Gonçalo Evangelista de França

Evolvimento de dióxido de carbono e mineralização de nitrogênio em Latossolo Vermelho-Escuro com diferentes manejos

The objective of this work was to verify the influence of different types of straw (maize and lablab) and soil management on evolving CO2 and N mineralization. A dystrophic clayey Dark-Red Latosol under Cerrado from the region of Sete Lagoas, MG, Brazil, was cultivated during five years with no-tillage, disc-plow and moldboard-plow. Soil samples (0-20 cm) were incubated at 25oC during 55 days, with and without N fertilizer applied at the beginning and 25 days afterwards. As a general rule, the maize straw had higher rates of evolved CO2 than the lablab (935 e 764 mg CO2 g-1 soil, respectively). The type of straw influenced the amount of CO2 evolved more than the type of soil management did. Nitrogen addition increases the rate of CO2 evolved only when applied at the beginning of the incubation period. The N availability and the duration of the immobilization are modified by the C/N ratio and by the type of soil management.

Acúmulo de nitrogênio e de fósforo em plantas de milho afetadas pelo suprimento parcial de fósforo às raízes

Two split root trials were carried out in nutrient solution to evaluate nitrogen accumulation as a function of phosphorus supply applied in partial contact to maize roots. After a seven day growth period in complete nutrient solution, maize seedlings were transplanted to joint pots containing 1.6 L of nutrient solution. Roots were equally shared between the pots. In the first trial, two phosphorus levels (0.02 mmol L-1 and 0.1 mmol L-1) and phosphorus and nitrogen placement were evaluated. In the second trial, two nitrogen sources (nitrate and ammonium) and the same nitrogen and phosphorus placement design adopted in the first trial were assessed. There was a greater phosphorus accumulation in the shoots as a consequence of phosphorus supplied to the whole root system as compared to just half of it. Phosphorus supplied to part of the root system did not properly provide this nutrient to the other part, a fact which raises the possibility of inner phosphorus cycling problems in maize plants. These results were verified for nitrogen as well. When jointly supplied to the whole root system, nitrogen and phosphorus caused greater accumulation of nitrogen in the shoots.

Transporte do amônio em colunas com agregados de um latossolo vermelho distrófico

To describe the transport of the ammonium ion in different classes of aggregates of a typic Haplortox, a laboratory experiment was carried out. The treatments corresponded to a 3 x 5 factorial, being three sources of NH 4 + [(NH 4 ) 2 SO 4 , NH 4 Cl, and NH 4 NO 3 ] and five aggregate classes (2.0-1.0, 1.0-0.5, 0.5-0.25, 0.25-0.105, and <0.105 mm). The experimental unit was a glass column saturated, under vacuum to which was applied a CaCl 2 0.005 mole L -1 solution. After saturation, the same solution was applied until constant percolation, followed by a seven pore volume pulse of solution of respective source - 0.01 mole L -1 NH 4 + (C o ). Fractions of the effluent, corresponding to 0.3 pore volume (p), were collected, and the NH 4 + concentrations were determined (C). C/C o relationships were calculated for every p fraction, and the experimental elution curves were traced. The highest retardation factors were calculated for the smallest aggregates, indicating a larger retention of ammonium, and the almost superimposed theoretical curves showed the predominance of the dispersive transport for ammonium. The NH 4 + percolation was not affected by the studied anions in the different aggregates classes.To describe the transport of the ammonium ion in different classes of aggregates of a typic Haplortox, a laboratory experiment was carried out. The treatments corresponded to a 3 x 5 factorial, being three sources of NH4 + [(NH4)2SO4, NH4Cl, and NH4NO3] and five aggregate classes (2.0-1.0, 1.0-0.5, 0.5-0.25, 0.25-0.105, and <0.105 mm). The experimental unit was a glass column saturated, under vacuum to which was applied a CaCl2 0.005 mole L -1 solution. After saturation, the same solution was applied until constant percolation, followed by a seven pore volume pulse of solution of respective source 0.01 mole L-1 NH4 + (Co). Fractions of the effluent, corresponding to 0.3 pore volume (p), were collected, and the NH4 + concentrations were determined (C). C/Co relationships were calculated for every p fraction, and the experimental elution curves were traced. The highest retardation factors were calculated for the smallest aggregates, indicating a larger retention of ammonium, and the almost superimposed theoretical curves showed the predominance of the dispersive transport for ammonium. The NH4 + percolation was not affected by the studied anions in the different aggregates classes.

NO3- and NH4+ transport in a typic Haplortox aggregates with and without biological activity

A laboratory experiment was carried out in a randomized block design with three replications, in which columns with aggregate classes 2.0-1.0; 1.0-0,5; 0.5-0.25 and 0.25-0.105 mm of a typic Haplortox were used. The treatments corresponded to a 23 x 4 factorial, with soil covering vegetation (savannah and maize); biological activity (with and without soil sterilization with methyl bromide); sources of N with 10 mmol L-1 of N for saturation of the columns (Ca(NO3)2 and NH4CI); and aggregate classes (2.0-1.0; 1.0-0.5; 0.5-0.25 and 0.25-0.105 mm). After seven days of incubation of the columns with aggregates at maximum water retention, percolations were made with water, after two days under saturated condition, totaling six samples (0, 2, 4, 6, 8 and 10 days after the first percolation). In the first eluition, aggregates of 0.25-0.105 mm presented smaller NO3- content in columns containing microorganisms activity and saturation with Ca(NO3)2. In sterilized system, aggregates of 0.25-0.105 mm presented larger NO3- content in the solution. For the saturated columns with NH4CI, in the first eluition the NH4+ content was larger in the aggregates of 0.25-0.105 mm for the combinations of soil covering and sterilization, while, with microorganisms activity aggregates of 0.5-0.25 mm and 0.25-0.105 mm presented the highest NH4+ content.

Ammonium transport in columns with aggregates of a typic of a haplortox

To describe the transport of the ammonium ion in different classes of aggregates of a typic Haplortox, a laboratory experiment was carried out. The treatments corresponded to a 3 x 5 factorial, being three sources of NH 4 + [(NH 4 ) 2 SO 4 , NH 4 Cl, and NH 4 NO 3 ] and five aggregate classes (2.0-1.0, 1.0-0.5, 0.5-0.25, 0.25-0.105, and <0.105 mm). The experimental unit was a glass column saturated, under vacuum to which was applied a CaCl 2 0.005 mole L -1 solution. After saturation, the same solution was applied until constant percolation, followed by a seven pore volume pulse of solution of respective source - 0.01 mole L -1 NH 4 + (C o ). Fractions of the effluent, corresponding to 0.3 pore volume (p), were collected, and the NH 4 + concentrations were determined (C). C/C o relationships were calculated for every p fraction, and the experimental elution curves were traced. The highest retardation factors were calculated for the smallest aggregates, indicating a larger retention of ammonium, and the almost superimposed theoretical curves showed the predominance of the dispersive transport for ammonium. The NH 4 + percolation was not affected by the studied anions in the different aggregates classes.To describe the transport of the ammonium ion in different classes of aggregates of a typic Haplortox, a laboratory experiment was carried out. The treatments corresponded to a 3 x 5 factorial, being three sources of NH4 + [(NH4)2SO4, NH4Cl, and NH4NO3] and five aggregate classes (2.0-1.0, 1.0-0.5, 0.5-0.25, 0.25-0.105, and <0.105 mm). The experimental unit was a glass column saturated, under vacuum to which was applied a CaCl2 0.005 mole L -1 solution. After saturation, the same solution was applied until constant percolation, followed by a seven pore volume pulse of solution of respective source 0.01 mole L-1 NH4 + (Co). Fractions of the effluent, corresponding to 0.3 pore volume (p), were collected, and the NH4 + concentrations were determined (C). C/Co relationships were calculated for every p fraction, and the experimental elution curves were traced. The highest retardation factors were calculated for the smallest aggregates, indicating a larger retention of ammonium, and the almost superimposed theoretical curves showed the predominance of the dispersive transport for ammonium. The NH4 + percolation was not affected by the studied anions in the different aggregates classes.