Biocarvão e efeito residual de adubação fosfatada em mudas de Castanheira-do-Brasil (Bertholletia excelsa Bonpl.) em latosolo da Amazônia

Abstract

The availability of phosphorus in Amazonian soils limits agricultural activity due to the high affinity of this nutrient with the soil, culminating in the low efficiency of the fertilizers. One of the techniques recently studied to reverse this scenario is the bio-coal, which is attributed to the ability to reduce processes that make phosphorus unavailable and increase its residual effect on the soil. Considering the above, the objective of this work was to verify the influence of doses of bio-carbon on the residual effect of phosphate fertilizer on soil and nutrition and development of Castanheira-do-Brasil seedlings. Considering the above, the objective of this work was to verify the influence of doses of bio-carbon on the residual effect of phosphate fertilizer on soil and nutrition and development of Brazil Nuts seedlings. The experiment was conducted in a greenhouse using a typical Yellow Latosol, in sequence to an experiment, verifying the immediate effect of the biochar and the phosphorus. A completely randomized design was used in a 5 x 2 factorial arrangement, with five doses of bio-carbon (0, 20, 40, 60 and 80 t ha -1 ) and two previously applied phosphorus (0 and 100 mg dm -3 P 2 O 5 ). The seedlings used in the experiment were assigned by Aruanã S.A company at 7 months of age, being standardized by uniformity and vigor. During the experiment, the height of the seedlings, the collection diameter and the number of leaves were evaluated monthly, and the dry matter production of shoots and roots, main root length and total volume of roots. From these data the rate and absolute growth in height and diameter, shoot / root ratio, leaf gain, number of final leaves and the Dickson quality index were calculated. In addition, the levels of macro and micronutrients foliars and soil attributes were evaluated: hydrogen ionic potential, potential acidity, exchangeable aluminum, macro and micronutrient contents and remaining phosphorus. From these, the saturation and sum of bases, saturation by aluminum, the effective and potential CTC were calculated. Regardless of the residual phosphorus, the biochar increased proportionally to the soil bases (K, Ca, Mg) and consequently the sum and base saturation. The biocarbon present in the substrate continued to positively influence the soil attributes after a year and a half of its application. The application of 20 and 40 t ha -1 of biochar in the substrate promoted the best residual effect of the phosphate fertilizer. Residual phosphorus did not influence in a clear way the foliate absorption of K, Ca and Mg. The increase of the biocharous doses in the substrate promoted decreases in the foliar absorption of phosphorus and favored the absorption of micronutrients. Except for the contents of N and Mn, the contents of the other elements are similar to those found in similar works. The presence of residual phosphorus in lower doses of biochar (<40 t ha -1 ) promoted a better monthly development in height of the seedlings and diameter of the collection. The presence of residual phosphorus promoted increases in the height of the Castanhaeira seedlings, however, it did not significantly influence the collection diameter. The doses above 40 t ha -1 of bio-carbon promoted lower leaf gain, higher height-to-diameter ratio, and lower gains of dry biomass of root and shoot. The presence of residual phosphorus did not positively influence these variables. Lower dry matter ratio of aerial part / roots were obtained at doses above 40 t ha -1 of bio-coal. Greater root length was obtained at biocharging doses above 40 t ha -1 , while lower root volume observed at doses below 40 t ha -1 . The highest quality index of dickson seedlings was obtained at doses below 40 t ha -1 of bio-carbon without the presence of residual phosphorus.