Oil yield and quality variation between sexes in Osyris lanceolata (African sandalwood) and its value as a fodder plant in Tanzania

African sandalwood (Osyris lanceolata) is widely harvested in East Africa for extraction of oil, which is used in the fragrance and perfumery industry. Over the years, harvesting of the species has been concentrated to female plants because it is claimed that they yield more and better quality oil compared to males. However, data to support these claims is lacking. Osyris lanceolata is also used extensively by pastoralists as feed supplement during the dry season, yet little information on the species’ nutritive value exists. Oil yield and quality variations between male and female O. lanceolata and its nutritive values were evaluated to ascertain the purported reasons for sex selectivity in harvesting, and to determine the potential value of the species as a fodder plant. Oil yield was determined by extracting oil from a known amount of wood, while quality assessment was done by determining the amount of santalol, a prime determinant of sandalwood oil quality. The species’ potential as a fodder plant was determined by analyzing the nutritive value and digestibility of leaves and fruits. There was no significant variation (p = 0.856) in oil yield between sexes, though populations differed significantly (P < 0.001). The highest oil yield was 9.32 ± 0.611%. Likewise, sexes did not differ significantly (P = 0.655) in oil quality, though populations differed significantly (P < 0.001). The highest santalol content was 11.1%. It is concluded that sex selectivity during harvesting has no relation to oil yield and quality. However, population selectivity is strongly justified due to the huge variation in oil yield and quality, and is likely to be the major reason for over-exploiting some populations. It is recommended that there is a need to refrain from overharvesting of females within populations, since the practice is likely to erode the genetic vigour of the species and affect its sustainability. Nutritive studies revealed the species to have 15.9–19.7% crude protein, 15.9–24.0% crude fibre, 0.77–0.81% fat/oil, 97.5–97.8% dry matter, 8.5–10.3% ash content, 72.2–72.4% digestibility. These figures are within the acceptable range, suggesting that both leaves and fruits of the species are a potential alternative source of animal protein where protein supplements are not available or expensive.     

A note on the chemical composition, intake and digestion of Striga hermonthica herbage by sheep

Striga hermonthica causes serious crop yield losses in West Africa. Hand pulling, an effective method for the reduction of light infestations, might be encouraged if farmers could use this weed as livestock feed. This study evaluated the chemical composition and the voluntary intake and digestion of S. hermonthica herbage by sheep. Crude protein (g kg⁻¹ dry matter (d.m.)) was 184 in the whole plant, 230 in the leaf and 87 in the stem. Ash content varied from 183 to 253 g kg d.m.⁻¹. The concentration of neutral and acid detergent fibre and lignin in whole pot-grown plants was 364, 278 and 127 g kg d.m.⁻¹ respectively. The digestibility of dry and organic (o.m.) matter was 493 and 657 g kg⁻¹, respectively, and intake of digestible o.m. was 27.1 g kg W^−0.75. The relatively high N and P levels in S. hermonthica warrant further evaluation in terms of its potential use as a source of protein or for compost. Its use as a feed appears to be limited by the high ash content and possibly by anti-nutritional effects on animals. These effects should be further investigated before recommending its use for this purpose.     

Variation of Parthenium hysterophorus in response to soil quality: implications for invasiveness

Summary The performance of Parthenium hysterophorus , native to the tropical Americas and invasive to several countries, was evaluated for response to soil quality. Phenological (six stages) and quantitative growth variables [relative growth rates in height (R_h) and diameter (R_d)] were measured every fortnight. Based on harvest data, the variables, root:shoot (R:S) ratio, specific leaf area (SLA), relative growth rate in biomass (R_w), net assimilation rate (NAR) and dry matter allocation to plant components, were determined. High clay content in soils prolonged the rosette stage, enhanced R_h and R_d and hampered root growth, but promoted biomass allocation to shoots. The extreme degree of plant mortality was observed, with only 33.3% individuals surviving to reproduce in the soils with highest clay contents. This appears to be one of the most important findings that certainly has a major bearing on the range of adaptation of the weed. Seed mass declined whereas seed production increased in relatively coarser soils with the exception of nearly pure sand. In soils rich in clay, plants produced a smaller number of larger seeds. These data suggest that variation in fundamental functional traits would enable P. hysterophorus to adjust to a variety of habitat conditions.