Solos arenosos representam um desafio para a produção agrícola. Assim, o objetivo deste estudo foi caracterizar o comportamento físico-hídrico de três classes de solos arenosos através da curva de retenção de água, índice S e distribuição de poros por tamanho no geombiente dos Tabuleiros Costeiros de Arez, no estado do Rio Grande do Norte. Amostras de solo com estrutura indeformada foram coletadas nos horizontes superficiais e subsuperficiais de três perfis de solos para caracterização físico-hídrica através dos seguintes atributos: Curva de retenção de água no solo, capacidade de água disponível às plantas, potencial matricial no ponto de inflexão, umidade no ponto de inflexão, água prontamente disponível, índice de vazios, capacidade de campo relativa (CCr), distribuição de poros por tamanho, carbono orgânico total e textura do solo. Tanto em superfície quanto em subsuperfície o teor de água disponível nos solos foi influenciado positivamente pelo conteúdo de carbono orgânico e, em subsuperfície pelo aumento do teor de argila e pelo percentual de areia fina. A distribuição de poros por tamanho se apresentou de forma regular, característica de solos arenosos, com predomínio de macroporos e mesoporos, exceto para os horizontes subsuperficiais do solo no terço inferior com caráter fragipânico, onde predominou micro e criptoporos. O índice S reduziu em profundidade e os valores de CCr ficaram abaixo de 0,6, indicando uma baixa capacidade de retenção de água no solo, independentemente da posição deles na paisagem. Embora, os solos no terço inferior tenham apresentado maiores teores de água disponível.

A demanda mundial por alimentos tem contribuído para a expansão de novas fronteiras agrícolas em solos arenosos. Contudo, esses solos são frágeis e necessitam ser bem manejados de forma que possam expressar seu potencial produtivo. O objetivo deste estudo foi avaliar a qualidade física de um Neossolo Regolítico sob sistema de integração lavoura-pecuária no semiárido da Paraíba. 11 tratamentos foram avaliados em delineamento inteiramente casualizado, com cinco repetições. As amostras com estrutura indeformada foram coletadas nas camadas de 0-0,1 e 0,1-0,2 m e utilizadas na determinação da porosidade total (PT), Macroporosidade (Ma), microporosidade (Mi), porosidade de aeração (Pa), Densidade do solo (Ds), condutividade hidráulica saturada (Kθ), capacidade de campo (θCC), ponto de murcha permanente (θPMP), água disponível (θAD), granulometria e o grau de floculação (GF). Os dados foram analisados por meio da análise de variância e análise de componentes principais. O solo sob Floresta apresentou qualidade física do solo superior a muito dos tratamentos avaliados, contudo, melhorias físicas substanciais foram observadas no solo sob capim Massai, Urochloa decumbens e Urochloa decumbes + milho. Conclui-se que os atributos macroporosidade, condutividade hidráulica saturada e porosidade de aeração estão sendo pelos sistemas integrados de produção agropecuária.

Reduced stability and structural resilience expose sandy soils to physical degradation under intensive production systems. This study aimed to evaluate the influence of different cover crops (CC) under no-tillage system (NTS) cotton cropping, grown either individually or in combination, on the soil physical quality (SPQ) of a sandy loam Oxisol (Latossolo) in southeastern Brazil. To quantify the effects of CC on soil physical quality indicators, an experiment in randomized blocks design was implemented with the treatments: CC1: single cultivation of Ruzi grass; CC2: Intercropping of Pearl Millet + Ruzigrass; CC3: Intercropping of Pearl Millet + Velvet bean; CC _Mixture : Intercropping of Ruzi grass, Pearl Millet and Velvet bean; and Control: maintenance of spontaneous plants. Undisturbed samples were taken from layers 0.00-0.10, 0.10-0.20, 0.20-0.40 and 0.40-0.60 m, in which were determined the soil bulk density (Bd), total porosity (TP), available water (AW), soil penetration resistance (PR) and the least limiting water range (LLWR). According to the multivariate analyses, the CC ₂ treatment resulted in better SPQ compared to the other treatments. The LLWR, air-filled porosity (θ _AFP ), and AW were responsible for differentiating the CC ₂ treatment compared to the other treatments evaluated. Regardless of treatments, values of Bd> 1.75 Mg m ^-3 result in loss of SPQ due to the significant increase in PR and decreases in AW and LLWR. In the CC ₃ and Control, there was a physical impediment caused by the increase in Bd in the 0.10-0.20 m layer, which could result in the confinement of cotton roots to the surface, making them more susceptible to water stress. Soil PR reached values greater than 2.5 MPa for water contents lower than the θ _PWP in most treatments. In treatment CC3, for water contents equivalent to the θ _PWP , the PR did not exceed 6 MPa, while for the other treatments, the PR reached values greater than 10 MPa. Only the PR was influenced using CC. Soil moisture is considered crucial to maintain PR below impeding values, determining the control of the physical quality of this sandy soil.

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.

The objective of this work was to evaluate the spatial variability of resistance to penetration in soil under sugarcane crops subjected to different harvest methods in the North Coast microregion of the state of Paraiba, Brazil. The study was conducted in a Typic Hapludult under sugarcane crops, at the farms Santa Emília-II and Maria da Luz-I of the company Miriri Food and Bioenergy S/A, in the municipalities of Rio Tinto and Capim, respectively, state of Paraíba, Brazil. Three sugarcane areas with different harvest methods (manual, mechanized, and manual/mechanized) were selected. The sampling was done in plots of 100 × 100 m, using a grid of 20 × 20 m, covering planting rows and interrows; each intersection point of the grid was georeferenced, and the soil mechanic resistance to penetration was evaluated with the aid of an impact penetrometer (IAA/Planalsucar-Stolf) up to the depth of 0-0.6 m. Soil disturbed and undisturbed samples from the 0.0-0.1 and 0.1-0.2 m layers were collected for analyses of soil moisture, texture, clay dispersed in water, flocculation degree. A pure nugget effect was found in the 0.0-0.1 and 0.4-0.5 m soil layers in the rows of the areas with manual/mechanized harvest. The spherical model was found for most conditions evaluated. The results for the areas were similar, with amplitude of 25-49 m, indicating that the harvest management had no effect on the soil resistance to penetration. No compacted areas were found, and the spatial dependency of the resistance to penetration was characterized as moderate to strong.

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.