The higher water‐holding capacity of Oxisols and Ultisols compared to that of the Vertisols and Inceptisols at 15 bars of suction is attributed to the presence of intra‐aggregate void spaces. Existence of such voids was verified with the aid of a scanning electron microscope. These voids are obvious in soils with kaolinitic and oxidic mineralogy but are not evident in soils of montmorillonitic or amorphous oxide composition.

Os frutos de pitaia apresentam grande importância nutricional e economicamente vem se estabelecendo em diversos países, como o Brasil. Apesar do grande potencial comercial da pitaia, ainda são escassos os estudos de caracterização físico-química, compostos bioativos e de atividade antioxidante e enzimática dos seus frutos, principalmente considerando a espécie Hylocereus undatus. Neste trabalho, objetivou-se analisar as características físico-químicas, compostos bioativos, atividade antioxidante e enzimática de frutos da pitaia (Hylocereus undatus) em dois períodos (após a colheita = 45 dias após a antese e armazenamento por 12 dias = 57 dias após a antese), a fim de avaliar as características em dois períodos de comercialização. As análises realizadas foram: DL/DT (diâmetro longitudinal/transversal), massa fresca dos frutos, cor (casca e polpa), acidez titulável, sólidos solúveis, sólidos solúveis/acidez titulável, pH, lipídios, cinzas, açúcares redutores e totais, ácido ascórbico, compostos fenólicos, flavonoides amarelos, atividade antioxidante e enzimática. Dos parâmetros avaliados, as características físicas e lipídios não foram influenciados em decorrência ao armazenamento, entretanto as demais características químicas, atividade antioxidante e enzimática e compostos bioativos apresentaram diminuição conforme a armazenamento dos frutos decorrente a reações bioquímicas. Destacando os frutos com 45 dias, com maiores teores de antioxidantes, compostos bioativos, açúcares e acidez, ao qual indica frutos com qualidade e maior aceitabilidade dos consumidores decorrente ao maior conteúdo de compostos benéficos e essenciais ao consumo, além de ser de grande importância industrial. PALAVRAS-CHAVE:Cactaceae. Qualidade. Alimento Funcional.

ABSTRACT:In irrigated soils, a continuous state of high moisture reduces resistance of the soil to applied external forces, favouring compaction. The aim of this study was to evaluate the susceptibility to compaction of developed calcareous soils in irrigated annual and perennial cropping systems of the Apodi Plateau, located in the Brazilian semi-arid region. Four areas of irrigated crops were evaluated: banana after two (B2) and 15 (B15) years cultivation, pasture (P), and a corn and beans succession (MB), as well as the reference areas for soil quality and corresponding natural vegetation (NVB2, NVB15, NVP and NVMB). Samples were collected at layers of 0.00-0.10 and 0.20-0.30 m; and for B2 and B15, samples were collected in the row and inter-row spaces. The following properties were determined: degree of compactness (DC), preconsolidation pressure (σ p ), compression index (Cc), maximum density (ρ max ), critical water content (WC crit ), total organic carbon (TOC) and carbon of light organic matter (C lom ). Mean values were compared by the t-test at 5, 10, 15 and 20 % probability. An increase was seen in DC at a layer of 0.20-0.30 m in MB (p<0.15), showing the deleterious effects of preparing the soil by ploughing and chiselling, together with the cumulative traffic of heavy machinery. The TOC had a greater influence on ρ max than the stocks of C lom . Irrigation caused a reduction in Cc, and there was no effect on σ p at field capacity. The planting rows showed different behaviour for Cc, ρ max , and WC crit, , and in general the physical properties displayed better conditions than the inter-row spaces. Values for σ p and Cc showed that agricultural soils display greater load-bearing capacity and are less susceptible to compaction in relation to soils under natural vegetation.

Soil and crop management systems change the soil structure, thereby affecting soil quality. The "profil cultural" method (PCM) has been used to identify the effects of management systems on soil structure; however, few studies relate the structures identified by the PCM to quantitative indicators of soil structural quality. This study aimed to quantify soil structures using the PCM and relate these structures to bulk density (Bd), critical bulk density (Bdc), soil aeration capacity (ε a ), least limiting water range (LLWR), and soil air permeability (K a ) under different soil and crop management systems. The study was developed in a long-term experiment (24 years) involving two systems of soil management (no-tillage and conventional tillage) and two systems of crop management (rotation and succession), resulting in four treatments: no-tillage with crop rotation (NTr), no-tillage with crop succession (NTs), conventional tillage with heavy harrowing and crop rotation (CTr) and conventional tillage with heavy harrowing and crop succession (CTs). The PCM was used to identify the different homogeneous morphological units (HMUs) in the soil profile. Undisturbed soil samples were collected for the HMUs that were most represented in the profiles to determine K a , LLWR, Bd, and ε a . ). The proportion of samples where Bd > Bdc was 23 % under CTs, 77 % under CTr, 32 % under NTs, and 39 % under NTr. The structures that were most restrictive to root development (CΔ, CΔμ, FmtΔμ, and FmtμΔ) show a lower K a and greater soil penetration resistance as the soil dries. Pores are more continuous and the structure is less restrictive to plant development in no-tillage than in conventional tillage.

Agroforestry systems provide many environmental benefits in semi-arid regions; however, trampling by cattle, and agricultural practices, can degrade physical quality of the soil. The aim of this study was to evaluate the degree of compaction and the compression behaviour of a Luvisol after 14 years under agro-silvopastoral (ASP) and silvopastoral systems (SILV), compared with a soil under natural vegetation (NV). We evaluated the degree of soil compactness, compaction index, pre-consolidation pressure, maximum bulk density, critical water content and the stocks of total organic carbon (C), organic matter (OM), C in light organic matter (LOM), and nitrogen (N) in LOM. The results indicated that agroforestry systems change the compressive behaviour of the soil, increasing maximum bulk density (P < 0.05) and reducing critical water content (P < 0.05). Despite the increases in maximum bulk density, changes induced by agroforestry system did not affect the pore space, as shown by similar values for degree of compactness (P > 0.05) under ASP, SILV and NV. This suggests a change in the quality of OM, as evidenced by the lower values for stocks of N in LOM (P < 0.10) and total organic C (P < 0.05) under ASP and SILV, whereas pre-consolidation pressure was unaffected (P > 0.05). After 14 years, the degree of compactness and load-bearing capacity of the soils under ASP and SILV had not increased, being suitable for plant growth.