Fabiano Ribeiro do Vale

Adubação mineral do angico-amarelo ( Peltophorum dubium (Spreng.) Taub.)

A greenhouse experiment was carried out with seedlings of the tropical tree Peltophorum dubium (Spreng.) Taub. in order to study its nutritional requirements. As substrate an oxisol with low nutrient availability was used and distributed in 10 treatments: a complete one (N, P, K, Ca, Mg, S, B and Zn), the others lacking one element in each treatment (-N, -P, -K, -Ca, -Mg, -S, -B and -Zn) and a control (natural soil). The following characteristcs were assessed: plant height and diameter growth, dry matter production and levels of nutrient into dry matter of shoots. It was concluded that seedlings are affected by the omission of all nutrients in the following order: P > N > S > Ca > Mg > K > B. The omission of K, Ca and Mg affects S absorption by plants.

Carbono, nitrogênio e enxofre em frações granulométricas de dois latossolos submetidos à calagem e adubação fosfatada

The amount and distribution of carbon, nitrogen, and sulfur in whole soil and in particle-size fractions were analyzed in two clayey Dark Red Latosols (LE1 and LE2). LE1 (forest as natural vegetation), from Cordeiropolis, Sao Paulo, cultivated with citrus since 1982 receiving two lime treatments, control and 18 t ha-1 applied twice in 1983 and 1994. Since 1976, LE2 (cerrado as natural vegetation) from Planaltina, Federal District (cerrado region), was cultivated with different crops (wheat, soybean, rice and sorghum) sown for 14 years with pasture grass (Andropogon gayanus L.), with and without the addition of 1.660 kg ha-1 of P2O5 as triple superphosphate. For reference purposes, additional samples were collected from uncropped soils in both LE1 and LE2 sites. Carbon, nitrogen and sulfur contents were determined in whole soils and in their particle-size fractions. The drastic reduction of carbon, nitrogen and sulfur contents in the cultivated areas of LE1 was followed by an intensive depletion in CEC at limed and control plots, stressing the importance of management and conservation of organic matter in this soil. In the LE2 soil, the reduction of C, N and S contents with cultivation was less intense and associated with a higher decomposition of organic compounds linked to the intermediate fraction. Liming resulted in a higher preservation of soil organic matter, although phosphorus addition did not affect carbon and nitrogen contents in the LE2 cultivated areas. Fine fraction plays a crucial role in the stabilization of soil organic matter, since the largest reservoirs of carbon, nitrogen and sulfur were associated to this particle-size. The distribution of carbon, nitrogen and sulfur between particle-size fractions is characterized by a depletion of organic materials associated to coarse, intermediate and fine fractions and a shift towards fine fraction associated materials.

Liming effects on growth of native woody species from Brazilian Savannah

Em condicoes de casa de vegetacao foram avaliados os efeitos da calagem no crescimento de quinze especies florestais nativas do Brasil. Foram utilizadas especies pertencentes aos grupos ecologicos de plantas pioneiras, secundarias e climax. Os tratamentos de solo consistiram na ausencia de calagem (-LIM) e calagem ate atingir pH=6,0 (+LIM). Em geral, as especies pioneiras e secundarias apresentaram as maiores respostas a calagem quanto a producao de materia seca total (TDM), enquanto que as especies climax nao foram afetadas pelos tratamentos de solo. A classificacao das quinze especies em relacao a tolerância a acidez do solo variou de altamente sensiveis a altamente tolerantes. As especies pioneiras e secundarias, quando cresceram em solo corrigido (+LIM), apresentaram maiores conteudos de Ca, Mg e P e baixa eficiencia de utilizacao de Ca e Mg (CaUE e MgUE, respectivamente); porem, a eficiencia de utilizacao de P (PUE) foi maior neste tratamento. Em contraste, os conteudos de Ca, Mg e P das especies climax foram apenas levemente afetados pela calagem. Em geral, as especies climax foram menos eficientes do que as pioneiras e secundarias em utilizar o Ca e o Mg.

Mineralização de nitrogênio e enxofre em solos brasileiros sob influência da calagem e fósforo

This study was carried out under laboratory conditions, from October 1995 to January 1996, in order to evaluate the influence of liming and phosphorus (P) application on nitrogen (N) and sulfur (S) mineralization in seven Brazilian (0-20 cm) soils with a wide variability in chemical and physical properties.Soilsamples,beforefertilizationwithP(KH 2PO4),were pre-incubated during seven days with CaCO3, and incubated again for another 70 days. The content of mineralized N (NH4+ and NO3-) and S (SO42-) were measured every other week, in aerobic conditions. Transformation of N and S showed different mineralization patterns from each other, with mineral N levels undergoing much greater variation than sulfate levels. Mineralized N amounts were not affected by soil acidity, although liming accelerated N mineralization in Humic Gley and Red-Yellow Latosol (colected in Rio de Janeiro) soils. Liming the soils to a pH around 6.0 resulted in increased net S mineralization in Low Humic Gley and Red-Yellow Latosol (colected in Rio de Janeiro) soils. Addition of superphosphate did not influence N and S mineralization processes. The greater prevalence of nitrate and sulphate in some of the limed soils suggests that the criterion used to choose time of lime application needs to be changed.

Efeitos de relações CaSO4/CaCO3 na mobilidade de nutrientes no solo e no crescimento do algodoeiro

The experiment was carried out in greenhouse at the Soil Science Departament - Federal University of Lavras, Minas Gerais, Brazil. The objective was to study the effects of different CaSO4/CaCO3 ratios on the movement of nutrients in soil and cotton growth. The treatments consisted of four CaSO4/CaCO3 percentage ratios (100/0, 75/25, 50/50, 25/75 and 0/100), in an equivalent basis. A control treatment, without application of either CaSO4 or CaCO3, was also established. Substantial calcium and sulfate movement downwards was observed with increasing CaSO4/CaCO3 ratios. On the contrary, N-NH4+ and K, N-NO3- and Mg movement increased with the CaSO4/CaCO3 ratios. Gypsum had little or no effect on subsoil acidity and exchange aluminum. Dry matter yield of cotton was reduced with increasing CaSO4/CaCO3 ratios, however, as compared to the control treatment. The application of gypsum was capable of markedly reducing the negative growth effect of acid soils.

Cultivo do feijoeiro em solução nutritiva sob proporções variáveis de amônio e nitrato

The experiment was carried out in nutrient solution, under greenhouse conditions at the Soil Science Department - Lavras Federal University, to evaluate the influence of different ammonium/nitrate proportions on the growth of Phaseolus vulgaris L. cultivars: Rio Tibagi, Eriparza and Carioca. Nitrogen in the nutrient solution was supplied at 4 mmol L-1 with different NH4+:NO3- proportions (0/4; 1/3; 2/2; 3/1 and 4/0). Throughout the growth period the pH of the nutrient solution was monitored. After harvesting, root and shoot dry matter were measured. The supply of both nitrogen forms to the nutrient solution in equal proportion resulted in higher dry matter production and higher nitrogen utilization efficiency than when only one of the nitrogen forms was supplied. When nitrate supplied 50% or more of the nitrogen, Carioca and Rio Tibagi showed the highest and the lowest nitrogen utilization efficiency, respectively, while with ammonium supplying 50% the situation was reversed. The detrimental effect of supplying only ammonium resulted in a drastic effect to the root system, with reduction of nutrient absorption, especially calcium.