SUBSTRATOS À BASE DE IODO SUÍNO E ADUBAÇÃO FOSFATADA NA PRODUÇÃO DE MUDAS DE Guazuma ulmifolia Lam. (Malvaceae)

Abstract

Guazuma ulmifolia Lam. (Malvaceae) has a high potential to be explored by the pharmaceutical and food sectors, however, little is known about the nutritional issues in the seedling phase. Thus, this study aimed to assess whether substrates based on swine wastewater (sw) and doses of phosphorus (P) influence the morphological and physiological characteristics of G. ulmifolia seedlings. For this, two experiments were carried out. In experiment 1, the seedlings were grown in 50 cm³ tubes, under a randomized block design, on seven substrates (T1-50% carbonized rice husk (crh) + 50% vermiculite (ve); T2 - 20% sw + 40% crh and 40% ve; T3 - 40% sw and 30% crh + 30% ve; T4 - 60% sw + 20% crh + 20% ve; T5 - 80 % sw + 10% crh + 10% ve; T6 - 100% sw and T7 - 100% Bioplant®). At 200 days after sowing, the Falker® indexes of chlorophylls and gas exchanges were evaluated, whereas height (H), diameter (D), number of leaves (NL), ratio between H and D, biomass, allometric ratios, Dickson's quality index (DQI) and mortality rate were taken 210 days after sowing. The results of this experiment show that for H, NL, gas exchange and shoot biomass, T4 and T5 promoted the best results. The largest diameters were provided by T3, T4 and T5, while the highest levels of chlorophyll and DQI by T4, T5 and T6. The highest mortality rate was obtained at T7 (85%) followed by T1 (37.5%). In experiment 2, the seedlings were grown in 4 liter pots containing Dystrophyc RED LATOSOL and subjected to five doses of P (0, 100, 200, 300 and 400 mg dm-³), under a completely randomized design. After 115 days of sowing, gas exchange and Falker® index of chlorophylls were evaluated, whereas H, D, NL, biomass, allometric ratios, DQI, P content in the aerial part of the seedlings were evaluated at 120 days after sowing. All studied variables were positively influenced by P doses, except for the specific leaf area and allometric ratios. For all variables, the dose that promoted the highest values was the highest dose studied (400 mg dm-³), indicating that G. ulmifolia seedlings require high P levels to have their physiological and morphological behavior enhanced. The P content was strongly and positively correlated with all tested variables. The gas exchange variables correlated with growth, biomass and DQI variables. In view of the results found for both experiments, it is possible to state that both substrates with swine sludge and phosphate doses are potentiators for growth and initial development of G. ulmifolia.