Floss silk tree sapling production in substrates with kaolin industry rejects

Abstract

The use of kaolin rejects in substrates for sapling production may constitute a viable alternative for the use of this material. This study was carried out to evaluate the production of floss silk tree (Ceiba speciosa (A. St.-Hil.) Ravenna) saplings in substrates with different proportions of kaolin rejects. The following substrates were evaluated: S₁: 40% vegetal soil (VS) + 30% cattle manure (CM) + 30% washed sand (WS) + 0% kaolin rejects (KR); S₂: 40%VS+30%CM+0%WS+30%KR; S₃: 40%VS+20%CM+0%WS+40%KR; S₄: 40%VS+10%CM+0%WS+50%KR; S₅: 30%VS+10%CM+0%WS+60%KR; S₆: 20%VS+10%CM+0%WS+70%KR; and S₇: 10%VS+10%CM+0%WS+80%KR. Seventy-five days after planting, the lap diameter, height, leaves number, dry mass production (root, aerial part and total), height/lap diameter ratio, dry mass of aerial part/dry mass of root ratio and Dickson Quality Index were statistically evaluated. The substrates S₁ and S₂ were responsible for statistically superior results for all evaluated characteristics of floss silk tree saplings. The other substrates resulted in statistically significant reductions on seedlings characteristics, especially the substrates S₆ and S₇. For the production of floss silk tree seedlings, a proportion of up to 30% of kaolin rejects can be used in the substrate without negative effects on the saplings’ growth and quality.