Condicionadores do solo como potencializadores do crescimento de forrageiras na agricultura biossalina

Abstract

The secondary salinization, resulting from inadequate soil management practices has grown substantially in recent yearsamong soil degradation processes in Brazilian semiarid region. Its evolution, without intervention, tends to make agricultural production unviable, followed by desertification and abandonment of salinized areas. In view of its social, environmental and economic impacts, it is necessary to develop remediation techniques for such degraded soils. Thus, this work aimed to evaluate the performance of three forage species adapted to the semiarid and the potential of mixing soil conditioners, as a strategy for the use of degraded areas by salts. The experiment was conducted in a completely randomized design, in a 3x4 factorial arrangement and four replications, the first factor was the forage species and the second one were the soil conditioners mixture. For this, a Cambisol was used, classified as a saline-sodic soil. The soilsamplewas collected in the upper layer (0-20 cm), sieved and standardized, for assembly of the experiment and for chemical characterization. Then, it was packed in polyethylene vessels with 14 kg of soil, where they received the mixtures of soil conditioners: T1: control (without soil conditioner), T2: gypsum + organic matter, T3: elemental sulfur + organic matter, T4: gypsum + organic matter + elemental sulfur. One month after soil conditioners application, seedlings of sorghum, gliricidia and atriplex were transplanted. Irrigation was performed on alternate days, with an irrigation level equivalent to 40% of field capacity. The applied gypsum rate was 16.9 t ha-1, the sulfur was 3.97 tha-1and the organic matter was 30 t ha-1. At 60 days after transplanting the seedlings were collected and fractionated in roots, stems and leaves to obtain their fresh, dry and total weights; allocation of biomass, sodium, chloride and potassium in plant compartments; electrical conductivity of the saturation extract, pH, sodium and potassium content, and exchangeable sodium percentage in the soil after the experiment. Also the sodium absorption efficiency and transferwere determined. For the conditions of studied salinity, Atriplex is the most suitable for forage production and recovery of this soil. The conditioners did not influence the biomass production of the plants, however, their use associated to the halophyte cultivation contributed to the improvement of the chemical attributes of soil, promoting a greater reduction of the EC, ESP, and sodium, chlorine and potassium contentsof the soil, compared to the crop in their absence. The combination of gypsum + organic matter allowed greater accumulation of sodium, potassium and chlorine in the leaves, as well as a greaterreduction of EC and ESP. Therefore, for the production of forage and remediation of the area whose soil was collected for this research, it is recommended the use of Atriplex nummulariaassociated to the application of gypsum + organic matter to accelerate the remediation process.