Castor bean husk (CBH) is a residue generated in large amounts in the castor bean processing. The aim of this study was to evaluate the chemical and physical characteristics of CBH and its effect used as substrate for plants. CBH characteristics were evaluated in a (2x3) factorial randomized block design, consisting of a combination of two husk types (CBH fresh and composted) and three grades (mesh 3 mm, 5 mm e 10 mm). Macro and micronutrient contents, pH, electrical conductivity, wet density, dry density, total porosity and air space were evaluated. The evaluation of CBH as substrate for plant growth was carried out using tomato (Lycopersicon esculentum Mill.) seedlings and golden dew drop (Duranta repens L.) cuttings as indicator species. Tomato seedlings were grown on CBH 3 mm grade, fresh or composted, mixed to Plantmax® in five ratios [0:100; 25:75; 50:50; 75:25; 100:0 (v/v)]. Rooting of golden dew drop cuttings was carried out on CBH, fresh or composted, using three grades (3, 5 and 10 mm). The composted 3 mm grade CFM showed the most suitable physical characteristics. The fresh CBH had negative effects both on seedling growth and rooting of cuttings, proving unsuitable as substrate. Composted CBH allowed for 100% of germination and normal tomato seedlings, as well as rooted golden dew drop cuttings, therefore it can be used as substrate, alone or in mixtures.
Castor bean; physical properties; residues
