Low Carbon Technologies for Agriculture in Dryland: Brazilian Experience

Anthropogenic activities have altered the atmospheric composition since the industrial era, especially with the increasing greenhouse gas emission due to fossil fuel combustion, cement production, and land-use change. The Brazilian semiarid, covering approximately 969.589 km2 with 21 million people, region has 1.6 million agricultural establishments and 95% are classified as family farms. The typical agricultural systems are characterized by high grazing density, slash and burn practices, and fruits and legumes by irrigated monocultures. Consequently, soil degradation occurs due unsustainable soil management, decreasing soil carbon stock, and the biodiversity. The soil carbon depletion is also associated with saline, water, and thermal stresses. Saline, water, and thermal stresses in dryland, the impact of the land-use change associated with climate change, and few technological resources available for use in agricultural systems are the main reasons responsible for low productivity in the Brazilian semiarid region. Low-cost agricultural practices can contribute to build healthy and sustainable agroecosystems: among these, the selection of plant species tolerant to saline, water, and thermal stresses, the use of rhizobial inoculants, adoption of no-tillage, sowing green manure, and adoption of technologies to stock water to improve its efficiency and productivity

Atributos químicos e qualidade da matéria orgânica do solo em sistemas de colheita de cana-de-açúcar com e sem queima

The objective of this work was to evaluate soil chemical attributes, to quantify soil contents and stocks of C and N, and to evaluate the chemical quality of soil organic matter in sugarcane harvest systems with or without burning. Cultivated sugarcane areas were evaluated with or without burning of the fields at 6 and 12 years after the last renovation of the sugarcane fields. In addition, a native vegetation area and another one cultivated for 19 years without burning were also evaluated. Soil C content in the unburnt areas was higher thanthat of the burnt ones and lower than that of the areas with native vegetation. Carbon stock at the 0.0–0.3-m soil depth in the burnt areas was 22% lower than in the 6-year unburnt area and 43% lower in the 12-year area. The highest humification degrees occurred in the 19-year unburnt area; and the lowest, in the native vegetation area. The cultivated soils showed higher concentration of phenolic and carboxylic groups in humic acids. Soil fertility increases in the unburnt sugarcane areas because of their more humified organic matter and of the higher quantity of carboxylic and phenolic groups.O objetivo deste trabalho foi avaliar atributos químicos do solo, quantificar os teores e os estoques de C e N, e avaliar a qualidade química da matéria orgânica do solo em sistemas de colheita de cana-de-açúcar com ou sem queima da palhada. Áreas cultivadas com cana-de-açúcar foram avaliadas com ou sem queima da palhada, aos 6 e aos 12 anos após a última reforma do canavial. Além disso, também foram avaliadas uma área de vegetação nativa e outra cultivada por 19 anos sem queima. O teor de C no solo das áreas sem queima foi superior ao daquelas queimadas e inferior ao da área com vegetação nativa. O estoque de C a 0,0–0,3 m deprofundidade, na área queimada, foi 22% menor do que o na área sem queima, aos 6 anos, e 43% menor, aos 12 anos. Os maiores graus de humificação ocorreram na área sem queima por 19 anos; e os menores, na área com vegetação nativa. Os solos cultivados apresentaram maior concentração de grupos fenólicos e carboxílicos nos ácidos húmicos. A fertilidade do solo aumenta em áreas de cana-de-açúcar sem queima, em razão da matéria orgânica do solo mais humificada e da maior quantidade de grupamentos carboxílicos e fenólicos

Mapeamento da desertificação do semiárido paraibano com base na sua cobertura vegetal e classes de solos

In the semiarid region of the state of Paraíba there are plenty biophysics where vegetation, climate, soils and the various faces and the relationships and processes that take place between them generate the formation of different ecosystems and habitats with great potential ecological and environmental . There are in the region of vegetation ranging from vegetation, shrubby areas with coverage up to very sparse and mostly absent, setting up in areas where high desertification process. Similarly a variety of soils that are in the region along with vegetation makes this a region of great variation from the viewpoint of environmental supply. This article deals with the realization of a diagnosis of environmental sensitivity to desertification of semiarid paraibano seeking spatialize the different situations in which the environment fulfills a greater or lesser extent, its role as provider of environmental services. For this, we used the mapping of existing vegetation and soil mapping of the state and the established criteria, as well edaphic vegetation cover, featuring the susceptibility to degradation and performed the intersection of these two bases of information to profile the sensitivity to desertification. The results show that the semi-arid region of Paraiba has the following values of areas undergoing desertification: 5.76% in class weak; 8.39% in the moderate class; 62.48% in class sharp and severe 23.36% in class.Pages: 3112-311

IMPACTO DO MANEJO CONVENCIONAL SOBRE PROPRIEDADES FÍSICAS E SUBSTÂNCIAS HÚMICAS DE SOLOS SOB CERRADO IMPACT OF CONVENTIONAL MANAGEMENT UPON BOTH PHYSICAL PROPERTIES AND HUMIC SUBSTANCES OF SOILS UNDER CERRADO

A utilização do manejo convencional em solos sob cerrado tem acarretado modificações nas suas propriedades, bem como no comportamento e qualidade da sua matéria orgânica. O objetivo desta pesquisa foi investigar o impacto do manejo convencional nas propriedades físicas e no conteúdo e qualidade de substâncias húmicas de um Latossolo Vermelho-Amarelo, originalmente sob cerrado. O estudo foi realizado em uma propriedade agrícola no município de São Desidério-BA. Foram avaliadas quatro áreas sob diferentes períodos de uso e uma sob cerrado nativo. Os tempos de uso foram de um, dois, três e seis anos, sendo que a área estudada após seis anos passou por um período de três anos de pousio. O sistema de preparo do solo utilizado foi o tradicional da região, que consiste no uso de duas passadas de grade pesada aradora e duas de grade niveladora. Também foram realizadas, na ocasião de cada plantio, uma adubação com N-P-K + micronutrientes e calagens com base em resultados de análise de solo. As áreas foram cultivadas com milho e soja em sistema de rotação. Verificou-se que o manejo adotado não foi sustentável, pois já nos primeiros três anos de uso agrícola, ocorreu grande deterioração das propriedades físicas do solo, como densidade, porosidade e conteúdo de água disponível. O processo de humificação e a qualidade da matéria orgânica foram influenciados pela aplicação de calcário e pela rotação de culturas (milho/soja) e, ainda, que o sistema de manejo utilizado mostrou-se mais benéfico para o processo de estabilização das substâncias húmicas do que para as propriedades físicas dos solos estudados.The utilization of intensive conventional management system on soils under cerrado biome has caused modification in their properties, as well as, in the behavior and quality of the organic matter. The objective of this research was to evaluate the impact of conventional soil management practices upon physical properties, contents and qualities of humic substances of a Red-Yellow Oxisol, formerly, under cerrado (savana-like) natural vegetation. The study was accomplished on an private agricultural property in the municipal district of São Desidério-BA. They were appraised four areas under different length of times of agricultural use and one area under native cerrado (savana-like). The length of time under agriculture use was one, two, three and six years, and after six years the studied area was left uncultivated for a period of three years. The soil has been prepared under traditional systems which consists of plowing the land twice with heavy disks followed by twice grading. It was also applied, during the seedling time, N-P-K fertilizer plus micronutrients and lime according to soil analysis. The areas have been cultivated with corn and soybeans in a rotation system. It was observed that the adopted management system was not sustainable, because, at the first three years under cultivation occurred a great deterioration of physical properties such as soil density, porosity and available water contents. The humification process and the quality of the organic matter were influenced by both utilization of lime and by the rotation system (corn/soybeans). The used system was more benefic for the process of stabilization of the humic substances than for the physical properties of the studied soils

Comportamento espectral do solo da Caatinga em diferentes tipos de manejos

The premise that guides this work is to discriminate, from reflectance measurements obtained in the laboratory, the chemical attributes of the same type of soil in three experimental areas of the Embrapa at systems of distinct management and land use. The systems of use and management of the soils are: organic mango crop, Caatinga degraded and Caatinga preserved. Thus, it is expected that the soil characteristics can be estimated by differences at reflected energy. From the spectral analysis was possible to identify the attributes existing in the samples because the absorption bands which varied in breadth and depth, but not in placement.In part, this can be attributed to organic matter that directly affects the biological characteristics of the soil acting as a carbon source, energy and nutrients for microorganisms and is significantly correlated with the intensity of reflectance across the spectrum. Thus, from the spectra, it was found that the content of organic matter is higher in the savanna preserved because it has a lower reflectance, while the cultivation of organic mango has a higher reflectance consequently a lower content of organic matter. This research aims to assist the technical progress of agriculture as the basis for planning without affecting the environmental aspects.Pages: 9080-908

Changing in chemical and physical attributes of a sandy soil under irrigated mango cultivation in semiarid region

Accelerated land use changes have been observed in Brazil. In Northeast, the Caatinga (native vegetation) has been replaced by fruit production, especially by mango and grapevine cultivation. Land use changes, tied to management techniques, can change the soil chemical and physical attributes. Thus, the present study aimed to evaluate the impact of irrigated mango cultivation in soil chemical and physical attributes in relation to the native Caatinga in the semi-arid region. The study was carried out at Boa Esperança Farm located in Petrolina, Pernambuco State, Brazil. In areas under irrigated mango and native Caatinga soil samples at 0-10 and 10-20 cm depth were collected. After collected and prepared soil samples, it was determined the macro (Ca2+, Mg2+, K+, P) and micronutrients (Cu2+, Fe2+, Zn2+, Mn2+) contents, Na content, electrical conductivity, pH, exchangeable acidity (Al3+) and potential acidity (H+Al). It was also determined soil texture, bulk density, particle density and total porosity. The mango cultivation increased the macronutrient contents, as well as, the micronutrients except for Fe2+ content. The physical attributes did not show difference comparing irrigated mango to native caatinga

Ácidos Húmicos em solo fertirrigado no Vale do São Francisco

A aplicação de ácidos orgânicos, principalmente húmicos (AH), associada à adubação mineral e orgânica pode levar a alterações nas propriedades dos AH do solo. No Vale do São Francisco, o uso de ácidos orgânicos vem despertando o interesse de produtores que usam sistema de irrigação. Entretanto, não são conhecidas as modificações que podem ocorrer nas características das substâncias húmicas do solo quando são aplicados ácidos orgânicos associados à fertilização mineral e estercos. Os objetivos deste trabalho foram avaliar e caracterizar, por métodos espectroscópicos (UV-Vis, Infravermelho, Fluorescência e RPE), as possíveis mudanças qualitativas no AH extraído de solo fertirrigado com duas fontes de fertilizantes (orgânica e mineral), associadas à aplicação de ácidos orgânicos comerciais na cultura da goiabeira. O experimento foi conduzido na Embrapa Semiárido, em Petrolina - PE. Os tratamentos utilizados foram: F - fertirrigação com fertilizantes minerais (ureia, fosfato monoamônio, cloreto de potássio); FE - F + aplicação de 20 dm³/planta de esterco; FH - F + fertirrigação com 30 dm³ ha-1 de Codahumus 20®; FEH - fertirrigação mineral + aplicação de 20 dm³/planta de esterco + fertirrigação com 30 dm³ ha-1 de Codahumus 20®, e R- tratamento testemunha, sem adubação. A relação E4/E6 dos AH variou de 4,8 a 5,4 para os tratamentos FEH e F. Os dados obtidos por meio da espectroscopia FTIR sugerem mistura de características aromático-alifáticas, grande quantidade de grupos carboxílicos e menor número de grupos nitrogenados para os AH dos tratamentos FEH, FH e FE. Os valores obtidos do índice A465 variaram de 1,04 a 1,74, referentes aos AH dos tratamentos FEH e FE. Verificou-se uma concentração de radicais livres orgânicos no AH do tratamento FEH (2,66 spins g-1 10(17)) três vezes maior do que o AH do tratamento F (0,95 spins g-1 10(17)). O esterco foi o responsável pelo maior de policondensação e grau de humificação do ácido húmico dos tratamentos FE e FHE