Prosopis juliflora (Swartz) DC.
This description is particular to: var juliflora Burkart, var.inermis Burkart & var. horrida Burkart
Evergreen shrub or tree up to 15 m high, bole short and crooked. Bark thick, rough, greenish-grey in the young, fissurated and scaly in the mature. Very thorny or thornless, thorns 1.2-5 cm long, straight, in axillary pairs or solitary or non-existent altogether. Leaves alternate, bipinnate, rachis 3-6 mm long, with 2-3 pairs of pinnae, each 7-15 cm long with 8-15 pairs of oblong, linear leaflets glabrous or ciliate, 1.5-5 cm long x 3-6 mm wide, terminal leaflet missing. Petiole and rachis canaliculate. A pitted gland is located at the base of the first pair of pinnae. Young branches and twigs are green. Flowers are set in cylindrical spikes 5-10 cm long x 1.5 cm wide, solitary or in clusters near the leaf axils. Individual flowers are small, densely crowded, fragrant, pale yellow to whitish-creamy. Pods are indehiscent, straw-yellow in colour, straight, 15-20 cm long x 1-1.5 cm wide, with 10-20 hard seeds 2-8 mm long. Deep rooting species, to 35 m, with lateral roots, strongly competing with herbaceous species.
It is sensitive to cold weather and frost, and on the contray, very heat tolerant.
P. juliflora, as most arid-zone Prosopis sp.pl., is a phreatophyte; in the case of the Sahel it is an obligate phreatophyte ; many attempts (including by the present author, Niono, Mali, 1976-80) to grow it in the absence of a water table or under full irrigation failed completely, seedlings being unable to survive their first dry season, whereas over a water table in nearby sites the growth was almost 2 m per annum. Ignoring this fact led to costly failures in Mauritania and elsewhere. P. juliflora is proven to be able to extract water from water tables 15 m deep and may be even more than double that depth. P. cineraria has been shown to reach a depth of 60 m in the Oman desert, (Brown, 1992, ).
It is tolerant to salinity and alkalinity, as shown in India (Abrol, 1986; Singh, 1998 ; Singh & Singh, 1993 ; Singh & al.1993) and in Argentina (Roig, 1993 ; Cony, 1993 ; Galera & al., 1992). and as witnessed in the delta of the Senegal river, between Rosso, Richard Toll, Ross Bethio and St Louis.
Central American lowlands, Carribean, South American lowlands (Venezuela, North East Brazil, Pacific shores), naturalized in many tropical zones, Pakistan, India, North Australia, East Africa, South Africa, the Sahel, Cape Verde Islands, the Arabian-Persian, Gulf, Southern Arabian Peninsula. It was introduced to Senegal and Mauritania in the early 19 th century (Pasiecznik et al., 2000)., and from there apparently spread in various Sahel countries ; it was introduced to the Sudan in 1917 and now banned because of its invasiveness (Wickens, pers.com., 2000) and to Rajasthan in 1914 (Bhandari, 1978), in the 3 cases to help combat "desertification" (already !). Surprisingly, the same scenario occurred in the 4 countries : the tree was introduced under its correct name, then identified as such by Burkart (1976) and Burkart & Simpson (1977) and later misidentified as P. chilensis (Mol.) Stuntz in the local floras in the 1950's onwards (Diagne, 1992, for the case of Senegal). It is now fairly common in all Sahelian countries from Mauritania to Sudan, although usually not invasive, contrary to its status in other tropics.
In North Senegal the tree is very sensitive to damage from wind, the main branches are liable to splitting from the bole.
Seeds should be pre-treated before they germinate (boiling water, as for acacias), seeds carried by moving cattle faeces do germinate readily in favourable ernvironments, most often, however, seedlings are then browsed out, needing stock control. There are 8,000 to 15, 000 seeds in a kg of dehulled material.
Due to the complex taxonomy in this group, great care should be exerted in controlling the provenance of the genetic material utilized, as morphogically similar species may have very different ecological requirements such as the complexes juliflora / pallida on one hand and glandulosa on the other, since even morphologically different species have been confused for decades. Planting in dunes can only be durably successful wherever a permanent water table is present below, be it fairly saline, up to 25 mS / cm of EC. Coppicing and root suckering are very active.
Other uses are firewood and charcoal, service wood, posts and poles, hedging, windbreak, bees are fond of mesquite flowers and the flowering lasts almost year-round. P. juliflora should be avoided as a windbreak in irrigated areas as a potential host to pathogen nematods (Dommergues et al., 1999). The nitrogen fixation in a solid plantation 6 x 6 m is evaluated at ca 30-40 kg N2 ha-1 yr-1 (Dommergues & al., 1999).
Pods are relished by livestock; they can be stored for 2 years, thus may be used as a concentrate feed. The feed value of the pods is fair in energy and high in CP : (5.0 +/- 1 Mj NE per kg of pod DM and 15 + / - 2 % CP). However one should be cautious when interpreting proximate analyses of pods. Proximate analysis is made from ground pods where the seeds have usually not been removed. But the seeds are about 50 % richer than the husk and pulp in CP, NFE and Fat (energy). As seeds represent some 20 % of the pod DM, and as they are, as a rule, not actually digested by ruminants, it follows that feed value is over-evalutaed in the analyses in respect to real life situations by some 10 % in both Energy and CP. Some strains or accessions may have leaves rich in tannins (condensed polyphenols) which are, therefore, not palatable.
Andrews 1952 ; Hutchinson et al. 1958 ; Berhaut 1975 ; Burkart 1976 ; Giffard 1974b ; Giffard 1975 ; Weber et al. 1977 ; Simpson, 1977 ; Solbrig et al.1977 ; Delwaulle 1978/79 ; Le Houérou 1980a ; Houérou 1980c ; Houérou 1980d ; Von Maydell 1983/86 ; Baumer 1983 ; Habit & Saavedra (eds) 1988 ; Barry & Celles 1991 ; Dutton et al. (eds) 1992 ; Speedy & Pugliese (eds) 1992 ; Diagne 1992 ; Verga 1995 ; Singh 1998 ; Earl 1999 ; Ramirez et al. 1999 ; Dommergues et al 1999 ; Pasiecznik et al. 2000.