There is a variation in the depth of subsurface horizon of Planosols in semi-arid region, which may influence the agricultural potential and affect food production. The general aim of this study was to identify potentialities and limitations of two Planosols as a function of subsurface horizon depth. The adjacent profiles P1 and P2 were studied in Pentecoste (Ceará, Brazil). Morphological, physical, and chemical analyses were done aiming at soil characterization. Soil bulk density (BD), porosity, and penetration resistance (PR) were analyzed in a completely randomized split-plot design with four replicates to compare P1 and P2 and the horizons Ap and Btf. Btf was found at 62cm depth in P1 and at 18 cm depth in P2. Indicatives of water saturation were more evident in P2. The profile P1 showed lower hardness and higher friability, as well as higher acidity in subsurface (pHH2O from 4.4 to 4.7) and higher aluminum content (1.2cmolc kg-1). Both profiles were eutrophic and showed low contents of organic carbon (1.5 to 8.5g kg-1) and phosphorus (0.9 to 3.9mg kg-1). The sodium percentage in CEC was 9.1% in P1 and 5.5% in P2. Water retention increases in Btf compared with Ap was 7.3% in P2 and 2.7% in P1. Both profiles showed increase in BD in Btf, reaching 1.7g cm-3, while PR was higher in P2 (1.5 MPa). There are potentialities and limitations common to both soil profiles, but P1 has more physical potentialities and more chemical limitations than P2.

RESUMOA baixa disponibilidade de água no solo é um dos fatores mais limitantes para o crescimento e sobrevivência das plantas. O objetivo deste trabalho foi avaliar as respostas dos processos fisiológicos ao longo do dia na fase inicial do crescimento do guanandi (Calophyllum brasilense Cambess), mogno africano (Khaya ivorensis A. Chev) e oiti (Licania tomentosa (Benth.) Fritsch) durante um período de estresse hídrico e outro de reidratação, em solo com e sem adição de matéria orgânica. O experimento foi conduzido em casa de vegetação, em delineamento experimental inteiramente casualizados, em arranjo fatorial 3 x 2 x 2, sendo composto por três espécies (guanandi, mogno africano e oiti), dois regimes hídricos (com e sem restrição hídrica) e dois níveis de fertilização orgânica (com e sem adição de matéria orgânica). A irrigação foi suspensa por 15 dias em metade das plantas, enquanto que a outra metade (controle) recebeu irrigação continuamente. Foram realizadas as seguintes avaliações: umidade gravimétrica do solo (θ) e trocas gasosas foliares (A, E e gs). A suspensão da irrigação reduziu o potencial hídrico e as trocas gasosas foliares das três espécies estudadas As plantas que sofreram estresse hídrico tiveram os maiores valores das trocas gasosas às 7:00 horas em seguida decrescendo ao longo do dia. No período de recuperação, as planta apresentaram as trocas gasosas semelhantes as plantas continuamente irrigadas, porém com os valores ainda reduzidos.Palavras-chave: trocas gasosas, umidade do solo, potencial hídrico. DAILY PHYSIOLOGICAL RESPONSES OF WOODY UNDER WATER STRESS IN SOIL WITH AND WITHOUT ADDITION OF ORGANIC MATTER ABSTRACTThe low availability of water in the soil is one of the limiting factors for the growth and survival of plants. The objective of this work was to evaluate the responses of physiological processes