ABSTRACT Application of organic fertilizers of animal origin can increase organic carbon in the soil and increase its content in macroaggregates. This study aimed to evaluate carbon contents and fractions in two classes of soil aggregates in response to the application of organic and mineral fertilizers in an integrated crop-livestock system. The experiment was established in Concórdia, Santa Catarina State, in a Nitossolo Vermelho Eutroférrico típico, (Rhodic Kandiudox according to the WRB system) (0.00-0.05, 0.05-0.10, and 0.10-0.20 m), in an integrated crop-livestock, with corn and soybean in the summer, black oat and rye in the winter, shepherded by sheep. The design used was randomized blocks, with treatments in factorial design (5 × 3 + 1), with four replications, five sources of fertilizers, three rates and the control with no fertilization. Three organic fertilizers were applied: poultry litter, pig manure and compost; and two minerals fertilizers: M1 (formulated according to the composition of the pig slurry) and M2 (adjusted according to the composition of the poultry litter), combined with three applications rates, corresponding to 75, 100 and 150 % of the recommendation for the crop of interest, based on the element with greater demand. Total organic carbon (TOC), particulate (POC) and mineral-associated organic carbon (MAC) contents were determined in two classes of soil aggregates C1 (8.00 to 4.76 mm) and C2 (4.76 to 2.00 mm), in samples collected in the 2018/2020 crop season. Crop yields were determined in every season. The results were analyzed using analysis of variance to compare sources and polynomial regression analysis for fertilizer rates. The soil has high aggregate stability, even so, the use of organic and mineral fertilizers increased aggregation. The poultry litter organic fertilizer increases aggregation, forming largely aggregates with a size of 8.00-4.76 mm, and increases the contents of total fractions of soil organic carbon, providing the system with a more stabilized carbon. In the 0.00-0.05 m layer, organic fertilizers increased the content of total organic carbon. The stabilized fraction (MAC) showed a higher proportion of total soil organic carbon than particulate organic carbon (POC).

ABSTRACT The use of organic fertilizers from pig slurry and poultry litter can increase soil organic carbon and crop productivity. This study aimed to evaluate soil organic carbon fractions and corn yield after applying organic and mineral fertilizers. The experiment was conducted in the western region of Santa Catarina State, southern Brazil on a Nitossolo Vermelho Eutroférrico típico (Rhodic Kandiudox). The production system was an integrated crop-livestock using corn and soybean in the summer and black oat and rye with grazing by sheep in the winter. The experimental design was randomized blocks, with treatments in factorial 5 × 3 + 1, with four replications, five sources of fertilizers, three rates and the control with no fertilization. The treatments were three organic fertilizers: poultry litter, pig slurry and compost from pig slurry and two minerals fertilizer (M1 and M2). Mineral fertilizers were formulated from pig slurry (M1) and poultry litter (M2), with the application of three rates, which represent 75, 100 and 150 % of the recommendation for the crop, based on the element that is most demanding by the plant (K for soybeans and N for corn). Soil samples were collected at the layers of 0.00-0.05, 0.05-0.10 and 0.10-0.20 m in which fractions of total soil organic carbon (TOC), namely particulate (POC) and mineral-associated organic carbon (MAC) were determined. Corn yield was evaluated in the 2018/2019 and 2019/2020 seasons. The results were analyzed through analysis of variance to compare sources and polynomial regression analysis for fertilizer rates. The MAC fraction has a higher proportion of TOC and its contents were higher with increasing rates of organic and mineral fertilizers, mainly in the surface layer. Poultry litter and compost fertilizers increased TOC’s particulate fraction (POC), showing the highest levels at the highest fertilization recommendation rate. Organic and mineral fertilizers positively increase corn yield, and animal-derived fertilizers show that they can be an alternative for high crop yields.

Abstract The objective of this work was to evaluate the use of bentonite as an additive in the composting of wastewater sludge from the poultry agroindustry regarding nitrogen conservation, carbon degradation, and nutrient content increase. The experimental design was completely randomized with five treatments with bentonite at 0, 0.5, 1.0, 3.0, and 6.0%, with three replicates. The organic compost used in the treatments consisted of pine sawdust and wastewater sludge from the treatment plant. During and after the composting process, the following were analyzed, respectively: pH, dry matter, temperature, and C, N, NH4+, NO2-, and NO3- contents; and P, K, Ca, Mg, Cu, and Zn contents and humic and fulvic acid concentrations. Bentonite at 6.0% increased C degradation, N losses, Mg content, and humification, but decreased Zn content and humidity. Bentonite, as an additive in the composting of sludge from the poultry agroindustry, promotes humification, decreases Zn content and humidity, but does not affect pH and P, K, Cu, NH4+, NO2-, and NO3- contents.

Resumo O objetivo deste trabalho foi avaliar o uso de bentonita como aditivo na compostagem de lodo de efluente da agroindústria avícola quanto à conservação de nitrogênio, à degradação de carbono e ao aumento no teor de nutrientes. O delineamento experimental foi inteiramente casualizado com cinco tratamentos com bentonita a 0, 0,5, 1,0, 3,0 e 6,0%, com três repetições. A compostagem orgânica utilizada nos tratamentos consistiu de serragem de pinus e lodo da estação de tratamento do efluente. Durante e após o processo de compostagem, foram analisados, respectivamente: pH, matéria seca, temperatura e teores de C, N, NH4+, NO2-e NO3-; e teores de P, K, Ca, Mg, Cu e Zn e concentrações dos ácidos húmico e fúlvico. A bentonita a 6,0% aumentou a degradação de C, as perdas de N, o teor de Mg e a humificação, mas diminuiu o teor de Zn e a umidade. A bentonita, como aditivo na compostagem do lodo da agroindústria avícola, promove a humificação, diminui a concentração de Zn e a umidade, mas não afeta o pH e os teores de P, K, Cu, NH4+, NO2- e NO3-.

ABSTRACT Use of organic fertilizers in integrated crop-livestock (iCL) systems may affect soil phosphorus fractions. This study aimed to determine phosphorus fractions in the soil under the iCL system after six years of application of organic or mineral fertilizers. The experiment was conducted on a Rhodic Kandiudox (Nitossolo Vermelho Distroférrico) in a randomized block design, using a 5 × 3 + 1 factorial scheme, with four replicates. The treatments consisted of three organic fertilizers (poultry litter, pig slurry, and compost) and two mineral fertilizers (M1, equivalent to pig slurry; and M2, equivalent to poultry litter) in interaction with three application rates, corresponding to 75, 100, and 150 % of the fertilizer recommendation for the crop of interest and a control (with no fertilizer). Soil sampling was performed in the 0.00-0.05, 0.05-0.10, and 0.10-0.20 m layers for determination of the phosphorus fractions. Successive use of organic or mineral fertilizers for six years in the iCL system considerably raises the labile and moderately labile P fractions up to the 0.20 m depth and, with less intensity, raises the non-labile fractions up to the 0.10 m depth. The soil P increase associated with fertilizer input raises soybean and corn yields, and it does not exceed the critical P limit according to local environmental legislation.

Resumo: O objetivo deste trabalho foi avaliar o teor nutricional e a produtividade de grãos de três cultivos de milho (Zea mays) em resposta à adubação fosfatada com fertilizante organomineral à base de cama de aves ou mineral, quando cultivado em Nitossolo Vermelho Distroférrico com elevado teor inicial de fósforo. O experimento foi conduzido em campo, em delineamento de blocos ao acaso, em arranjo fatorial 2×4+1 (fertilizantes organomineral ou mineral × 20, 40, 60 ou 80 kg ha-1 de P + controle sem adubação fosfatada), com quatro repetições cada um. Foram determinados os teores de P disponível e carbono orgânico total (COT) no solo ao final do ciclo da cultura, os teores de P no tecido vegetal e a produtividade de grãos. O índice de eficiência agronômica (IEA) foi estimado com base na produtividade de grãos. Após três safras, os teores de P disponível e COT no solo não aumentaram significativa com uso dos fertilizantes, mas apresentaram relação direta com as doses de P. Em um Nitossolo Vermelho Distroférrico com elevado teor inicial de P, o uso de fertilizante organomineral à base de cama de aves proporciona maior produtividade de milho, com IEA 20% superior ao do fertilizante mineral.

Abstract: The objective of this work was to evaluate the nutritional content and grain yield of three corn (Zea mays) crops in response to phosphate fertilization with an organomineral fertilizer based on poultry litter or a mineral fertilizer, when cultivated on a Rhodic Khandiudox with a high initial phosphorus content. The experiment was carried out in the field in a randomized complete block design in a 2×4+1 factorial arrangement (organomineral or mineral fertilizer × 20, 40, 60, or 80 kg ha-1 P + control treatment with no phosphate fertilization), with four replicates each. Available P and total organic carbon (TOC) contents in the soil at the end of the crop cycle, plant tissue P contents, and grain yield were determined. The agronomic efficiency index (AEI) was estimated based on corn grain yield. After three harvests, soil available P and TOC contents did not increase significantly due to fertilizer use, but were directly related to P doses. In a Rhodic Khandiudox with a high initial P content, the use of an organomineral fertilizer based on poultry litter promotes higher corn crop yield, with an AEI 20% higher than that of the mineral fertilizer.

Resumo: O objetivo deste trabalho foi avaliar o efeito da aplicação de fertilizantes organominerais e minerais em solos com fertilidade construída sobre o índice de manejo de carbono (IMC) e as frações e o estoque de carbono. O experimento foi realizado em um Cambissolo e em um Nitossolo sob sistema plantio direto, por três anos agrícolas. Os tratamentos consistiram de dois fertilizantes organominerais e de dois fertilizantes minerais nas formas sólidas e fluídas, além do controle sem adubação. A aplicação de fertilizantes organominerais e minerais, nas formas sólidas e fluídas, às diferentes classes de solo com fertilidade construída, promoveu alterações no carbono orgânico total, particulado e associado aos minerais, bem como nos estoques de carbono e no IMC. Nos tratamentos com fertilizante mineral fluído e fertilizante organomineral sólido, houve alterações apenas no Cambissolo, em razão do menor grau de intemperização deste solo. Os maiores valores do IMC, com fertilizante mineral fluido no Cambissolo, permitem inferir sobre qual seria a melhor prática de manejo para o aumento e a manutenção de carbono no sistema solo-planta, justificada pelos resultados de produtividade de trigo, sorgo e milho, que foram semelhantes aos obtidos com os outros fertilizantes.

Abstract: The objective of this work was to evaluate the effect of the application of organomineral and mineral fertilizers to highly fertile soils on the carbon management index (CMI) and carbon fractions and stock. The experiment was carried out on an Oxisol and Inceptisol, under no-tillage, in three crop seasons. The treatments consisted of two organomineral fertilizers and of two mineral fertilizers in solid and fluid forms, besides a control without fertilization. The application of organomineral and mineral fertilizers, in solid and fluid forms, to the different soil classes with high fertility promoted changes in total organic carbon, particulate organic carbon, and carbon associated with minerals, as well as in carbon stocks and the CMI. In the treatments with fluid mineral fertilizer and solid organomineral fertilizer, such changes occurred only in the Inceptisol due to the lower degree of weathering of this soil. The higher values of the CMI, with the fluid mineral fertilizer in the Inceptisol, allow inferring on which would be the best management practice aiming at the increase and maintenance of carbon in the soil-plant system, based on the yield results of wheat, sorghum, and corn, which were similar to those obtained with the other fertilizers.

Resumo: O objetivo deste trabalho foi avaliar os efeitos de fertilizantes organominerais e minerais, em suas formas sólidas e fluidas, em solos de carga variável com elevada fertilidade construída sobre os conteúdos de nitrogênio, fósforo e potássio no solo e nas plantas, bem como nas produtividades de milho (Zea mays) e aveia-preta (Avena strigosa). Os tratamentos foram constituídos de um controle e de quatro fertilizantes - dois organominerais e dois minerais -, nas formas sólida (SO e SM) e fluida (FO e FM), aplicados em Cambissolo e Nitossolo, sob plantio direto. O uso de fertilizantes organominerais e minerais nas formas sólidas e fluidas contribui para elevar o teor de N total no solo e manter o teor de K trocável em ambos os solos e pode elevar o teor de P disponível até a profundidade de 0,6 m em Cambissolo. Esses fatores permitiram aumentar significativamente a produtividade de milho, independentemente do fertilizante, e estabelecer maior efeito residual para a forma fluida do organomineral na produção de aveia-preta no inverno, mesmo em solos sob elevada fertilidade.

Abstract: The objective of this work was to evaluate the effects of organomineral and mineral fertilizers, in their solid and fluid forms, on soils with variable charges with high fertility built up from nitrogen, phosphorus, and potassium contents in the soil and plant, as well as on corn (Zea mays) and black oat (Avena strigosa) yield. The treatments consisted of one control and four fertilizers - two organomineral and two mineral - in solid (SO, solid organomineral; and SM, solid mineral) and fluid (FO, fluid organomineral; and FM, fluid mineral) forms applied in Rhodic Kandiudox and Distrochrept soils with no-tillage. The use of organomineral or mineral fertilizers in fluid and solid forms increases total N content in the soil, maintains exchangeable K content in both soils, and may enhance available P content to the depth of 0.6 m in Distrochrept. These factors allowed significantly increasing corn yield, regardless of the fertilizer, and establishing greater residual effect for fluid organomineral fertilizer in the winter black oat yield, even in soils with high fertility.

Resumo: O objetivo deste trabalho foi avaliar as aplicações superficial e injetada de dejeto líquido de suínos e ureia ao solo, quanto aos seus efeitos sobre as propriedades físicas de um Nitossolo Vermelho distroférrico, em um sistema de semeadura direta. Os tratamentos foram: dejeto injetado no sulco, com injetor de dejeto líquido de suínos (IDLS); dejeto em superfície, aplicado às linhas com o IDLS erguido; ureia injetada, por meio de abertura do sulco com o IDLS, e distribuída manualmente; e milho, em semeadura direta, como controle. A semeadura e a injeção de dejeto líquido ou de ureia não modificam o teor de carbono orgânico, o pH e a agregação, mas alteram a densidade e a porosidade do solo na linha mobilizada, e aumentam os macroporos.

Abstract: The objective of this work was to evaluate the superficial and injected applications of swine slurry and urea to the soil, regarding their effects on the physical properties of a Nitossolo Vermelho distroférrico under a no-tillage system. The treatments were: injected slurry into the groove with a liquid swine slurry injector (LSSI); slurry on surface, applied on the lines by the LSSI kept raised; urea injected by opening the groove with the LSSI and distributed manually; and corn, under no-tillage, as a control. Sowing and the injection of liquid slurry or urea do not modify the organic carbon content, pH, and aggregation, but alter the soil bulk density and porosity in the mobilized line, and increase the macropores.

Resumo: O objetivo deste trabalho foi recomendar doses de nitrogênio a partir de fertilizantes orgânicos produzidos com cama de aves, nas formas farelada e peletizada, em comparação ao fertilizante mineral, na cultura do milho de alto potencial produtivo, em sistema plantio direto. Os tratamentos foram dispostos em arranjo fatorial 3×3+1, com: três fertilizantes, dois orgânicos com cama de aves nas formas farelada (OF) e peletizada (OP) e um mineral (M); três doses de nitrogênio de 65, 100 e 135% da necessidade de N recomendada para milho; e controle sem adubação. Após cinco safras de milho em sistema plantio direto, em Nitossolo Vermelho distroférrico, as doses recomendadas para adubação com fertilizantes orgânicos a partir de cama de aves, com expectativa de produtividade igual ou superior a 8.000 kg ha-1, poderá ser realizada a partir das doses de 100 kg ha-1 de N na forma de OP e M e 121 kg ha-1 de N na OF. Doses crescentes dos fertilizantes OP, OF e M elevam os teores de carbono orgânico, N e P disponível no solo, na camada superficial (0,0-0,1 m), e de K trocável até 0,2 m, o que permite obter teores de N, P e K no tecido vegetal dentro da faixa de suficiência na cultura do milho.

Abstract: The objective of this work was to recommend nitrogen doses from poultry litter-based organic fertilizers in powder and pellet forms, compared with mineral fertilizer, in a high-yield corn crop under no-tillage. The treatments consisted of a 3×3+1 factorial arrangement, with: three fertilizers, two organic derived from poultry litter in powder (OPo) and pelletized (OPe) forms and one mineral fertilizer (M); three N doses of 65, 100, and 135% of the recommended N requirement for corn; and an unfertilized control. After five corn crops farmed under no-tillage in a Rhodic Kandiudox, the recommended doses for fertilization with poultry litter organic fertilizers, with an expected yield equal to or greater than 8,000 kg ha-1, could be achieved from doses of 100 kg ha-1 N in OPe and M and of 121 kg ha-1 N in OPo. Increasing doses of the OPe, OPo, and M fertilizers raise the contents of organic carbon, N, and available P in the surface soil layer (0.0-0.1 m) and of exchangeable K up to a depth of 0.2 m, allowing to obtain N, P, and K contents in the plant tissue within the sufficiency range of the corn crop.

Resumo: O objetivo deste trabalho foi avaliar os atributos químicos do solo, o teor de nitrogênio foliar e a produtividade de milho e trigo, em sistema plantio direto, em resposta à aplicação de fertilizantes orgânicos, organominerais e minerais, com ou sem inibidores da urease e da nitrificação. O experimento foi realizado em campo, com um cultivo de trigo e dois de milho, em Nitossolo Vermelho distroférrico, em delineamento de blocos ao acaso, com seis repetições. Os tratamentos avaliados foram: controle, sem adubação; O, fertilizante orgânico de cama de aves; O+I, cama de aves e inibidores; OM, fertilizante organomineral; OM+I, fertilizante organomineral e inibidores; U, ureia como fertilizante mineral; e U+I, superureia com inibidor da urease apenas. O uso de fertilizantes orgânicos, organominerais e minerais, com ou sem inibidores, aumentou o teor de N disponível na camada de 0,00-0,05 m do solo. Nas camadas mais profundas, apenas OM+I, na camada de 0,05-0,10 m, e U+I, na de 0,10-0,20 m, proporcionaram maiores teores do que o tratamento-controle. Os teores foliares de N foram adequados, independentemente do fertilizante utilizado. Os tratamentos O, O+I, OM e OM+I aumentam o teor de P disponível e a saturação por bases, e reduzem H+Al na camada superficial do solo. Além disso, todos os fertilizantes aumentam a produtividade total de grãos das duas culturas estudadas, na seguinte ordem: OM+I > U+I ≥ U > OM ≥ O+I ≥ O.

Abstract: The objective of this work was to evaluate soil chemical attributes, leaf nitrogen content, and corn and wheat yields under a no-tillage system in response to the application of organic, organomineral, and mineral fertilizers with or without urease and nitrification inhibitors. The experiment was carried out on the field, with one wheat and two corn crops, on a Rhodic Kandiudox, in a randomized complete block design with six replicates. The evaluated treatments were: control, without fertilization; O, poultry litter as an organic fertilizer; O+I, poultry litter and inhibitors; OM, organomineral fertilizer; OM+I, organomineral fertilizer and inhibitors; U, urea as a mineral fertilizer; and U+I, super urea with the urease inhibitor alone. The use of organic, organomineral, and mineral fertilizers, with or without inhibitors, increased available N content in the 0.00-0.05-m soil layer. In deeper layers, only OM+I in the 0.05-0.10-m layer and U+I in the 0.10-0.20-m layer provided higher contents than the control treatment. Leaf N contents were adequate, regardless of the fertilizer used. The O, O+I, OM, and OM+I treatments increase available P content and base saturation, and decrease H+Al on soil surface. Moreover, all fertilizers increase total grain yield of the two studied crops, in the following order: OM+I > U+I ≥ U > OM ≥ O+I ≥ O.

ABSTRACT Organic fertilizers derived from poultry litter and pig slurry are alternatives to mineral fertilizers in increasing soil nutrient availability. The aim of this study was to evaluate soil response, through characterization of organic C and available N, P, and K contents, and corn yield response to increasing amounts of poultry litter, pig slurry, and mineral fertilizers in an integrated crop-livestock production system (ICL) from 2011 to 2013. The experimental design consisted of randomized blocks in a 4 × 3 + 1 factorial arrangement with four replicates. The treatments consisted of four types of fertilizer, two organic (poultry litter and pig slurry) and two mineral, balanced with the same amounts of N, P and K as the organic fertilizers, one of which corresponded to the levels in the pig slurry (M1) and the other to the levels in the poultry litter (M2) in combination with three .increasing application rates of N (100, 200, and 300 kg ha-1 N) and control without fertilizer. For two years after implementing the ICL system, the application of the different rates of N using organic (pig slurry and poultry litter) or mineral (M1 and M2) fertilizers increased corn yields and K and P availability in the soil; these results were accompanied by small changes in organic C and total N content. There are similar efficiencies between the treatments pairs (pig slurry/M1 and poultry litter/M2).

ABSTRACT Nutrient content in soil solution may vary in response to the applied amount of pig slurry (PS). Thus, the aim of this research was to evaluate the nutrient content in soil solution and its relationship to nutritional status and yield of corn under 12 years of annual fertilization with increasing doses of PS, soluble mineral fertilizer (MF) and PS combined with MF. The experiment was conducted under field conditions in a Latossolo Vermelho Distroférrico (Typic Hapludox). The treatments consisted of pig slurry at annual rates of 50 and 100 m3 ha-1 (PS50 and PS100), soluble mineral fertilizer (MF), and pig slurry at a rate of 25 m3 ha-1 complemented with mineral fertilizer (PS25 + MF), distributed in a randomized block design. Soil solution was sampled at two depths, 0.40 and 0.80 m, on six dates after the fertilizer applications. The nitrate (NO−3-N) and K levels in the soil solution were measured 40, 108 and 135 days after the last application of fertilizer (DAAF), being subsequently correlated with corn yield. PS50 provide contents of NO−3-N, P and K to the soil solution similar to those supplied by MF or PS25+MF. The critical limit of 10 mg L-1 NO−3-N in the soil solution was exceeded on 108, 135 and 230 DAAF, at rates of 100 and 50 m3 ha1 of PS and on 230 DAAF when using MF.

ABSTRACT Quantification of ammonia volatilization after addition of animal residues and nitrogen (N) mineral fertilizers to the soil is important for N management in fertilization programs. The objective of this study was to evaluate the effect of adding a urease inhibitor to N fertilizers to minimize ammonia losses following soil application. The experiment was carried out in a laboratory with samples of a Brazilian Oxisol containing 790 g kg-1 clay and 23 g kg-1 organic matter. Treatments consisted of addition of poultry litter (PL), organic mineral fertilizer (OMF) and urea to the soil, with and without the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), plus a control with no fertilizer. We applied the fertilizers over the soil surface, with no soil incorporation, at a rate of 200 mg kg-1 N. Experimental units consisted of PVC tubes with a diameter of 0.15 m, containing 1.0 kg of soil (dry basis). Ammonia volatilization was measured for 56 days following fertilizer application to the soil using sponge discs impregnated with phosphoric acid and glycerin, which were fitted inside the tubes 0.15 m above the soil surface. Ammonia volatilization peaks varied according to the fertilizer, and most of them occurred in the first 15 days following application to the soil. Total ammonia volatilized from the soil treated with PL or OMF had no influence on the urease inhibitor, probably because the losses were small, attaining a maximum of 2.5 and 9 % of the total N applied, respectively. In the treatment that received urea, NBPT delayed the peak of volatilization by three weeks and decreased the loss of ammonia from 22 to 9 % of the N applied. Use of urease inhibitor does not always decrease ammonia volatilization, especially when mixed with fertilizers in which urea is not the only source of N.

Pesquisas sobre o uso agronômico de corretivos à base de silicatos têm apontado o grande potencial desses insumos, no sentido de promover melhorias químicas do solo. Há poucas informações, porém, sobre as taxas de reatividade de suas frações granulométricas. O objetivo deste estudo foi verificar se a eficiência relativa de reatividade das frações granulométricas, obtidas experimentalmente, poderiam ser consideradas no cálculo do PRNT para prática da calagem, proporcionando adequado desenvolvimento de plantas de alfafa. Utilizaram-se seis tratamentos, que consistiram em duas escórias, aplicadas em duas doses, uma utilizando-se do PRNT medido experimentalmente e, a outra, do PRNT determinado em laboratório; calcário dolomítico e wollastonita, aplicados em uma dose, utilizando-se o PRNT determinado em laboratório. As doses dos corretivos foram calculadas a fim de elevar a saturação por bases a 80 %, considerando o PRNT experimental e de laboratório. Os tratamentos foram aplicados a dois solos: Latossolo Vermelho distrófico e Nitossolo Vermelho eutrófico. Os métodos de determinação de PRNT preconizados para calcários podem ser aplicados para escórias de siderurgia. A aplicação das escórias proporcionou ação corretiva do solo, com consequente maior acúmulo de Ca, P, e Si nas plantas de alfafa, favorecendo sua produção de matéria seca.

Studies on the use of silicate correctives in agriculture show that they have great potential to improve soil chemical characteristics, however, little information is available on the reactivity rates of their particle-size fractions. This study investigated whether the reactivity rates obtained experimentally could be considered in the calculation of ECC (effective calcium carbonate) for soil liming, promoting adequate development of alfalfa plants. Six treatments were evaluated in the experiment, consisting of two slag types applied in two rates. The experimental ECC was used to calculate one of the rates and the ECC determined in the laboratory was used to calculate the other. Rates of limestone and wollastonite were based on the ECC determined in laboratory. The rates of each soil acidity corretive were calculated to increase the base saturation to 80%. The treatments were applied to a Rhodic Hapludox and an Alfisol Ferrudalfs. The methods for ECC determination established for lime can be applied to steel slag. The application of slag corrected soil acidity with consequent accumulation of Ca, P, and Si in alfalfa, favoring DM production.

A eficiência dos corretivos de acidez do solo depende da taxa de reatividade (RE) e do poder de neutralização (PN), sendo indicada pelo poder relativo de neutralização total (PRNT). Para os silicatos, existem poucos estudos que estabeleçam taxas de reatividade para suas frações granulométricas e, portanto, utilizam-se as mesmas taxas de reatividade do calcário. Assim, este estudo teve como objetivo avaliar a reatividade de materiais silicatados, em função de sua granulometria, no decorrer de períodos de incubação, em comparação com a do calcário, e calcular a eficiência relativa de reatividade das frações granulométricas dos silicatos. Utilizaram-se seis materiais corretivos, sendo três escórias de aciaria de origens distintas, calcários dolomítico e calcítico, separados em quatro frações granulométricas (material retido entre as peneiras ABNT 10; 10-20; 20-50 e < 50), e a wollastonita como tratamento adicional. A combinação dos tratamentos foi aplicada a três solos de diferentes classes texturais. A dose foi aplicada em quantidades iguais de material neutralizante (óxidos de cálcio e magnésio), possibilitando ter como variação apenas a granulometria do material. Após 90 dias de incubação dos corretivos, calculou-se a eficiência relativa de reatividade para cada fração granulométrica, a reatividade (RE) e o PRNT experimental dos corretivos. As reações de neutralização da acidez do solo de uma mesma fração granulométrica, com os diferentes corretivos, mostraram que ocorrem solubilidade e reação distintas entre silicatos e calcários. As taxas de eficiência relativa para a reatividade das escórias foram superiores às determinadas pela legislação brasileira, podendo-se inferir que o método utilizado para calcários não é adequado para os silicatos.

The efficiency of sources used for soil acidity correction depends on reactivity rate (RR) and neutralization power (NP), indicated by effective calcium carbonate (ECC). Few studies establish relative efficiency of reactivity (RER) for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves), and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides) was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.