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	[[Category:Cenchrus\|purpureus]]		[[Category:Cenchrus\|purpureus]]
	[[Category:Bunchgrasses of Africa]]		[[Category:Bunchgrasses of Africa]]
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{{short description|Species of grass}}
{{Speciesbox
|image= Starr 061211-2254 Pennisetum purpureum.jpg
|genus = Cenchrus
|species = purpureus
|authority = (Schumach.) Morrone
|synonyms=
|synonyms_ref =
}}

'''''Cenchrus purpureus''''', [[Synonym (taxonomy)|synonym]] '''''Pennisetum purpureum''''',<ref>{{Cite journal|last1=Paudel|first1=Dev|last2=Kannan|first2=Baskaran|last3=Yang|first3=Xiping|last4=Harris-Shultz|first4=Karen|last5=Thudi|first5=Mahendar|last6=Varshney|first6=Rajeev K.|last7=Altpeter|first7=Fredy|last8=Wang|first8=Jianping|date=2018-09-26|title=Surveying the genome and constructing a high-density genetic map of napiergrass ( Cenchrus purpureus Schumach)|journal=Scientific Reports|language=en|volume=8|issue=1|pages=14419|doi=10.1038/s41598-018-32674-x|issn=2045-2322|pmc=6158254|pmid=30258215|bibcode=2018NatSR...814419P}}</ref> also known as '''Napier grass''', '''elephant grass''' or '''Uganda grass''', is a species of perennial tropical grass native to the African grasslands.<ref name="Farrell">[Farrell, G., Simons, S. A., & Hillocks, R. J. (2002). Pests, diseases, and weeds of Napier grass, ''Pennisetum purpureum'': a review. International Journal of Pest Management, 48(1), 39-48.]</ref> It has low water and nutrient requirements, and therefore can make use of otherwise uncultivated lands.<ref name="Strezov">[Strezov, V., Evans, T. J., & Hayman, C. (2008). Thermal conversion of elephant grass ''Pennisetum purpureum'' Schum) to [[biogas]], bio-oil and charcoal. Bioresources Technology, 99, 8394-8399.]</ref>

Historically, this wild species has been used primarily for grazing,<ref name="Khan" /> recently, however, it has been used as part of a [[push–pull agricultural pest management]] strategy. Napier grasses improve [[soil fertility]], and protect arid land from [[soil erosion]]. It is also utilized for firebreaks, windbreaks, in paper pulp production and most recently to produce bio-oil, biogas and charcoal.<ref name="Strezov" />

==Description==
''Cenchrus purpureus'' (or napier grass) is a monocot C4 perennial grass in the family [[Poaceae]].<ref name="Khan" /> It is tall and forms in robust bamboo-like clumps.<ref name="Farrell" /> It is a heterozygous plant, but seeds rarely fully form; more often it reproduces vegetatively through stolons which are horizontal shoots above the soil that extend from the parent plant to offspring.<ref name="Farrell" /> It requires low water and nutrient inputs.<ref name="Strezov" /> Napier grass plantations produce about 40 tonnes of dry biomass per hectare per year<ref name="Strezov" /> with an average energy content 18 GJ per tonne,<ref>See page 831: {{cite journal | last1=Flores | first1=Rilner A. | last2=Urquiaga | first2=Segundo | last3=Alves | first3=Bruno J. R. | last4=Collier | first4=Leonardo S. | last5=Boddey | first5=Robert M. | title=Yield and quality of elephant grass biomass produced in the cerrados region for bioenergy | journal=Engenharia Agrícola | volume=32 | issue=5 | date=1990-01-06 | issn=0100-6916 | doi=10.1590/S0100-69162012000500003 | pages=831–839 | url=https://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162012000500003 | access-date=2020-09-15| doi-access=free }}</ref> and the grass can be harvested many times per year.<ref name="Farrell" />

Generally, the grass is harvested in relatively short intervals (every 1 to 3 months) when it is to be used as fodder for animals (its main use), and relatively long intervals (4–12 months) when used for bioenergy. Longer intervals increases the stem/leaf ratio, making the forage harder to chew and digest, but in many cases the annual dry yield increases. The grass can reach a height of 7-8 meters after 4 months of growth.<ref name="Ansah Osafo Hansen 2010 pp. 923–929">{{cite journal | last1=Ansah | first1=T. | last2=Osafo | first2=E. | last3=Hansen | first3=Hanne | title=Herbage yield and chemical composition of four varieties of Napier (''Pennisetum purpureum'') grass harvested at three different days after planting | journal=Agriculture and Biology Journal of North America | publisher=Science Hub | volume=1 | issue=5 | year=2010 | issn=2151-7525 | doi=10.5251/abjna.2010.1.5.923.929 | page=928, table 4| doi-access=free }}</ref> It produces best growth between 25 and 40 °C, and little growth below about 15 °C, with growth ceasing at 10 °C. Tops are killed by frost, but plants re-grow with the onset of warm, moist conditions. Grows from sea level to over 2,000 m elevation.<ref name="Tropical Forages">{{cite web | title=Cenchrus purpureus & hybrids | website=Tropical Forages | url=https://www.tropicalforages.info/text/entities/cenchrus_purpureus__hybrids.htm?zoom_highlight=napier | access-date=2020-10-04}}</ref>

It can be propagated through seeds, however as seed production is inconsistent, collection is difficult.<ref name="Farrell" /> Alternatively, it can be planted through stem cuttings of the stolons. The cuttings can be planted by inserting them along furrows 75 cm apart, both along and between rows.<ref name="Aminah">[Aminah, A. Wong, C. C. & Eng P. K. (1997). Techniques for rapid vegetative multiplication for pasture species and commercial production. Regional Forage Development, FAO, Rome, pp167-178.]</ref>

==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).<ref>The soil was fertilised, rainfall was 2700 mm. For yield results, see table 2, page 40: {{cite journal | title=Yield and nutritive quality of nine Napier grass varieties in Malaysia | website=Semantic Scholar | s2cid=59143548 | url= https://pdfs.semanticscholar.org/3931/7fee98db55b8d07806b4bb4d23ec26e5cf0f.pdf?_ga=2.187851307.2005664686.1567405962-2026873589.1567251126 |format=PDF | access-date=2020-08-29}}</ref> In Colombia, Cardona et al. estimates a yield range of 40–60 dry tonnes for the napier variant King Grass, under optimal conditions.<ref>See page 206: {{cite journal | last1=Cardona | first1=Eliana | last2=Rios | first2=Jorge | last3=Peña | first3=Juan | last4=Peñuela | first4=Mariana | last5=Rios | first5=Luis | title=King Grass: A very promising material for the production of second generation ethanol in tropical countries | journal=Biomass and Bioenergy | publisher=Elsevier BV | volume=95 | year=2016 | issn=0961-9534 | doi=10.1016/j.biombioe.2016.10.008 | pages=206–213}}</ref> In drier areas however, yields decline; Gwayumba et al. estimate 15–40 dry tonnes as the general yield range for Kenya.<ref>See page 516: {{cite journal | last1=Gwayumba | first1=W. | last2=Christensen | first2=D. A. | last3=McKinnon | first3=J. J. | last4=Yu | first4=P. | title=Dry Matter Intake, Digestibility and Milk Yield by Friesian Cows Fed Two Napier Grass Varieties | journal=Asian-Australasian Journal of Animal Sciences | publisher=Asian Australasian Association of Animal Production Societies | volume=15 | issue=4 | date=2002-04-01 | issn=1011-2367 | doi=10.5713/ajas.2002.516 | pages=516–521|url=https://www.ajas.info/upload/pdf/15-79.pdf}}</ref>

At the top end of the range, napier grasses have been shown to yield up to 80 dry tonnes per hectare per year,<ref>Zhang et al. measured a bana grass yield of 74 dry tonnes per hectare per year with light fertilisation and 1000 mm rainfall. See pages 96, 98: {{cite journal | last1= Zhang | first1= Xia | last2= Gu | first2=Hongru | last3=Ding | first3=Chenglong | last4=Zhong | first4=Jianli | last5=Xu | first5=Nengxiang | title=Path coefficient and cluster analyses of yield and morphological traits in ''Pennisetum purpureum'' | journal=Tropical Grasslands | publisher=Institute of Animal Science, Jiangsu Academy of Agricultural Sciences, Nanjing, China | volume=44 | date=2010 | pages=95–102 | s2cid= 55554503 | url=https://www.tropicalgrasslands.info/public/journals/4/Historic/Tropical%20Grasslands%20Journal%20archive/PDFs/Vol_44%20(1_2_3_4)/Vol%2044%20(2)%20Zhang%20et%20al%2095.pdf }}</ref><ref>Hoshino et al. measured a yield of 75.6 dry tonnes per hectare per year the second year of growth under heavy fertilisation and with rainfall level 1000 mm annually. See pages 310, 311, 315: {{cite journal | last1= Hoshino | first1= Masao | last2= Ono | first2=Shigeru | last3=Sirikiratayanond | first3=Nittaya | title=Dry Matter Production of Tropical Grasses and Legumes and its Seasonal Change in Thailand | journal=Japanese Journal of Grassland Science | volume=24 | date=1979 | pages=310–317 |url=https://www.jstage.jst.go.jp/article/grass/24/4/24_KJ00004773224/_pdf/-char/en |format=PDF |doi=10.14941/grass.24.310 }}</ref><ref>Vicente-Chandler et al. found that heavily fertilized napiergrass produced 75,661 pounds of dry matter per acre per year when cut at 90-day intervals, equivalent to 84.8 tonnes per hectare per year. See page 202: {{cite journal | last1=Vicente-Chandler | first1=Jose | last2=Silva | first2=Servando | last3=Figarella | first3=Jacinto | title=The Effect of Nitrogen Fertilization and Frequency of Cutting on the Yield and Composition of Three Tropical Grasses | journal=Agronomy Journal | publisher=Wiley | volume=51 | issue=4 | date=1959 | issn=0002-1962 | doi=10.2134/agronj1959.00021962005100040006x | pages=202–206 }}</ref> 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).<ref>"The total water requirements are approximately 100 mm (4 inches) per month rainfall equivalent. [...] The yield of Giant King Grass depends on the time between harvests. For example, a six-month harvest of tall Giant King Grass, one can expect to obtain 80 or more US tons per acre (180 metric tons per hectare) of fresh grass at approximately 70-75% moisture. For two harvests per year, double these figures." {{cite web |title=Giant King® Grass: Grow and Harvest |author=Viaspace|date= 2020| access-date=11 July 2020 | url=http://www.viaspace.com/giant_king_grass_info.php }}</ref><ref>Mackay quotes yields of 360 wet tonnes per hectare per year, but does not quantify moisture content. {{cite web |title=Mackay Bana Grass |author=Mackay|date= 2020| access-date=11 July 2020 | url=https://mackaygreenenergyinc.com/mackay-bana-grass/ }}</ref> 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.<ref> See pages 85-86: {{cite book | last=Smil | first=Vaclav | title=Power density: a key to understanding energy sources and uses | publisher=The MIT Press | location=Cambridge, Massachusetts | year=2015 | isbn=978-0-262-02914-8 | oclc=897401827 | url=https://books.google.com/books?id=Mj87CQAAQBAJ&pg=PR5 |url-access=limited }}</ref>

==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.<ref name="Khan">[Khan, Z. R., Midega, C. A. O., Wadhams, L. J., Pickett, J. A., & Mumuni, A. (2007). Evaluation of Napier grass (Pennisetum purpureun) varieties for use as trap plants for the management of African stemborer (Busseola fusca) in a push-pull strategy Entomologia Experimentalis et Applicata, 124, 201-211.]</ref> Napier grass has shown potential at attracting stemborer moths (a main cause of yield loss in Africa) away from maize<ref name="Khan" /> and hence is the "pull" crop. This strategy is much more sustainable, serves more purposes and is more affordable for farmers than [[insecticide]] use. Stemborers (''[[Busseola fusca]]'' and ''[[Chilo partellus]]'') are the cause of 10% of total yield loss in Southern and Eastern Africa and on average 14-15% in sub-Saharan Africa.<ref name="Farrell" /> The larvae cause immense damage to maize and sorghum by burrowing into their stems and eating from within. This not only makes them difficult to detect and remove but also damages the vascular tissue necessary for plant growth.<ref name="Khan" />

Insecticide effectiveness is low against stemborers, as larvae are protected by protective cell wall layers around the stem.<ref name="Aminah" /> Insecticides are also expensive for poor farmers and can build chemical resistance by the pests.<ref name="Miller">[Miller, J. R., & Cowles, R. S. (1990). Stimulo-deterrent diversion: A concept and its possible application to onion maggot control. Journal of Chemical Ecology, 16(11), 3197-3212.]</ref> In addition, chemicals are carried into final food products.<ref name="Miller" /> Instead of trying to prevent the occurrence of pests, the push-pull strategy (also known as stimuli-deterrent) aims to guide their inevitable biological evolution to prevent damage to valued crops.<ref name="Miller" /> The method proposes that sorghum or corn be intercropped with [[Desmodium]] (the "push" plant), which repels the moths as they look to lay their eggs. Desmodium also provides a ground cover and is nitrogen fixing, which improves soil fertility while decreasing labour involved with weeding.<ref name="Khan" /> This deterrent is used in combination with Napier grass planted around the perimeter of the plot.<ref name="Khan" /> A study of Kenyan farmers using the push-pull strategy reported an 89% reduction in [[Striga]] (a parasitic weed), an 83% increase in soil fertility, and 52% effectiveness in stemborer control.<ref name="Khan_a">[Khan, Z. R., Amudavi, D. M., Midega, C. A. O., Wanyama, J. M., & Pickett, J. A.(2008). Farmers' perceptions of a 'push-pull' technology for control of cereal stemborers and striga weed in western Kenya. Crop Protection, 27, 976-987.]</ref> 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,<ref name="Khan_a" /> the implementation of this technique could significantly reduce food insecurity.

Although promising as a sustainable and affordable option, the success of [[Push–pull agricultural pest management|push-pull]] pest management highly depends on proper implementation in combination with other good ecological practices. Firstly, not all varieties of Napier grass function as a trap. In a study of eight varieties, only two bana and Ugandan hairless Napier varieties significantly attracted female moths for egg placement over maize.<ref name="Khan" /> Of these two, only bana significantly decreased survival rates.<ref name="Khan" /> In a farmer's field, it is recommended that three rows of bana Napier grass be planted as a border crop around the entire field.<ref name="Aminah" /> Potential exists to improve the push-pull strategy through further trials with different intercrops, by manipulating allelochemicals in each intercrop, as well as by investigating insect sensitivity to natural chemicals.<ref name="Miller" /> Once prominent in a field, it is difficult to rid the area of the stemborer pests as larvae can remain dormant, and therefore push-pull management will not have the intended effect.<ref name="Khan" /> It is recommended that if an infestation is particularly severe, neither corn, nor sorghum should be planted in the same field the following year but instead rotated with other crops.<ref name="Khan" /> It is also important to burn infested stalks or, if they have an intended use, to leave them out in the sun for three days.<ref name="Khan" /> The use of push-pull pest management must be used in combination with good ecological practices to yield the desired results.

Finally, the establishment of a push-pull system requires increased labour in the primary stages and a large enough land plot to allow space for a non-food crop to be planted; these factors often deter its adoption.<ref name="Khan_a" /> A program could increase adoption rates through promoting its use in combination with livestock, giving economic value to the planting of Napier.

==Other uses==
[[Image:Harvesting Napier.jpg|thumb|Use as fodder crop in Kenya]]
Napier grass is the most important [[fodder crop]] for the [[dairy farmer]]s in [[East Africa]].<ref name="Farrell" /> Its high productivity makes it particularly suited to feed cattle and buffaloes.<ref>{{Cite web|url=https://www.africanews.com/2020/01/31/scientists-back-use-of-napier-grass-as-sustainable-way-to-feed-herds/|title=Scientists back use of Napier grass as sustainable way to feed herds|date=2020-01-31|website=Africanews|language=en|access-date=2020-02-07}}</ref> Hairless varieties, such as Ugandan hairless, have much higher value as fodder.<ref name="Farrell" /> As it is able to grow with little water and nutrients, grazing has made productive use of arid lands for food production. Furthermore, livestock can be incorporated into the pull-push management system providing another economically viable purpose for the ‘trap’ plant. Napier grass is valuable to African landscapes as it prevents [[soil erosion]]. It can also serve as a fire break, a wind break, and to improve soil fertility.<ref name="Farrell" />

More recently, Napier has been used to alleviate pressure on food production as there is 2Gha of non-arable land suitable for [[energy crop]] production.<ref name="Strezov" /> Thermal pyrolytic conversion is used to produce charcoal, biogas and bio-oil.<ref name="Strezov" /> Although this technology is not currently in use, it could be implemented as a means of providing energy to African communities, while enriching the soils of the local landscape.<ref name="Strezov" /> It is also used as source of fuel. The young leaves and shoots are edible and are cooked to make soups and stews.<ref name="feedipedia">Heuzé V., Tran G., Giger-Reverdin S., Lebas F., 2016. Elephant grass (''Pennisetum purpureum''). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/395 Last updated on June 23, 2016, 17:09</ref>

A Dutch company has turned the grass into a plastic that can be used for packaging.<ref>{{Cite web|url=https://vibers.nl/about/bioplastic/|title=Bioplastic – Vibers|language=en-US|access-date=2020-02-13}}</ref>

==References==
{{Reflist}}

==External links==
{{Commons category|Pennisetum purpureum}}
{{Wikispecies-inline}}
* [http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/plant-finder/plant-details/kc/e476/pennisetum-purpureum-prince.aspx Missouri Botanical Garden horticultural treatment — ''Pennisetum purpureum'']
* More information can be found at http://www.push-pull.net/

{{Taxonbar|from1=Q41531378|from2=Q420834}}

[[Category:Cenchrus|purpureus]]
[[Category:Bunchgrasses of Africa]]
[[Category:Flora of Africa]]
[[Category:Flora of Oman]]
[[Category:Biological pest control]]
[[Category:Phytoremediation plants]]
[[Category:Biofuels]]
[[Category:Forages]]
[[Category:Afromontane flora]]
[[Category:Plants described in 1827]]
[[Category:Taxa named by Heinrich Christian Friedrich Schumacher]]

Cenchrus purpureus - Revision history

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