An experiment was carried out in EMEPA, João Pessoa, Brazil between September 98 and June 99 to quantify the dry matter, starch and ash content of yam rhizomes, cv. Da Costa, in relation to harvest time and organic fertilization. The area consisted of a red-yellow podzolic sandy soil. Four levels of cattle manure (5; 10; 15 and 20 t/ha), four levels of chicken manure (2.8; 5.6; 8.4 and 11.2 t/ha), and two harvest times [seven and nine months after planting date (APD))] plus a treatment without organic residue, were studied, arranged in a factorial cheme 2x4x2+1 in randomized blocks, with four replications. Dry matter was of 33% and 36% in rhizomes harvested seven and nine months APD, respectively. At seven months APD, dry matter decreased from 35.80% and 34.71%, without cattle or chicken manure, respectively, to 30.03% and 29.25%, for highest levels of cattle manure (20 t/ha) and chicken manure (11.2 t/ha). Starch content increased from 26% at seven months APD to 29% at nine months APD. Nine months APD, starch content in rhizomes increased (31.6%) with increasing levels of chicken manure (4.8 t/ha). Ash content was not affected by harvest dates. However, applying 12.8 t/ha of cattle manure and 6.7 t/ha of chicken manure, rhizomes presented increase in ash content of 0.78% and 0.67% respectively, when harvested nine months APD.
Dioscorea cayennensis Lam.; harvest time; cattle manure; chicken manure; chemical composition
