PRODUCTION OF Prosopis laevigata (Humb. et Bonpl. ex Willd.) M.C. Johnst. WITH DIFFERENT SUBSTRATE MIXTURES

Abstract

Five substrate mixtures were evaluated with the purpose of determining their effect on the quality of Prosopis laevigata seedlings growing in a nursery; substrates were composed by base mix (50 % peat moss + 24 % agrolite + 21 % vermiculite) and composted pine bark. The mixtures were: 1) 50 % composted pine bark + 50 % base mix, 2) 60 % composted pine bark + 40 % base mix, 3) 70 % composted pine bark + 30 % base mix, 4) 80 % composted pine bark + 20 % base mix, and 5) 100 % base mix. During substrate preparation 7 kg m-3 of Multicote® granular fertilizer were added. Polystyrene trays of 77 cavities with 170 mL per cavity were used. Experimental design was completely randomized and each treatment was constituted by four replicates. Response variables were: height, root collar diameter, dry total biomass and Dickson quality index. When the seedlings attained the age of five months, significant statistical differences were found due to substrate mixtures, with the mix composed by 50 % composted pine bark + 50 % base mix showing superiority in most of variables. After this, the other mixtures showed similar results, except for the substrate composed by 80 % composted pine bark + 20 % base mix, which had the lowest values for all the variables. The results indicate that composted pine bark is a possible alternative substrate that may contribute to reduce production costs compared to the base mix, which has a high cost.