Resumo

Bulk density (BD) is a soil physical property used as a soil quality indicator and variations in this measurement influence soil water content and carbon stock estimates. This study aims to compile a database of samples of bulk density, textural fractions, and organic carbon values, as well as evaluate the accuracy of published pedotransfer functions (PTF) that predict bulk density, and propose a hierarchical PTF to predict the bulk density of Brazilian Soils. The performance of eleven PTFs and the newly proposed PTFs were evaluated and compared using the root mean square error (RMSE) and coefficient of determination (R2) based on a testing soil database collected from the literature. We noticed a slight improvement in accuracy when organic carbon and coarse and fine sand fractions were included as predictors alongside silt and clay. The best results with existing PTFs were obtained by PTF-A in Tomasella and Hodnett (1998) (RMSE = 0.20 g cm-3) and PTF-F in Benites et al. (2007) (RMSE = 0.17 g cm-3). Our proposed PTFs use textural fractions and organic carbon as predictors in a hierarchical form. The proposed PTF-4, which uses fine sand, coarse sand, clay, and organic carbon, presented the lowest value for RMSE (0.14 g cm-3) for BD prediction.

Resumo

Abstract Liupan Mountains are an important region in China in the context of forest cover and vegetation due to huge afforestation and plantation practices, which brought changes in soil physio-chemical properties, soil stocks, and soil stoichiometries are rarely been understood. The study aims to explore the distribution of soil nutrients at 1-m soil depth in the plantation forest region. The soil samples at five depth increments (0-20, 20-40, 40-60, 60-80, and 80-100 cm) were collected and analyzed for different soil physio-chemical characteristics. The results showed a significant variation in soil bulk density (BD), soil porosity, pH, cation exchange capacity (CEC), and electric conductivity (EC) values. More soil BD (1.41 g cm-3) and pH (6.97) were noticed in the deep soil layer (80-100 cm), while the highest values of porosity (60.6%), EC (0.09 mS cm-1), and CEC (32.9 c mol kg-1) were reflected in the uppermost soil layer (0-20 cm). Similarly, the highest contents of soil organic carbon (SOC), total phosphorus (TP), available phosphorus (AP), total nitrogen (TN), and available potassium (AK) were calculated in the surface soil layer (0-20 cm). With increasing soil depth increment a decreasing trend in the SOC and other nutrient concentration were found, whereas the soil total potassium (TK) produced a negative correlation with soil layer depth. The entire results produced the distribution of SOCs and TNs (stocks) at various soil depths in forestland patterns were 020cm > 2040cm > 4060cm 6080cm 80100 cm. Furthermore, the stoichiometric ratios of C, N, and P, the C/P, and N/P ratios showed maximum values (66.49 and 5.46) in 0-20 cm and lowest values (23.78 and 1.91) in 80-100 cm soil layer depth. Though the C/N ratio was statistically similar across the whole soil profile (0-100 cm). These results highlighted that the soil depth increments might largely be attributed to fluctuations in soil physio-chemical properties, soil stocks, and soil stoichiometries. Further study is needed to draw more conclusions on nutrient dynamics, soil stocks, and soil stoichiometry in these forests.

Resumo As montanhas de Liupan são uma região importante na China no contexto de cobertura florestal e vegetação devido às enormes práticas de florestamento e plantação, que trouxeram mudanças nas propriedades físico-químicas do solo, e estoques e estequiometrias do solo raramente são compreendidos. O estudo visa explorar a distribuição de nutrientes do solo a 1 m de profundidade do solo na região da floresta plantada. As amostras de solo em cinco incrementos de profundidade (0-20, 20-40, 40-60, 60-80 e 80-100 cm) foram coletadas e analisadas para diferentes características físico-químicas do solo. Os resultados mostraram uma variação significativa nos valores de densidade do solo (BD), porosidade do solo, pH, capacidade de troca catiônica (CEC) e condutividade elétrica (CE). Mais DB do solo (1,41 g cm-3) e pH (6,97) do solo foram observados na camada profunda do solo (80-100 cm), enquanto os maiores valores de porosidade (60,6%), CE (0,09 mS cm-1) e CEC (32,9 c mol kg-1) foram refletidos na camada superior do solo (0-20 cm). Da mesma forma, os maiores teores de carbono orgânico do solo (SOC), fósforo total (TP), fósforo disponível (AP), nitrogênio total (TN) e potássio disponível (AK) foram calculados na camada superficial do solo (0-20 cm). Com o aumento do incremento da profundidade do solo, uma tendência decrescente no SOC e na concentração de outros nutrientes foi encontrada, enquanto o potássio total do solo (TK) produziu uma correlação negativa com a profundidade da camada do solo. Todos os resultados produziram a distribuição de SOCs e TNs (estoques) em várias profundidades de solo em padrões de floresta 0 20cm> 20 40cm> 40 60cm 60 80cm 80 100 cm. Além disso, as relações estequiométricas de C, N e P, as relações C / P e N / P, apresentaram valores máximos (66,49 e 5,46) em 0-20 cm, e valores mais baixos (23,78 e 1,91) em solo de 80-100 cm profundidade da camada. Embora a relação C / N fosse estatisticamente semelhante em todo o perfil do solo (0-100 cm). Esses resultados destacaram que os incrementos de profundidade do solo podem ser amplamente atribuídos a flutuações nas propriedades físico-químicas do solo, estoques e estequiometrias do solo. Mais estudos são necessários para tirar conclusões adicionais sobre a dinâmica dos nutrientes, estoques de solo e estequiometria do solo nessas florestas.

Resumo

Liupan Mountains are an important region in China in the context of forest cover and vegetation due to huge afforestation and plantation practices, which brought changes in soil physio-chemical properties, soil stocks, and soil stoichiometries are rarely been understood. The study aims to explore the distribution of soil nutrients at 1-m soil depth in the plantation forest region. The soil samples at five depth increments (0-20, 20-40, 40-60, 60-80, and 80-100 cm) were collected and analyzed for different soil physio-chemical characteristics. The results showed a significant variation in soil bulk density (BD), soil porosity, pH, cation exchange capacity (CEC), and electric conductivity (EC) values. More soil BD (1.41 g cm-3) and pH (6.97) were noticed in the deep soil layer (80-100 cm), while the highest values of porosity (60.6%), EC (0.09 mS cm-1), and CEC (32.9 c mol kg-1) were reflected in the uppermost soil layer (0-20 cm). Similarly, the highest contents of soil organic carbon (SOC), total phosphorus (TP), available phosphorus (AP), total nitrogen (TN), and available potassium (AK) were calculated in the surface soil layer (0-20 cm). With increasing soil depth increment a decreasing trend in the SOC and other nutrient concentration were found, whereas the soil total potassium (TK) produced a negative correlation with soil layer depth. The entire results produced the distribution of SOCs and TNs (stocks) at various soil depths in forestland patterns were 0→20cm > 20→40cm > 40→60cm ≥ 60→80cm ≥ 80→100 cm. Furthermore, the stoichiometric ratios of C, N, and P, the C/P, and N/P ratios showed maximum values (66.49 and 5.46) in 0-20 cm and lowest values (23.78 and 1.91) in 80-100 cm soil layer depth. Though the C/N ratio was statistically similar across the whole soil profile (0-100 cm). These results highlighted that the soil depth increments might largely be attributed to fluctuations in soil physio-chemical properties, soil stocks, and soil stoichiometries. Further study is needed to draw more conclusions on nutrient dynamics, soil stocks, and soil stoichiometry in these forests.

As montanhas de Liupan são uma região importante na China no contexto de cobertura florestal e vegetação devido às enormes práticas de florestamento e plantação, que trouxeram mudanças nas propriedades físico-químicas do solo, e estoques e estequiometrias do solo raramente são compreendidos. O estudo visa explorar a distribuição de nutrientes do solo a 1 m de profundidade do solo na região da floresta plantada. As amostras de solo em cinco incrementos de profundidade (0-20, 20-40, 40-60, 60-80 e 80-100 cm) foram coletadas e analisadas para diferentes características físico-químicas do solo. Os resultados mostraram uma variação significativa nos valores de densidade do solo (BD), porosidade do solo, pH, capacidade de troca catiônica (CEC) e condutividade elétrica (CE). Mais DB do solo (1,41 g cm-3) e pH (6,97) do solo foram observados na camada profunda do solo (80-100 cm), enquanto os maiores valores de porosidade (60,6%), CE (0,09 mS cm-1) e CEC (32,9 c mol kg-1) foram refletidos na camada superior do solo (0-20 cm). Da mesma forma, os maiores teores de carbono orgânico do solo (SOC), fósforo total (TP), fósforo disponível (AP), nitrogênio total (TN) e potássio disponível (AK) foram calculados na camada superficial do solo (0-20 cm). Com o aumento do incremento da profundidade do solo, uma tendência decrescente no SOC e na concentração de outros nutrientes foi encontrada, enquanto o potássio total do solo (TK) produziu uma correlação negativa com a profundidade da camada do solo. Todos os resultados produziram a distribuição de SOCs e TNs (estoques) em várias profundidades de solo em padrões de floresta 0 → 20cm> 20 → 40cm> 40 → 60cm ≥ 60 → 80cm ≥ 80 → 100 cm. Além disso, as relações estequiométricas de C, N e P, as relações C / P e N / P, apresentaram valores máximos (66,49 e 5,46) em 0-20 cm, e valores mais baixos (23,78 e 1,91) em solo de 80-100 cm profundidade da camada. Embora a relação C / N fosse estatisticamente semelhante em todo o perfil do solo (0-100 cm). Esses resultados destacaram que os incrementos de profundidade do solo podem ser amplamente atribuídos a flutuações nas propriedades físico-químicas do solo, estoques e estequiometrias do solo. Mais estudos são necessários para tirar conclusões adicionais sobre a dinâmica dos nutrientes, estoques de solo e estequiometria do solo nessas florestas.

Resumo

In a no-tillage system, the absence of soil disturbance combined with increased machine traffic has led to soil compaction in the top layer, negatively affecting its physical quality and hampering crop growth and production. This experiment aimed to assess the impact of tractor traffic, occurring under a no-tillage system, on soil physical properties and their relationship with the growth and yield of white oat crops. The research was conducted in an Oxisol, utilizing a randomized block design with five replications. The treatments consisted of ten consecutive years of no-tillage and additional traffic by 2, 4, 6, and 8 passes of a tractor wheel across the entire plot area. Various soil parameters were evaluated in two soil layers, including soil bulk density, total porosity, macroporosity, and soil resistance to penetration. Additionally, plant height, stem diameter, dry plant mass, mass of one thousand grains, and grain yield were determined.The collected data were analyzed using analysis of variance and linear regression. The results indicated that higher tractor traffic intensity led to increased soil bulk density and reduced macroporosity and soil resistance to penetration in the 0-0.10 m layer compared to the 0.10-0.20 m layer. In the 0-0.10 m layer, bulk density values exceeding 1.44 Mg m-3were found to restrict the growth and yield of white oat crops, while in the 0.10-0.20 m layer, grain yield was limited when soil bulk density surpassed 1.35 Mg m-3. Our results show that farmers should be aware of the consequences of machine traffic on soil properties as it can have negative effects on crop yields, especially those of white oats grown in clayey soil similar to the one evaluated in thisexperiment.(AU)

Em plantio direto, o não revolvimento do solo aliado à intensificação do tráfego de máquinas tem ocasionado compactação da camada superficial do solo prejudiciais à sua qualidade física, impactando negativamente no crescimento e produção das culturas. Este experimento teve como objetivo avaliar o impacto do tráfego de tratores, ocorrido em um sistema de plantio direto, nas propriedades físicas do solo e sua relação com o crescimento e rendimento da cultura de aveia branca. A pesquisa foi conduzida em um Latossolo Vermelho distroférrico, utilizando um delineamento em blocos casualizados com cinco repetições. Os tratamentos consistiram em dez anos consecutivos de plantio direto (zero passagens), juntamente com tráfego adicional de 2, 4, 6 e 8 passagens de roda de trator em toda a área da parcela. Diversos parâmetros do solo, incluindo densidade aparente, porosidade total, macroporosidade, microporosidade e resistência do solo à penetração, foram avaliados em duas camadas do solo. Além disso, altura da planta, diâmetro do colmo, massa seca da planta, massa de mil grãos e produtividade de grãos foram determinados. Os dados coletados foram analisados por meio de análise de variância e regressão linear. Os resultados indicaram que uma maior intensidade de tráfego de tratores resultou em aumento da densidade aparente do solo e redução da macroporosidade e da resistência do solo à penetração na camada de 0-0,10 m em comparação com a camada de 0,10-0,20 m. Na camada de 0-0,10 m, valores de densidade aparente acima de 1,44 Mg m-3foram encontrados como limitantes para o crescimento e produtividade da aveia branca, enquanto na camada de 0,10-0,20 m, a produtividade de grãos foi limitado quando a densidade aparente do solo ultrapassou 1,35 Mg m-3. Nossos resultados demonstram que os produtores devem estar atentos às consequências do tráfego de máquinas nas propriedades do solo, pois pode comprometer a produtividade das culturas, principalmente de aveia branca cultivada em solo argiloso como o avaliado neste estudo.(AU)

Resumo

The bulk density values indicative of compaction in clayey soils correspond to a wide range of values (1.30-1.47 Mg m-3), due to the diverse types of soil management. Our hypothesis is that if we consider bulk density values within similar management groups (those that fall to the ground and those that do not fall), the values will be more accurate within each management group. Our objective in this work was to analyze using the concepts of (Yates & Cochran, 1938; Whitehead, 2002) what is a suitable statistical way of grouping these results to reach a consensus regarding a tested hypothesis, the greatest number of density values surveyed between 1977 and 2021, considered for the study of compaction in clayey Oxisols under different managements, to verify whether our hypothesis will be confirmed. We selected 1,521 studies with bulk densities in the literature, corresponding to 44 years (1977 and 2021), which were analyzed by a statistical technique that integrates the results of two or more independent studies on the same subject and combines them into a summary measure (portion forestry). From the data collected in the literature, it was possible to separate two groups of bulk density and management in clayey soils indicative of compaction: the managements that perform little or no manipulation of the soil, such as pasture and no-tillage, densities between 1.41-1.45 Mg.m-3 (average 1.43 Mg m-3), and for the others, such as conventional plowing and minimum tillage, soil densities between 1.31-1.38 Mg.m-3 (average 1.35 Mg m-3). Finally, we conclude that compaction must be analyzed considering the texture and type of soil management.(AU)

Os valores de densidade do solo indicativos de compactação em solos argilosos correspondem a uma ampla faixa de valores (1,30-1,47 Mg m-3), devido aos diversos tipos de manejo do solo. Nossa hipótese é que se considerarmos os valores de densidade do solo dentro de grupos de manejo semelhantes (os que caem no chão e os que não caem), os valores serão mais precisos dentro de cada grupo de manejo. Nosso objetivo neste trabalho foi analisar usando os conceitos de (Yates & Cochran, 1938; Whitehead, 2002) qual é uma forma estatística adequada de agrupar esses resultados para chegar a um consenso sobre uma hipótese testada, o maior número dos valores de densidade levantados entre 1977 e 2021, considerados para o estudo da compactação em Latossolos argilosos sob diferentes manejos, para verificar se nossa hipótese será confirmada. Selecionamos 1.521 estudos com densidades do solo na literatura, correspondentes a 44 anos (1977 e 2021), que foram analisados por uma técnica estatística que integra os resultados de dois ou mais estudos independentes sobre o mesmo assunto e os combina em uma medida resumida (forest plot). A partir dos dados levantados na literatura, foi possível separar dois grupos de densidade do solo e manejo em solos argilosos indicativos de compactação: os manejos que realizam pouca ou nenhuma manipulação do solo, como pastagem e plantio direto, densidades entre 1,41 -1,45 Mg.m-3 (média 1,43 Mg m-3), e para as demais, como aração convencional e preparo mínimo, densidades de solo entre 1,31-1,38 Mg.m-3 (média 1,35 Mg m-3). Por fim, concluímos que a compactação deve ser analisada considerando a textura e o tipo de manejo do solo.(AU)

Resumo

Soil compaction is a main physical problem in many growing areas. The use of ground cover crops for soil decompaction hasbeen a subject of many studies. That has promising results both used alone and in association with mechanical chiseling. The objective of this studywas to evaluate the influence of cover crops associated or not with mechanical chiseling, for that, on the physical attributes of the soil, and the wheat grain yield, in an Ultisolfrom the Central Depression of RS. The experimental design used was randomized blocks with 3 replications in each block, in a 2 x 5 factorial scheme. Where the factor A: soil chiseling-chiseledand non-chiseled, and P fator:cover crops­pigeon pea(Cajanus cajan), Crotalariajuncea(Crotalaria juncea), pearl millet(Pennisetum americanum)and velvet bean (Mucuna aterrima). The chiselingwas adjusted to a depth of 0.30m, with 5 rods spaced 0.3m apart.The determinations carried out were: macroporosity, microporosity, total soil porosity, bulk density(BD), penetration resistance (RP), and grain yield. The physical attributes of the soil showed improvements in the second year evaluated, highlighting the treatments with pearl milletand velvet beanthat showed higher differences. The maximum RP of the Soil was observed at a depth of 0.25m with 1.64 Mpa. There was a significant difference in the RP of the soil between the treatments of factor A at depths of 0.15 -0.20 and 0.25m. Mechanical chiselingprovided a 15% increase in wheat grain yield compared to non-chiselingtreatment, while P factor treatments did not provide any gain.(AU)

A compactação do solo constitui um problema físico importante em muitas áreas de cultivo. A utilização de plantas de cobertura do solo para a descompactação do solo tem sido objeto de muitos estudos, com resultados promissores, tanto usadas isoladamente quanto em associação com a escarificação mecânica. O objetivo deste estudo foi avaliar a influência de plantas de cobertura associadas ou não com escarificação mecânica, nos atributos físicos do solo e no rendimento de grãos de trigo, em um Argissoloda Depressão Central do RS. O delineamento experimental utilizado foi de blocos ao acaso com 3 repetições em cada bloco, no esquema fatorial 2 x 5, onde o fator A: escarificação do solo-escarificado e não escarificado, e o fator P:plantas de cobertura­guandu (Cajanus cajan), Crotalariajuncea(Crotalaria juncea) milheto(Pennisetum americanum)e mucuna (Mucuna aterrima). A escarificação foi ajustada a 0,3m de profundidade, com 5 hastes espaçadas a 0,30 m entre si. As determinações realizadas foram: macroporosidade, microporosidade, porosidade total do solo, densidade do solo (Ds), resistência a penetração (RP) e rendimento de grãos. Os atributos físicos do solo apresentaram melhorias no segundo ano avaliado, destacando os tratamentos com milhetoemucuna os quais apresentaram maiores diferenças. A RP máxima do solo, foi observada na profundidade de 0,25m com 1,64 Mpa. Houve diferença significativa na RP do solo entre os tratamentos do fator A nas profundidades de 0,15 -0,20 e 0,25m. A escarificação mecânica proporcionou um incremento de 15% no rendimento de grãos de trigo em comparação ao tratamento não escarificado, enquanto os tratamentos do fator P não proporcionaram nenhum ganho.(AU)

Resumo

Lowlands have been cultivated with irrigated rice (Oryza sativa) in a monoculture cropping system for more than a century in southern Brazil. Shallow topsoil with high bulk density and deficient water infiltration favors the of production paddy rice; however, this condition does not favor species non-tolerant to flooding or oxygen restriction. Thus, soil and irrigation management may be necessary to raise the rice-soybean (Glycine max) rotation systems to sustainable levels. We carried out a two-year field experiment to assess the effects of irrigation treatments and soil management on soil physical properties, soybean growth, and grain yield in lowland systems. The experiment comprised a randomized block design with two factors and three replications. The main factor comprised the following irrigation treatments: sprinkler; surface, and rainfed. Four soil managements composed the second factor: conventional tillage (CT), no-tillage (NT), conventional tillage with raised-seedbed, and no-tillage with raised-seedbed. Soil physical properties, soil penetration resistance, crop parameters, grain yield and water productivity were evaluated. CT increased the soil penetration resistance near the soil surface layer. The highest soil bulk density at the 0.05-0.10 m layer in the CT reduces grain yield in rainfed soybean compared to NT. Supplementary irrigation increased soybean yield of about 36 % in years of uneven rainfall distribution. Sprinkler irrigation resulted in higher irrigated water productivity (90 %) compared to surface irrigation, contributing to a more sustainable increase in grain yield. Crop rotation in a no-tillage cropping scheme could improve the sustainability of diversified agriculture in lowlands.

Resumo

Spiders are part of the soil biodiversity, considered fundamental to the food chain hierarchy, directly and indirectly influencing several services in agricultural and forest ecosystems. The present study aimed to evaluate the biodiversity of soil spider families and identify which soil properties influence their presence, as well as proposing families as potential bioindicators. Native forest (NF) and reforested sites (RF) with Araucaria angustifolia (Bertol.) Kuntze were evaluated in three regions of the state São Paulo, both in the winter and summer. Fifteen soil samples were collected from each forest to evaluate the biological (spiders and microbiological), chemical and physical soil properties, in addition to properties of the litter (dry matter and C, N and S contents). For soil spiders, two sampling methods were used: pitfall traps and soil monoliths. In total, 591 individuals were collected, and distributed in 30 families, of which 306 individuals (22 families) came from pitfall traps and 285 individuals (26 families) from monoliths. Only samples obtained by the monolith method revealed seasonal differences in the mean density and richness of spiders between NF and RF. Canonical discriminant analysis showed the separation of these forests of Araucaria. Principal Component Analysis demonstrated the correlation of a number of spider families with certain soil properties (organic carbon, basal respiration, metabolic quotient, litter carbon, total porosity, bulk density and soil moisture). We identified 10 families (Anapidae, Corinnidae, Dipluridae, Hahniidae, Linyphiidae, Lycosidae, Nemesiidae, Palpimanidae, Salticidae, Scytodidae) that contributed most to separating native forest from the replanted forest, indicating the possibility of the spiders being used as bioindicators.

Resumo

Regiões semiáridas são caracterizadas pela elevada evapotranspiração e baixa precipitação pluvial, favorecendo o acúmulo de sais quando irrigado com água salobra. Objetivou se avaliar o efeito do cultivo de milheto com níveis de água salobra e fertilização orgânica nas propriedades químicas e físicas do solo. Adotou-se o delineamento de blocos ao acaso, com arranjo fatorial, em parcelas subdivididas, com três repetições. As parcelas foram constituídas por quatro lâminas de irrigação (25, 50, 75 e 100% da evapotranspiração da cultura) e as subparcelas foram compostas por quatro níveis de fertilização orgânica (0; 15; 30 e 45 Mg ha-1). No final do ciclo de produção do milheto, o solo foi coletado nas camadas de 0-0.20 e 0.20-0.40 m, para aspectos físicos (densidade do solo, densidade de partículas e porosidade) e químicos (CE, pH, K, Na, Ca, Mg, H + Al, SB, CTC, V). Não houve interação entre a água salobra e a fertilização orgânica nas propriedades químicas do solo. A água salobra reduziu o potássio na camada de 0,20-0,.40 m. Observou-se efeito linear negativo para densidade na camada 0,20 - 0,40 m sob níveis de fertilização orgânica. Níveis de água salobra e fertilizante orgânico no cultivo do milheto não altera as propriedades químicas e físicas do solo na camada de 0-0,20 m. Porém, o uso de água salobra reduz a concentração de potássio no solo e a aplicação de fertilização orgânica reduz a densidade do solo na camada de 0.20-0,40 m.

Semi-arid regions are characterized by high evapotranspiration and low rainfall, favoring the accumulation of salts when irrigated with brackish water. The aim of this study was to evaluate the effect of pearl millet cultivation with brackish water levels and fertilized with organic fertilizer on the chemical and physical properties of the soil. A split plot randomized block design was adopted, in a factorial arrangement, with three repetitions. Plots consisted of four irrigation levels (25, 50, 75 and 100% crop evapotranspiration) and subplots consisted of four levels of organic fertilizer (0; 15; 30 and 45 Mg ha-¹). At the end of the pearl millet production cycle, soil was collected from layers 0-0.20 m and 0.20-0.40 m, for physical (soil bulk density, particle density and porosity) and chemical (EC, pH, K, Na, Ca, Mg, H + Al, SB, CEC, V) properties. There was no effect of interaction of brackish water levels and organic fertilizer levels on soil chemical properties. Brackish water reduced potassium on layer 0.20-0.40 m. A negative linear effect was found for density in the 0.20-0.40 m layer under different levels of organic fertilizer. Brackish water levels and organic fertilizer levels in the cultivation of pearl millet does not alter soil chemical and physical properties at the 0-0.20 m layer. However, the use of brackish water reduces the concentration of potassium in the soil and the application of organic fertilizer reduces soil density at the 0.20-0.40 m layer.

Resumo

Semi-arid regions are characterized by high evapotranspiration and low rainfall, favoring the accumulation of salts when irrigated with brackish water. The aim of this study was to evaluate the effect of pearl millet cultivation with brackish water levels and fertilized with organic fertilizer on the chemical and physical properties of the soil. A split plot randomized block design was adopted, in a factorial arrangement, with three repetitions. Plots consisted of four irrigation levels (25, 50, 75 and 100% crop evapotranspiration) and subplots consisted of four levels of organic fertilizer (0; 15; 30 and 45 Mg ha-1). At the end of the pearl millet production cycle, soil was collected from layers 0-0.20 m and 0.20-0.40 m, for physical (soil bulk density, particle density and porosity) and chemical (EC, pH, K, Na, Ca, Mg, H + Al, SB, CEC, V) properties. There was no effect of interaction of brackish water levels and organic fertilizer levels on soil chemical properties. Brackish water reduced potassium on layer 0.20-0.40 m. A negative linear effect was found for density in the 0.20-0.40 m layer under different levels of organic fertilizer. Brackish water levels and organic fertilizer levels in the cultivation of pearl millet does not alter soil chemical and physical properties at the 0-0.20 m layer. However, the use of brackish water reduces the concentration of potassium in the soil and the application of organic fertilizer reduces soil density at the 0.20-0.40 m layer.

Regiões semiáridas são caracterizadas pela elevada evapotranspiração e baixa precipitação pluvial, favorecendo o acúmulo de sais quando irrigado com água salobra. Objetivouse avaliar o efeito do cultivo de milheto com níveis de água salobra e fertilização orgânica nas propriedades químicas e físicas do solo. Adotou-se o delineamento de blocos ao acaso, com arranjo fatorial, em parcelas subdivididas, com três repetições. As parcelas foram constituídas por quatro lâminas de irrigação (25, 50, 75 e 100% da evapotranspiração da cultura) e as subparcelas foram compostas por quatro níveis de fertilização orgânica (0; 15; 30 e 45 Mg ha-1). No final do ciclo de produção do milheto, o solo foi coletado nas camadas de 0-0.20 e 0.20-0.40 m, para aspectos físicos (densidade do solo, densidade de partículas e porosidade) e químicos (CE, pH, K, Na, Ca, Mg, H + Al, SB, CTC, V). Não houve interação entre a água salobra e a fertilização orgânica nas propriedades químicas do solo. A água salobra reduziu o potássio na camada de 0,20-0,.40 m. Observou-se efeito linear negativo para densidade na camada 0,20 - 0,40 m sob níveis de fertilização orgânica. Níveis de água salobra e fertilizante orgânico no cultivo do milheto não altera as propriedades químicas e físicas do solo na camada de 0-0,20 m. Porém, o uso de água salobra reduz a concentração de potássio no solo e a aplicação de fertilização orgânica reduz a densidade do solo na camada de 0.20-0,40 m.

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Concerns about the negative effects of agriculture on soil physical quality and soil organic carbon (SOC) pools have spurred on the adoption of conservation tillage systems in tropical regions. This study aimed to evaluate the long-term impacts (16th year) of conventional (CT), minimum (MT) and no-tillage (NT) practices and different cover crops (sunn hemp and a bean/millet sequence) on soil physical properties and SOC content of a corn cultivated Ultisol in the northeast of Brazil. Soil bulk density (Bd), soil penetration resistance (SPR), soil aggregation, and total aggregate-associated carbon (C) (4-2 mm) were evaluated. Tillage practices exerted strong control on soil physical properties and total aggregate-C content but were influenced by cover crop species. Minimum tillage presented the lowest Bd, irrespective of cover crop, while NT with bean/millet sequence resulted in the lowest SPR. However, as regards soil aggregation and total aggregate-C, the results indicated that there were no differences between MT and NT, with both systems presenting greater mean weight diameter (MWD) and total aggregate-C content than CT. Total aggregate-C content in the 0.00-0.05 m soil layer in conservation tillage was increased by the adoption of a bean/millet sequence. Increased mechanical disturbance through CT practices was harmful to Bd, soil aggregation and SOC accrual. Overall, more conservative tillage practices and the proper choice of cover crops might yield greater soil quality. Low intensity of soil disturbances due to the adoption of MT favors soil aggregation and the accrual of SOC in weakly structured soils through increases in contact between organic and mineral particles while not causing significant destruction of soil aggregates.

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Agricultural areas in the region of Turuçu, on the Southeast Hillside in the state of Rio Grande do Sul (RS), Brazil present many examples of soil physical degradation. Accordingly, strategies aimed at evaluating and ameliorating the structural quality of soils should be developed to ensure the sustainable use of these areas. This study aimed to evaluate the least limiting water range (LLWR), S-index, compressibility parameters, organic carbon and the organic matter granulometric fractions of a Udalf under different agricultural uses. Soil samples with disturbed and non-disturbed structure from the 0.00 to 0.10 m layer were collected on farms in the Southeast Hillside, Turuçu region, RS, for analyzing soil under: i) conventional system of corn after tobacco crop, (CT); ii) conventional system of corn after native field (CNF), iii) native field (NF) and iv) native area (NA). Both the CT and the CNF systems had a negative influence on the values of bulk density, soil porosity, least limiting water range, compressibility parameters and total organic carbon, coarse fraction carbon and carbon associated with minerals.

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Chemical and physical properties of soil can be altered with the successive application of liquid swine manure (LSM), also known as slurry. Therefore, monitoring the impact of LSM is essential to an assessment of the potential agronomic and environmental benefits and risks associated with management practices. The aim of this study was to evaluate the effects of LSM on the chemical and physical attributes of soil under pasture (Cynodon spp.), located in southern Brazil. Four areas were sampled: three areas cultivated with Cynodon spp. pasture with successive applications of 200 m3 ha1 y1 of LSM for three, eight and 15 years; and untreated native forest as a reference. The soil attributes evaluated were: organic carbon (OC), active (pH water) and potential acidity (H + Al+ 3), nutrient availability (i.e., P, K, Ca, Mg, Cu and Zn), soil bulk density, macro, micro and total porosity. Successive applications of LSM on pasture reduced soil active acidity, and increased the soil organic C and plant-available N, P, Ca, Mg, Cu and Zn contents. These effects were more intense with time and in the shallowest layers, i.e. 0-10 cm. Excessive increases in P, Cu and Zn in the soil should be carefully monitored to minimize the contamination risks to soil, ground and surface waters. Soil physical attribute changes were more associated with land use (pasture versus native forest) than LSM use, and LSM applications induced slight improvements in the soil structural quality over time.

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Os sistemas integrados de produção agropecuária visam a sustentabilidade, procurando explorar o máximo da área, além de diminuir os impactos sobre as propriedades do solo. O presente trabalho teve objetivo estudar a distribuição do tamanho de poros de um Latossolo Vermelho em um sistema integrado de produção agropecuária após três anos de implantação do sistema. O experimento foi realizado na Fazenda pertencente ao grupo Facholi, no município de Caiuá/SP. O delineamento experimental utilizado foi em blocos casualizados, com três repetições e compostos por 7 tratamentos: 1 - Soja–Milho + B. ruziziensis (pastejo); 2 - Soja – Milho + Piatã (pastejo); 3 - Soja – Milho + Paiaguás (pastejo); 4 - Soja - Piatã (pastejo 2 anos) – Soja - Piatã (pastejo); 5 - Soja - Paiaguás (pastejo 2 anos) – Soja - Paiaguás (pastejo); 6 -Soja – milho (Plantio direto); 7 - Soja – milho (Preparo convencional). Foram realizadas as avaliações dos seguintes atributos do solo: macroporosidade, microporosidade, porosidade total e densidade do solo, em duas camadas do solo; 0,00-0,10 e 0,10-0,20 m de profundidade, em três épocas de coleta, utilizando o teste Tukey a 5% de probabilidade para a comparação de médias. Os resultados mostram que a macroporosidade aumentou com o tempo (3 anos de avaliação), e houve uma diminuição da densidade do solo, mostrando que os sistemas avaliados influenciaram positivamente os atributos do solo estudados. De forma geral, todos ao tratamentos aumentaram a macroporosidade em relação a caracterização inicial, com destaque para os tratamentos soja+piatã e soja+milho+piatã, camada de 0-0,10m que obtiveram valores médios superiores aos demais.

Integrated agricultural production systems aim at sustainability, seeking to exploit the maximum of the area, as well as reducing impacts on soil properties. The objective of this work was to study the distribution of pore size of an Oxisol in an integrated agricultural production system after three years of system implantation. The experiment was carried out at Fazenda belonging to the Facholi group, in the municipality of Caiuá / SP. The experimental design was a randomized complete block with three replicates and composed of 7 treatments: 1 - Soya - Maize + B. ruziziensis (grazing); 2 - Soybean - Maize + Piatã (grazing); 3 -Soya - Maize + Paiaguás (grazing); 4 - Soya - Piatã (grazing 2 years) - Soya - Piatã (grazing); 5 - Soybean - Paiaguás (grazing 2 years) - Soybean - Paiaguás (grazing); 6 - Soybean - maize (Direct planting); 7 - Soybean - corn (Conventional preparation). The following soil attributes were evaluated: macroporosity, microporosity, total porosity and soil density in two depths of soil; 0.00-0.10 and 0.10-0.20 m depth, in three sampling periods, using the Tukey test at 5% probability for the comparison of means. The results show that the macroporosity increased with time(3 years of evaluation), and there was a decrease in soil density, showing that the evaluated systems positively influenced the soil attributes studied. In general, all treatments increased the macroporosity in relation to the initial characterization, especially the soybean + piatan and soy + maize + piatã treatments, 0-0.10 m depth, which obtained higher, average values than the others.

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O objetivo deste estudo foi avaliar, no campo, a respiração e a densidade do solo em áreas sob agricultura convencional e orgânica. As avaliações foram feitas em diferentes parcelas estabelecidas com sistema de cultivo orgânico com seis, nove, doze, quinze, dezoito e vinte e um meses de implantação em comparação com o sistema convencional. As parcelas foram divididas em quatro transectos (subparcela) e em cada subparcela foram avaliadas a respiração, a densidade e a porosidade do solo. A respiração do solo foi significantemente maior no sistema de cultivo orgânico com quinze, dezoito e vinte e um meses de implantação quando comparando com o cultivo convencional. A densidade do solo diminuiu após quinze meses de adoção do sistema orgânico. Os resultados mostraram que a adoção de práticas do sistema orgânico aumenta a atividade biológica e decresce a densidade do solo ao longo do tempo.

The aim of this study was to evaluate, in the field, the soil respiration and bulk density under conventional and organic farming plots. The evaluations were made in different plots established as conventional farming system and organic farming system with six, nine, twelve, fifteen, eighteen and twenty one months old. Plots were divided in four transects (subplots) and in each subplot were evaluated soil respiration, bulk density and porosity. The soil respiration was significantly greater in organic farming system with fifteen, eighteen and twenty-one months old as compared with conventional farming. Soil bulk density decreased fifteen months after adoption of organic system. The results showed that the adoption of practices in organic farming plots increases microbial activity and decreases soil bulk density over time.

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The aim of this study was to evaluate the performance of pedotransfer functions (PTFs) available in the literature to estimate soil bulk density (b) in different regions of Brazil, using different metrics. The predictive capacity of 25 PTFs was evaluated using the mean absolute error (MAE), mean error (ME), root mean squared error (RMSE), coefficient of determination (R2) and the regression error characteristic (REC) curve. The models performed differently when comparing observed and estimated b values. In general, the PTFs showed a performance close to the mean value of the bulk density data, considered as the simplest possible estimation of an attribute and used as a parameter to compare the performance of existing models (null model). The models developed by Benites et al. (2007) (BEN-C) and by Manrique and Jones (1991) (M&J-B) presented the best results. The separation of data into two layers according to depth (0-10 cm and 10-30 cm) demonstrated better performance in the 10-30 cm layer. The REC curve allowed for a simple and visual evaluation of the PTFs.

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The southern Brazilian lowlands have been historically used for flooded rice cultivation. Over time, heavy machinery and intensive tillage practices have resulted in soil structure disruption, soil compaction, higher production costs and lower agricultural profitability. This study aimed to evaluate the effect of different deployment times of no-tillage (NT). Soil properties including bulk density (BD), compression index (CI), preconsolidation pressure (σp), bulk density at preconsolidation pressure (BDσp), degree of compactness (DC), soil water retention curve (SWRC), plant available water (PAW) and total organic carbon (TOC) content were evaluated using a 30-yr non-cultivated field (NC), adjacent to the experimental plots as a control. The BD, σp, BDσp and DC decreased in response to NT adoption time while the soil water holding capacity increased, allowing for higher PAW. Results from this study demonstrated the positive effects of NT on the overall quality of soils.

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ABSTRACT Studies of the successive application of manure as fertilizer and its combined effect with long-term soil management systems are important to the identification of the interdependence of physical attributes. The aim of this study was to evaluate changes in the physical properties of a Rhodic Kandiudox under management systems employing successive applications of pig slurry and poultry litter, and select physical indicators that distinguish these systems using canonical discriminant analysis (CDA). The systems consisting of treatments including land use, management and the application time of organic fertilizers are described as follows: silage maize under no-tillage (NT-M7 years); silage maize under conventional tillage (CT-M20 years); annual pasture with chisel plowing (CP-P3 years); annual pasture with chisel plowing (CP-P15 years); perennial pasture without tillage (NT-PP20 years); and no-tillage yerba mate (NT-YM20 years) and were compared with native forest (NF) and native pasture (NP). Soil samples were collected from the layers at the following depths: 0.0-0.05, 0.05-0.10, and 0.10-0.20 m, and were analyzed for bulk density, porosity, aggregation, flocculation, penetration resistance, water availability and total clay content. Canonical discriminant analysis was an important tool in the study of physical indicators of soil quality. Organic fertilization, along with soil management, influences soil structure and its porosity. Total porosity was the most important physical property in the distinction of areas with management systems and application times of manure for the 0.0-0.05 and 0.10-0.20 m layers. Soil aeration and micropores differentiated areas in the 0.05-0.10 m layer. Animal trampling and machinery traffic were the main factors inducing compaction of this clayey soil.

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The mechanisms of seeding machines to cut the mulch, mobilize the topsoil and deposit the seeds in the furrows modify soil properties and interfere in crop growth. This study sought to evaluate the effects of furrow openers and scarification on the attributes of a South Brazilian latosol (Bruno oxisol) and crop yields. The treatments were: double disc furrow opener (DD); shovel type furrow opener (S); shoe type furrow opener (SH); and scarification followed by double disc furrow opener (SC+DD). Samples were collected at 0-10, 10-20 and 20-40 cm and evaluated for soil physical (bulk density, total porosity, macro and microporosity), chemical (pH, Ca, Mg, K and P) and organic carbon content. The normality of data was tested, and the analysis of the variance was performed (F test, p 0.05), and the means was compared by Tukeys test (p=0.05). Soil attributes were analyzed for each layer separately. After four years it was observed that the bulk density is still affected by scarification, which reduces it. The successive use of DD in the winter for the implantation of the crops caused the homogenization of the soil, although with no differences on the other physical and chemical properties. In general, grain yield and dry mass were higher in the treatment that used scarification and the double disc during the summer, and the shoe type when compared to shovel type.

Os mecanismos das semeadoras para cortar os resíduos vegetais, mobilizar a camada superficial do solo e depositar as sementes nos sulcos modificam os atributos do solo e interferem no crescimento das culturas. Portanto, comparar os efeitos destes mecanismos é necessário. Este estudo objetivou avaliar o efeito de diferentes mecanismos sulcadores de semeadora-adubadoras, e da escarificação, sobre atributos de um Latossolo Bruno alumínico típico, e na produtividade de culturas. Os tratamentos avaliados foram: sulcadores tipo disco duplo (DD); sulcadores tipo guilhotina (GUI); sulcadores tipo facão (FA); e escarificação seguido de disco duplo (ESC+DD). Amostras de solo foram coletadas nas camadas de 0-10, 10-20 e 20-40 cm para avaliar atributos físicos (densidade, porosidade total, macro e microporosidade), químicos (pH, Ca, Mg, K e P) e conteúdo de carbono orgânico. Avaliou-se a matéria seca da parte aérea da soja e a produtividade das culturas em três safras distintas. Foi testada a normalidade dos dados, e realizada a análise da variância (teste F a p 0,05), e apresentando significância as médias foram comparadas pelo teste de Tukey a 5%. Os atributos de solo foram analisados para cada camada separadamente. Após quatro anos observou-se que a densidade do solo ainda é afetada pela escarificação, que a reduziu. A utilização sucessiva de DD no inverno para a implantação das culturas provocou homogeneização do solo, não diferindo as demais propriedades físicas e químicas. De maneira geral a produtividade de grãos e massa seca foram superiores no tratamento onde houve escarificação, utilização do disco duplo no verão e utilização do facão, em comparação a guilhotina.

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A compactação do solo constitui um fator limitante ao crescimento e desenvolvimento vegetativo, reduzindo a produtividade agrícola. Neste contexto, objetivou-se com o presente trabalho, avaliar os efeitos da profundidade da camada compactada e do nível de compactação de um Latossolo Vermelho-Amarelo distrófico no crescimento de plântulas de milho. O delineamento experimental foi inteiramente casualizado, em parcelas subdividas no tempo, disposto em um esquema fatorial 2×2 + 1, sendo duas densidades do solo (1,5 e 1,7 g cm-3), duas profundidades da camada compactada (0 -3 cm e 8 -11 cm) e um controle com densidade natural do solo (1,3 g cm-3), com três repetições. Foi cultivado o milho híbrido AG 1051 em colunas durante o período de 38 dias. Durante o período experimental, foram avaliados: a área foliar (AF), o número de folhas (NF), o diâmetro do caule (DC), comprimento do caule (CC), volume radicular (VR), massa seca foliar (MSF), do caule (MSC) e das raízes (MSR), a taxa de crescimento absoluto (TCA) e relativo (TCR). De acordo com os resultados obtidos, o aumento da densidade do solo promoveu alterações morfológicas no diâmetro do caule (DC), e no volume da raiz (VR), e, consequentemente, na massa seca da raiz (MSR) e massa seca total (MST). A compactação na camada superficial é mais prejudicial ao crescimento da cultura do que na camada subsuperficial.

Soil compaction is a limiting factor to growth and vegetative development, reducing agricultural productivity. In this context, the aim of the present study was to evaluate the effects of the depth of the compacted layer and the level of compaction of a Dystrophic Red-Yellow Oxisol on the growth of maize seedlings. The experimental design was completely randomized in split plots in time, arranged in a factorial 2 ×2 + 1, being two soil densities (1.5 and 1.7 g cm-3), two layers of compacted layer (0 -3 cm and 8 -11 cm) and a control with natural soil density (1.3 g cm-3), with three replications. Hybrid maize AG 1051 were cultivated in columns, over the period of 31 days. During the trial period, were evaluated: the leaf area (LA), the number of leaves (NL), stem diameter (SD), stem length (SL), root volume (RV), leaves dry matter (LDM), stem (SDM) and root (RDM), the absolute growth rate (AGR) and relative (RGR). According to the results, the increase in soil density promoted morphological changes in stem diameter, and the volume of the root, and consequently, the root dry mass and total dry matter. The compression in the surface layer is more harmful to crop growth than in the subsurface layer.