Biofertilizante e inoculação rizobiana no feijão-caupi em solo salino-sódico tropical

Abstract

The development of crops such as cowpea (Vigna unguiculata (L.) Walp) can be limited by the excess of salts and/or exchangeable sodium in the soils, being necessary the correction of areas that present these problems in order to make them viable for the agriculture. The application of products such as agricultural gypsum are commonly used to reduce salinity, but are not able to contribute to the reduction of soil pH. In this case, it is necessary to use acidifying products such as elemental sulfur, which when associated with bacteria of the genus Acidithiobacillus thiooxidans promotes the reduction of soil pH. The objective of this work was to correct a saline-sodic soil and determine through the use of different conditions: Sulfur, Gypsum, and Sulfur + Gypsum (S, G, S+G), to determine which is the most efficient for the reduction of soil pH. and to enable the increase of soil nutrient contents as a function of the application of different doses of biofertilizer (BNPK) inoculated or not with Bradyrhizobium (BR3267). The study was carried out in a greenhouse at the Universidade Federal Rural de Pernambuco in Recife PE, using a Fluvic Saline-Sodium Neosol collected (0-20 cm) in the region of Ibimirim-PE. A completely randomized design (DIC) was used in a 3x3x2 + 1 factorial scheme, where the interactions between 3 types of conditioning (sulfur + A. thiooxidans; gypsum; sulfur + A. thiooxidans + gypsum), 3 doses of BNPK (50 , 100 and 150% of the recommended dose of N for the cowpea crop, taking into account the soil analysis), in the absence and presence of Bradyrhizobium sp. (BR 3267), with a control treatment (soil only), 3 replications, totaling 57 experimental plots. Each experimental plot consisted of a pot (6 kg of soil) with a cowpea plant. The development of the experiment consisted of the application of the conditioners for 45 days, followed by the application of a leaching depth, corresponding to three times the total volume of soil pores. Then, the fertilization of the biofertilizer with different doses was carried out and the sowing of cowpea inoculated or not with Bradyrhizobium. The application of the conditioner S + A. thiooxidans provided the soil with a reduction in the pH value of the soil, when associated with the application of leaching depth, this conditioner also contributes to the reduction of exchangeable sodium in the soil. In addition, the incorporation of high doses of BNPK contributed to the increment of nutrients in the soil such as K, Ca and Mg. The inoculation of Bradyrhizobium associated with BNPK influenced the number of nodules, the growth of cowpea and the accumulation of nitrogen in the shoot.