Elisandra Pocojeski

Perdas de nitrogênio por volatilização de amônia com aplicação de uréia em solo de várzea com diferentes níveis de umidade

The first topdressing nitrogen (N) application to flooded rice can be done on dry soil or soil after ponding water, affecting ammonia volatilization rate and, consequently, nitrogen fertilization efficiency. This study was aimed at quantifing N losses by ammonia volatilization after urea application in a wetland soil with different soil water status. The experiment was carried out in a greenhouse, using 5kg pots with a Albaqualf with following treatments: N0 - control without urea application (wet soil); USSE - urea application on dry soil; USUM - urea application on wet soil; USSA - application on saturated soil; and USLA - urea application on soil after ponding water. The ammonia loss evaluations were made using a semi-open static collector at 10, 24, 34, 48, 72, 96, 144, 192, and 264 hours after urea application. At the end of 264 hours, the ammonia losses were similar for wet, saturated or ponding water soils, and the higher emission peaks were between 34 and 48 hours in wet and saturated soils and 72 hours in soil after ponding water. The N-urea application on ponding water did not avoid the N losses by volatilization.

Dinâmica da emissão de metano em solos sob cultivo de arroz irrigado no sul do Brasil

Paddy soils under flooded rice produce nearly 18% of all methane (CH4) emissions in the state of Rio Grande do Sul. However, CH4 release depends on the intensity of soil reduction. The objective of this study was to evaluate the dynamics of emissions of this greenhouse gas from six representative soils [Albaqualf (2), Endoaqualf (2), Udorthent and Hapludoll] of rice cultivation in southern Brazil, to identify the relation with soil proprieties and electrochemical changes in the soil solution after flooding. The experiment was carried out in a greenhouse with three replications in a randomized block design. Rice was grown in PVC pots filled with soil and covered with a 10 cm water layer. CH4 emissions were evaluated weekly from the 3rd to the 66th day after flooding, using a gas trap fixed on top of the pots. The gas was collected every five minutes, four times, to estimate CH4 emission rates. Soil solution was collected and analyzed as well. The beginning of CH4 emissions varied according to the soil type and usually occurred when 90 % of Fe3+ had been reduced to Fe2+ and pH and Eh stabilized. Total CH4 emission varied from 8.5 to 44.2 g m-2 and had a sigmoid relation to soil organic C (r2 = 0.83, p < 0.05), suggesting that C availability only limited methanogenesis when levels were below 8 g kg-1 C soil. The results illustrate that the dynamics and total fluxes were strongly affected by the soil type and efforts must be directed toward determining CH4 emission factors for the different representative soil types of rice cultivation in southern Brazil, and agricultural practices to mitigate greenhouse gases from the different soils should be evaluated.

Metais pesados, agrotóxicos e combustíveis: efeito na população de colêmbolos no solo

The aim of this research was to evaluate the collembola development in soils with different levels of heavy metals, fuels and pesticides, in laboratory conditions. Treatments were: Cadmium - 1, 10 and 100mg kg-1 soil; Copper - 50, 500 and 5000mg kg-1 soil; Zinc - 100, 1000 and 10000 mg kg-1 soil; fungicide epoxiconazol + piraclostrobina - 1 and 2L ha-1; fungicide epoxiconazol - 0,75 and 1,5L ha-1; herbicide glyphosate - 2 and 4L ha-1; burned lubricating oil - 5, 50 and 100mL kg-1 soil and diesel oil - 5, 50 and 100mL kg-1 soil and control. In the 1mg kg-1 dose of Cd there was a great increase of the collembola population and the soil pH decreased as the Cd, Zn and Cu doses in the soil increased. In the presence on fuels the collembola presented incapacity to procreate regardless the dose applied in the soil. The number of collembola showed an increase with increasing glyphosate and epoxiconazole level. The heavy metal Cu and Zn have negative impact over the collembola population and just Cd (1mg kg-1 soil) offers increase on their population in the soil. The presence of burned oil and diesel in the soil inhibit the collembolan development in the soil. The pesticides glyphosate, epoxiconazol and epoxiconazol + piraclostrobina do not negatively influence the collembola population in the soil.

Adubação nitrogenada sobre rendimento industrial e composição dos grãos de arroz irrigado

O efeito de doses em cobertura de adubacao nitrogenada foi avaliado sobre o rendimento do beneficiamento, a incidencia de graos gessados e barriga branca, os teores de proteina e de amilose nos graos polidos da variedade de arroz irrigado IRGA 422CL. Utilizando a ureia como fonte de nitrogenio (N), os tratamentos constituiram-se de doses crescentes distribuidas em cobertura na primeira aplicacao (0, 40, 63, 80 e 120kg ha-1 de N), na parcela principal (10x5m), e na segunda aplicacao (0, 25, 50 e 75kg ha-1 de N), na subparcela (2,5x5m). Assim, foram obtidos 20 tratamentos com variacao de 0 a 195kg ha-1 de N aplicado durante o cultivo. As doses em cobertura de adubacao nitrogenada influenciaram quadratica e positivamente o rendimento de graos inteiros (R2=0,75) e negativamente a percentagem de graos quebrados (R2=-0,89), nao apresentando efeitos significativos na percentagem de casca + farelo. As doses de nitrogenio influenciaram de forma linear positiva sobre o teor de proteina (R2=0,81) e linear negativa sobre o teor de amilose (R2=-0,66), nos graos polidos da variedade de arroz irrigado IRGA 422CL.

Teores de macronutrientes em cultivares de arroz irrigado de acordo com a parte da planta analisada e do estádio de desenvolvimento

Macronutrient contents in irrigated rice cultivars as a function of plant parts and development stages Leaf analysis is based on the determination of the nutrient content in the plant tissue during cultivation. Nevertheless, the recommended period for such analysis (flowering stage) does not allow fertilization corrections to be made within the crop cycle, providing only complementary information for the next crop. This study aimed at verifying the cultivar , part of plant and sampling time influence on the macronutrient contents in the leaf tissue of flooded rice (Oryza sativa L.). The field experiment was carried out with five rice cultivars (BR-IRGA 409 and 410, IRGA 417 and 421 and EPAGRI 108) and a hybrid. Moreover, five collections of the plant aerial part and the most recently expanded leaf were carried

A APLICAÇÃO LOCALIZADA DE MONOAMÔNIO FOSFATO FAVORECE A DISPONIBILIDADE DE P NO SOLO E SUA ABSORÇÃO

O objetivo do presente trabalho foi avaliar a absorcao de fosforo pelas plântulas de milho em funcao da aplicacao localizada de fosfatos de calcio e de amonio, em dois solos catarinenses. O trabalho foi realizado em 2011, com amostra de um Cambissolo Humico (CH) e um Nitossolo Vermelho (NV). Os tratamentos consistiram da aplicacao de superfosfato triplo (SFT), superfosfato simples (SS), diamonio fosfato (DAP) e monoamonio fosfato (MAP), alem de uma testemunha sem a adicao de P. Em todos os tratamentos com P adicionou-se 200 mg kg -1 de P e 100 mg kg -1 de K, na forma de KCl; a quantidade de N adicionada pelo DAP (160 mg kg -1 ) foi ajustada nos demais tratamentos pela adicao de CaNO 3 . A producao de massa seca da parte aerea (MSPA) foi maior nos tratamentos com SFT, SS e MAP, nas quais os incrementos foram respectivamente 71, 67 e 62% maiores que a testemunha; enquanto com o DAP foi de 38%. Os teores de P na parte aerea e nas raizes foram maiores no solo tratado com MAP. O SFT, MAP e DAP aumentaram as concentracoes de P no solo, cuja media foi 93% superior a testemunha. A disponibilidade de P no solo e sua absorcao sao aumentadas pela aplicacao localizada de MAP; por outro lado, a aplicacao localizada de DAP inibe o crescimento de raizes.

Comportamento de superfosfato simples contendo fosfato de ferro de baixa solubilidade em água em solos de várzea do Rio Grande do Sul

Some rocks used in fertilizer production contain low water-soluble impurities, such as iron and aluminum phosphates. The industrialization processes of these rocks may generate simple superphosphate with an insufficient solubility degree to meet the requirements established by Brazilian fertilizer law. If applied to waterlogged soils, reduction reactions can increase the solubility of such fertilizers. The objective of this study was to evaluate phosphorus release from these fertilizers from flooded lowland soils of Rio Grande do Sul State. Six lowland samples were collected: two Albaqualf (Santa Maria and Pelotas); two Alfissol (Santa Maria and Cachoeirinha) and two Molisol (Santa Vitoria do Palmar and Uruguaiana). Each soil received two phosphate sources - simple superphosphate and superphosphate with iron phosphate impurities - and a treatment without phosphorus addition. In the treatments with phosphorus, an amount equivalent to 100 mg kg-1 P was applied. Soils in 8 L plastic buckets were flooded and a 5cm water layer was maintained over the soil surface, in a complete randomized design with three replications. Soil solution was collected weekly and, immediately, the pH and redox potential (Eh) measured; afterwards, P and Fe were extracted in the lab. Results show that Eh decreased and pH, P and Fe content increased in the soil solution in all tested soils. The P increase in soil solution was independent of the phosphate source, indicating simple superphosphate with iron phosphate impurities for use in lowland soils where flooded rice is grown in Rio Grande do Sul, even though it does not comply with the solubility requirements established by the Brazilian fertilizer legislation.