Bean-pod cultivation in pots with different substrates and electrical conductivity of nutrient solution

Abstract

The consumer’s demand for healthier products along with issues such as salinization, soil affections and successive planting and cropping foment the pursuit for more sustainable production systems that the ones in practice currently. To such an extent, the present study aimed to evaluate the nutrition of plants due to electrical conductivity of nutrient using different substrates. The experiment was conducted at the Agrarian Sciences Center at UEL. For the cultivation was used UEL-2 bean pod type, which has determined growth, average height of 40 cm, straight pods with flat section and harvest around 55 days after planting. The experiment outline was randomized blocks with subdivided plots. The plots were composed by treatments holding nutrient solutions with electrical conductivity of: 0.5, 1.0, 1.5 and 2.0 mS cm-1 and subdivisions composed by substrates consisting of: carbonized rice hulls, Pinus bark and a combination of 50% carbonized rice hulls + 50% pine bark. A total of 60 pots of 5 liters each were used, each one holding two plants that were watered twice a day, with the aid of manual watering, containing 150 ml of variable nutrient solution, depending on each of the treatments electrical conductivity. The levels of fresh and dry matter of roots, stems, leaves and pods, pod length and diameter, electrical conductivity and pH’s of eluviated ones were analyzed throughout the whole cycle. The obtained results were submitted to analysis of variance and the substrates averages compared by the Tukey test at 5% probability, and the quantities of electrical conductivity by means of regression. The use of nutrient solution with electrical conductivity of 1.5 mS cm-1 and the substrate containing 50% pine bark over 50% carbonized rice hulls resulted in increased productivity, with 182 g pot-1, corresponding to 1.09kg m2. At the same time, the use of carbonized rice hulls substrate with the electrical conductivity of 0.5 mS cm-1 showed the worst results, with production of 47.6 g pot-1, and extrapolated to 0.286 kg m2. The substrate composed by the combination of carbonized rice hulls over pine bark was proved to be more suitable in substrate applications in such cases. Among the treatments tested, the best results were obtained using higher electrical conductivities between 1.5 and 2.0 mS cm-1.