Cenchrus purpureus, synonym Pennisetum purpureum, also known as Napier grass, elephant grass or Uganda grass, is a species of perennial tropical grass native to African grasslands. It has low water and nutrient requirements, and therefore can make use of otherwise uncultivated lands.

Historically, this wild species has been used primarily for grazing, and the grass can be harvested many times per year.

It can be propagated through seeds, however as seed production is inconsistent, collection is difficult.

Yield

Yield depends on management techniques (e.g. fertilizer), soil quality, rain, sunshine and temperature. Recognizing its potential as a bioenergy crop, some yield trials have been carried out around the world. In Malaysia, Halim et al. tested 9 different napier variants and found that regular napier grass yielded the most (65 dry tonnes per hectare per year), with the King Grass variant second (62 tonnes). In Colombia, Cardona et al. estimates a yield range of 40–60 dry tonnes for the napier variant King Grass, under optimal conditions. In drier areas however, yields decline; Gwayumba et al. estimate 15–40 dry tonnes as the general yield range for Kenya.

At the top end of the range, napier grasses have been shown to yield up to 80 dry tonnes per hectare per year, and commercial napier grass developers advertise yields of roughly 100 dry tonnes per hectare per year, provided there is an adequate amount of rain or irrigation available (100 mm per month). These yields are high compared to other types of energy crops. For large-scale plantations with pines, acacias, poplars and willows in temperate regions, Smil estimates yields of 5–15 dry tonnes per hectare per year, and for similarly large plantations, with eucalyptus, acacia, leucaena, pinus and dalbergia in tropical and subtropical regions, his estimate is 20–25 dry tonnes. In Brazil, the average yield for eucalyptus is 21 t/ha, but in Africa, India and Southeast Asia, typical eucalyptus yields are below 10 t/ha.

Push-pull pest management

The push-pull pest management technique involves the desired crop being planted alongside a 'push' plant, which repels pests, in combination with a 'pull' crop around the perimeter of the plot, which draw insects out of the plot. Napier grass has shown potential at attracting stemborer moths (a main cause of yield loss in Africa) away from maize In addition, chemicals are carried into final food products. Considering that striga, stemborers, and low soil fertility together cause yield losses of an estimated 7 billion US dollars or enough to feed 27 million people, Hairless varieties, such as Ugandan hairless, have much higher value as fodder.

A Dutch company has turned the grass into a plastic that can be used for packaging.

References

  • Missouri Botanical Garden horticultural treatment — Pennisetum purpureum
  • More information can be found at http://www.push-pull.net/