ABSTRACT Amazonian soils have been suffering severe changes resulting from human activities in the region, causing significant changes in soil attributes that can contribute to greater susceptibility to erosion processes. Therefore, the present work aimed to estimate the erodibility in natural and anthropic environments in the southern region of the Amazon. Eight areas in the region were selected, including areas of native forest, savannah, cerradão, pasture and reforestation, delimiting 32 sampling points per area, with collections at a depth of 0.00-0.20 m, totaling 256 samples. Next, texture analysis and quantification of soil organic carbon were performed, and then erodibility was estimated by indirect prediction methods, Tukey’s test, Pearson’s correlation and factorial analysis of principal components. According to the results obtained, it was observed that the evaluated areas of native forest 1 and 2, cerradão and pasture present high susceptibility to erosion in relation to the cerrado, reforestation with genipap, teak and mixed areas. Therefore, it was noted that the high level of erodibility is associated with a greater predominance of sand fraction, K factor, Ki Kr and low clay content, as well as with the management employed in the areas.

RESUMO Os solos do semiárido brasileiro estão sob um constante processo de degradação e estratégias sustentáveis de produção agropecuária devem ser adotadas de forma a mitigar este problema. Sendo assim, o objetivo deste trabalho foi avaliar o comportamento físico-hídrico do solo quatro anos após a implantação de sistemas de integração lavoura-pecuária-floresta no semiárido Brasileiro. O experimento foi instalado no município de Alagoinha, PB, em um Planossolo Háplico de textura franco-arenosa. Foram avaliados cinco sistemas de integração em delineamento de blocos ao acaso (DBC) com quatro repetições: i) Ipê roxo (Tabebuia impetiginosa) + Urochloa decumbens (iPF1); ii) Gliricídia (Gliricidia sepium) + Urochloa decumbens (iPF2); iii) Sabiá (Mimosa caesalpiniifolia) + Urochloa decumbens (iPF3); iv) Milho (Zea mays) + Urochloa decumbens (iLP); v) Urochloa decumbens (Pastagem). Os dados submetidos a análise de variância e teste de Tukey (p<0,05) demonstraram que a integração Lavoura-Pecuária-Floresta, após o período de quatro anos, ainda não promoveu melhoria física significativa dos atributos físicos do Planossolo em estudo, porém, o índice S apresentou valores satisfatórios. Em relação a condição antecedente a implantação dos sistemas, verifica-se uma alteração positiva na estrutura, refletindo na redução da densidade do solo e aumento da porosidade total.

ABSTRACT The soils of the Brazilian semi-arid are under a constant process of degradation and sustainable agricultural production strategies must be adopted in order to alleviate this problem. Therefore, the objective of this work was to evaluate the physical-water behavior of an Albaqualfs four years after the implantation of crop-livestock-forest integration systems in the Brazilian semiarid. The experiment was installed in the county of Alagoinha, PB, in an Albaqualfs with a sandy-loam texture. Five integration systems in randomized block design (DBC) with four replications were evaluated: i) Purple Ipe (Tabebuia impetiginosa) + Brachiaria decumbens (iPF1); ii) Gliricidia (Gliricidia sepium) + Urochloa decumbens (iPF2); iii) Sabiá (Mimosa caesalpiniifolia) + Urochloa decumbens (iPF3); iv) Maize (Zea mays) + Urochloa decumbens (iLP); v) Urochloa decumbens (pasture). The data submitted to analysis of variance and Tukey's test (p<0.05) demonstrated that the crop-livestock-forest integrated system, after the period of four years, has not yet promoted significant physical improvement of the attributes of the Albaqualfs under study, however, an attribute such as the S index, presented satisfactory values. Regarding the condition prior to the implantation of the systems, there is a positive change in the structure, reflecting in the reduction of the bulk density of the soil and an increase in the total porosity.

ABSTRACT In the Amazon region, soil patches with an anthropic A horizon are found, called Indian black earths (IBEs). Indian black earths are highly fertile and, therefore, are deforested by small local farmers to cultivate without basic management that maintains soil and crop sustainability. Therefore, in order to evaluate the effect of using different cultures on the spatial variability of soil chemical attributes, three cultivated IBEs and one IBE under natural forest were selected for georeferencing and sample collection. The collection was made with a mesh system with 88 points per IBE, stratified in three layers: 0–0.05, 0.05–0.10 and 0.10–0.20 m. The soil was sampled, dried in the shade and sieved to obtain the fine earth fraction for analysis of chemical attributes. Descriptive statistical and geostatistical analyses were applied to the results. The use and management of soil influenced the spatial behavior of the chemical attributes of IBEs. The cultivation of Brachiaria over many years favored the reduction of the spatial variability of chemical attributes. The use of cacao and coffee crops also favored the homogeneity of the IBEs in relation to the natural forest, but not as much as for Brachiaria, likely due to the succession of crops that preceded these crops. The IBE in the forest contains a high natural spatial correlation in the first 0.1 m of the surface; however, more than 70% of this correlation is linked to a random variation.

RESUMO Sistemas integrados de produção agropecuária são estratégias promissoras para a recuperação de pastagens e solos degradados. Objetivou-se avaliar o efeito de arranjos com sistemas integrados de produção agropecuária, aos quatro anos de implantação, sobre a fertilidade, estoque de carbono e estabilidade de agregados de um Planossolo Háplico, no semiárido da Paraíba. O delineamento experimental foi de blocos casualizados, com 5 tratamentos e 4 repetições: Brachiaria decumbens; B. decumbens + ipê; B. decumbens + gliricídia; B. decumbens + sabiá; e B. decumbens + milho. Avaliaram-se os atributos químicos e de fertilidade, estoque de carbono, estabilidade estrutural e de agregados do solo nas camadas de 0,00-0,10; 0,10-0,20; e 0,20-0,30 m. O sistema B. decumbens + milho apresentou teor de matéria orgânica 11,93 % maior que B. decumbens e foi superior aos demais sistemas avaliados. Em relação ao estoque de carbono na camada de 0,00-0,10 m, em B. decumbens o aporte foi 2,66 Mg ha-1 maior que em B. decumbens + milho e, em média, 4,69 Mg ha-1 superior aos sistemas com o componente arbóreo. No médio prazo, B. decumbens mostra-se mais eficiente no aporte de carbono ao solo. A estabilidade estrutural, o índice de estabilidade de agregados e a fertilidade do solo não apresentaram alteração, em relação aos arranjos, após quatro anos de implantação.

ABSTRACT Integrated farming systems are promising strategies for the recovery of pastures and degraded soils. This study aimed to evaluate the effect of integrated farming systems arrangements, after four years of implementation, on the fertility, carbon stock and aggregate stability of an Alfisol, in the semiarid region of the Paraíba state, Brazil. A randomized block experimental design was used, with 5 treatments and 4 replications: Brachiaria decumbens; B. decumbens + Tabebuia impetiginous; B. decumbens + Gliricidia sepium; B. decumbens + Mimosa caesalpiniifolia; and B. decumbens + maize. The soil chemical attributes, fertility, carbon stock and structural and aggregate stability were evaluated in the 0.00-0.10, 0.10-0.20 and 0.20-0.30 m layers. The B. decumbens + maize system presented an organic matter content 11.93 % higher than B. decumbens, and was higher than the other systems evaluated. Concerning the carbon stock in the 0.00-0.10 m layer, in B. decumbens the uptake was 2.66 Mg ha-1 higher than that of the B. decumbens + maize system and, on average, 4.69 Mg ha-1 higher than for the systems with the arboreal component. In the medium-term, B. decumbens is more efficient in adding carbon to the soil. The soil structural stability, aggregate stability index and fertility were not affected by the different arrangements after four years of implementation.

RESUMO Os sistemas integrados de produção agropecuária, envolvendo lavoura, pecuária e floresta (ILPF) são estratégias que promovem a qualidade do solo. Objetivou-se com esse trabalho avaliar a influência do sistema de integração Lavoura-Pecuária-Floresta na disponibilidade de água em um Planossolo na mesorregião do Agreste da Paraíba. O experimento foi conduzido na estação experimental da Empresa de Pesquisa Agropecuária da Paraíba (EMEPA), em Alagoinha (PB). O solo é um Planossolo Háplico, horizonte A moderado.Em junho de 2015, foram implantados os seguintes consórcios: I. Gliricídia (Gliricidia sepium (Jacq.) Steud.) + Brachiaria decumbens; II. Sabiá (Mimosa caesalpiniifolia) + Brachiaria decumbens; III. Ipê amarelo (Tabebuia alba (chamiso) sandwith) + Brachiaria decumbens; IV. Milho (Zea mays L.) + Brachiaria decumbens; V. Brachiaria decumbens. Utilizou-se o delineamento de blocos casualizados (DBC), com cinco tratamentos. As variáveis analisadas foram: capacidade de campo - θCC, ponto de murcha permanente - θPMP, água disponível - θAD, granulometria, grau de floculação (GF), porosidade (total - α, macro - Ma e micro - Mi), condutividade hidráulica saturada - Kθ, resistência a penetração - Rp, índice de estabilidade de agregados - IEA. De acordo com os resultados observa-se que a disponibilidade de água na integração lavoura-pecuária-floresta implantada no agreste paraibano não apresentou variação significativa após um período de três anos. A integração, após o período de três anos, ainda não promoveu melhoria física significativa dos atributos do Planossolo em estudo.

ABSTRACT Integrated agricultural production systems, involving agriculture, livestock, and forest are strategies that improve soil quality. The objective of this work was to evaluate the effect of the integrated crop-livestock-forest system (ICLF) on water availability of a Planosol in the Agreste region of the state of Paraíba (PB), Brazil. The experiment was conducted at the experimental site of the Agricultural Research Company of Paraíba (EMEPA), in Alagoinha, PB. The soil evaluated was a Eutric Planosol, with a moderate A horizon. The following intercrops (treatments) were implemented in June 2015: I. Gliricidia sepium + Brachiaria decumbens; II. Mimosa caesalpiniifolia + Brachiaria decumbens; III. Tabebuia alba + Brachiaria decumbens; IV. Zea mays + Brachiaria decumbens; and V. Brachiaria decumbens. A randomized block experimental design was used, with five treatments. The analyzed variables were field capacity, permanent wilting point, soil available water, granulometry, degree of flocculation, total porosity, macroporosity, microporosity, saturated hydraulic conductivity, resistance to penetration, and aggregate stability index. The results showed that the water availability in the ICLF implemented in the Agreste region of Paraíba had no significant variation after three years. After the three-year period, the ICLF promoted no significant physical improvement in the attributes of the evaluated Planosol.

ABSTRACT The Seridó Desertification Region is a result of inadequate management of the native Caatinga vegetation, which generated degraded areas with little or no capacity for plant production. The area has experienced a succession of different land uses, but little is known about the impact of these changes. The present study tested the hypothesis that the intense degradation of the Caatinga drastically decreased vegetal biomass production, which favored direct soil exposure and resulted in a lower abundance and diversity of species and groups of vegetation as well as microorganisms. This study aimed to quantify some of the main physical, chemical, and microbiological properties of Alfisol ( Luvissolo Crômico órtico lítico ) and Entisol ( Neossolo Litólico eutrófico típico ) under different plant covers in the Seridó Desertification Region, in the municipality of Parelhas, in the state of Rio Grande do Norte (RN), Brazil. Three different areas were studied: an area of preserved Caatinga, a recovery area with jurema [ Mimosa tenuiflora (Willd.) Poir.], and a degraded area. Soil samples were collected from the 0.00-0.10 m soil layer and later characterized in terms of their physical and chemical properties. The microbiological characteristics analyzed were microbial activity (microbial biomass carbon and microbial respiration) and glomalin. The soil under the Caatinga vegetation exhibited better properties than the other analyzed soils. Aggregate stability was the physical property with the highest potential for differentiating between areas. Glomalin, which is associated with the presence of mycorrhizae, and which, in turn, is related to the uptake of P, which is often deficient in these soils, was the most discriminating microbiological variable according to an analysis of canonical variables. The total of Ca2+ and Mg2+ was the most discriminating chemical properties, and played a positive role in soil aggregation, especially Ca2+.

A cobertura vegetal do solo é decisiva para redução dos efeitos erosivos do impacto direto das gotas de chuva na superfície do solo. Desta forma, objetivou-se com este estudo determinar o índice de cobertura vegetal (CV) e desenvolver modelos para sua estimativa para a cultura da soja, usando os atributos climáticos no período de chuvas intensas no Sul de Minas Gerais. As determinações da CV foram feitas semanalmente, na área experimental do Departamento de Ciência do Solo, Universidade Federal de Lavras, no período de novembro de 1999 a maio de 2000, em 28 cultivares de soja com potencial para cultivo nesta região. Para avaliação da cobertura vegetal foi utilizada a metodologia descrita por Stocking (1988). Na modelagem procurou-se relacionar a CV com os valores acumulados dos seguintes atributos climáticos: temperatura média (Tmed), precipitação (PREC) e umidade relativa do ar (UR). Os valores de cobertura vegetal apresentaram uma amplitude de variação de 56 a 83%, sendo BR 162, LO 12 L e M. Soy 108 as cultivares mais eficientes e FT Abyara e Tucano as menos eficientes. O hábito diferencial de crescimento das cultivares ajuda a explicar esse comportamento. O modelo ajustado adequado para estimativa da CV foi: CV = 116589,976 + 0,422 . Tmed + 0,132 . PREC - 0,095 . UR + 0,000024 . Tmed², R² = 0,99 (P < 0,01). A determinação da CV nas diferentes fases de desenvolvimento da cultura é de grande importância, uma vez que seu estabelecimento coincide com o período de maior potencial erosivo das chuvas na região estudada.

Vegetal cover of soil is decisive to reduce the erosive effects of direct impact of raindrops on the soil surface. Therefore, the objective of this study was to determine the vegetal cover (CC) index and to develop models to estimate it for soybean cultivars, using climatic attributes in the period of intense rains in the South of the State of Minas Gerais in Brazil. CC was measured weekly in the experimental area of the Department of Soil Science, Federal University of Lavras, from November 1999 to May 2000, for 28 soybean cultivars with yield potential in this region. To evaluate the vegetal cover, the method described by Stocking (1988) was used. In the modeling, CC was related with the accumulated values of following climatic attributes: medium temperature (Tmed), precipitation (PREC), and relative humidity of the air (RH). Vegetal cover values presented an amplitude from 56 to 83%, being BR 162, LO 12 L and M. Soy 108, the more efficient cultivars, and the FT Abyara and Tucano, the least efficient ones. The differential growth habit of the cultivars helps to explain this behavior. The best adjusted model for the estimative of CC was: CC = 116589.976 + 0.422, Tmed + 0.132, PREC - 0.095, RH + 0.000024 Tmed², R² = 0.99 (P < 0.01). The knowledge of CC for different development phases of the crop is of great importance, taking into account that its establishment time coincides with the highest erosive potential of the rains in the studied region.

Entre os fatores climáticos que interferem na erosão hídrica, a precipitação pluvial, expressa pela erosividade da chuva, é o de maior importância. Portanto, seu conhecimento torna-se fundamental na recomendação de práticas de manejo e conservação do solo que visem à redução da erosão hídrica. Nesse contexto, os objetivos deste trabalho foram: a) determinar a erosividade da chuva e sua distribuição, na região do Vale do Rio Doce, MG, para nove sub-regiões; b) estimar o índice EI30 mensal, no período de 1969 a 2005, para os municípios de Ferros e Guanhães e c) determinar o tempo de retorno dos índices mensais e anuais de erosividade. O valor médio de erosividade obtido foi de 12.913 MJ mm ha-1 h-1 ano-1, sendo classificado como muito alto. Entre as sub-regiões, os valores de erosividade variaram de 8.243 a 26.676 MJ mm ha-1 h-1 ano-1. O período crítico em relação à erosão hídrica, em razão da ocorrência de chuvas erosivas, é de janeiro-março e novembro-dezembro, contribuindo com 88,6% da erosividade anual. De abril a outubro, praticamente inexiste a ocorrência de erosividade crítica. Os valores máximos individuais estimados para os tempos de retorno de 1, 10, 50 e 150 anos foram de 5.508, 15.534, 18.110, 19.632 e 5.542, 17.653, 20.954, 22.931 MJ mm ha-1 h-1 ano-1, para Ferros e Guanhães, respectivamente. A determinação dos valores de erosividade ao longo do ano permite identificar os meses nos quais os riscos de perdas de solo e água são mais elevados, o que exerce relevante papel no planejamento das práticas conservacionistas.

Among the climatic factors that interfere in water erosion, precipitation, expressed by the rainfall erosivity, is of great importance. Therefore, its knowledge becomes fundamental for the recommendation for soil management and conservation practices that seek the reduction of water erosion. In that context, the objectives of this work were: a) to determine the rainfall erosivity and its distribution at Rio Doce Valley, Minas Gerais State, for nine sub-regions, b) to estimate the monthly EI30 index in the period from 1969 to 2005 for Ferros and Guanhães counties, and c) to determine the return periods of the monthly and yearly erosivity indexes. The average erosivity value obtained was 12.913 MJ mm ha-1 h-1 year-1, being classified as very high. Among the sub-regions, the erosivity values varied from 8.243 to 26.676 MJ mm ha-1 h-1 year-1. The critical periods in relation to water erosion due to the occurrence of erosive rains are January-March and November-December, contributing with 88.6% of the annual erosivity. From April to October, the occurrence of critical erosivity practically does not exist. The estimated individual maximum values for the return periods of 1, 10, 50, and 150 years were of 5.508, 15.534, 18.110, 19.632, and 5.542, 17.653, 20.954, 22.931 MJ mm ha-1 h-1 year¹ for Ferros and Guanhães, respectively. The determination of the erosivity values throughout the year allows to identify the months in which the risks of soil and water losses are higher, which is important for planning the conservation practices.