Reatividade e eficiência agronômica do hydropotássio e pó de rocha sienítica ultrapotássica como fontes de silício e potássio para as plantas

Abstract

The use of silicates as a source of silicon has provided innumerable benefits for agriculture, the main ones being related to the fertilizing and corrective action of the same. Among the main sources of Si are those of natural origin (rocks), steel aggregates and by-products from the manufacture of phosphate fertilizers. There are several sources of Si today, however, it is necessary to identify those with the highest agronomic efficiency and the necessary guarantees so that they can be marketed as fertilizers or soil correctives. In order to evaluate the reactivity and efficiency of different sources of Si and potassium, two incubation studies and one biological test were developed. The experiments were carried out in two different soils, the first one was Typical Quartzianic Ozonum (RQo) and the second was the Typical Red Latosol (LVd), testing three silicon sources. The incubation experiment was installed in a 3x2 + 1 factorial, with three sources (Hydropotassium, Rock Powder and Wollastonite as standard source), two doses (200 and 400 mg kg -1 of Si) and additional treatment without Si. Randomized blocks. There was also the application of the standard source at the dosages of 100 and 600 mg kg -1 of Si, to determine the source release curve. After 60 days of incubation, samples were analyzed for Si content analyzes in 0.01 mol L-1 calcium chloride and 0.5 mol L-1 acetic acid, pH, Ca, Mg exchangeable. The calcium silicate equivalence was calculated using the Si results, which, when higher than 45% [average of two soils (sandy and clayey) and two doses of Si (200 and 400 kg ha-1), will be able to do The Register with the Ministry of Agriculture. For the biological test, an experiment was carried out in a greenhouse at the Federal University of Uberlândia (UFU), in Uberlândia - MG. The experiment was set up in a randomized complete block design with four replications and 10 treatments arranged in a 3x3 + 1 factorial scheme. The sources of Si (Hydropotassium, Ultrapotassic Sienitic Rock Powder and the standard Wollastonite source) were three Si doses 400, 600 and 800 kg ha-1) and the control without application of Si. The amount of product applied was calculated based on the total Si content of each source. The rice was sown and harvested after 70 DAS (days after sowing), before flowering. Each experimental plot consisted of a pot with 5 kg of soil and 7 rice plants of the cultivar BRS Atalanta. The evaluated variables were Si, Ca, Mg, K and pH of the soil, nutrients in the aerial part of the plant, accumulated nutrients and dry mass production. Among the sources studied, in the incubation test, Wollastonite, the standard source, was the most efficient in providing silicon, calcium and magnesium to Quartzarenic Neosol after a period of reactivity. It also showed higher pH correction power. In Typical Red Latosol (LVd), Wollastonite was the most efficient in providing silicon, calcium. Hydropotassium was superior in providing magnesium and soil correction power. Thus, the results of the incubation test indicated that Hydropotassium is suitable for registration as fertilizer containing Si at the Ministry of Agriculture, because it presented a Calcium Silicate Equivalent of 45% or higher in the two soils studied. For the biological test, the application of Hydropotassium, the increase in the dose in LVd causes reduction in the content of nutrients in the aerial part. Wollastonite (standard), was the best source for silicon supply, Ultrapotassic Sienitic Rock Powder did not show significant release of silicon to the plants. Hydropotassium increased silicon content in leaf content, but was lower than standard treatment (Wollastonite). Hydropotassium at the dose of 400 kg ha-1 presented lower efficiency for dry mass production. In RQo, Ultrapotassic Sienitic Rock Powder was the source that presented the highest efficiency to supply potassium to the plants. In soil RQo, Hydropotassium at the dose of 400 kg ha-1 showed higher efficiency in providing Si for plants. Ultrapotassic Sienitic Rock Powder in RQo, did not release silicon to the plants. Ultrapotassic Sienitic Rock Powder in RQo soil was the most efficient source for potassium accumulation by plants and in LVd it was the one that presented the lowest efficiency along with Hydropotassium.