Investigation of hidrogel application on the culture of beans to optimie water resourse and productivity

Abstract

Gels are cross-linked polymers which, in the presence of a compatible solvent, can swell, absorbing the solvent, but not dissolving in it. Hydrogels are those which can absorb water. Moreover if they can absorb and retain one hundred or more times its own weight they are called superabsorbent polymer. They are known as hydrophilic network structured polymers having hydrophilic functional groups such as hydroxyl, carboxylic acid, carboxylates and amines. Acrylates have been used to develop hydrogels capable to absorb more than six hundred times its own weight, although water absorption capacity is a property which can vary according to the medium properties, such as pH and ionic concentration. Due to some of their properties such as hydrophilicity, high swelling capacity, lack of toxicity and controlled release, the applications on agriculture have been suggested for these materials. Since most of the hydro resources used for human beings are destined for agriculture proposes, studies focused on the development of technologies to optimise the use of water turns out to be essentially important. Considering that hydro deficit is one of the major limitations for vegetal productivity and seedlings cultivation and that new technologies for better use of water should be studied, the main objective of this research is to analyse the water absorption capacity of a commercial hydrogel (Stockosorb®) and to investigate if its use can improve the development of the culture of Phaseolus vulgaris beans. Firstly, the water absorption capacity was analyzed using the gravimetric methods. The solution in which the hydrogel samples are immerged had pH between 4,5 and 6,5 which are the characteristic values of Brazilian soil. Moreover, a randomized experimental design, in a 5x3 arrangement, with three replications totalizing 15 treatments, was used to investigate the hydrogel efficiency on the bean culture. Besides the control (soil with no amendments), two different concentrations of hydrogel were added to the pots (0.4 or 0.8g for each pot of 3 L) and five levels of irrigation were applied to the experiment. The parametrs height, number of leaves, flowers and bean pods were recorded at weekly intervals to evaluate the growth of the plants. At the end of the experiment, dry weights of leaves, stems and roots and the productivity, indicated by the number and the dry weight of the grains, were evaluated. In the first experiment it was observed that the hydrogel achieved more than 200 times its own initial weight. This result indicates that they might be used as water resource regardless the pH of the soil. Also the results of the culture beans shown the addition of hydrogel to the soil was efficient to the growth of the plants. This effect of the hydrogel amendment could be observed irrespective of irrigation levels. Furthermore it was observed that beans culture productivity had been influenced by the different concentrations of hydrogel applied in which experiment treatment. This research presented relevant agronomical and environmental results. It proves the efficiency of the use of the hydrogel Stockosorb® on the culture of Phaseolus vulgaris beans, since satisfactory productivity was achieved with less water quantity for irrigation. Further studies will be carried out so as to evaluate hydrogel application on field experiments, focused on the compatibility of the sustainable use of water along with the improvement of productivity and the economic feasibility.