Boro em materiais de três solos do município de Lavras, Estado de Minas Gerais

Abstract

Materials of LV, LR, PV, located in the Municipal of Lavras, State of Minas Gerais, and representative of the area of agricultural importance in the region, were studied with the objective of determining the levels of total and available B by the biological method of the sunflower (Helianthus annus L.), hot water and chemical extractants, as well as correlating the available B by the extractants with the parameters of production like the properties and/or characteristics that affect the availability of B and between thenselves. The experiment was conducted in a glasshouse in the Department of Soil Science of the Escola (ESAL). A competely randomised experimental design was used with a 3 x 6 factorial scheme, that is there soils and six doses of B (0,0; 0,1; 0,2; 0,4; 0,8.e 1,6 ppm) and with for replicates. Tins of lubricating oil were used as pots. The this had a capacity of 1,000 ml and were cut in height to give a capacity of 600 ml. The containers were coated on the inside with "undersill" and each one received 0,5 kg of soil material in which five plants of sunflower were grown for 45 days. The plants were harvested, aeral parts and roots separately and were analysed for B and Ca the soil materials, after cultivation, were analyzed using thre extractant (hot water, HCl 0,0 5 N and CH COOH 0,05 N). Available B was considered as the sun of the extracted quantities in each extractant and those extracted by the whole plant. The available B in the original soil materials was determined only by the method of hot water. Among the soil materials studied, LV was shown to be most efficient in supplying B for the plants, providing greatest total production of dry matter, greatest plant height, largest quantity of absorbed B and largest quantity of available B by all of the extractions used, followed by LR and PV. This soil material (LV ) originally showed the highest level of total and available B (hot water) as well as the lowest total B:available B ratio. The level of total B appeas to be a good index .of its availability, at least in the case of the soil materials studed. The extractant that showed greater correlation with the production of dry matter, height and accumulated B by sunflower was hot water, followed by HCl. Also better correlation was obtained between these extractants than between these and CH COOH. The assessment of the availabilitv of B by the biological method of the sunflower was reflected well by the levels of B originally extracted with hot water. High Ca:B ratios in the tissues of sunflower were associated with problems of deficiency of B for this crop.