Resumo -O objetivo deste trabalho foi calibrar uma câmara prática e de baixo custo, para quantifi car a amônia volatilizada do solo. A calibração da câmara foi realizada pela técnica do balanço do isótopo 15 N. A amônia volatilizada foi capturada por uma câmara semiaberta livre estática (SALE), confeccionada a partir de garrafa de plástico transparente de politereftalato de etileno (PET) de 2 L. O interior da câmara apresentava livre circulação de ar, e possuía uma lâmina de espuma de poliuretano, com 2,5 cm de largura e 25 cm de comprimento, pendurada verticalmente, com a extremidade inferior inserida em frasco com solução ácida, que mantinha a espuma saturada. A recuperação do 15 N-NH 3 no coletor aumentou de forma linear com o aumento da taxa de volatilização de NH 3 do solo. Os testes de campo mostraram efi ciência de 57% na recuperação do N-NH 3 volatilizado do solo. O intervalo de coletas das espumas pode variar de um a seis dias, sem comprometer a efi ciência do sistema. Para estudos de campo, com uso do método proposto, o fator de correção de 1,74 deve ser usado para estimar a real taxa de volatilização de amônia do solo.Termos para indexação: fator de emissão de amônia, isótopo 15 N, sistema coletor de NH 3 , ureia, volatilização de amônia. Calibration of a semi-opened static chamber for the quantifi cation of volatilized ammonia from soilAbstract -The objective of this work was to calibrate a practical and low-cost chamber for the quantifi cation of ammonia volatilization from soil. The chamber was calibrated using the 15 N isotope balance technique. The volatilized ammonia was captured by a semi-opened free static chamber built with a 2 L ethylene polyterephthalate (PET) plastic bottle. The inner side of the chamber had free-air circulation and a stripe of polyurethane foam, with 2.5 cm wide and 25 cm long, hanged vertically with the lower end inserted in a bottle containing acid solution, which kept the foam moistened. The recovery of 15 N-ammonia by the chamber increased linearly with the increase in the rate of soil ammonia volatilization. Field tests showed an effi ciency of 57% in the volatilized ammonia recuperation. The sampling interval of foam can vary from one to six days without impairing the system effi ciency. For studies in the fi eld using the proposed method, a correction factor of 1.74 should be used to estimate the real rate of ammonia volatilization from soil.

Abstract:The addition of biochar to soils can improve soil fertility and increase agricultural productivity. We carried out a field experiment in which biochar produced from Gliricidia sepium (Jacq.) Kunth ex Walp. was added to low-fertility Brazilian planosol and tested to increase the yield of maize (Zea mays) and snap beans (Phaseolus vulgaris L.) in sequential, organic cultivation. Biochar was applied at a 15 t/ha rate, combined or not with Azospirillum Brasiliense inoculation and organic fertilizer (Bokashi). The application of biochar resulted in an increase in soil pH and of the content of macronutrients such as phosphorus and potassium. Contrary to evidence from elsewhere, biochar had a limited effect on increasing maize yield. In the case of beans, when combined with fertilizer, biochar increased the production of beans pods and biomass, but the significant increase was observed only for inoculation. Beans are the principal component of Brazilian diet and increasing productivity of beans is of upmost importance for the poorest in Brazil, and in other tropical countries.

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RESUMOA viabilidade econômica da compostagem está relacionada à utilização de matérias-primas abundantes, de custo competitivo e com níveis reduzidos de contaminação química e biológica. Seguindo esses critérios identifica-se a biomassa de capim-elefante e a torta de mamona como materiais bastante promissores. Objetivou-se, neste trabalho, determinar as características dos produtos finais e os índices de eficiência do processo de compostagem em três formulações da mistura de capim-elefante (Pennisetum purpureum) e torta de mamona com diferentes relações C:N, além de um tratamento de referência com a mistura de capim-elefante e biomassa de Crotalaria juncea. A compostagem da mistura de capim-elefante com torta de mamona possibilitou a obtenção de material orgânico estabilizado com elevado teor de N, sem a necessidade de utilização de qualquer inoculante ou aditivo. Os compostos se estabilizaram aproximadamente aos 60 dias após o início da compostagem e apresentaram reduções de cerca de 50% de sua massa e 65% de seu volume, após 90 dias de compostagem. Compostos com os menores valores iniciais de relação C:N apresentaram as maiores perdas proporcionais de N durante a compostagem. Palavras-chave: adubo orgânico, substrato, composto orgânicoComposting of elephant grass and castor bean cake mixed with different C:N ratios ABSTRACT The economic viability of composting is related to the use of abundant raw materials, with competitive cost and low levels of chemical and biological contamination. Following these criteria, the biomass of elephant grass and castor cake are identified as very promising materials. The aim of this study was to determine the characteristics of end products and efficiency indices of the composting process in three formulations of the mixture of elephant grass (Pennisetum purpureum) and castor bean cake with different C: N ratios, and a reference treatment with the mixture of elephant grass biomass and Crotalaria juncea. The composting of the mixture of elephant grass with castor bean cake allows to obtain stabilized organic material, with high N content, with no need to use any inoculant or additive. Composts stabilized at approximately 60 days after initiation of composting provided reductions of approximately 50% of its mass and 65% of its volume after 90 days of composting. Composts with smaller initial C:N ratios presented greater proportional loss of nitrogen during composting.

An understanding of the interaction between rice and dark septate endophytic (DSE) fungi, under green fertilization, may lead to sustainable agricultural practices. Nevertheless, this interaction is still poorly understood. Therefore, in this study, we aimed to evaluate the accumulation of macro- and micronutrients, dry matter, and protein and N recovery efficiency from Canavalia ensiformis (L.)-15N in rice inoculated with DSE fungi. An experiment under greenhouse conditions was conducted in a randomized complete block design comprising split-plots, with five replicates of rice plants potted in non-sterilized soil. Rice (Piauí variety) seedlings were inoculated with DSE fungi, A101 and A103, or left uninoculated (control) and transplanted into pots containing 12 kg of soil, which had previously been supplemented with dry, finely ground shoot biomass of C. ensiformis enriched with 2.15 atom % 15N. Two collections were performed in the experiment: one at 54 days after transplanting (DAT) and one at 130 DAT (at maturation). Growth indicators (at 54 DAT), grain yield, nutrient content, recovery efficiency, and the amount of N derived from C. ensiformis were quantified. At 54 DAT, the N content, chlorophyll content, and plant height of inoculated plants had increased significantly compared with the control, and these plants were more proficient in the use of N derived from C. ensiformis. At maturation, plants inoculated with A103 were distinguished by the recovery efficiency and amount of N derived from C. ensiformis and N content in the grain and shoot being equal to that in A101 inoculation and higher than that in the control, resulting in a higher accumulation of crude protein and dry matter in the full grain and panicle of DSE-rice interaction. In addition, Fe and Ni contents in the grains of rice inoculated with these fungi doubled with respect to the control, and in A103 inoculation, we observed Mn accumulation that was three times higher than in the other treatments. Our results suggest that the inoculation of rice with DSE fungi represents a strategy to improve green manure-N recovery, grain yield per plant, and grain quality in terms of micronutrients contents in cropping systems with a low N input.