção e recuperação dos conteúdos de C e N da biomassa microbiana (BMS) e da matéria orgânica leve (MOL) do solo. Os incrementos e, ou, reduções de C e N nos compartimentos BMS e MOL, comparativamente à área nativa de referência, foram proporcionalmente maiores que os valores obtidos, quando considerados somente os estoques de C orgânico e N totais, principalmente na área sob sistema de cultivo convencional. Isto indica serem tais compartimentos sensíveis às mudanças no estado da matéria orgânica de acordo com o manejo. Os sistemas de manejo orgânico e pastagem constituem estratégias de manejo importantes que devem ser consideradas para a conservação e, ou, aumento da matéria orgânica e, conseqüentemente, para a melhoria da qualidade do solo e implementação do seqüestro de C na região da Chapada da Ibiapaba, Ceará.