Luiz Francisco da Silva Souza

Alteração de propriedades físicas e atividade microbiana de um latossolo amarelo álico após o cultivo com fruteiras perenes e mandioca

This study aimed at evaluating changes in the physical properties of an alic sandy-clay loam Yellow Latosol (Haplortox), located at Cruz das Almas, Bahia, Brazil, cropped for 15 years with banana, 38 years with citrus, 15 years with mango, and 14 years with cassava, compared with soil covered by native forest. In 1991, soil samples were collected for the A, AB, Bw1 and Bw2 horizons and soil bulk density, soil density, macroporosity, microporosity were determined, as well as the distribution of aggregates by size and microbiological activity. Soil bulk density increased and macroporosity decreased in mango and citrus areas, mainly in the upper horizon. Microporosity was lower for the soil under mango, in the upper horizon. The percentage of stable aggregates in water larger than 0.50 mm decreased in the soils under banana and mango. The soil microbiological activity was higher in the area covered by native forest.

Resposta da laranjeira-pêra à adubação com nitrogênio, fósforo e potássio em um Latossolo Amarelo dos Tabuleiros Costeiros

The effects of N, P, and K applications on yield and fruit quality of orange (Citrus sinensis (L.) Osbeck) was studied in a factorial experiment carried out in a Yellow Latosol, of the Coastal Plateau of the Northeast of Brazil. Zero, 150 e 300 kg ha-1 N as urea; 0, 26 and 52 kg ha-1 of P as concentrated superfosfate and 0, 96 and 192 kg ha-1 of K as KCl were used. A linear yield response to N was observed in one, out of four years of observation. Nitrogen decreased fruit size and had no influence on fruit quality measured by percentage of juice, total soluble solids, acidity and ratio total soluble solids/acidity. Yield was highly responsive to P in each year observed. The nutrient increased percentage of juice and the total soluble solids/acidity ratio. Potassium increased yield and fruit size, but decreased the total soluble solids/acidity ratio.

Água no solo influenciada pela posição na paisagem, em uma toposseqüência de solos de tabuleiro do estado da Bahia

Soil landscape position is important in relation to the amount of stored and available water for the plants. The cohesive layer in the tableland soil of the Northeast of Brazil hinders the water flow in the profile. During rainy periods, the formation of transitory water tables above cohesive horizons is possible, due to the restriction of descending vertical flow caused by such horizons. Therefore, the occurrence of interflow (downhill lateral subsuperficial water flow) on the cohesive horizons in slope areas is possible. This hypothesis was evaluated in a toposequence with a length of 190 m and a medium slope of 0.097 m m-1, composed by cohesive argisolic Yellow Latosol-LAx (upper third), cohesive Yellow Argisol-PAx (middle third), transitional soil-PAx/PAC, and non-cohesive Gray Argisol-PAC (lower third). Soil water data estimated weekly during the year of 1996 (53 weeks), in ten points along the toposequence and at seven depths, allowed to prove the mentioned hypothesis; interflow, on the cohesive horizons, caused a larger and more continuous moisture contribution on the long term, in the order LAx → PAx → PAx/PAC → PAC.