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 11th 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.Em um sistema agrossilvipastoril, que vem sendo implantado anualmente desde 1993, em Paracatu/MG, foi estudado o efeito de sua introdução sobre as mudanças nos teores de Carbono e Nitrogênio em diferentes compartimentos da matéria orgânica do solo. O sistema foi implantado em solo sob floresta de eucaliptos, abandonada após três cortes. No primeiro ano, além dos eucaliptos plantados em espaçamento de 10 x 4 m, nas entre linhas e entre linhas, respectivamente, foi realizado um cultivo com arroz (Oryza sativum sp), no segundo ano cultivou-se soja (Glicyne max sp) e no terceiro ano, a braquiária (Brachiaria bizantina sp). Após o terceiro ano, a prática de pastejo da braquiária por bovinos de corte foi iniciada, permanecendo na área até o final do ciclo do sistema, previsto para o 11° ano. Uma área de cerrado e outra área com eucaliptos em sistema de cultivo convencional foram usadas, como referência à condição natural e às condições existentes antes da implantação do sistema agrossilvipastoril, respectivamente. Foram coletadas amostras nas idades de 1, 2, 3, 6 e 10 anos do eucalipto. De acordo com os resultados, verificou-se que houve significativa diminuição nos teores e estoques de carbono e nitrogênio totais, bem como na biomassa microbiana. Com o avanço da idade do sistema, iniciou-se uma tendência para recuperação dos teores e estoques dessas frações. Entre as substâncias húmicas, a fração ácido fúlvico foi a menos afetada pela introdução do sistema. Verifica-se que o sistema agrossilvipastoril foi desfavorável a manutenção da matéria orgânica do solo nos primeiros anos, porém, apresenta potencial para recuperação da mesma com o avanço da idade

CARBON AND NITROGEN CHANGES IN DIFERENT COMPARTIMENTS OF THE ORGANIC MATTER UNDER AGRO-FORESTRY PASTURE SYSTEM

Em um sistema agrossilvipastoril, que vem sendo implantado anualmente desde 1993, em Paracatu/MG, foi estudado o efeito de sua introdu\ue7\ue3o sobre as mudan\ue7as nos teores de Carbono e Nitrog\ueanio em diferentes compartimentos da mat\ue9ria org\ue2nica do solo. O sistema foi implantado em solo sob floresta de eucaliptos, abandonada ap\uf3s tr\ueas cortes. No primeiro ano, al\ue9m dos eucaliptos plantados em espa\ue7amento de 10 x 4 m, nas entre linhas e entre linhas, respectivamente, foi realizado um cultivo com arroz ( Oryza sativum sp), no segundo ano cultivou-se soja ( Glicyne max sp) e no terceiro ano, a braqui\ue1ria ( Brachiaria bizantina sp). Ap\uf3s o terceiro ano, a pr\ue1tica de pastejo da braqui\ue1ria por bovinos de corte foi iniciada, permanecendo na \ue1rea at\ue9 o final do ciclo do sistema, previsto para o 11\ub0 ano. Uma \ue1rea de cerrado e outra \ue1rea com eucaliptos em sistema de cultivo convencional foram usadas, como refer\ueancia \ue0 condi\ue7\ue3o natural e \ue0s condi\ue7\uf5es existentes antes da implanta\ue7\ue3o do sistema agrossilvipastoril, respectivamente. Foram coletadas amostras nas idades de 1, 2, 3, 6 e 10 anos do eucalipto. De acordo com os resultados, verificou-se que houve significativa diminui\ue7\ue3o nos teores e estoques de carbono e nitrog\ueanio totais, bem como na biomassa microbiana. Com o avan\ue7o da idade do sistema, iniciou-se uma tend\ueancia para recupera\ue7\ue3o dos teores e estoques dessas fra\ue7\uf5es. Entre as subst\ue2ncias h\ufamicas, a fra\ue7\ue3o \ue1cido f\ufalvico foi a menos afetada pela introdu\ue7\ue3o do sistema. Verifica-se que o sistema agrossilvipastoril foi desfavor\ue1vel a manuten\ue7\ue3o da mat\ue9ria org\ue2nica do solo nos primeiros anos, por\ue9m, apresenta potencial para recupera\ue7\ue3o da mesma com o avan\ue7o da idade.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 11th 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

Effects of phosphate, carbonate, and silicate anions on CO2 emission in a typical oxisol from cerrado region

The effects of agricultural practices on greenhouse gases emissions (e.g. CO2) at the soil-atmosphere interface have been highlighted worldwide. The use of ground limestone has been considered as the main responsible for CO2 emission from soils. However, liming is need as conditioner of acidic soils and the CO2 emission can be compensated due to carbon sequestration by plants. This study simulated under laboratory conditions the effects of two common agricultural practices in Brazil (P-fertilization and liming) on soil CO2 emission. Columns made of PVC tubes containing 1 kg of a typical Dystrophic Red Latosol from Cerrado region were incubated with CaCO3 (simulating liming), CaSiO3 (simulating slag), and different doses of KH2PO4 (simulating P-fertilization). The soil columns were moistened to reach the field capacity (0.30 cm3 cm-3) and, during 36 days, CO2 emissions at the soil surface were measured using a portable Licor LI-8100 analyzer coupled to a dynamic chamber. The results showed that CO2 emission was influenced by phosphate, carbonate, and silicate anions. When using CaSiO3, accumulated CO2 emission (36-day period) was 20% lower if compared to the use of CaCO3. The same amount of phosphate and liming (Ca-carbonate or Ca-silicate) added to the soil provided the same amount of CO2 emission. At the same P dose, as Si increased the CO2 emission increased. The highest CO2 emission was observed when the soil was amended with the highest phosphate and silicate doses. Based on this experiment, we could oppose the claim that the use of limestone is a major villain for CO2 emission. Also, we have shown that other practices, such as fertilization using P + CaSiO3, contributed to a higher CO2 emission. Indeed, it is important to emphasize that the best practices of soil fertility management will undoubtedly contribute to the growth of crops and carbon sequestration

Recalcitrant carbon and nitrogen in agriculture soils with residue accumulation and fertilization under tropical conditions

Soil organic matter has a strong relation to total organic carbon, and about 85% of organic carbon consists of humic substances (HS), classified as humin (HU), humic (HA) and fulvic acids (FA), and denominated as recalcitrant carbon in soil. HS are formed by complex, heterogeneous and polydisperse molecules, which have significant influence on the soil physical and chemical characteristics. The study evaluates the hypothesis that agricultural soils treated with organic residues may present higher carbon stocks as presented in forest soils.  The aim of this study was to evaluate alterations in recalcitrant carbon and nitrogen stocks in Oxisol (Forest - FL, unfertilized Brachiaria - UB, and fertilized Brachiaria - FB) and Cambisol (Forest - FC, Coastcross - CC, sugarcane - CA, and silage corn - SM) at surface (0.0 - 0.1) and subsurface (0.1 - 0.2 m), in the Zona da Mata in Minas Gerais state, Brazil. Result shows that fertilization, low soil disturbance and residual removal promoted increase of C and N content in HS, being close to native forests. Both, carbon and nitrogen recalcitrant, presented reduction with soil depth. HU ranged from 10.5 to 16.7 g kg-1 and presented the highest concentration compared to FA and HA. In Oxisol, FL and FB presented the highest SH concentration and demonstrate the positive effect of fertilization on carbon stocks improving soil quality in well-managed and productive areas. While, In Cambisol, FC and CC presented higher carbon and nitrogen in HS, mainly for HU and HA fractions, and SM showed the lowest concentrations in all fractions. Our results suggest that soil managements with lower soil disturbance and residual removal promotes increasing of carbon and nitrogen in recalcitrant fraction, with concentration close to native forests. Pasture should be fertilized to improve recalcitrant carbon and nitrogen stocks, avoiding process of degradation in tropical soil. It is an important outcome due to high levels of degraded areas in Brazil caused by inadequate use of soil mainly with pasture

Effects of the use and management on the physical properties and on the organic carbon of a red latossol in the triangle of Minas Gerais-Brasil

Este estudo foi realizado com o objetivo de avaliar propriedades físicas de cinco áreas submetidas a diferentes usos e manejos. As amostras de solo foram coletadas em agosto de 2002, no final do período seco, em Capinópolis-MG. O solo do local é classificado como Latossolo Vermelho, textura franco-argilo-arenosa, com relevo suavemente ondulado. O clima é do tipo Aw, segundo a classificação de Köppen, com temperatura média anual de 23°C, precipitação média anual em torno de 1300 mm e vegetação nativa fase floresta subcaducifólia. Os tratamentos consistiram de diferentes usos: mata nativa e áreas cultivadas; e diferentes manejos: sistema de preparo convencional e plantio direto, onde dentro do último ainda foram avaliados três diferentes sistemas de manejo. Para a discussão dos resultados foram estabelecidos contrastes ortogonais para isolar os efeitos cultivo, plantio direto, tifton (gramínea perene) e silagem (de milho). Concluiu-se que: (i) o cultivo do solo levou a degradação física, comprovada pela redução da porosidade, da capacidade de aeração, dos teores de carbono orgânico total, da estabilidade de agregados e aumento da densidade do solo; (ii) o plantio direto contribuiu para a melhoria destas propriedades, porém ainda muito distante da mata nativa; (iii) entre os sistemas de plantio direto, aquele que utilizou a gramínea perene tifton, apresentou o melhor potencial para recuperação de propriedades físicas degradadas, podendo, portando, ser usada com sucesso para essa finalidade; (iv) a prática da silagem reduziu os teores de carbono orgânico total do solo, porém, as demais propriedades físicas avaliadas não foram afetadas significativamente; e (v) índices relacionando capacidade de aeração e capacidade de campo com porosidade total, foram sensíveis à adoção de diferentes usos e manejos.The goal of this study was to evaluate the physical properties of five areas subjected to different uses and managements. Samples were collected in August 2002, in Capinópolis-MG, at the end of the dry period. The soil of the location is a red latossol (Tipic Haplorthox, with textural class sandy-clay-loam). The climate belongs to the type Aw, according to Köppen's classification, with annual average temperatures of 23°C, annual average precipitation around 1300 mm. The treatments consisted of different uses: native forest and cultivated areas; and different managements: conventional cultivation and no tillage. Orthogonal contrasts were done among the treatments to isolate the effects of: cultivation, no tillage, tifton (hay) and silage (of corn). It concluded that: (i) the cultivation of the soil caused a physical degradation, proved by the reduction of the porosity, of the aeration capacity, of the contents of total organic carbon, of the aggregate stability and increase of the soil density; (ii) the no tillage contributed to the improvement of the physicals properties, however still very distant of the native forest; (iii) among of no tillage systems, perennial tifton grass introduced presented the best potential to recover the degraded physical properties, and can be used with success for this purpose; (iv) the practice of silage reduced drastically the contents of organic carbon of the soil, however the other physical properties evaluated were not significantly affected and; (v) the values of the relations: air capacity/total porosity and field capacity/total porosity can be used as indicators of the good physical quality of the soil.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Carbon and nitrogen in the soil under different uses and managements and your modelling by the Century

Toda mudança no uso e manejo pode induzir alterações nos estoques de C e N do solo. Neste sentido, este estudo foi realizado com os objetivos de verificar essas alterações em diferentes sistemas de uso e manejo, bem como verificar a capacidade do modelo Century em simular essas alterações, através da comparação dos estoques medidos com os simulados. Em Paracatu/MG, em um sistema agrossilvipastoril com eucalipto e arroz, soja e braquiária no primeiro, segundo e a partir do terceiro ano nas entre linhas, respectivamente, verificou-se que este sistema afeta negativamente o C e N do solo nos anos iniciais, e que, após o sexto ano, já percebe-se sinais de recuperação, que passam a ser significativos no décimo ano. Neste sistema testou-se também o uso de frações lábeis diferentes da usualmente usada para o cálculo do índice de manejo de C (IMC), onde, a fração de C extraída com H2SO4 3M/L e o C da fração leve livre particulada, apresentaram bom potencial para esse fim, por apresentarem resultados semelhantes ao método usual, que utiliza KMnO4 para extrair o C. Já em Sete Lagoas/MG, a superioridade do plantio direto em relação ao cultivo convencional nas culturas de milho e soja foi observada, principalmente nas frações mais lábeis, as quais respondem de maneira mais prematura as mudanças de manejo. Essa superioridade também foi constatada com o uso do modelo Century, que simulou estoques semelhantes aos medidos no campo. Ainda em Sete Lagoas/MG, em plantação de pinus, verificou-se pelas simulações com o modelo Century, que os estoques de C e N totais e respectivos compartimentos, são reduzidos nos anos iniciais, mas que são recuperados a medida que a cultura começa a incorporar material orgânico no sistema, através da queda da casca e acículas, bem como através das raízes. Em Coronel Pacheco/MG, verificou-se que o modelo Century simulou de maneira satisfatória os estoques de C e N totais, comprovado pela semelhança entre os estoques simulados e medidos. Nesse mesmo local, para a cultura da braquiária, verificou-se também pelos valores medidos e simulados pelo Century, que o uso de adubação química aumenta consideravelmente os estoques de C e N no solo. Na cultura do milho para silagem, também observou-se estoques menores em relação as demais culturas (cana-de-açúcar, tifton e braquiária) causados pelo uso intensivo de revolvimento do solo e retirada da parte aérea do milho e culturas olerículas cultivas anteriormente.Every change in the use and management can induce alterations in the C and N stocks of the soil. In this sense, this study was carried out to verify those alterations in the different use and management systems, as well as the capacity of the Century model to simulating those alterations, by comparing the measured stocks with the simulated ones. In Paracatú county-MG, in an agrosylvopasture system with eucalypts and rice, soybean and brachiaria on the first, second and from the third year in the interlines, respectively, it was verified that this system negatively affects C and N of the soil on the initial years, but recovery signs observed after the sixth year begin to be significant on the 10th year. In this system, the use of labile fractions different from that usually used for calculation of the C management index (IMC) were also tested, in which the C fraction extracted with H2SO4 3M/L and C of the particulate free light fraction showed good potential for this purpose, because their results were similar to the usual method that uses KMnO4 to extracting C. In Sete Lagoas county-MG, however, the superiority of the no-till planting in relation to the conventional cropping in maize and soybean crops was observed, mainly in the more-labile fractions that respond more prematurely to the management changes. This superiority was also verified, when using the Century model Century, that simulated stocks similar to those measured in the field. Also in pinus plantation in Sete Lagoas county, the simulations with the Century model showed that the stocks of C and total N and their respective compartments are reduced on the initial years, but they are recovered as the crop begins to incorporate organic material into system through the fall of the needles, as well as through the roots. In Colonel Pacheco county-MG, the Century model satisfactorily simulated the stocks of C and total N, which is proven by the similarity between the simulated and measured stocks. In this same place, for the brachiaria, the values measured and simulated by the Century model showed the use of the chemical fertilization considerably increases the stocks of C and N in the soil. In the crop of the maize for silage, lower stocks were also observed in relation to other crops (sugarcane, tifton and brachiaria) caused by intensive revolving of the soil and removal of the maize aerial part and vegetables previously cropped.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

How Does N Mineral Fertilizer Influence the Crop Residue N Credit?

In no-tillage systems, there is an accumulation of crop residues (CR), which plays an essential role in the availability of soil-N. A study was set up to provide information regarding the N credit and the influence of N mineral fertilizer. There was the addition of a similar rate of residue (10 Mg ha−1; sugarcane, soybean, and brachiaria) and N mineral fertilizer (urea; 120 kg N ha−1) in loam soil. After the stabilization of biological activity (73 days), soil and remaining residues were collected, and C and N monitored. The results showed that the N credit was positive with the application of soybean, sugarcane, and brachiaria. There was a positive balance of the soybean N credit in soil with a reduction from 2.49 to 0.90 g kg−1 of N in remaining residue, and a direct increase of 90% of soil-N. There is no need of N fertilizer to potentialize the soybean N credit, but it is required to potentialize N credit of brachiaria and sugarcane. The urea demonstrated to be an excellent enhancer of brachiaria N credit, but it was not adequate for sugarcane residues. Based on our result, the accumulation and incorporation of CR can be considered as N credit with a positive contribution in soil-N