Abstract Biochar has been used to reuse the agro-industrial wastes and improve soil quality. Several studies have been carried out to show the impact of biochar on physical and chemical soil attributes. However, there are still gaps regarding the effects on as microbial biomass and enzymatic activities that are important to determine sensitive indicators to evaluate changes in management practices. The objective of this study was to assess the effect of two biochars on the chemical, microbial biomass carbon, and the enzymatic activities in an Entisol cultivated with bean. We evaluate two types of coffee biochar: ground and husks, four doses (4, 8, 12, and 16 Mg ha-1) and control. All treatments received organic fertilization with cow manure. Husks biochar increase the soil pH, Ca, and K, also contributing to the reduction of toxic aluminum contents and raising the concentrations of P labile. The treatments that received ground biochar showed higher soil organic carbon, microbial biomass, β-glucosidase, and fluorescein diacetate. Biochar produced from coffee residues increased sandy soil quality. We showed the first report on the beneficial impact of coffee biochar on enzymatic and microbiological quality of sandy soil cultivated with the bean.

ABSTRACT The conversion of native forests into intensive agricultural cropping affects soil quality and ecosystem functionality in tropical dry areas. Although many indicators have been used to assess soil quality, the most sensitive indicators are biochemical attributes. Absolute enzymatic activity (fluorescein diacetate hydrolysis, dehydrogenase, (-glucosidase, urease, arylsulfatase, and acid and alkaline phosphatases), soil organic C (SOC), microbial biomass C (MBC), and specific enzymes per unit of SOC and MBC were measured in forests and perennial (tomato, pangola grass, cotton passion fruit, and cashew nuts) and annual (bean, cabbage, pigeon pea, and fennel) crops. The changes in soils covered with perennial crops differed from those covered with annual crops as regards biochemical soil attributes. The multivariate analysis grouped the Entisols covered with annual crops far from the forest soils, which indicated that intensive management results in drastic changes in the biochemical quality of Entisols in tropical dry areas. The absolute (-glucosidase activity varied from 18.3 to 100.6 (g p-nitrophenol g-1 soil h-1. The tomato areas showed higher dehydrogenase activity with a value of 181.5 (L H g-1 soil. The absolute (-glucosidase, arylsulfatase, and alkaline phosphatase activity and the specific fluorescein diacetate hydrolysis/SOC, (-glucosidase/SOC, arylsulfatase/SOC, acid phosphatase/SOC, (-glucosidase/MBC, and acid phosphatase/MBC can be used as quality indicators of Entisols cultivated with perennial and annual crops. In addition, pasture soil could have a similar biochemical quality as forest soils in tropical dry areas.

O efeito da adubação verde sobre o crescimento e a produtividade do sorgo forrageiro BR 601, foi estudado em experimento desenvolvido na UFERSA, em Mossoró, RN, no qual o delineamento utilizado foi em blocos casualizados completos, em esquema de parcelas subdivididas no tempo com três repetições. Testaram-se sete espécies de leguminosas, Mucuna aterrima, Canavalia ensiformis, Cajanus cajan, Dolichos lab-lab, Crotalaria juncea, Crotalaria spectabilis e Vigna unguiculata, uma mistura das leguminosas mais milho, sorgo e girassol, e a vegetação espontânea, como testemunha. Determinaram-se, para cada tratamento, a quantidade de massa verde, massa seca e teores de N, P, K, Na, Ca e Mg da parte aérea, a partir dos quais foi calculada a quantidade de nutrientes acumulada por hectare. As quantidades de matéria fresca e seca da parte aérea, altura de plantas e número de folhas do sorgo semeado após a incorporação dos adubos verdes, foram avaliadas aos 20, 40, 60, 80 e 100 dias após o plantio. A Mucuna aterrima mostrou-se a melhor opção como adubo verde em virtude de proporcionar os maiores valores das características avaliadas ao final do ciclo do sorgo podendo-se, também, recomendar a Crotalaria juncea e o Dolichos lab-lab, o qual apresentou a maior massa seca e quantidade de nutrientes na parte aérea.

The effect of green manure on growth and yield of forage sorghum BR 601 was studied in a trial carried out at the UFERSA, Mossoró, RN, Brazil. The experimental design was completely randomized blocks in a scheme of split plots in time, with three replications. Treatments tested were seven legume species, Mucuna aterrima, Canavalia ensiformis, Cajanus cajan, Dolichos lab-lab, Crotalaria juncea, Crotalaria spectabilis, and Vigna unguiculata, a mixture of the legumes plus corn, sorghum and sunflower, and spontaneous vegetation as a control. For each treatment the amount of fresh mass, dry mass and contents of N, P, K, Na, Ca and Mg in shoots were determined, from which the amount of nutrients accumulated per hectare was calculated. Fresh mass of shoot, dry mass of shoot, plant height and number of leaves of sorghum, sowed after incorporation of green manures, were evaluated at 20, 40, 60, 80 and 100 days after seeding. Mucuna aterrima was the best option as a green manure because of its better performance in all characteristics evaluated at the end of sorghum cycle. Also recommended are Crotalaria juncea, and Dolichos lab-lab which had the higher dry mass and amount of nutrients in shoots.

Com a utilização intensiva de agroquímicos, os solos cultivados podem ter o teor de metais pesados disponíveis às plantas aumentado com possível contaminação subsequente da cadeia trófica. Propôs-se, no presente trabalho, avaliar a influência do tempo de uso agrícola de um Cambissolo Háplico cultivado com meloeiro (Cucumis melo L.) sob o acúmulo de metais pesados e as características químicas do solo. O solo com plantios de meloeiro com um, dois e três anos de implantação foram avaliados, além de uma área de vegetação natural, nas camadas de 0-20 e 20-40 cm de profundidade. Os resultados mostraram que o tempo de cultivo alterou as características químicas do solo, com aumento do pH e do teor de N, P e K nas duas camadas de solo estudadas; já os teores de Ca foram diminuídos pelo cultivo. Houve acréscimos no teor total e disponível de Ni, Pb, Cu e Mn, na camada superficial, em função do tempo de cultivo do solo, enquanto os teores totais de Fe e Zn foram reduzidos em ambas as camadas avaliadas, no entanto, os teores disponíveis ainda são relativamente baixos.

Soil cultivation using agrochemicals may increase the concentration of availability of heavy metals to plant and cause contamination of the trophic chain as well. This work was carried out to evaluate the influence of length of time under cultivation with melon (Cucumis melo L.) on the heavy metals accumulation and chemical alterations in Ultisol. Melon plantations of one, two and three years were studied. A benchmark area under natural vegetation was used to compare the data obtained. The results showed that the lengthiest time under cultivation altered the chemical characteristics of the soil. An increase in pH and contents of N, P and K was observed for the two soil layers evaluated. On the other hand, Ca contents were decreased by cultivation. The larger the cultivation time the higher the concentration of N, Pb, Cu, and Mn in the soil surface layer, whereas the Fe and Zn concentrations were diminished in both analyzed soil layers, though available concentrations are still regarded as low in soil.

Atualmente, a preocupação com a degradação ambiental renovou o interesse por adubos orgânicos, como por exemplo, os estercos. Além disso, a manutenção da matéria orgânica no solo é um dos principais fatores limitantes ao desenvolvimento da sustentabilidade nas regiões semi-áridas. Em trabalho anterior, realizado para avaliar os efeitos diretos da aplicação de doses de esterco sobre o cultivo de milho, verificaram-se efeitos positivos dessa adubação sobre os rendimentos de espigas verdes e de grãos. Verificou-se ainda, que o esterco aumentou a retenção e a disponibilidade de água e os teores de fósforo, potássio e sódio, na camada do solo de 0-20 cm, mas não influenciou o pH e os teores de cálcio e de matéria orgânica e a soma de bases. O objetivo do presente trabalho foi avaliar o efeito residual da adubação realizada sobre o rendimento de espigas verdes e de grãos das cultivares AG 9012 e AG 4051. Verificou-se ausência de efeito residual do esterco sobre o número e peso total de espigas verdes, número e peso de espigas empalhadas e despalhadas, comercializáveis, altura da planta e de inserção da espiga, matérias fresca e seca da parte aérea, rendimento de grãos e seus componentes, das duas cultivares. A cultivar AG 9012 foi a melhor quanto às características relativas ao rendimento de milho verde, enquanto a cultivar AG 4051 foi superior quanto à altura da planta e peso de 100 grãos. As cultivares não diferiram no que se refere às demais características avaliadas.

The present concern about environmental degradation has produced a renewed interest in organic fertilizers, such as animal manures. In addition, the soil organic matter conservation is one of the most important limiting factors for sustainability development in semiarid regions. In a previous experiment, carried out to evaluate the direct effects of application of manure rates in corn, positive effects of this fertilization were observed on green ear yield and grain yield. It was also verified that manure increased water retention and availability, and phosphorus, potassium, and sodium contents in the soil layer from 0-20 cm, but did not influence pH, calcium, organic matter contents and the sum of bases. The objective of this work was to evaluate the residual effect of applied fertilization on green ear yield and grain yield in cultivars AG 9012 and AG 4051. In both cultivars, a lack of manure residual effects was verified on total number and weight of green ears; number and weight of marketable ears, either unhusked or husked; plant height and ear height; fresh and dry matter in the above-ground part; and grain yield and its components. Cultivar AG 9012 performed best with regard to characteristics employed to evaluate green corn yield, and cultivar AG 4051 was superior with reference to plant height and 100-grain weight. The cultivars were not different with respect to the other traits evaluated.

Os solos de Fernando de Noronha, PE, possuem alta fertilidade natural e elevados teores de fósforo (P) em decorrência do material de origem vulcânica e da deposição de guano. Com este trabalho objetivou-se, mediante o fracionamento de P, avaliar a distribuição das frações orgânicas e inorgânicas em perfis de solo, auxiliando nos estudos pedogenéticos e na identificação das formas disponíveis do nutriente nesses solos; para isto, utilizam-se 24 amostras de solo provenientes de cinco perfis coletados em uma área agrícola com extensão de aproximadamente 16 ha, as quais foram submetidas aos fracionamentos de P orgânico e inorgânico. As frações obtidas foram correlacionadas entre si e com características químicas dos solos. Os resultados demonstram que os altos teores de fósforo observados nos solos de Fernando de Noronha são decorrentes, sobretudo, do material de origem, ressaltando-se que o fósforo orgânico foi menos importante que as formas inorgânicas na contribuição para o fósforo total desses solos. P-Fe e P-Ca são as frações predominantes nos perfis estudados. Os extratores Mehlich 3 e Olsen, melhor correlacionados com as frações mais lábeis de P, foram mais eficientes que o Mehlich 1 para estimar o P disponível nos solos estudados.

The soils of Fernando de Noronha Island present high natural soil fertility and high contents of phosphorus (P) derived from vulcanic soil parent material and probably "guano" deposits. Soil phosphorus fractionation was carried out in these soils in order to define the distribution of organic and inorganic fractions in soil horizon, providing information for studies on soil genesis and prediction of plant available P forms in soils. Five soil profiles were selected and twenty four soil samples were analysed aiming to determine organic and inorganic P fractions, which were correlated with each other as well as with soil chemical properties. The results showed that the high P contents found in the soil samples were derived mainly from the soil parent material and, as a consequence, the organic phosphorus was less important than inorganic forms in contributing to the total phosphorus in such soils. P-Ca and P-Fe fractions are the most important chemical forms in the soil samples. The Mehlich-3 ond Olsen extractors, which were better correlated to labile fractions of phosphorus, were more efficient than Mehlich-1 for predicting the available phosphorus in the soils.