Variations in the chemical composition of the solution extracted from a Latosol under fertigation with vinasse

ABSTRACT The aim of this work was to evaluate the change in electrical conductivity and pH of a soil solution and its composition, with regard to the levels of nitrate and potassium, in a Latosol cultivated with pineapple and subjected to applications of different levels of vinasse. The experiment was conducted in a greenhouse at the Department of Biosystems Engineering of ESALQ/USP. The treatments comprised the application of five levels of vinasse: T1 - 0 m3 ha-1, T2 - 231 m3 ha-1, T3 - 347 m3 ha-1, T4 - 462 m3 ha-1, and T5 - 578 m3 ha-1. Application was every 20 days, using a localised irrigation system with emitters having a nominal flow rate of 4 L h-1 and spaced 0.40 m apart. The applied doses of vinasse were calculated by following the recommendations of CETESB standard P4.231, so that treatment T4 would supply the demand of the pineapple plant for potassium. The solution was collected by means of porous capsule extractors at 30, 120 and 210 days from the start of vinasse application. It was found that increases in the volume of the applied levels resulted in greater values for the electrical conductivity of the soil (ECs) and in the concentration of potassium (K) and nitrate (NO3), with higher values being obtained in the 0.20 m layer. The results demonstrated that pH decreased with increases in the vinasse being applied.

摘要
本研究旨在评估种植菠萝的砖红壤（Latosol）施加不同梯度酒精废液（vinasse）后，其土壤溶液的电导率、pH值及组分（以硝酸盐与钾素水平为指标）的变化情况。本试验于圣保罗大学（USP）路易斯·德·凯罗兹高等农学院（ESALQ）生物系统工程系的温室中开展。试验设置5个酒精废液施加梯度处理：T1组（0 m³·ha⁻¹）、T2组（231 m³·ha⁻¹）、T3组（347 m³·ha⁻¹）、T4组（462 m³·ha⁻¹）以及T5组（578 m³·ha⁻¹）。采用额定流量为4 L·h⁻¹、间距0.40 m的滴头组成的局部灌溉系统，每20天施加一次酒精废液。酒精废液的施加剂量参照巴西圣保罗州环境公司（CETESB）P4.231标准制定，其中T4组的施加剂量可满足菠萝植株的钾素需求。分别于酒精废液施加开始后的第30天、120天和210天，采用多孔胶囊提取器采集土壤溶液样品。研究发现，随着酒精废液施加量的提升，土壤溶液电导率（ECs）、钾（K）与硝酸盐（NO₃⁻）浓度均显著升高，且该类指标在0.20 m土层中数值最高。结果表明，土壤溶液pH值随酒精废液施加量的增加而降低。