Avaliação do desempenho de aluminossilicatos na estabilização de macronutrientes e na mitigação da salinidade do solo

Abstract

A new possibility of cultivation called zeoponic system consists of plants which are cultivated in artificial substract composed mainly by the zeolitic mineral and it works as controlled and renewable delivery system of nutrients and water for the plants. When zeolites are treated um nitrogen salts, these are introduced through the zeolite pores, filled all the cavities. This way, zeolites acts as fertilizers and soil amendmenter, gradually delivering the nutrients and avoiding wastage. The technological importance of zeolites, justified by the optimization of their production and control of their properties, have been evaluated by means of sunflower cultivation, in which LTA type zeolite was added to cultivation soil in order to provide fertilizer (occluded nitrogen salts), and in the cultivation of kidney beans, in the mitigation of damages caused by several salinity levels due to the presence on sodium ions in the irrigation water. The retention of sodium by the zeolite present in the cultivation soil is associated to its high concentration of negative charges, giving a favorable electrolytic performance to the zeolite towards the sodium ions interaction/retention. The spectroscopic properties associated to the zeolite A synthesis mechanism were also assessed, including the thermokinetic studies of the minerals used as raw materials, the red Campos Sales kaolin (Campos Sales-CE, Brazil) and the processed Campina Grande kaolin (Campina Grande-PB, Brazil), the later treated as pattern. The activation energies of the kaolin samples related to the presence of the clay mineral kaolinite presented different behavior due to structural iron presence (isomorphic) on Campos Sales kaolin, that resulted in lower thermal stability. X-ray diffraction analyses regarding the synthesis stages proved that the crystallization process is strongly dependent on the ageing stage that precedes the crystallization. Infrared spectroscopic analyses revealed the presence of bands that suggest a stabilizing interaction to took place between ammonium nitrate and the different zeolite sites. The cultivation with nitrogen fertilizing by using occluded zeolite showed itself feasible in reducing nitrogen loss by leaching, what contributes to minimize environmental damages. In kidney beans cultivation with sandy soil, the sodium contents remained constants in the treatments with salinity between 3.6 and 5.0 dS m-1, indicating zeolite saturation by sodium even in the 3.0 dS m-1 salinity level, that is, after successive watering there was the possible saturation as showed by the results, the rapid passage of salty water through the sandy substract, not allowing a salinity dynamic equilibrium, what makes the salty solution used in the watering to go pass through all the vase, increasing the leached sodium content. For the cultivation in the clay soil, on the other hand, the results indicate that the zeolite acts in a more significant way Avaliação do desempenho de aluminossilicatos na estabilização de macronutrientes. . . 10 in higher sodium concentration, as in the 5.0 dS m-1 salinity level, and mainly after the first 20 days of cultivation. During this period a higher sodium retention took place, possibly because of the change in the porosity with consequent water retention by the soil, favoring this way a longer residence period of sodium in the soil and consequent retention by the zeolite. This implies that the presence of a clay fraction in the soil was determinant in the process. The fitotechinique results show the watering with low conductivity produced more dry matter in the fertilizing management with zeolite, and as the sodium contents in the watering increase, the dry matter does not depend on the presence of the zeolite. Keywords: