Use of a water-retaining polymer in the cultivation substrate of palmito-juçara (Euterpe edulis Mart.)

Abstract

Over the years, the natural landscape of Atlantic forest has undergone significant changes. Inventories carried out by the Fundação SOS Mata Atlântica and by the National Institute for Space Research (SOS Mata Atlântica and INPE, 2017), showed that 83.7% of the São Paulo territory initially covered by this biome has already been transformed into pasture, monoculture and other uses. This intensive exploration resulted in extensive degraded areas, resulting from abandonment after the loss of the productive capacity of the soil. For the recovery of physical and chemical characteristics and the reduction of soil loss due to erosive processes, forest species are planted. During planting and in the first weeks of plant growth, the lack or excess of water can limit development. In this case, an alternative used is to add water-retaining polymers to the soil that have the ability to increase water retention. This study evaluated the effect on the growth of Palmito-Juçara (Euterpe edulis Mart) seedlings of different doses of water-retaining polymer incorporated into the growing substrate, with watering on five consecutive days and with alternating watering for a period of three months in a nursery. The experiment started when the seedlings presented 220 days after sowing. The juçara plants were grown in plastic bags filled with 850 g of substrate composed of a mixture of peat, carbonized rice husk, horse manure, chicken manure, tanned bovine manure, mineral fertilizer and dolomitic limestone. To study the effect of the hydro-retaining polymer, the following doses of a polyacrylic potassium copolymer were added to the dry substrate: D0 = without adding the polymer to the substrate (control); D2 = 2g of polymer; D3 = 3 g of polymer; D4 = 4 g of polymer; and, D5 = 5 g of polymer. Each dose was combined with two irrigation regimes, watering for five consecutive days or alternating, in a 5 x 2 factorial arrangement, with 15 repetitions, totaling 150 experimental plots in a randomized block design. The transplanting of the seedlings to the bags took place in April 2019 and every 30 consecutive days, five individuals were collected from each dose and each type of irrigation (50 experimental plots / collection), that is, 3 collections (250 days, 280 days and 310 days after sowing). In each collection, the length of the leaves and the root system, the diameter of the stem, the height of the plant, the dry mass of the aerial part, the dry mass of the root and the total dry mass were measured. After checking the normality of the data and the homoscedasticity of the variances, analyses of variances were performed (ANOVA, p <0.05) and the differences between the means were compared using the Tukey test (p <0.05). The analysis of the results showed significant differences between the irrigations, with greater growth for the variables of leaf length, stem diameter, plant height and dry mass of the aerial part in the initial period of development of juçara plants. In the condition of irrigation in five consecutive days, the highlight was for dose D3 and, in alternate watering, for dose D5.