Paulo Roberto Ernani

Acidificação de um Latossolo sob plantio direto

Soil tillage affects soil acidification and nutrient cycling and possibly causes effects on crop development and yields. In this study, the long-term (21 yr) effect of the no-tillage system (NT) on soil chemical characteristics (solid phase and solution) was evaluated in a south Brazilian Oxisol (Guarapuava, Parana State), focussing on acidity components. NT caused an acidification process in the top soil layer, demonstrated by lower pH values (2-10 cm) and higher concentration and saturation values of Al (6-20 cm), in comparison to soil with conventional tillage (CT). However, the highest values of exchangeable and soil solution Ca, Mg and K, bases saturation, available P (Mehlich-1 and Resin), and total and soluble organic carbon in no-tilled soil off-set the negative effect of the soil acidification and contribute to a 22 % higher accumulated crop yield (39 harvests) than under conventionally tilled soil.

Chemical Modifications Caused by Liming Below the Limed Layer in a Predominantly Variable Charge Acid Soil

Abstract Despite the low mobility in soil, surface liming has increased plant growth and yield. Since only the topsoil is affected by this technique, the benefits may be caused by improvements in soil solution. This experiment aimed to assess chemical changes in the solid phase and leached solutions after addition of calcitic limes to a Humic Hapludox. Calcium carbonate or calcium hydroxide was throughly mixed with soil samples at rates of 0, 0.25, 0.50, 1.0, and 1.50-times that required to raise soil pH to 6.0 (equivalent to 0, 3.5, 7.0, 14, and 21 t ha−1). After 60 days, treated samples were transferred to the top (30 cm) of leaching columns, filled with unlimed soil in the bottom (23 cm). Water was percolated weekly through the columns during 12 weeks. Chemical determinations were performed on all leached solutions, and at different soil depths below the limed layer at the end of the experiment. Calcium (Ca), magnesium (Mg), and aluminum (Al) increased linearly in the percolated solution with increases on lime sources; the opposite occurred for leachate pH, probably due to hydrolysis of Al that was replaced from the negative charges on unlimed soil by added calcium. Calcitic limes increased pH and Ca, and decreased Al and Mg in the solid phase below the limed layer up to a maximum of 3 cm. Lime, thus, positively affected only the top of the unlimed solid phase; its effect on leached solution, however, was similar to that caused by neutral salts on acid soils, with increases in cations and decreases in pH.

Mobilidade vertical de cátions influenciada pelo método de aplicação de cloreto de potássio em solos com carga variável

The magnitude of the vertical movement of nutrients in the soil profile determines their contact with plant roots and leaching, thus affecting the timing and method of fertilizer application. This study aimed to assess the K mobility in the soil as influenced by rate and method of potassium chloride addition. The experiment was carried out in 1998, using 7.5 cm wide and 35 cm long PVC leaching columns. Potassium was applied at rates of 0, 150 and 300 mg kg-1 on the soil surface or incorporated 15 cm deep into two acid soils. Distilled water (300 mL per column) was percolated every seven days, for eight weeks. The volume of percolated water, and its Ca, Mg and K concentrations were determined. KCl addition on the soil surface caused a downward movement of K to a depth beyond 10 cm. Nevertheless, K leaching was small, and was evident in the initial percolations, was proportional to the applied rate, and was higher in the soil-incorporated treatments. KCl addition increased Ca and Mg leaching in the first five percolations, which may temporarily raise the availability of these nutrients because it coincides with the period of crop establishment when the plant nutrient demand is high. Even in these highly buffered soils, K spread on the soil surface moved downward to reasonable depths, without promoting significant leaching.

Maize response to nitrogen fertilization timing in two tillage systems in a soil with high organic matter content

No-tillage systems, associated to black oat as preceding cover crop, have been increasingly adopted. This has motivated anticipated maize nitrogen fertilization, transferring it from the side-dress system at the stage when plants have five to six expanded leaves to when the preceding cover crop is eliminated or to maize sowing. This study was conducted to evaluate the effects of soil tillage system and timing of N fertilization on maize grain yield and agronomic efficiency of N applied to a soil with high organic matter content. A three-year field experiment was conducted in Lages, state of Santa Catarina, from 1999 onwards. Treatments were set up in a split plot arrangement. Two soil tillage systems were tested in the main plots: conventional tillage (CT) and no-tillage (NT). Six N management systems were assessed in the split-plots: S1 - control, without N application; S2 - all N (100 kg ha-1) applied at oat desiccation; S3 - all N applied at maize sowing; S4 - all N side-dressed when maize had five expanded leaves (V5 growth stage); S5 - 1/3 of N rate applied at maize sowing and 2/3 at V5; S6 - 2/3 of nitrogen rate applied at maize sowing and 1/3 at V5. Maize response to the time and form of splitting N was not affected by the soil tillage system. Grain yield ranged from 6.0 to 11.8 t ha-1. The anticipation of N application (S2 and S3) decreased grain yield in two of three years. In the rainiest early spring season (2000/2001) of the experiment, S4 promoted an yield advantage of 2.2 t ha-1 over S2 and S3. Application of total N rate before or at sowing decreased the number of kernels produced per ear in 2000/2001 and 2001/2002 and the number of ears produced per area in 2001/2002, resulting in reduced grain yield. The agronomic efficiency of applied N (kg grain increase/kg of N applied) ranged from 13.9 to 38.8 and was always higher in the S4 than in the S2 and S3 N systems. Short-term N immobilization did not reduce grain yield when no N was applied before or at maize sowing in a soil with high organic matter content, regardless of the soil tillage system.

Modificações químicas em solos ácidos ocasionadas pelo método de aplicação de corretivos da acidez e de gesso agrícola

The increase on crop yield caused by lime addition on the soil surface may be associated to improvements in the chemical composition of the percolating water. This study was carried out to evaluate chemical changes in the solid phase and in the percolating water in two acid soils (Oxisol and Inceptisol) caused by the application method (incorporated or on soil surface) of gypsum, CaCO3, or MgCO3. Calcium carbonate was used at a rate equivalent to 0.25 of that recommended by the SMP method to raise soil water pH to 6.0; gypsum and MgCO3 were used at the same molarity rate. Additional CaCO3 were (0, 0.50, 1.0 and 1.5 times that recommended by the SMP method) was also incorporated. Treated soil samples (1.5 kg) were transferred to leaching columns, and distilled water (200 mL column-1 week-1) were added on soil surface during twelve weeks. Incorporation of lime (CaCO3 and MgCO3) into the soils increased pH of both phases, decreased exchangeable Al, but had no effect on Al in the percolated solution. When carbonates were applied on soil surface, they had no effect on the leached solution, and affected the chemical composition of the solid phase only in the top 2.0 centimeters. Addition of gypsum decreased soil and solution pH, had no effect on exchangeable Al, but leached greater amounts of Ca, Mg and Al than limestone, especially when gypsum was incorporated. Cation mobility from limestone materials was negligible, and surface liming had no chemical effects in the solution collected 30 cm below soil surface.

Increase of grain and green matter of corn by liming

Despite the fact that aluminum toxicity to crops is eliminated near soil water pH of 5.5, lime recommendation in many regions aims to increase soil pH up to 6.0 or even higher. For highly buffered soils, high rates of limestone are required to raise the pH from 5.5 to 6.0, resulting in additional, sometimes unnecessary, costs. The objective of this study was to evaluate the effect of soil pH on corn yield in a very acid Hapludox. The experiment was carried out in Lages, Southern Brazil, from 1992 to 1996. The soil had water pH of 4.7, Al3+ of 33 mmolc kg-1, O.M. of 45 g kg-1 and lime requirement to pH 6.0 of 9.0 t ha-1. Dolomitic limestone at rates of 0, 4.5, 9.0, 13.5 and 18.0 t ha-1 (equivalent to pure CaCO3) was incorporated into the soil down to 17 cm depth, in 1992. Liming increased linearly the values of soil pH (from 4.7 to 6.6) and Ca and Mg, eliminated Al3+ with rates of 9.0 t ha-1 or higher, decreased slightly Al-CuCl2, Fe and Cu, and did not affect Zn and Mn. Maximum average corn yield for grain (7.9 t ha-1) and for green matter for silage (GM) (59 t ha-1) was obtained, respectively, at soil pH of 6.0 (12 t ha-1 of limestone) and of 6.1 (14 t ha-1 of limestone); maximum economic efficiency for grain was obtained at pH 5.6 (7.5 t ha-1 of limestone). Maximum yield increments due to liming were 17% for grain and 20% for GM.

Volatilização de N-NH3 em decorrência da forma de aplicação de uréia,manejo de resíduos e tipo de solo, em laboratório

A volatilizacao de amonia (NH3) e a principal perda de nitrogenio (N) responsavel pela baixa eficiencia da ureia aplicada na superficie do solo. Este trabalho objetivou avaliar os efeitos do modo de aplicacao da ureia e da forma de manejo dos residuos de aveia preta sobre a volatilizacao de amonia, em dois solos com diferentes teores de argila e materia orgânica, sob condicoes de laboratorio. Foram conduzidos dois experimentos num Nitossolo Vermelho (NV) e num Neossolo Quartzarenico (NQ), contendo 520 e 50g kg-1 de argila, respectivamente. Os tratamentos consistiram de tres formas de manejo do fertilizante nitrogenado (sem N, ureia aplicada na superficie e ureia incorporada ao solo) e tres metodos de manejo dos residuos de aveia (sem palha, palha aplicada na superficie e palha incorporada ao solo). Utilizou-se o equivalente a 4,0mg ha-1 de palha e 255kg ha-1 de N. As unidades experimentais foram constituidas por colunas de PVC, contendo 1,47kg de solo argiloso e 2,1kg de solo arenoso. As colunas foram hermeticamente vedadas e a parte superior foi conectada, atraves de uma mangueira plastica, a frascos coletores com acido sulfurico. A quantidade de N-NH3 volatilizada foi determinada por arraste de vapor, em diferentes periodos, apos a implantacao do experimento. A aplicacao superficial da ureia proporcionou maior volatilizacao de N-NH3 do que sua incorporacao, nos dois solos. A manutencao da palha sobre a superficie do solo estimulou a perda de N-NH3 no solo arenoso, independentemente da forma de aplicacao da ureia ao solo. A perda de N-NH3 foi numericamente maior e o periodo de maxima volatilizacao ocorreu antes no NQ, provavelmente devido ao menor teor de argila, a materia orgânica e a menor capacidade de troca de cations, relativamente ao NV.

Propriedades físicas e eletroquímicas de um Latossolo Bruno afetadas pela calagem

Liming influences some electrochemical properties of soils of variable charge that may affect clay dispersion and aggregate stability. This hypothesis was tested after five years of incorporation of increasing rates of limestone (0, 4.5, 9.0, 13.5 and 18 t ha-1) into a Brown Latosol (Haplohumox). Dolimitic limestone was plowed down to 17 cm depth into the soil during the spring of 1992 when field plots began to be cultivated annually with continuous corn. Soil samples used in this work were collected in the spring of 1997. Liming increased the amount of clay dispersed in water (R2 = 0.93**), negative surface electric potential (R2 = 1.00**), point of zero salt effect PZSE (R2 = 0.85*) and slightly decreased soil organic matter (R2 = 0.83*), but had no effect on soil aggregate stability. The increase on PZSE was probably caused by the decrease of soil organic matter. Clay dispersion was positively associated with surface electric potential (R2 = 0.93**) and its increase was probably due to higher repulsive forces among soil particles as a consequence of either increases on CEC and on thickness of electric double layer.

Volatilização de amônia do solo após a aplicação de ureia convencional ou com inibidor de urease

Ammonia volatilization is an important process of N loss which decreases the use efficiency of N by plants when urea is applied on the soil surface. To overcome this problem, some chemical compounds were mixed with urea to inhibit the urease action. The purpose of this study was to compare applications of an alternative fertilizer with urease inhibitor to reduce ammonia volatilization with conventional urea, under certain environmental and soil conditions. Four experiments were carried out in 2007 and 2008, under laboratory conditions, with samples of a Humic Haplumbrept. The treatments varied according to each experiment in terms of soil conditions, such as pH (4.0, 5.5, 6.3 and 6.8), soil water content (5, 10 or 20 % moisture), temperature (18 or 35 oC), aside from the fertilizer physical state (solid or liquid) and application method (over the surface or soil-incorporated). The experimental units consisted of plastic trays into which 12 kg of soil (dry basis) were filled in a 15 cm layer. Ammonia gas traps were installed across the soil surface. Frequent measurements were performed during the first 28 days of soil-fertilizer incubation. The peak of ammonia volatilization from the soil occurred in the first week after the application of traditional urea, and two or three days later for urea with urease inhibitor. Ammonia loss was not always higher from conventional than from treated urea, nor from solid than from liquid fertilizers. Ammonia volatilization increased with increases in soil pH, temperature and N rate and was lower at the lowest (5 %) and highest (20 %) soil moisture content. For surface-applied fertilizers, the maximum daily N loss rate was 14 kg ha-1 and the total cumulative loss ranged from 2 to 50 % of the applied N, depending mainly on the physical state of the fertilizer, temperature and on soil moisture. Soil incorporation of urea fertilizers was the best option to minimize ammonia volatilization in all treatments.

Influência da combinação de fósforo e calcário no rendimento de milho

The existence of soil exchangeable Al in toxic levels inhibits root growth and elongation, with negative effects on water and nutrient uptake, especially of P. Thus, as soil P increases, plants become less dependent on a large root system, that may decrease crop response to liming. This study was carried out to evaluate the effect of liming and phosphorus fertilization on corn yield. The experiment was conducted in Lages, Southern Brazil, from 1994 to 1998, in a clayed Oxisol (Hapludox) with pH 4.7, exchangeable Al of 39 mmolc kg-1, P of 1.0 mg kg-1, and liming requirement of 9 t ha-1 to raise soil water pH to 6.0. Treatments consisted of a factorial with three rates of liming (0, 4.5 and 9.0 t ha-1) and four of P2O5, respectively 60, 120, 180 and 240 kg ha-1 in the first crop; 40, 80, 120 and 160 kg ha-1 in the second and fourth crop; and 30, 60, 90, and 120 kg ha-1 in the third crop. The effect of liming increased with time from null in the first year up to increments of 39% on corn yield. On most growing seasons, yield increased up to pH 5.4, where half of the liming required to achieve pH 6.0 was applied. On treatments that received the two highest rates of P2O5 (127 and 170 kg-1 ha-1 per crop), liming had no effect on corn yield. Addition of P increased corn yield in all seasons but the magnitude decreased as soil pH increased. The highest productivities were obtained with recommended P rate in two growing seasons, but in the remaining two, it was necessary to apply 50% more.