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Soil acidification, as influenced by N fertiliser, stubble management, and crop rotations, was investigated using soil samples from a long-term rotation trial at Tarlee, South Australia. With the effects of combination of treatment inputs (wheat–lupin, stubble retention and N-fertiliser application), the pHCa (0–10 cm depth) declined from the starting value of 6.12 to 4.50 after a 14-year period. All of the treatments caused the soil pH to decrease. The mean acidification rates for the period 1978–1992 varied from 0.5 to 2.22 kmol H+/ha.year for different treatments. Although the rainfall at Tarlee (483 mm) is not sufficient to cause regular drainage events, it is likely that downward movement of NO3– in the soil profile has caused acidification in the surface soil. Also the retention of stubble caused more acidification than where there was regular stubble burning or removal. The acidification resulted in an increase in soil exchangeable Al and Mn and extractable Al and Mn, and the decrease in soil exchangeable base cations. The values for soluble Al (extracted in CaCl2) in 1992 were 1.58 and 2.45 mg/kg (0–10 cm depth) for the wheat–bean and wheat–lupin rotations, but the percentage of Al in the ECEC was low. It is not known whether this acidity has any impact on yields of field crops at this stage. But with soluble Al and the percentage of Al in ECEC increasing, it is possible that Al toxicity may occur in the high input-output cropping soils in South Australia. acidity, pH, aluminium, manganese.

Rice husk ash (RHA) is a waste material produced in large quantities in many regions worldwide, and its disposal can be problematic. This work describes a method for using RHA to synthesize silicon and potassium slow-release fertilizer. The extraction of silica from RHA was accomplished by alkaline leaching with KOH. Different KOH concentrations and reaction times were evaluated and the best production of K 2 SiO 3 solution was achieved using 6 mol L -1 and 6 h, respectively. The fertilizer was synthesized by the reaction of K 2 SiO 3 with KAlO 2 in aqueous medium, followed by calcination at 500 °C. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses indicated that the fertilizer composition was similar to mineral kalsilite. Solubility essays indicated lower K + and Si 4+ release percentage in neutral medium. Kinetic mechanisms of release tests can be well explained by the pseudo-second order model. The proposed synthesis seems to be a viable process offering economic and environmental benefits.Keywords: rice husk ash, silicon, potassium, slow-release fertilizer IntroductionNowadays, one of the most important goal of agronomic management is the development of environmentalfriendly fertilizers, which promote a sustainable nutrient management to ensure growth crop yield.1 One method of reducing fertilizer nutrient losses involves the use of slowrelease fertilizers, which have been designed to gradually release nutrients to plants at a rate to coincide with the requirement of crops. The advantages of using slow-release fertilizers instead of the conventional type are various, such as the increased efficiency of the fertilizer, the continuous supply of nutrients for a prolonged period and a decrease of nutrient losses by volatilization and leaching out to surface and ground water. 2,3 Potassium (K) is known as one of the most required nutrient during plant growth. K plays an important role in the energy state of the plant, translocation and storage of assimilates and maintenance of water in plant tissues. 4 For many crops, silicon (Si) is also an important nutrient and its availability to plants is often associated to increase of crop yield. 5Plants under intensive cultivation that require high absorption of Si, such as rice, sugar cane, and grasses in general, can quickly deplete the soluble Si content of soil. This element, therefore, needs to be replaced by fertilization. The application of Si fertilizer can influence plants in two ways: (i) by improvement of the fertility and chemical properties of the soil, and (ii) by direct effects on plant growth and development.6 Positive effects that have been reported include improved plant structure, such as upright leaves and stems, 7 and increased resistance to fungi and insects due to deposition of Si under the plant cuticle. 8 The high Si content of rice husk ash (RHA) has led to interest in its use as a source of Si for plants and for the production of numerous Si-based materials.9 RHA is generated after burning the rice husk, which is a waste from the ric...

This work describes the removal of pesticides from water using activated and magnetized biochars produced from exhausted husk, and dry tannin from barks of black wattle (Acacia mearnsii De Wild.). These materials were characterized using chemical, spectroscopic, thermal, solid structure and surface area techniques. The activated and magnetized biochars were effective in removing the pesticides thiacloprid and thiamethoxam from both ultrapure water and Marcela Water Reservoir, Itabaiana, Sergipe State, Brazil. At the longest time examined, the amounts of thiacloprid and thiamethoxam adsorbed per gram of activated biochar adsorbent were 1.02 and 0.97 mg, respectively, while values of 0.73 mg (thiacloprid) and 0.40 mg (thiamethoxam) were obtained using magnetized biochar. A pseudo-second order model correctly described the kinetics of adsorption of both pesticides (R 2 ≥ 0.922). Desorption experiments revealed that the spent biochars could not be easily regenerated, which indicated that the forces holding the adsorbed fluid molecules to the solid surface were relatively strong.

Abstract:In this first part of our work about innovation in biorefineries, the biomass is previously treated to separate cellulose from other components of the vegetal biomass, followed by acid hydrolysis to produce glucose, which is then fermented to produce second generation (2G) ethanol. The unwanted biomass generated in this first stage will be submitted to pyrolysis to produce biochar, bio-oil, and biogas in a subsequent bio-refinery procedure. In this work, elephant grass (Pennisetum purpureum) and sugarcane bagasse (Saccharum officinarum) were subjected to acid hydrolysis, under atmospheric pressure, as an example of the initial part of the process. Higher cellulose yield was obtained for sugarcane bagasse than for elephant grass, with values of 45 % and 32 %, respectively. In evaluation of the sugar produced, the two grasses showed values of approximately 13 g/100 g of dry biomass. In terms of the 2G ethanol obtained, sugarcane bagasse presented a yield of 96 L.t -1 of dry biomass, while the elephant grass yielded 79 L.t -1. Despite the fact that sugarcane bagasse showed a higher 2G ethanol production potential, elephant grass is a good alternative, due to its adaptability and capacity to grow in various climates and under adverse soil conditions. Keywords: Biorefineries; elephant grass; sugarcane bagasse; 2G ethanol; acid hydrolysis. ResumoNesta primeira parte do nosso trabalho sobre inovação em biorrefinarias, a biomassa é previamente tratada para separar a celulose de outros componentes da biomassa vegetal, seguida de hidrólise ácida para produzir glicose, a qual é fermentada para produzir etanol de segunda geração (2G). A biomassa residual gerada nesta primeira será submetida à pirólise para produzir biochar, bio-óleo, e biogás em um procedimento subsequente de biorrefinaria. Neste trabalho, capim-elefante (Pennisetum purpureum) e bagaço de cana (Saccharum officinarum) foram submetidos à hidrólise ácida, sob pressão atmosférica, como um exemplo da parte inicial do processo. O maior rendimento de celulose foi obtido para o bagaço de cana do que para o capim-elefante, com valores de 45 % e 32 %, respectivamente. Na avaliação do açúcar produzido, as duas gramíneas mostraram valores de cerca 13 g/100 g de biomassa seca. Em termos do etanol 2G obtido, o bagaço de cana apresentou um rendimento de 96 L.t -1 de biomassa seca, enquanto o capim-elefante rendeu 79 L.t -1. Apesar do fato de que o bagaço de cana apresentar maior potencial de produção 2G etanol, o capim-elefante não deixa de ser uma boa alternativa, devido à sua adaptabilidade e capacidade de crescer em vários climas e sob condições adversas de solo.Palavras-chave: Biorrefinarias; capim elefante; bagaço de cana; etanol 2G; hidrólise ácida.

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