Clair Rampazzo

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.

Lixiviação de nitrogênio afetada pela forma de aplicação da uréia e manejo dos restos culturais de aveia em dois solos com texturas contrastantes

Nitrate leaching is normally the most important process affecting nitrogen losses in the soil. This experiment aimed to evaluate the effect of methods of urea application and different management strategies of black oat residue on N leaching in soils with different clay and organic matter contents. Two laboratory studies were conducted using two kinds of soil: an UDULT (UD) and a PSAMENT (PS), containing 520 and 50g.dm-3 of clay, respectively. Treatments included a combination of three management systems of oat residue (without straw, superficial straw and incorporated straw) and three methods of nitrogen application (without N, superficial N and incorporated N). Oat straw was applied at a rate of 4Mg.ha-1 and nitrogen at rates of 129 and 90mg.kg-1 for the UD and PS, respectively, as urea. When no N was applied, leaching values were approximately four times larger in the UD than in the PS. Application of urea to the soil surface decreased the amount of N leached when compared to incorporation of urea, in both soils. There was higher N leaching when oat straw was kept at the soil surface than with its incorporation in the UD, regardless of nitrogen management. Superficial N application and oat straw incorporation yielded higher quantities of mineral remaining nitrogen (N-NO3-1 + N-NH4+1) in the soil. The remaining nitrogen values were greater in the UD than in the PS at the end of the experimental period.

Desempenho de híbridos de milho com ciclos contrastantes em função da desfolha e da população de plantas

The speed of maize development from emergence to anthesis may affect the response of the crop to important management practices and interfere on the ability of corn to cope with stresses at flowering. This experiment was conducted objecting to evaluate the relationship between earliness and maize response to the increase in plant population and defoliation. The trial was performed in Lages, SC, Brazil, during 1999/2000. Three contrasting hybrids in terms of heat unit requirement to reach flowering were tested: P32R21, very early; Premium, early; and C333B, late. These hybrids were submitted to four plant populations: 25,000, 50,000, 75,000 and 100,000 pl ha-1. Genotypes were evaluated with full leaf area and removing half of their green leaves at silking. The plant population required to maximize grain yield was lower for late than for early hybrids. Hybrid P32R21 presented a smaller leaf area and greater grain yield than C333B, regardless of defoliation. This was accomplished due to P32R21 higher capacity to mobilize its stem stored compounds to match the sink demand of the grain.

A forma de aplicação da uréia e dos resíduos vegetais afeta a disponibilidade de nitrogênio

Management of both crop residues and nitrogen fertilizers affects soil N reactions especially on no-till systems. The magnitude of these effects on N availability to maize was evaluated in a greenhouse study. Combinations of oat straw and urea (absence, soil incorporated or surface applied) were added to experimental units (7-dm3 per pot) of two soils, in a 3 x 3 x 2 factorial combination. Plants were sown just following treatments addition, and grown for thirty days in two soils (Typic Quartzipsammnets and Humic Hapludox) with 50 and 520g kg-1 clay and 8 and 48g kg-1 organic matter respectively. Oat straw, especially when surface applied, had a positive effect on plant growth, most likely caused by increases on soil water retention. Urea application, however, had no effect on any plant parameter on the clayey soil probably because the amount of N released from soil organic matter mineralization was greater than that immobilized during residue decomposition. On the sandy soil, however, urea was beneficial when incorporated into the soil, but was detrimental when surface applied possibly due to ammonia toxicity. Thus, soil organic matter content influences the effect of oat straw decomposition on N availability to maize.

Crescimento inicial de milho e sua relação com o rendimento de grãos

This study was conducted aiming to identify morphological and physiological traits associated with the initial growth speed and to determine the importance of a vigorous early growth to set high grain yields. The study was conducted in Lages, SC, during 1998/99 and 1999/00 growing seasons. A randomized complete block design was used. Hybrids C901, AS 3601, C 505, AS 3466 and AS 32 were avaluated in 1998/99, whereas in 1999/00 the studied hybrids were C 909, AS 3601, DINA 500, AS 3466 and AS 32. Maize initial growth was evaluated through six samplings. Samples were taken weekly from plant emergence the ten fully expanded leaves stage. Leaf area, leaf area index, dry mass accumulation, cellular growth rate (CGR) and cellular expansion rate (CER) were estimated. Hybrid AS 3601 presented larger values of leaf area, IAF and CER than the other genotypes in 1998/99. In the second growing season, Hybrid AS 3466 had the highest values for dry mass and CGR. There was no significant difference among hybrids for grain yield. Low correlation values between initial growth parameters and maize grain yield were found. Otherwise, leaf area, leaf area index, dry mass accumulation, CGR and CER showed high correlation.

Lixiviação e imobilização de nitrogênio num nitossolo como variáveis da forma de aplicação da uréia e da palha de aveia

SUMMARY : EFFECT OF OAT STRAW AND UREA APPLICATION FORMSON SOIL NITROGEN LEACHING AND IMMOBILIZATION The magnitude of nitrogen reactions in the soil varies according to climate conditions,soil type, soil tillage, method of nitrogen application, and plant residue management. Thisstudy tried to evaluate the effect of nitrogen application methods and of black oat ( Avenastrigosa ) residues on N leaching and immobilization in a Brazilian Haplumbrept by twoexperiments carried out in a greenhouse. The treatments were combinations of three Nfertilization methods (without urea, urea incorporated into the soil and urea applied overthe soil surface) with three management practices of oat residues (without straw, strawincorporated into the soil and straw applied over the soil surface). As additional factors,the effect of soil pH (5.5 or 7.0) was also evaluated in the leaching experiment and the effectof the sowing date (0, 30, or 60 days after N and straw additions) in the experiment of Nimmobilization. An amount of 4.0 Mg ha