Uso de efluente de fossa como biofertilizante nitrogenado em mudas de açaí (Euterpe oleraceam Mart.) e pracaxi (Pentaclethra macroloba (Willd.) Kuntze) sob duas condições de luminosidade

Abstract

Açaí has become the main non-timber forest product in the Amazon, generating demand for seedlings for plantations and enrichment of managed areas. With the densification of the species, nitrogen deficiency (N) has been observed, generating demands for information about its nitrogen nutrition. This N can be supplied by biofertilizers, as an alternative to the use of mineral fertilizers. Thus, the development and nitrogen nutrition of açaí seedlings, isolated or in consortium with pracaxi, under different nitrogen sources and light conditions were evaluated. This study was conducted for 7 months in the Embrapa Amapá hatchery, in a complete factorial scheme (3 nitrogen sources x 3 species arrangements x 2 luminosity conditions). There were significant differences and interactions of the factors as a function of the time of cultivation. There was a general tendency of shaded saplings to present higher height, but after 120 days, those consorted and receiving effluent grew more in full sun. For the diameter, those that received domestic effluent presented an average of 15 mm at 7 months, superior to those that received mineral fertilization, with greater differences in the last measurements. This shows that the biofertilizer has greater long-term effect. The shoot and root biomass were related, both being statistically lower in mineral fertilization and higher in the consortium açaí, under full sun. The average N content in leaves was higher in shaded plants (16.3 g kg -1) than in full sun (12.6 g kg -1). The residual soil content was lower in shaded vessels (1.6 g kg -1) than at full sun (1.9 g kg -1), evidencing the negative relation between absorbed N and its residual availability in the soil. For the pracaxi, combination of the factors of full sun and domestic effluent as a source of nitrogen was the one that presented the highest absolute values for height, reaching the maximum value at 210 days of experiment of 632mm. The consortium with açaí seedlings did not alter growth parameters and DAS did not obtain significant results for the factors. No root nodules were found in the pracaxi seedlings. The highest absolute value of nitrogen in the pracaxi foliar tissue was found in the treatment with fossa effluent as a biofertilizer consortium with açaí. The pit effluent can be used as a biofertilizer to meet the nutritional needs of açaí and pracaxi seedlings. In the beginning, açaí seedlings grow best in a shaded environment, but later development is greater under direct solar radiation and when in consortium with pracaxi seedlings, and the pracaxi seedlings grow best in full sun