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RESUMOLodos de esgoto podem ser reciclados no solo agrícola como fonte de nutrientes para as plantas e visando o aumento no teor de matéria orgânica. O objetivo do presente trabalho foi caracterizar a fração orgânica de lodos de esgoto (teores totais, orgânicos e inorgânicos de carbono, nitrogênio e fósforo; concentrações de carbono solúvel em água, açúcares solúveis, proteína bruta, lipídeos, hemicelulose, celulose, lignina, fenóis e taninos totais), de modo a auxiliar no planejamento de seu uso na agricultura. Foram utilizados cinco tipos de lodos de esgoto com diferenças quanto às etapas posteriores de condicionamento químico e/ou tratamento complementar para desidratação, sendo três provenientes de processo anaeróbio: cal e cloreto férrico, desidratado mecanicamente (LAC); polímero sintético e desidratado mecanicamente (LAP); polímero sintético e desidratado termicamente (LAS), e dois de processo aeróbio de digestão: condicionamento com polímero sintético e secagem em leitos (LLP); LLP após processo de compostagem em pilhas aeradas em mistura com bagaço de cana-de-açúcar e restos de poda urbana, composto de lodo (CL). O condicionamento com polímero e secagem térmica conservou mais a matéria orgânica do resíduo, o que foi evidenciado pela presença de maiores teores de compostos orgânicos facilmente degradáveis, bem como de carbono (337,24 g kg -1 ), nitrogênio (39,02 g kg -1 ) e fósforo (2,93 g kg -1 ) no compartimento orgânico. Em todos os lodos houve expressiva participação do conteúdo protéico na matéria orgânica, que foi de aproximadamente 43, 42, 28 e 25 % para os lodos de esgoto LAC, LAP, LAS, LLP e CL, respectivamente. Palavras-chave: biossólidos, compostos orgânicos, fertilizante orgânicoChemical composition of sewage sludge organic matter ABSTRACT Sewage sludge can be recycled in agricultural soil as a source of plant nutrients and in order to increase the organic matter content. The objective of this study was to characterize the organic fraction of sewage sludge (contents of carbon, nitrogen and total organic and inorganic phosphorus; concentrations of protein, fat, fiber, phenol and tannin) in order to assist in planning their use in agriculture. Five types of sewage sludge with differences were used for the later stages of chemical conditioning and / or complementary treatment for dehydration, three from anaerobic process: lime and ferric chloride, mechanically dehydrated (LAC); synthetic polymer and dehydrated mechanically (LAP); synthetic polymer and thermally dehydrated (LAS), and two aerobic digestion process: etching synthetic polymers with drying beds (LLP); LLP after the composting process in aerated piles mixed with bagasse from sugar and urban pruning debris, sludge compost (CL). The conditioning polymer and heat drying the organic matter retained in the residue, which was evidenced by the presence of higher concentrations of readily degradable organic compounds and carbon (337.24 g kg -1 ), nitrogen (39.02 g kg -1 ) and phosphorus (2.93 g kg -1 ) in the organic compartment. In all sludg...

O lodo de esgoto é um resíduo urbano-industrial que tem causado preocupação, quanto ao uso agrícola. Sua utilização pode ser viável, após a devida suplementação potássica, em substituição a fertilizantes minerais, especialmente em culturas como a do girassol. O presente trabalho objetivou avaliar a produtividade e nutrição mineral do girassol cv. CATISSOL 01, além da fertilidade de um Latossolo Vermelho eutroférrico adubado com lodo de esgoto, em comparação à adubação mineral, por dois anos consecutivos. O experimento utilizou delineamento em blocos casualizados, com 4 tratamentos (fertilização mineral, 5 t ha-1 ano-1, 10 t ha-1 ano-1 e 20 t ha-1 ano-1 de lodo de esgoto) e 5 repetições. Foram analisadas a produtividade de grãos de girassol, a concentração de macro e micronutrientes na folha diagnóstico e a fertilidade do solo. A produtividade de sementes do girassol adubado com o resíduo, em todas as doses, foi equivalente à adubação mineral, e os teores foliares situaram-se na faixa adequada, tanto para macro quanto para micronutrientes. O uso de lodo de esgoto, com suplementação potássica, mostrou-se eficiente na substituição total ou parcial da adubação mineral, sem prejudicar a produtividade da cultura do girassol.

Despite scientific evidence suggesting that warm‐season grasses can respond favorably to K and P fertilization, the increasing costs of fertilizers limit the extent to which these nutrients are used in pastures and hayfields. Two field studies evaluated ‘Jiggs’ bermudagrass [Cynondon dactylon (L.) Pers.] and ‘Floralta’ limpograss (Hemarthria altissima Stapf. and Hubbard) herbage accumulation (HA), nutritive value, and persistence to reduced fertilization strategies during 2012 to 2014. Treatments were allocated in a split‐plot design with N (90 or 180 kg N ha−1, bermudagrass study) or harvest frequency (6 vs. 12 wk, limpograss study) as the main factors and P (0, 8.7, and 17.4 kg P ha−1) and K (0, 33, and 66 kg K ha−1) levels as subplots. Bermudagrass HA increased linearly (up to 377% in Year 3) as K level increased. Similarly, K fertilization increased limpograss HA from 8.4 to 11.6 Mg ha−1 in 2013 and from 5.8 to 15.7 Mg ha−1 in 2014 as K levels increased from 0 to 66 kg K ha−1; however, no effect was observed in 2012. Bermudagrass HA and ground cover decreased from 2012 to 2014 in all K treatments. Conversely, decreases in limpograss HA and ground cover over time were observed only in the control (no K) treatments. Bermudagrass and limpograss crude protein concentrations generally decreased with increased K level. No effects of N or P were observed. Continuous aboveground removal without proper K fertilization is detrimental to bermudagrass and limpograss production and persistence.

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Increased grazing land management intensification through the selection of productive species and the use of N affects the amount and quality of C and N inputs to the soil. This study evaluated the short-term impacts of litter quality on litter decomposition and C and N distribution among soil size-density fractions. A 168-d litter bag mesocosm experiment and a 120-d incubation study evaluated the decomposition of three perennial species [rhizoma peanut (Arachis glabrata Benth., RP), bahiagrass (Paspalum notatum Flügge; BG), and sawpalmetto (Serenoa repens Bartr., SP)] on grazing land soils with contrasting C concentrations (3.4 and 18 g C kg −1 ; Buck Island Ranch and Ona, respectively). Soil did not affect litter decomposition. There was less remaining biomass at the end of incubation for RP and BG (58%) than SP (79%). Nitrogen immobilization occurred on SP litter, probably because of its high initial lignin/N and fiberbound N/N ratios (43 and 384 g kg −1 organic matter, respectively). Litter had no effect on soil C and N concentrations in size-density fractions; however, greater proportions of C and N (∼47 and 59%, respectively) were found in the light-free fraction. Nitrogen addition promoted C and N accumulation in the mineral fraction. These results suggest plant litter chemical characteristics played a more important role on litter decomposition than soil C and N concentrations. Management intensification through changes in plant species and N fertilization had positive effects on C and N dynamics in coarse-textured soils, with enhanced decomposability of cultivated forage species relative to native vegetation.