| dc.description.abstract | A study was conducted to evaluate the dry matter yields and silage qualities of six sweetpotato varieties (Gweri, Naspot-I, Wagabolige, Musinyamu, 103001.152 and Kemb-23) at the Faculty of Agriculture field station, University of Nairobi. The experiment.was laid out
in a split plot randomized block design with the six varieties as the main plots and two
harvesting regimes (at 75 and 150 days) as the subplots. At the 75 day harvest, the vines were
weighed prior to chopping and wilting for silage making and determination of DM yield and
nutrient content. At 150 days, both subplots were harvested (vines and roots), fresh weight
taken, chopped and wilted prior to silage making and DM determination. Crude Protein (CP),
Neutral Detergent Fiber (NDF) , Acid Detergent Fiber (ADF) and Acid Detergent Lignin
(ADL) of fresh vines were determined.
The vines were ensiled alone, mixed with roots, with additives or no additives in silos
(polythene bags) and stored (or 90 days. Additives included salt, cassava meal, sun-dried
layer manure, molasses and maize meal. , compacted and packed into mini silos. At opening
the pH, ammonia nitrogen, DM, digestibility and CP content of the silage were determined.
Dry matter yields of vines harvested at 75d ranged from 1.13 (103001.152) to 2.07 (Kemb-
23) t/ha and were similar between varieties. The mean DM yield of un-ratooned crop at 150d
was 5.37 t/ha, higher than 4.07 t/ha for the ratooned crop with a significant difference
between varieties. In both harvesting regimes, 103001.152 had the lowest vine yields (2.03
and 1.74), Gweri the (5.20 and 7.18) for the ratooned and unratooned vines respectively.
The effect of variety on root dry matter yields was only significant among the unratooned
crop where Gweri had the lowest root yields (1.37) tons dry matter per hectare (tDMlha) than
both Kemb-23 (4.78) and Naspot-l (6.49).
Root to vine ratios for the ratooned crop ranged between 0.20 (Gweri) to 1.30 (103001.157) and 0.20 (Gweri) to 2.21 (103001.152) for the unratooned crop respectively. Naspot-I had highest CP content (17.97) while Wagabolige (15.61) and Gweri (15.08) had the lowest. CP content of vines harvested after rattooning was t not different among varieties. CP of vines harvested at 150 days continous growth were different among varieties Wagabolige had higher CP (12.50) and 103001.152 (7.18) lowest. 103001.152 and Gweri were significantly different from Wagabolige and Musinyamu.
The CP content decreased with age at harvest. The pH of silages of vines alone or mixture of vines and roots was influenced by both variety and treatment. Among varieties, the highest pH (5.6 and 5.2) were observed for Naspot-l, the lowest values (4.7 and 4.5) for Gweri. Ammonia nitrogen (NH3-N) content ranged between 2.2 to 2.7 % of total N in silages made from vines alone and 2.1 to 2.2 % in silages made from mixtures of vines and roots. Treatment and variety had no effects on ammonia nitrogen content. The CP content of silage was not affected by treatment for both types of silages, while the same was significantly affected by variety in silages made from vines alone, the CP content in 103001.152 (16.7%) was higher than that of Kemb-23 (13.5%).
Dry matter content of silages ranged from 24.3 to 38.2 % and was affected by both variety and treatments for both types of silages. Addition of cassava meal and maize meal resulted in silages with the lowest pH values (4.93 and 4.84) for silages made from vines, and 4.66 and 4.68 for
silages made from mixtures of vines and roots respectively. Silages treated with poultry
manure and salt had the highest pH values of 5.32 (poultry manure) and 5.20 (salt) for vine silages and 4.91 (poultry manure) and 4.88 (salt) for vine and root silages. Ammonia nitrogen
and crude protein content of the silages were not affected by treatments.
From this study, Gweri had the highest vine yields; Naspot-l the highest root yield. The
ratooned crop at 150d had lower vine and root yields than the unratooned crop, while vines
harvested at 75 days had higher CP content than those harvested at 150 days. The best quality
(low pH and low NH3-N) silage was obtained for treatments with cassava or maize meal as
additive for both silages made from vines alone or mixtures of vines and roots. | en_US |
