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Title: KENAF DRY MATTER PRODUCTION, CHEMICAL COMPOSITION AND IN SITU DISAPPERANCE WHEN HARVESTED AT DIFFERENT INTERVALS

Author
item PHILLIPS, WILLIAM
item MCCOLLUM, F. - OKLAHOMA STATE UNIVERISTY
item FITCH, G. - OKLAHOMA STATE UNIVERSITY

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: In an integrated Southern Great Plains winter wheat-livestock production system, the wheat fields are fallow during the summer when the livestock component needs high quality forage to maintain production. A series of experiments were conducted to determine the DM yield and feeding value of kenaf, a tropical annual, planted in wheat fields during the summer fallow period. Kenaf leaves were higher in protein and more digestible than the stalks. Early in the growing season, leaves made up a larger proportion of the whole plant than stalks, but whole plant yield was greater if harvesting was delayed until later in the season. Harvest date can be manipulated to maximize yield and control nutrient density. Kenaf can be grown in fallow wheat fields and harvested as a high quality feed for ruminants.

Technical Abstract: Kenaf (Hibiscus cannabinus L.) is a tropical plant that has potential as a forage crop to augment livestock production in the Southern Great Plains. However, data on the amount and quality of forage produced by kenaf is unavailable. The objectives were to determine 1) the dry matter (DM) yield, proportions of leaf and stalk, and chemical composition of kenaf harvested through the growing season and 2) the in situ organic matter (OM and N disappearance of the leaves and stalks. Kenaf ('Everglades 41') was planted in June of 1990, 1991 and 1993. The seeding rate was 5.6 kg/ha and 100 kg of N /ha was applied shortly before or after planting. Harvesting began 40 days after planting (DAP) with additional harvests at 10-d (1991 and 1993) or 20-d (1990) intervals. Daily whole plant DM accumulation ranged from 12.6 to 17.2 g/m2. At 101 DAP 726 to 974 g/m2 DM was harvested. As kenaf matured the proportion of the total plant DM represented in leaves decreased ( p < 0.01 ). Leaf DM contained more ( P 0.01 ) than twice the crude protein (CP)as stalk DM at all harvests. Delaying harvest decreased (P < 0.01) whole plant CP concentration, because the stalks made up a larger proportion of the total dry biomass. The OM and N concentrations in the leaves were more (P < 0.01) digestible than in the stalks. Kenaf can be grown during the summer season and harvested as high quality forage as early as 40 DAP. Whole plants harvested at 80 DAP produced from 426 to 729 g/m2 of DM and had a CP content of 14 to 19%. Harvesting later after 80 DAP will increase DM yield, but the stalks will make up a larger percentage of the total DM. As a result, the CP content and in situ OM and N disappearance will be lower than if the kenaf was harvested prior to 80 DAP.