Ivo Jucksch

Crescimento e acúmulo de nutrientes por plantas espontâneas e por leguminosas utilizadas para adubação verde

As especies vegetais espontâneas, nas areas de cultivo agricola, tem sido tratadas como “plantas daninhas”, “ervas invasoras”, “incos” e outras denominacoes, do ponto de vista dos prejuizos que podem acarretar as especies cultivadas. No entanto, as espontâneas podem promover os mesmos efeitos de protecao do solo e ciclagem de nutrientes que especies cultivadas ou introduzidas para adubacao verde. O crescimento e o acumulo de nutrientes pela parte aerea de espontâneas e de leguminosas utilizadas como adubos verdes foram medidos em um experimento de campo em Sete Lagoas (MG), na Embrapa Milho e Sorgo. O experimento consistiu de cinco especies de leguminosas (feijao-de-porco, feijaobravo do Ceara, mucuna-preta, lab-lab e guandu), submetidas a duas condicoes de manejo (com e sem capina), e uma testemunha (somente espontâneas). No florescimento das leguminosas, foram obtidos a massa da materia seca e o teor de nutrientes da parte aerea de cada especie de leguminosa e das espontâneas presentes nas parcelas. O sistema com apenas as espontâneas produziu menos biomassa e acumulou menos nutrientes que os sistemas com leguminosas. Foram poucas as espontâneas que apresentaram teores de carbono, calcio e nitrogenio proximos ou superiores aos das leguminosas. No entanto, para potassio, magnesio e fosforo, ocorreu o inverso. A maioria das espontâneas apresentou teores de potassio, magnesio e de fosforo superiores aos das leguminosas, destacando-se: Portulaca oleracea, Euphorbia heterophylla, Bidens pilosa, Commelina benghalensis e Melanpodium perfoliatum.Spontaneous plant species in agricultural areas have been regarded as weeds, invasive or unwanted plants, when considering the damages that they can bring to cultivated species. However, spontaneous species can bring about the same effects of soil protection and nutrient cycling that cultivated or introduced species used for green manure do. Biomass productivity and nutrient accumulation for the aerial part of spontaneous and leguminous plants used as green fertilizers were measured at the experimental station Embrapa Corn and Sorghum, in Sete Lagoas, Minas Gerais (Brazil). The experiment comprised five leguminous species (Canavalia ensiformes, Canavalia brasiliensis, Mucuna aterrima, dolichos lablab and Cajanus cajan) tested in two growing conditions (with and without weeding), and a control (only spontaneous species). At flowering of the leguminous species, dry matter and nutrient level of the aerial part, for each leguminous and spontaneous species present in the parcels, were obtained. The system which had only spontaneous species produced less biomass and accumulated less nutrient than the systems with leguminous species. Few spontaneous species presented carbon, calcium and nitrogen levels which were close to or larger than the leguminous one. However, the inverse occurred for potassium, magnesium and phosphorus. Most spontaneous species presented potassium and magnesium levels, and several of them, phosphorus levels , larger than the leguminous ones. With regard to levels of phosphorus, potassium and magnesium, the following spontaneous species stood out: Portulaca oleracea, Euphorbia heterophylla, Bidens pilosa, Commelina benghalensis and Melanpodium perfoliatum.

Carbono e nitrogênio em agregados de Latossolo submetido a diferentes sistemas de uso e manejo

The objective of this work was to evaluate the changes occured in the forms of carbon (C) and nitrogen (N), in aggregates of an Oxisol with loam texture, submitted to different uses and managements, in Capinopolis, MG, Brazil. Soil samples were collected in the different layers 0-5, 5-10 and 10-20 cm. The treatments were: no-tillage, during four years, succession corn (ensilage)/soybean (PDs); no-tillage during four years, succession corn/corn/corn/soybean (PDg); no-tillage with tifton (hay) for tree years and soybean in the last year (PDtf); conventional tillage system for 30 years with crop system (corn/soybean), being soybean in the last four years (SC); and native forest (MN). Three aggregate classes (4-2; 2-0.25 e 0.25-0.105 mm) were studied, from which humic fractions were extracted (fulvic acids, humic acids and humins). The largest contents of humic substances were associated with the larger aggregates. There was decrease of C and N contents with decrease in the size of aggregates classes. The less recalcitrant organic matter was associated with the smaller aggregates. The use and management systems cause changes in the C and N contents in the different classes of aggregate sizes, and the soil cultivation reduces the C and N contents of the humic fractions.

Organic-Matter Pools of Soil under Pines and Annual Cultures

When submitted to different uses and managements, soils can suffer alterations in the amount and in the quality of carbon and nitrogen present in the soil. This studys objective was to evaluate carbon and nitrogen in different compartments of the organic matter of the soil under savannah, 30-year-old pine plantation, and annual cultivations with corn and soy under conventional preparation and direct planting after 10 years of age. The substitution of the savannah for the pines and annual cultures reduces the carbon and total nitrogen in the soil. Among the compartments, only the particulate-free light fraction is not reduced in the Pinus in relation to the savannah. No tillage presents potential for improvement of the quality of the soil to make the fractions of carbon more labile in the soil. The more labile fractions reflect the alterations well imposed in the use and management of the soil, and they can be used as sensitive and premature indicators of the quality of the soil. They can be used for calculation of the carbon management index.

Distribution and Quality of the Organic Matter in Light and Heavy Fractions of a Red Latosol under Different Uses and Management Practices

The objective of this study was to evaluate changes in distribution and quality of organic matter in light and heavy fractions of a medium-texture Red Latosol under different uses and management practices in Capinópolis, Brazil. Soil samples were collected from different layers in the profile (0–5, 5–10, and 10–20 cm). The following treatments were evaluated: NTs, no till (no tillage) for 4 years with maize (silage) / soybean in succession; NTg, no till for 4 years with maize/maize/maize/soybean in succession; NTtf, no till for 3 years with tifton (hay) and soybeans in the last year; CS, about 30 years with conventional cultivation system (maize/soybean) with only soybean in the past 4 years; and NF, native forest. The heavy fraction contributed 75–98% of total carbon and 94–99% of total nitrogen, indicating that most carbon and nitrogen in the soil are associated with the mineral fraction, which is fundamental for the maintenance of their stocks. Tifton grass in no tillage was efficient in increasing the amounts of light fraction (free and occluded). Increases of occluded light fraction in no-till systems were greater than in conventional cultivation system. The light fraction was shown to be sensitive to soil cultivation and can be considered indicative of soil degradation. Light-fraction analysis by Fourier transform infrared spectroscopy (FTIR) allowed the study of changes in the chemical structure of these fractions under different uses and management practices. Occluded light fraction was shown to be more recalcitrant and condensed than the free light fraction. The surface layer in the conventional cultivation system has a more aromatic and condensed free light fraction than in no-tillage system. In general, the upper layers were less aromatic than the deepest ones.

Lipid abundance and composition of a humic Oxisol as a function of land use

Soil organic matter of a humic Oxisol has been characterized by analyzing litter and soil lipid composition under vegetal covers (coffee, pasture and fragment of native forest). Soil and litter samples were collected from each site at two depths (0-10 and 60-100 cm). Lipid composition was determined by gas chromatography-mass spectrometry (CG-MS). In the solvent extracts of the soil lipids, even-numbered n-alkanoic acids in the range of C16-C32 indicate a soil organic matter input from higher plant waxes. The major compound classes in both the soil and the litter included saturated n-alkanoic acids, with average values in the total spectrum of 58 and 53%, respectively Clear differences in lipid composition were found between the topsoil and subsurface. Long chain alkylic compounds (alkanoic acids and alkanes) accumulated preferably at depths of 60-100 cm. On the surface, the soil from natural vegetation had a total lipid value higher than those cultivated soils, and showed a predominance of unsaturated alkanoic acids at 60-100 cm. Preservation of alkylic moieties with depth was observed under forest and pasture, indicating that these systems of land use are prone to lipid accumulation. Lipids, especially the long-chain (> C20) ones, may be important with regard to C stabilization and humification processes in subsoil of humic Oxisols, highlighting the importance of lipids compounds in the bulk structure of organic matter these soils.

Impacto do monocultivo de café sobre os indicadores biológicos do solo na zona da mata mineira

This study aimed to evaluate the effect of the coffee monoculture in an oxisol of the Zona da Mata (MG, Brazil) through changes in total organic carbon in the soil and microbiological indicators of soil quality. Four areas were selected: a) culture of coffee (Novo Mundo) during 22 years (C22); b) culture of coffee (Catuai) during 16 years (C16) c) secondary forest with approximately 30 years old (M30) and d) secondary forest during 40 years (M40). Soil samples were collected in the depth of 0-10cm in January, April, July and October. The biological variables studied were sensitive to characterize changes in soil quality from coffee monoculture. The results varied with the season and climate. In the driest period, a reduction in the values occurred, affecting more drastically the coffee systems. The index of soil quality showed that the C22 system presented greater loss of quality in relation to the M40, indicating less sustainability commitment.

Organic‐Matter Lability and Carbon‐Management Indexes in Agrosylvopasture System on Brazilian Savannah

Abstract The effect of the introduction of an agrosylvopasture (SASP) system on the changes in the carbon (C) of the soil and its lability were studied. Since 1993, this system has been annually implanted in Paracatu, MG. It was planted under eucalyptus forest abandoned after three cuts, when the brachiaria grass was established. The eucalyptususes were planted at 10×4 m spacing, and the following crops have been grown between the lines: rice in the first year, soybean in the second, and brachiaria in the third. After the third year, pasture of the meat cattle begins on brachiaria and remains until the end of the system cycle that was foreseen for the 11th year. A savannah area and another one with eucalyptusus under a conventional system were used as references to natural condition and the way the area is used before plantation of the SASP, respectively. Some samples aged 1, 2, 3, 6, and 10 years were collected in SASP. According to the obtained results, the following conclusions were drawn: (i) the C contents and stocks were affected before and during the plantation of the SASP by the use and management of SASP, as they were reduced in the first years of the system establishment but improved at the 10th year; (ii) the C from the particulate free light fraction (CFLLP) that was extracted by potassium permangate (KMnO4) was sensitive to the use and management, and so reflected the changes in total organic C (TOC); (iii) the more labile fractions of C that were extracted at different concentrations of sulfuric acid (H2SO4) satisfactorily reflected the changes in both use and management, whereas the less labile fractions were just slightly affected; and (iv) the C management index (IMC) calculated from CFLLP was the most sensitive to the changes in use and management. However, when calculated from the C fraction 1 extracted by 3M H2SO4 (CF1), it showed better reliability.

Mudanças no carbono e nitrogênio em diferentes compartimentos da matéria orgânica sob sistema agrossilvipastoril

Since 1993, an agro-forestry pasture system has been annually implanted in Paracatu, Minas Gerais State. So, the effects from its introduction upon the changes in carbon and nitrogen at different compartments of the soil organic matter were studied. This system is implanted in soil under eucalypt forest that was abandoned after three removal cuts. In the first year, besides planting the eucalyptuses in interlines at spacing 10 x 4 m, the following crops are grown: rice in the first year; soybean in the second one; and the brachiaria in the third one. After the third year, the brachiaria pasture by meat cattle was begun and remaining in that area until the end of the system cycle, what is foreseen for the 11 th year. A savannah area and another one with eucalypt planting under the conventional system were used as reference to natural condition and previous conditions to implantation of the agrosylvopasture system. Samples aged 1, 2, 3, 6, and 10 years were collected. The results show significant decrease in the contents and stocks of both total carbon and nitrogen, as well as in microbial biomass. As the system becomes older, it starts a tendency for the recuperation of the contents and stocks of those fractions. Among the humic substances, the fulvic acid fraction was less affected by the introduction of this system. Briefly, the results show the system is unfavorable to the maintenance of the soil organic matter at the first years, but presents a potential for recovering as its age advances.

Simulation using the Century Model of the Carbon and Nitrogen Stocks in Latosols of the Brazilian Cerrado

O uso de modelos matematicos pode ser util para o entendimento das alteracoes do uso e manejo do solo e fornecem subsidios para testar cenarios futuros, possibilitando desenvolver estrategias de manejo menos impactantes ao meio ambiente. Os objetivos deste trabalho foram: (a) usar o modelo Century v4.5 para simular os efeitos dos usos e manejos sobre os estoques de carbono e nitrogenio do solo em diferentes compartimentos, (b) comparar os estoques medidos e simulados pelo Century, e (c) testar impacto de cenarios futuros ate o ano de 2100. Os tratamentos avaliados foram Pinus, plantio direto e plantio convencional, com historico das areas ate o momento da coleta de solo (2004). Para o Pinus foram testados tres cenarios futuros, um deles simulando o mesmo manejo adotado ate o momento da coleta de solo, outro reduzindo os eventos de fogo, alem do uso sem preparo do solo para o replantio. Para o plantio direto e plantio convencional, simularam-se dois cenarios futuros, um com rotacao milho/soja e outro com monocultura de milho. O modelo Century foi sensivel as mudancas de manejo adotadas, os compartimentos mais labeis apresentam maior sensibilidade (ativo e lento), do que o mais estavel (passivo). Em relacao ao estoque de C, o modelo simulou estoques proximos aos medidos no campo, com um erro minimo de 0,36%. Para os estoques de N, os valores simulados apresentaram erro de 5,71% para os compartimentos mais labeis. Os cenarios futuros mostraram a importância de se evitar queimadas no Pinus e o uso de monocultivo.

Percepção ambiental e uso do solo por agricultores de sistemas orgânicos e convencionais na Chapada da Ibiapaba, Ceará

The increase of the organic food market has been promoting the interest of farmers in the organic production systems. Agents who adopt this system implement substantial changes in their production methods, by acquiring technical and empirical associated knowledge. Therefore, it is necessary to elaborate studies to evaluate organic agriculture systems in this scenario, comparing it with the conventional production model, focusing on social, economic and environmental aspects. This study aimed the regional diagnostic of the social, economic and environmental aspects of the organic and conventional agricultural systems in the Sussuanha district, located in North Guaraciaba and Sao Benedito municipalities (Ceara State). Seven farmers that practice organic agriculture were interviewed, as well as 20 conventional producers, characterizing all the social context and changes on life quality along the time. In the organic agricultural system, interactions between farmers and environment carried out the improvement of life quality. On the other hand, in the conventional production system, characterized by the use of pesticides and chemical fertilizers, the interest to obtain maximum production with no concerning with the environment prevails. This situation is a result of the continuous use of pesticides, marketing restrictions and land degradation by lowering the natural fertility of the soil on this type of production system.