Phosphorus extractants in Amazonian soils amended with phosphate fertilizers
01/Dec/1997
Aiming to evaluate the phosphorus availability in five Amazonian soil samples, amended with different phosphates, a pot trial was carried out under greenhouse conditions at the Centro de Energia Nuclear na Agricultura, Piracicaba (SP,Brazil), from october, 1993 to march, 1994, using the soils: medium texture Yellow Latosol, clayey Yellow Latosol, very clayey Yellow Latosol, clayey Red-Yellow Podzolic and very clayey Red-Yellow Podzolic. Four phosphate sources were applied (triple superphosphate, fine yoorin thermophosphate, granular yoorin thermophosphate and North Caroline rock phosphate) […]
Transfer of nitrogen between plants interconnected by arbuscular mycorrhizal fungi (AMF)
01/Dec/1997
This work was undertaken at the State University of North Fluminense (UENF), State of Rio de Janeiro, Brazil, under greenhouse conditions, in the first semester of 1996, to evaluate the role of arbuscular mycorrhizal fungi (AMF) in the process of nitrogen transfer from bean to maize plants using the isotope 15N. Special pots divided in three sections (A, B and C), were constructed and either no barrier and a nylon mesh screen (40 ∝m) (which allowed the AMF hyphae to […]
Mycorrhizae, phosphorus and nitrogen supply on initial growth of “trema” and “fedegoso”
01/Dec/1997
The response of “trema” (Trema micrantha (L) Blum.) and “fedegoso” (Senna macranthera Rich.), both native woody species, to phosphorus (P), nitrogen (N) and inoculation with arbuscular mycorrhizal fungus (AMF) was studied in pots using a low-fertility clayey Dark Red-Latosol (Oxisol) Sample. The study, composed of two experiments, was carried out under greenhouse conditions at the Soil Science Department of Universidade Federal de Lavras, state of Minas Gerais, Brazil, from march 1993 to april 1994. Both species grew poorly in the […]
Extraction of soil water by plants: development and validation of a model
01/Dec/1997
A quantitative model of water movement within the immediate vicinity of an individual root is developed and results of an experiment to validate the model are presented. The model is based on the assumption that the amount of water transpired by a plant in a certain period is replaced by an equal volume entering its root system during the same time. The model is based on the Darcy-Buckingham equation to calculate the soil water matric potential at any distance from […]
Sewage sludge pelletization and CaCO3 addition on corn growth and Zn, Cu and Ni absorption in three hapludox from Brazil
01/Dec/1997
The effect of sewage sludge pelletization added at rates of 0, 1 and 5% (v/v) of dry material was studied on corn growth and absorption of Zn, Cu and Ni, with or without the addition of CaCO3 to increase soil pH to 6.0. Three Hapludox soil samples from the State of São Paulo, Brazil, “latossolo roxo”, “latossolo vermelho-escuro” e “latossolo vermelho-amarelo” (LR , LE and LV, respectively) were used in a greenhouse experiment conducted in Campinas, State of São Paulo, […]
Carbon and nitrogen microbial biomass of soils under different forest types
01/Sep/1997
The fumigation-extraction method was used for measuring soil microbial biomass of C (BM-C) and N (BM-N) in a red-yellow latosol under different forest types. Soil samples from eucalypt and pine plantations presented higher values of BM-C (223.72 and 207.39 mg kg-1 of C in the soil, respectively) than samples from Piptadenia rigida and regenerating secondary forest (82.94 and 79.47 mg kg-1 of C in the soil, respectively). Similar results were obtained for the litter layer. On the other hand, the […]
Rainfall erosivity indices, soil losses and erodibility factor for two soils from the cerrado region – first approximation
01/Sep/1997
The objectives of this paper were: to verify the adequacy of different rainfall erosivity indices, to compare two equations to calculate the rainfall kinetic energy and to estimate the USLE K-factor (soil erodibility) of two soils (Dark – Red Latosol and Red – Yellow Podzolic soil) from the Sete Lagoas (MG) region. There was not a significant difference between the studied equations to calculate rainfall kinetic energy. The EI30 index showed to be a good rainfall erosivity predictor and can […]
Productivity of a lithosol in association with control of erosion using stone barrier contours
01/Sep/1997
Previous studies showed the effectiveness of stone barrier contours on reducing slope lengths, retaining sediment and nutrients, and decreasing runoff, erosion rate and siltation of reservoirs. The extent of these benefits regarding to soil productivity in semiarid regions, however remained unknown. The aim of this study was to determine the effects of stone barrier contours on the productivity of a lithosol thirteen years after its construction. Experiments were carried out in areas of retained sediment and in areas where the […]
Mineralization of nitrogen incorporated as green manure in three soils of Central Amazon, Brazil
01/Sep/1997
This study was carried out under laboratory conditions from September to December, 1992. The objective was to evaluate the mineralization of nitrogen in cowpea (Vigna unguiculata L.) green manure, using 15N as tracer, in three major soils of Central Amazon: an Oxisol, an Ultisol and a Low-Humic Gley. The variation in amount and form of the mineral N from cowpea residues was related to the chemical characteristics of each soil. In the Oxisol and Ultisol the incorporation of green manure […]
Spatial variability of soil characteristics in the Planalto Médio region, state of Rio Grande do Sul, Brazil: I. nested analysis of variance
01/Sep/1997
The spatial variability of the soil characteristics colour, clay content, pH and penetrometer resistance was evaluated in seven areas on which strongly weathered and intensively cropped soils occur, in the Planalto Médio region, State of Rio Grande do Sul, Brazil. Nested analysis of variance was performed with the objective of assessing their homogeneity and optimal soil sampling density. Representative soil profiles were characterized and classified in these areas. Field work was performed from August to November, 1989. Kandiudox, Hapludox and […]