Effect Of Soil Management Systems Research Articles

Effects of agricultural management and of climate change on N2O emissions in an area of the Brazilian Cerrado: Measurements and simulations using the STICS soil-crop model

Soil-plant simulation models have been ever more used as predictive tools to evaluate productivity and environmental impacts of agriculture practices. The aims of this work were to evaluate the STICS model’s capacity of simulate the emissions of nitrous oxide (N2O) under different management systems. And, to predict, by applying the calibrated and validated STICS model, the N2O emissions, under different management systems, in the edaphoclimatic conditions of the Brazilian Cerrado. The study was conducted in a long-term experiment at Embrapa Cerrados, located in Planaltina/DF, Brazil. The experiment started in 1995. The following land use systems were evaluated: CT - conventional tillage with disc harrow, and biannual grass/legume rotation; NT1 - No-tillage, with biannual crop rotation – soybean/sorghum; NT2 - No-tillage, with biannual crop rotation – maize/pigeon pea.Closed static chambers and gas sample analysis by gas chromatography were used to measure N2O fluxes. The model was calibrated with the data measured in the CT and NT1 treatments. The attributes used in the calibration were: growth, development and yield of crops and N2O fluxes. To test the model, data from the NT2 treatment was used. Data for all treatments were collected at the same time. After calibration and validation, the STICS model was used to predict the effects of soil management systems, conventional (CT) and no-tillage (NT) on greenhouse gas emissions and on grain and biomass crops production. The simulation was made for the period from 2021 to 2070. The STICS model performed well at simulation of the following parameters: N2O emissions, soil water dynamics, soil temperature; and leaf area, aerial biomass and grain yield of soybean and maize. The performance of the model was good for the conventional soil management system as well as in the no-tillage system. Based on the predicted increase in temperature for the period 2021–2070, we can conclude from the data generated through the STICS model that there is strong evidence that grain yield and total aerial biomass of plants will decrease. The data show that there is a rising tendency in N2O emissions over the simulated period. This is expected to occur for the two soil management systems studied (NT and CT). We believe this increase in emissions along the years is related to temperature increase and to the reduction of crop cycle.

Effect of soil management systems on the rhizosphere bacterial community structure of tobacco: Continuous cropping vs. paddy-upland rotation

Rhizosphere bacteria play important role in soil nutrient cycling and plant growth, and their richness and diversity are influenced by soil management systems. However, the specific changes in tobacco rhizosphere bacterial community structure in continuous and tobacco-rice rotation cropping systems remain uninvestigated. In this study, soil properties and the composition of the rhizosphere bacterial community in tobacco monocropping and tobacco-rice rotation cropping systems were analyzed. Moreover, the comparison of rhizosphere bacterial community structure between tobacco continuous and tobacco-rice rotation cropping systems was performed via high-throughput sequencing. The changes in the composition of the rhizosphere bacterial community were investigated at different tobacco growth stages. The results showed that continuous tobacco cropping increased the soil soluble organic carbon (SOC), total nitrogen (TN), and the content of other nutrients (e.g., available phosphorus and available potassium) compared to tobacco-rice rotation cropping. However, monocropping decreased bacterial alpha-diversity and altered the community composition when compared to the rotation cropping system. At the phylum level, the relative abundance of Proteobacteria, Gemmatimonadetes, and Bacteroidetes increased in the continuous cropping soil, while that of Acidobacteria, Firmicutes, and Actinobacteria decreased. At the genera level, the average abundance of the dominant genus Bacillus varied from 12.96% in continuous cropping libraries to 6.33% in the rotation cropping libraries (p < 0.05). Additionally, several other taxa, such as o_Acidobacteriales and Candidatus_Solibacter decreased from 7.63 to 6.62% (p < 0.05) and 4.52 to 2.91% (p < 0.05), respectively. However, the relative abundance of f_Gemmatimonadaceae and c_Subgroup_6 showed an increase of 1.46% (p < 0.05) and 1.63% (p < 0.05) in the tobacco-rice rotation cropping system, respectively. The results of NMDS indicated that the rhizobacteria community structure differed in the two cropping systems. In tobacco, the rhizosphere bacterial community structure showed no significant changes in the prosperous long-term stage and topping stage, but the composition changed significantly in the mature stage.

Long-term effects of tillage systems on liming efficiency, soil chemical properties and wheat yield in Southern Brazil

Context Sustainable management of the soil is one of the pillars of conservation agriculture (CA). Aims The objective of this study was to evaluate the long-term effects of soil management systems (SMS) on liming efficiency, soil chemical properties and wheat yield. Methods This study was part of a long-term experiment established in 1986 in Passo Fundo, Rio Grande do Sul, Brazil, but using data from 2008 to 2015 to explore the effects of agricultural lime applied in 2008. The experiment was laid out in a split-plot design where the main plot (SMS) were arranged in randomised blocks and the cropping systems (sub-plot treatments) were randomised within the main plots. This study assessed the effects of the SMS; i.e. two CA systems [no-tillage (NT) and reduced tillage] and two conventional tillage (CT) systems (disk ploughing + disk harrowing annually, and mouldboard ploughing + disk harrowing annually). Key results The NT system was the most sustainable due to improvements in soil organic carbon concentration. After liming, CT systems were more effective than CA systems in decreasing Al3+ toxicity and increasing soil pH and Ca2+ and Mg2+ concentrations at deeper soil layers. The NT system had a considerable advantage over other SMS, due to a greater average wheat yield (18%). Conclusions The SMS evaluated in this study modified chemical properties when compared with the native forest area. The NT system was the least detrimental to soil organic carbon, an important indicator of soil quality. Implications The NT system provided greater average wheat yield (18%), and thus was the most viable SMS for subtropical spring wheat production.

Establishing reference values for soil microbial biomass-C in agroecosystems in the Atlantic Forest Biome in Southern Brazil

Abstract Soil microbial biomass plays a key role in the biogeochemical cycles, degradation of organic pollutants and soil aggregation, and its estimation through soil microbial biomass-C (MB-C) is often referred as a potential indicator of soil functioning. This study aimed to identify reference values of MB-C that would relate to crop yield. Soybean and maize grain yields and microbial biomass-C (MB-C) data were gathered from studies listed in “Web of Science” performed in agroecosystems located in the Atlantic Forest Biome in Southern Brazil. Database was composed by 78 datasets, where soil samplings for evaluation of MB-C were performed at the 0–10 cm layer at flowering stage, and evaluated by the fumigation-extraction method. A meta-regression using the Mitscherlich model was applied to determine the MB-C reference value corresponding to 80% of maximum yield. The effects of soil management systems and crop systems were verified by comparing the confidence intervals. Soil tillage decreased MB-C and yield, while crop rotation increased yield but not MB-C. It was not possible to find a reference value for soybean, because of the variability not explainable by the MB-C. The reference value related to high maize yield (>6,752 kg ha−1) was of 170 μg C g−1 soil, but further results must be included to decrease the variability.

Phenolic Compounds, Antioxidant and Cytotoxic Activity in Berry and Leaf Extracts of Black Currant (Ribes nigrum L.) as affected by Soil Management Systems

This experiment evaluated the effect of soil management systems (bare fallow, sawdust mulch and black plastic mulch) on the contents of phenolic compounds (total phenolics, flavonoids, gallotannins and condensed tannins), antioxidant activity (DPPH free radical scavenging activity, hydroxyl radical scavenging activity, lipid peroxidation) and cytotoxic activity in berry and leaf extracts of seven black currant cultivars. Soil management systems and cultivars showed highly significant differences in the content of phenolic compounds, antioxidant and cytotoxic activity. Sawdust mulch and bare fallow treatments had a significant positive effect on the synthesis of phenolic compounds and antioxidant activity in both berries and leaves. On the other hand, black currants grown on black plastic mulch had the highest cytotoxic activity. The tested extracts showed strong antioxidant and cytotoxic potential. Antioxidant activity expressed as the 50% inhibition concentration (IC50 value) ranged from 31.62 to 59.13 µg/mL and from 64.06 to 81.90 µg/mL, while cytotoxic activity varied from 15.91 to 37.89 µg/mL and from 26.28 to 38.18 µg/mL for berries and leaves extracts, respectively. Generally, the results suggested that black currants grow well under varied soil management systems, and indicated that soil management systems had a significant effect on the synthesis and accumulation of the tested parameters.

Soil management and application of agricultural gypsum in a Planosol for soybean cultivation

ABSTRACT: This study investigated the effects of soil management systems, tillage, and application of gypsum agricultural to soil, on soybean development in lowland areas. The experiment was carried out on an Alfisol in a randomized complete block design in a factorial arrangement. The two soil tillage practices were without deep tillage and with deep tillage. Gypsum treatments were no gypsum application, 500kg of gypsum ha-1, 1000kg of gypsum ha-1, and 1500kg of gypsum ha-1. Deep tillage resulted in less soil resistance to root penetration during ryegrass cultivation during the soybean offseason, 11 months after applying the management treatments, resulting in higher dry mass of ryegrass in the offseason and higher soybean yield in the following year.

Leguminosas isoladas e consorciadas com milheto em diferentes sistemas de manejo do solo no feijão orgânico.

Vários estudos têm demonstrado as vantagens da utilização de plantas de cobertura em manter ou melhorar a qualidade do solo e produtividade da cultura. No entanto, os efeitos dessa gestão em feijão comum orgânico em condições de savana, ainda são desconhecidos. Este estudo teve como objetivo avaliar o efeito de leguminosas, mucuna (Mucuna pruriens (L.) DC, feijão guandu (Cajanus cajan L.) HUTH, feijão de porco (Canavalia ensiformis), crotalária (Crotalária juncea) em monocultura e em consórcio com milheto (Pennisetum glaucum L.) R. Br. de 1810, na produção de grãos no feijoeiro comum em sistema orgânico de produção sob o sistema do manejo do solo convencional e plantio direto. O experimento foi realizado com a cultivar BRS Pontal, em um delineamento em blocos casualizados. Aos 90 dias após a germinação das plantas de feijão foram avaliadas, o número de vagens por planta (NVP), número de grãos por vagem (NGV), número de grãos por planta (NGP) , peso de 100 grãos (M100G) e produção de grãos. Os resultados mostraram que o número de vagens, número de grãos e produtividade do feijoeiro no sistema orgânico, foram influenciados pelas culturas de cobertura do solo e sistemas manejo do solo, com destaque para mucuna associados com milheto e sistema de plantio direto, que proporcionou o melhor desempenho destes parâmetros. A maior produção de grãos foi observado com a mucuna associados com milho em sistema de plantio direto. A produtividade média de grãos orgânicos foi de 3.8 Mg ha-1. A análise de agrupamento mostrou um efeito marcante de sistemas de manejo do solo sobre os componentes de produção do feijoeiro.

Relationship between Soil Management System and Cultivar in Black Currant (Ribes nigrum L.)

Summary This experiment evaluated the effect of soil management systems in a black currant planting on the generative potential (number of flowers per inflorescence, number of berries per cluster and yield per bush), physical attributes of the cluster and fruit (berry weight and cluster weight) and chemical properties of the fruit (soluble solids content, total sugars, titratable acidity, total anthocyanins, total phenolic content and vitamin C) of black currant cultivars. Three soil management systems were used: treatment I – bare fallow i.e. continuous tillage; treatment II – sawdust mulch, and treatment III – black polyethylene foil mulch. Four black currant cultivars were included - ‘Ben Lomond’, ‘Titania’, ‘Čačanska crna’ and ‘Tiben’. The soil management systems had a significant effect on the tested parameters. The cultivars also showed highly significant differences. Soil management system x cultivar interactions were observed for generative potential, and physical properties of the cluster and fruit, but not for fruit chemical traits, except in the soluble solids content.

Interpretation and Use of Penetrometer Data to describe Soil Compaction in Vineyards.

A portable recording penetrometer was used for in situ field measurements of soil strengths in existing experiments with known profile characteristics. The data reported include effects of soil preparation methods, tractor wheel compaction and soil moisture on soil strength, as well as a case study in a productioll'vineyard. The penetrometer proved to be a useful instrument in identifying and quantifying soil compaction problems and the effects of soil management systems in vineyards. The data revealed that serious subsoil compaction can exist which may result in very poor vine performance and even death of the vines.

Soil organic matter as affected by management systems, phosphate fertilization, and cover crops

Abstract The objective of this work was to evaluate the effects of soil management systems, cover crops, and phosphate fertilization on soil humic fractions in a long-term experiment. The treatments consisted of conventional tillage and no-tillage with pearl millet (Pennisetum glaucum) or velvet bean (Mucuna aterrima) as cover crops, at two doses of phosphorous: 0 and 100 kg ha-1 P2O5 per year. Soil samples were taken 11 years after the establishment of the experiment and analyzed for soil total organic carbon and carbon content of humic fractions at 0.00-0.05, 0.05-0.10, and 0.10-0.20-m depths. The humic fractions are sensitive to soil management, except free fulvic acid, which was the only one that did not reduce its carbon contents on the surface layer (0.00-0.05 m) with conventional tillage. The main changes occurred on the soil surface layer, in which the no-tillage system with pearl millet as a cover crop provided the highest carbon levels in humic fractions. Long-term phosphate fertilization under no-tillage, with pearl millet as a cover crop, promotes the accumulation of organic carbon in soil humic fractions.

Effect of Soil Management Systems on the Vegetative Growth Potential of Black Currant (Ribes nigrum L.) Cultivars

Summary This experiment evaluated the effect of soil management systems on the vegetative growth potential of black currant (Ribes nigrum L.) cultivars. Three soil management systems were used: I – bare fallow i.e. continuous tillage; II – sawdust mulch, and III – black polyethylene foil mulch. Six black currant cultivars were included: ‘Ben Lomond’, ‘Ben Sarek’, ‘Titania’, ‘Čačanska Crna’, ‘Tisel’ and ‘Tiben’. The highest values of vegetative growth parameters were obtained in 'Čačanska Crna' and 'Ben Lomond' and the lowest in 'Ben Sarek'. Bare fallow and sawdust mulch treatments showed no differences in the tested parameters, whereas significantly lower values were recorded under foil mulch treatment.

Physical Properties of a Hapludox after Three Decades under Different Soil Management Systems

Changes in soil physical properties due to different management systems occur slowly, and long-term studies are needed to assess soil quality. The objectives of this study were to evaluate the effects of soil management systems and liming methods on the physical properties of a Latossolo Bruno Aluminico tipico (Hapludox). A long-term experiment that began in 1978 with conventional and no-tillage systems was assessed. In addition, different liming methods (no lime, incorporated lime, and lime on the soil surface) have been applied since 1987 and were also evaluated in this study. Moreover, an area of native forest was evaluated and considered a reference for the natural condition of the soil. Soil physical properties were evaluated in layers to a depth of 1.00 m. Compared to native forest, the conventional tillage and no-tillage systems had higher soil bulk density, penetration resistance, and microporosity, and lower aggregate stability and macroporosity. Compared to the conventional tillage system, long-term no-tillage improved the structure of the Hapludox, as evidenced by increased microporosity and aggregate stability, especially in the soil surface layer. In no-tillage with lime applications sporadically incorporated, soil physical properties did not differ from no-tillage without lime and with lime applied on the soil surface, indicating that this practice maintains the physical quality of soil under no-tillage. Liming in a conventional tillage system improved soil aggregation and reduces penetration resistance in the soil layers near the soil surface. No-tillage was the main practice related to improvement of soil physical quality, and liming methods did not influence soil physical properties in this soil management system.

Efeito de sistemas de manejo do solo e velocidade de semeadura no desenvolvimento do sorgo forrageiro

O sorgo forrageiro é uma gramínea indicada para cultivo em ambientes secos e quentes, nos quais a produtividade de outras forrageiras pode ser antieconômica. Objetivou-se, com este trabalho, estudar diferentes sistemas de manejo e diferentes velocidades de semeadura, no desenvolvimento do sorgo forrageiro cv. BRS 610. O solo da área experimental foi um Nitossolo Vermelho distroférrico. O experimento foi instalado em condições de campo, na FCA/UNESP, Campus de Botucatu-SP, utilizando-se o delineamento em blocos ao acaso, em esquema de parcela subdividida, com dezesseis tratamentos (quatro sistemas de manejo e quatro velocidades de semeadura). Os sistemas de manejo utilizados foram: semeadura direta; gradagem pesada; gradagem pesada + duas gradagens leves e escarificação. As velocidades na operação de semeadura utilizadas foram: 3, 5, 6 e 9 km h-1. Foram analisadas as seguintes variáveis: população de plantas, altura de plantas, diâmetro do colmo, massa de mil grãos e produtividades de massa verde e de massa seca. O sistema de semeadura direta foi o que proporcionou maior população de plantas, maior diâmetro do colmo e maior produção de massas verde e seca. Com o aumento da velocidade na operação de semeadura, houve redução da população de plantas e aumento do diâmetro do colmo. A velocidade de 5 km h-1 foi a que proporcionou maior produção de massas verde e seca (kg ha-1), seguida da velocidade de 3 km h-1.

Long-term effect of different soil management systems and winter crops on soil acidity and vertical distribution of nutrients in a Brazilian Oxisol

“Strategies” to sustain crop productivity by reducing the fertilizer and lime demands must be developed. The use of plant species that use more efficiently the soil nutrients and tillage systems that provide nutrients accumulation in more labile forms are prerequisites for sustainable agroecosystems. This study aimed to evaluate the long period effect of cultivating different winter species under different soil management systems on vertical distribution of soil nutrients and the soil acidity distribution in soil profile. The experiment was established in 1986 with six winter treatments (blue lupine, hairy vetch, oat, radish, wheat and fallow) under conventional tillage (CT) and no-tillage (NT) in a very clayey Rhodic Hapludox in Southern Brazil. As a result of 19 years of no soil disturbance, soil chemical attributes related to soil acidity and the availability of P and K were more favorable to crops growth up to 10cm in the soil under no-tillage than in the conventional tillage. On other hand, lime applications in low doses on the soil surface were not efficient in neutralizing the aluminum toxicity below 10cm depth. It shows that repeated use of lime on the soil surface under NT system can be a viable alternative strategy only when soil acidity and aluminum toxicity in subsurface has been previously eliminated using the adequate amount of lime and incorporating it into the arable layer. Moreover, in the conventional tillage system P and K availability were higher below 10cm depth compared to the no-tillage system. Even after 19 years of no soil disturbance in the NT system the available P content below 10cm soil layer was lower than the optimal content of available P recommended to cash crops. The reduced surface K application over time was sufficient to gain adequate crop yields and to maintain the optimal content of soil available K in both soil management systems. The effects of soil management systems were predominant on the soil acidity attributes, and no effects of winter cover crops were observed on soil acidity attributes. Black oat and blue lupine were more efficient in P cycling, increasing the soil available P content especially in the surface soil under NT. The lower amount of biomass produced over time when no cover crops were used in the winter period resulted in lower P and K availability in the soil, showing the important role of growing winter species to maintain soil fertility.

Estoques e frações de carbono orgânico em Latossolo Amarelo submetido a diferentes sistemas de manejo

O objetivo deste trabalho foi determinar os efeitos de sistemas de manejo do solo sobre os estoques e as frações de carbono orgânico de um Latossolo Amarelo, no cerrado do Piauí. Foram avaliados os sistemas: plantio convencional por três anos; plantio direto por três e cinco anos, com uso de milheto como cultivo de cobertura; e plantio direto por nove anos, dos quais sete com uso de milheto e dois com forrageira (Urochloa brizantha). Utilizou-se área de cerrado nativo como referência. Amostras de solo foram coletadas nos períodos chuvoso e seco, das camadas de 0,00-0,05, 0,05-0,10, 0,10-0,20 e 0,20-0,40 m, para determinação de: estoques e totais de carbono orgânico e nitrogênio; teores de substâncias húmicas; e índice de humificação. Na camada de 0,00-0,05 m, em ambos os períodos, foram observados os maiores teores de carbono no solo sob cerrado. No entanto, nos dois períodos e nas quatro profundidades, verificaram-se os maiores estoques de carbono e nitrogênio bem como os maiores teores de substâncias húmicas nos solos sob plantio direto por cinco e nove anos. Os maiores índices de humificação também foram observados nesses solos, no período seco. O plantio direto, associado ao uso de cultivos de cobertura, diminui a mineralização da matéria orgânica do solo, estoca carbono no solo em profundidade e favorece o sequestro de carbono em áreas do cerrado do Piauí.

Postharvest nitrous oxide emissions from a subtropical oxisol as influenced by summer crop residues and their management

Nitrous oxide (N2O) is the most important non-CO2 greenhouse gas and soil management systems should be evaluated for their N2O mitigation potential. This research evaluated a long-term (22 years) experiment testing the effect of soil management systems on N2O emissions in the postharvest period (autumn) from a subtropical Rhodic Hapludox at the research center FUNDACEP, in Cruz Alta, state of Rio Grande do Sul. Three treatments were evaluated, one under conventional tillage with soybean residues (CTsoybean) and two under no-tillage with soybean (NTsoybean) and maize residues (NTmaize). N2O emissions were measured eight times within 24 days (May 2007) using closed static chambers. Gas flows were obtained based on the relations between gas concentrations in the chamber at regular intervals (0, 15, 30, 45 min) analyzed by gas chromatography. After soybean harvest, accumulated N2O emissions in the period were approximately three times higher in the untilled soil (164 mg m-2 N) than under CT (51 mg m-2 N), with a short-lived N2O peak of 670 mg m-2 h-1 N. In contrast, soil N2O emissions in NT were lower after maize than after soybean, with a N2O peak of 127 g m-2 h-1 N. The multivariate analysis of N2O fluxes and soil variables, which were determined simultaneously with air sampling, demonstrated that the main driving variables of soil N2O emissions were soil microbial activity, temperature, water-filled pore space, and NO3- content. To replace soybean monoculture, crop rotation including maize must be considered as a strategy to decrease soil N2O emissions from NT soils in Southern Brazil in a Autumn.

Preliminary study of the effect of soil management systems on the adventitious flora of a vineyard in northwestern Spain

The necessity to develop low-input, environmentally friendly agronomic techniques has encouraged changes in soil management systems in vineyards. The study and characterisation of adventitious flora is important if the integrated management of vineyards is to be achieved. The composition of vineyards weed flora is strongly affected by agricultural practises. This preliminary work reports an inventory of the adventitious flora growing in a vineyard in north-western Spain at different times of year, the response of weed vegetation to different soil management systems (such as the use of tillage, herbicides, or the maintenance of a plant cover) was recorded. The objectives of the study were: (1) to analyse the changes in plant cover and species richness in the vineyard between different soil management systems and along the temporal gradient and (2) to test whether life forms spectrum shows different patterns in each management system. Two soil management systems were compared: tillage and permanent plant coverage (sown with Lolium perenne and Trifolium repens or natural), this permanent covers were managed by either: mowing, chemical control (contact herbicide or systemic herbicide treatment). Vegetation was studied by using floristic spectrum, Raunkiaer life forms and soil cover levels. A total of 56 species belonging to 26 families were recorded. The plant spectrum was dominated by therophytes (annual weeds that germinate from seeds and complete their life cycle within one growing season or year) and hemicryptophytes (biennial or perennials weeds with resting buds at or near the level of the soil in a rosette form). The subplots sown with L. perenne and T. repens showed less serious infestation by weed species. T. repens was more stable over the long term. The highest plant coverage levels were obtained in the sown subplots that underwent mowing. Species associated with particular management types and particular seasons were determined.

Métodos para avaliação das emissões de gases do efeito estufa no sistema solo-atmosfera

A escolha do método para avaliar as emissões de gases do efeito estufa (GEE) é uma etapa importante para o conhecimento e/ou desenvolvimento de práticas agrícolas com potencial de mitigação do aquecimento global. A presente revisão tem por objetivo apresentar vantagens e limitações de métodos utilizados para quantificação dos fluxos de dióxido de carbono (CO2), metano (CH4) e óxido nitroso (N2O) no sistema solo-atmosfera. O balanço dos estoques de C orgânico no solo em sistemas conservacionistas de manejo permite avaliar o influxo líquido anual de C-CO2 atmosférico no solo em comparação a sistemas de manejo convencional. Maior sensibilidade na determinação direta das emissões de CO2 in situ pode ser obtida pelo uso de câmaras sobre o solo. Nesse caso, podem ser determinadas taxas diárias com o método da captura do CO2 em solução alcalina e quantificação por titulação, e taxas horárias com o uso de analisadores automáticos de infravermelho ou cromatógrafos a gás. Pelo uso de cromatografia, é possível também a avaliação das emissões de N2O e CH4 os quais apresentam, respectivamente, potencial de aquecimento global 296 e 23 vezes superior ao do CO2. A análise dos três GEE é necessária quando se objetiva avaliar o potencial de um dado sistema de manejo na mitigação do aquecimento global, o qual pode ser expresso em C equivalente.

Efeito de sistemas de manejo na estabilidade de agregados de um Nitossolo Vermelho

Com o objetivo de avaliar o efeito do manejo do solo na estabilidade de agregados de um Nitossolo Vermelho distroférrico, localizado na Fazenda Experimental Lageado da FCA/UNESP, em Botucatu - SP, amostraram-se, em outubro de 2001, três sistemas de manejo de solo: (i) mata (MA), (ii) preparo convencional por 10 anos seguido de semeadura direta por 12 anos (PC/SD) e (iii) preparo convencional por 22 anos (PC), em quatro camadas: 0,0-0,10; 0,10-0,20; 0,20-0,30 e 0,30-0,40 m. O delineamento experimental empregado foi o inteiramente casualizado, com três repetições. As amostragens foram feitas após a cultura do milho (safra 2000-2001). As amostras foram submetidas às análises físicas e químicas, e as médias, comparadas pelo teste de Tukey. O diâmetro médio ponderado dos agregados (DMP), o índice de estabilidade dos agregados (IEA) e a percentagem de agregados em classes de diâmetro médio foram obtidos com os resultados do peneiramento obtidos pelo método por via úmida. O diâmetro médio ponderado e o índice de estabilidade dos agregados foram menores para o preparo convencional do solo. Os três sistemas de manejo apresentaram maior percentagem de agregados com diâmetro entre 7,93 e 2,00 mm. A substituição do preparo convencional pela semeadura direta favoreceu a estabilidade dos agregados do solo. O diâmetro médio ponderado, o índice de estabilidade de agregados e a percentagem de agregados por classe de diâmetro médio evidenciaram diferenças entre os sistemas de manejo do solo.

Adubação verde e sistemas de manejo do solo na produtividade do algodoeiro

A adoção de sistemas de manejo conservacionistas e a sucessão de culturas com adubos verdes são práticas que visam preservar a qualidade do solo e do ambiente, sem prescindir da obtenção de produtividade elevada das culturas de interesse econômico. O objetivo deste trabalho foi avaliar os efeitos de sistemas de manejo do solo e adubos verdes na produtividade do algodoeiro (Gossypium hirsutum L.). O experimento foi realizado num Latossolo Vermelho distrófico, originalmente sob vegetação de Cerrado. O delineamento utilizado foi o de blocos ao acaso, em esquema de parcela subdividida e quatro repetições. Nas parcelas, utilizaram-se quatro adubos verdes: mucuna-preta, guandu, crotalária e milheto, e área de pousio (vegetação espontânea). Nas subparcelas foram adotados dois sistemas de manejo do solo: plantio direto e preparo convencional (uma gradagem pesada + duas gradagens leves). Os sistemas de manejo do solo não interferiram na produtividade do algodoeiro. O algodoeiro apresentou produtividade semelhante quando cultivado em sucessão a diferentes espécies de adubos verdes, no sistema de plantio direto e convencional de preparo do solo.