RESUMO

The growth of cover crops can contribute to the increase in phosphorus content at depth by root decomposition. The aim of this work was to verify the effect of cover crops on soil phosphorus availability and use by successive plants, and the accumulation of soil P in a no-tillage system conducted for 14 years. This research was carried out during the 2016/2017 and 2017/2018 crop seasons, whose treatments have been installed and maintained since 2003. The experimental design was a randomized block design, and the plots consisted of spring crops: pearl millet, forage sorghum, sunn hemp, and additionally, a fallow/chiseling area. The evaluation of available P was determined by P fractionation. In general, in the two years of evaluation, the accumulation of P in the shoot dry matter was higher in sunn hemp growth, on average 25% higher than pearl millet in 2016 and 40% higher than sorghum in 2017. The highest contents of labile inorganic P were in the sorghum-soybean and fallow/chiseling-soybean successions, with values higher than 50 mg kg-1 of P in the 0-0.1 m soil layer. However, in the other layers analyzed, the cover crops obtained higher availability of labile inorganic P. The systems using cover crops recovered 100% of the P fertilized in soybean.

RESUMO

Phosphorus (P) cycling by microbial activity is highly relevant in the eutrophication of lakes. In this context, the contents of organic (Po) and inorganic (Pi) phosphorus, the activity of acid (ACP) and alkaline (ALP) phosphomonoesterase (Pase), and the abundances of bacterial Pase genes (phoD, phoC, and phoX) were studied in sediments from Budi Lake, a eutrophic coastal brackish water lake in Chile. Our results showed spatiotemporal variations in P fractions, Pase activities, and Pase gene abundances. In general, our results showed higher contents of Pi (110-144 mg kg-1), Po (512-576 mg kg-1), and total P (647-721 mg kg-1) in sediments from the more anthropogenized sampling sites in summer compared with those values of Pi (86-127 mg kg-1), Po (363-491 mg kg-1) and total P (449-618 mg kg-1) in less anthropogenized sampling sites in winter. In concordance, sediments showed higher Pase activities (µg nitrophenyl phosphate g-1 h-1) in sediments from the more anthropogenized sampling sites (9.7-22.7 for ACP and 5.9 to 9.6 for ALP) compared with those observed in less anthropogenized sampling sites in winter (4.2-12.9 for ACP and 0.3 to 6.7 for ALP). Higher abundances (gene copy g-1 sediment) of phoC (8.5-19 × 108), phoD (9.2-47 × 106), and phoX (8.5-26 × 106) genes were also found in sediments from the more anthropogenized sampling sites in summer compared with those values of phoC (0.1-1.1 × 108), phoD (1.4-2.4 × 106) and phoX (0.7-1.2 × 106) genes in the less anthropogenized sites in winter. Our results also showed a positive correlation between P contents, Pase activities, and abundances of bacterial Pase genes, independent of seasonality. The present study provided information on the microbial activity involved in P cycling in sediments of Budi Lake, which may be used in further research as indicators for the monitoring of eutrophication of lakes.

Assuntos

RESUMO

Phosphorus (P) is one of the most critical macronutrients in forest ecosystems. More than 70 years ago, some Chilean Patagonian temperate forests suffered wildfires and the subsequent afforestation with foreign tree species such as pines. Since soil P turnover is interlinked with the tree cover, this could influence soil P content and bioavailability. Next to soil microorganisms, which are key players in P transformation processes, a vital component of Patagonian temperate forest are lichens, which represent microbial hotspots for bacterial diversity. In the present study, we explored the impact of forest cover on the abundance of phosphate solubilizing bacteria (PSB) from three microenvironments of the forest floor: Peltigera frigida lichen thallus, their underlying substrates, and the forest soil without lichen cover. We expected that the abundance of PSB in the forest soil would be strongly affected by the tree cover composition since the aboveground vegetation influences the edaphic properties; but, as P. frigida has a specific bacterial community, lichens would mitigate this impact. Our study includes five sites representing a gradient in tree cover types, from a mature forest dominated by the native species Nothofagus pumilio, to native second-growth forests with a gradual increase in the presence of Pinus contorta in the last sites. In each site, we measured edaphic parameters, P fractions, and the bacterial potential to solubilize phosphate by quantifying five specific marker genes by qPCR. The results show higher soluble P, labile mineral P, and organic matter in the soils of the sites with a higher abundance of P. contorta, while most of the molecular markers were less abundant in the soils of these sites. Contrarily, the abundance of the molecular markers in lichens and substrates was less affected by the tree cover type. Therefore, the bacterial potential to solubilize phosphate is more affected by the edaphic factors and tree cover type in soils than in substrates and thalli of P. frigida lichens. Altogether, these results indicate that the microenvironments of lichens and their substrates could act as an environmental buffer reducing the influence of forest cover composition on bacteria involved in P turnover.

RESUMO

Wood contains the majority of the nutrients in tropical trees, yet controls over wood nutrient concentrations and their function are poorly understood. We measured wood nutrient concentrations in 106 tree species in 10 forest plots spanning a regional fertility gradient in Panama. For a subset of species, we quantified foliar nutrients and wood density to test whether wood nutrients scale with foliar nutrients at the species level, or wood nutrient storage increases with wood density as predicted by the wood economics spectrum. Wood nutrient concentrations varied enormously among species from fourfold in nitrogen (N) to > 30-fold in calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P). Community-weighted mean wood nutrient concentrations correlated positively with soil Ca, K, Mg and P concentrations. Wood nutrients scaled positively with leaf nutrients, supporting the hypothesis that nutrient allocation is conserved across plant organs. Wood P was most sensitive to variation in soil nutrient availability, and significant radial declines in wood P indicated that tropical trees retranslocate P as sapwood transitions to heartwood. Wood P decreased with increasing wood density, suggesting that low wood P and dense wood are traits associated with tree species persistence on low fertility soils. Substantial variation among species and communities in wood nutrient concentrations suggests that allocation of nutrients to wood, especially P, influences species distributions and nutrient dynamics in tropical forests.

Assuntos

RESUMO

In order to identify plants with greater capacity of P uptake in Cerrado soils fertilized with phosphate rock this work was carried out with the following objectives: a) to evaluate the phosphorus (P) uptake and initial development of soybean, brachiaria, sorghum and millet in soils fertilized with soluble and rock phosphates; b) to estimate the kinetic parameters of P uptake for each species. Two experiments were conducted at Santa Catarina State University, Brazil, in the year of 2010. The first experiment consisted of plant development under the application of phosphate fertilizers to the soil. Treatments consisted of growth of four plant species (soybean, brachiaria, sorghum and millet) as affected by application of rock phosphate, triple superphosphate, and a control without P. The four replications were arranged in a 4x3 factorial using a completely randomized design. It was evaluated the plant dry matter yield and P accumulated in plant tissue. In the second experiment, we estimated the kinetic parameters of P uptake (Imax, Km and Cmín) of each species after 23 days of growth in solution culture, using a completely randomized design with four replications. Soybean did not respond to fertilization, but presents the highest dry mass yield and the greatest accumulation of P in the tissue. Triple superphosphate is the P source that caused the greatest dry matter yield for al

A fim de identificar plantas com maior capacidade de absorção de P em solos de cerrado adubados com fosfato natural, visando à ciclagem deste nutriente, objetivou-se: a) avaliar a capacidade de absorção de fósforo e o desenvolvimento inicial de soja, sorgo, milheto e braquiária em função da aplicação de fosfato solúvel e natural ao solo; b) estimar os parâmetros cinéticos de absorção de P dessas espécies cultivadas em solução nutritiva. Para tanto, foram realizados dois experimentos no Centro de Ciências Agroveterinárias da Universidade do Estado de Santa Catarina (CAV/UDESC), no ano de 2010. O primeiro experimento constou do desenvolvimento de plantas (soja, braquiária, sorgo e milheto) em solos adubados com fosfato natural e superfosfato triplo, além de um tratamento sem aplicação de P, arranjados em um fatorial 4x3, sob delineamento inteiramente casualizado, com quatro repetições. Foram avaliadas a produção de massa seca das plantas e a quantidade de P acumulada no tecido. No segundo experimento foram estimados os parâmetros cinéticos de absorção de P (Imax, Km e Cmín) de cada uma das espécies após 23 dias de desenvolvimento em solução nutritiva, utilizando-se o delineamento inteiramente casualizado com quatro repetições. A soja, em fase inicial de desenvolvimento, não responde à adubação fosfatada, apresentando mais massa seca de tecido e acúmulo de P no tecido, comparativa

RESUMO

In order to identify plants with greater capacity of P uptake in Cerrado soils fertilized with phosphate rock this work was carried out with the following objectives: a) to evaluate the phosphorus (P) uptake and initial development of soybean, brachiaria, sorghum and millet in soils fertilized with soluble and rock phosphates; b) to estimate the kinetic parameters of P uptake for each species. Two experiments were conducted at Santa Catarina State University, Brazil, in the year of 2010. The first experiment consisted of plant development under the application of phosphate fertilizers to the soil. Treatments consisted of growth of four plant species (soybean, brachiaria, sorghum and millet) as affected by application of rock phosphate, triple superphosphate, and a control without P. The four replications were arranged in a 4x3 factorial using a completely randomized design. It was evaluated the plant dry matter yield and P accumulated in plant tissue. In the second experiment, we estimated the kinetic parameters of P uptake (Imax, Km and Cmín) of each species after 23 days of growth in solution culture, using a completely randomized design with four replications. Soybean did not respond to fertilization, but presents the highest dry mass yield and the greatest accumulation of P in the tissue. Triple superphosphate is the P source that caused the greatest dry matter yield for al

A fim de identificar plantas com maior capacidade de absorção de P em solos de cerrado adubados com fosfato natural, visando à ciclagem deste nutriente, objetivou-se: a) avaliar a capacidade de absorção de fósforo e o desenvolvimento inicial de soja, sorgo, milheto e braquiária em função da aplicação de fosfato solúvel e natural ao solo; b) estimar os parâmetros cinéticos de absorção de P dessas espécies cultivadas em solução nutritiva. Para tanto, foram realizados dois experimentos no Centro de Ciências Agroveterinárias da Universidade do Estado de Santa Catarina (CAV/UDESC), no ano de 2010. O primeiro experimento constou do desenvolvimento de plantas (soja, braquiária, sorgo e milheto) em solos adubados com fosfato natural e superfosfato triplo, além de um tratamento sem aplicação de P, arranjados em um fatorial 4x3, sob delineamento inteiramente casualizado, com quatro repetições. Foram avaliadas a produção de massa seca das plantas e a quantidade de P acumulada no tecido. No segundo experimento foram estimados os parâmetros cinéticos de absorção de P (Imax, Km e Cmín) de cada uma das espécies após 23 dias de desenvolvimento em solução nutritiva, utilizando-se o delineamento inteiramente casualizado com quatro repetições. A soja, em fase inicial de desenvolvimento, não responde à adubação fosfatada, apresentando mais massa seca de tecido e acúmulo de P no tecido, comparativa

RESUMO

O objetivo deste trabalho foi avaliar a biomassa e absorção de fósforo por espécies vegetais de cobertura submetidas a fontes de fósforo em solos distintos. O experimento foi realizado em casa de vegetação no Departamento de Ciência do Solo da Universidade Federal de Lavras. Utilizou-se o delineamento inteiramente casualizado, em esquema fatorial 5 x 2 x 2, sendo cinco forrageiras (Brachiaria decumbens, Brachiaria brizantha cv. Marandu, Panicum maximum cv. Tanzânia, Avena strigosa - aveia preta cv. Comum e Lupinus albus L.- tremoço cv. Comum), duas fontes de fósforo (superfosfato triplo - ST e fosfato natural de araxá ­ FNA) e dois tipos de solos (LATOSSOLO VERMELHO Distroférrico ­ LVdf e NEOSSOLO QUARTZARÊNICO ­ RQo), com quatro repetições. As doses de fosfatos utilizadas foram 90 e 50 mg.dm-3 de P, baseado no P2O5 total, respectivamente no LVdf e no RQo. A colheita foi realizada aos 70 dias após a emergência das plântulas. O ST proporcionou maior valor de matéria seca da parte aérea, das raízes e acúmulo de P e índice de utilização de P pelas plantas de cobertura nos solos estudados. A aveia preta, com aplicação de ST e o tremoço com o FNA mostraram-se promissores na produção de cobertura vegetal e ciclagem de fósforo.

This work aimed to evaluate biomass production and phosphorus uptake by cover crops growing in two different soil types fertilized with two different sources of phosphorus. The experiment was carried out under greenhouse condition, at the Department of Soil Science, Federal University of Lavras. The experimental set up was a completely randomized design, in a 5 x 2 x 2 factorial scheme, testing five cover crops (Brachiaria decumbens, Brachiaria brizantha cv. Marandu, Panicum maximum cv. Tanzania, Avena strigosa ­ oat cv. Common and Lupinus albus L. - lupine cv . Common), two P fertilizers (triple superphosphate - ST and rock phosphate araxá - FA), and two soil types (Oxisol - LVdf and Entisol - RQo), with four replications. Doses of phosphate used were 90 and 50 mg.dm-3 of P, based on the total P2O5 in LVdf and RQo, respectively. Plants were harvested 70 days after seedling emergence. In both soils, shoot and root biomass was higher in the ST treatment than in FNA treatment. This was probably due to the higher P accumulation in the plants. Satisfactory vegetative cover was observed when oat was cultivated using ST as a P source. For lupine, best results were obtained using FA as a P source.

Assuntos

RESUMO

This work aimed to evaluate biomass production and phosphorus uptake by cover crops growing in two different soil types fertilized with two different sources of phosphorus. The experiment was carried out under greenhouse condition, at the Department of Soil Science, Federal University of Lavras. The experimental set up was a completely randomized design, in a 5 x 2 x 2 factorial scheme, testing five cover crops (Brachiaria decumbens, Brachiaria brizantha cv. Marandu, Panicum maximum cv. Tanzania, Avena strigosa oat cv. Common and Lupinus albus L. - lupine cv . Common), two P fertilizers (triple superphosphate - ST and rock phosphate araxá - FA), and two soil types (Oxisol - LVdf and Entisol - RQo), with four replications. Doses of phosphate used were 90 and 50 mg.dm-3 of P, based on the total P2O5 in LVdf and RQo, respectively. Plants were harvested 70 days after seedling emergence. In both soils, shoot and root biomass was higher in the ST treatment than in FNA treatment. This was probably due to the higher P accumulation in the plants. Satisfactory vegetative cover was observed when oat was cultivated using ST as a P source. For lupine, best results were obtained using FA as a P source.

O objetivo deste trabalho foi avaliar a biomassa e absorção de fósforo por espécies vegetais de cobertura submetidas a fontes de fósforo em solos distintos. O experimento foi realizado em casa de vegetação no Departamento de Ciência do Solo da Universidade Federal de Lavras. Utilizou-se o delineamento inteiramente casualizado, em esquema fatorial 5 x 2 x 2, sendo cinco forrageiras (Brachiaria decumbens, Brachiaria brizantha cv. Marandu, Panicum maximum cv. Tanzânia, Avena strigosa - aveia preta cv. Comum e Lupinus albus L.- tremoço cv. Comum), duas fontes de fósforo (superfosfato triplo - ST e fosfato natural de araxá FNA) e dois tipos de solos (LATOSSOLO VERMELHO Distroférrico LVdf e NEOSSOLO QUARTZARÊNICO RQo), com quatro repetições. As doses de fosfatos utilizadas foram 90 e 50 mg.dm-3 de P, baseado no P2O5 total, respectivamente no LVdf e no RQo. A colheita foi realizada aos 70 dias após a emergência das plântulas. O ST proporcionou maior valor de matéria seca da parte aérea, das raízes e acúmulo de P e índice de utilização de P pelas plantas de cobertura nos solos estudados. A aveia preta, com aplicação de ST e o tremoço com o FNA mostraram-se promissores na produção de cobertura vegetal e ciclagem de fósforo.