In the United States there are four species: P.glandulosa var. torreyana (in California), P. velutina (in Arizona), P. glandulosa var. glandulosa (in Texas), and P. pubescens i.e. screwbean (minor distribution in all regions). There are 44 Prosopis species worldwide. Prosopis is prominent in Mexico, Peru, Chile, Argentina, Brazil, Sahelian Africa, Haiti, Pakistan, and the arid parts of India. In many these locations it is useful for firewood, livestock feed (the pods), and soil improvement. In Peru its pods are used in human food preparations and in Argentina and Texas fine furniture and flooring are made from its wood.
Prosopis wood is perhaps the most dimensionally stable of all woods in having equal radial and tangential shrinkage values of only 2%-3% and in having total volumetric shrinkage values of 4%-5%. Other fine woods i.e. oak, cherry, walnut, teak, mahogany and Indian rosewood have volumetric shrinkage values in the range of 8%-15% (Felker et al. 1994). The result of the low shrinkage value is that furniture made from mesquite will have less expansion and contraction when ambient humidity levels change, such as from summer to winter in northern regions. Thus furniture will not crack and drawers will not stick with changing humidity levels.
In many regions of southwestern United States, dense nearly impenetrable stands of mesquite have occurred on rangelands much to the displeasure of ranchers (Cornejo-Oveido et al. 1991; Felker et al. 1988). The worse stands have occurred on overgrazed rangeland sites or sites that have been subjected to mechanical manipulation. It has been hypothesized that a major reason for the spread of mesquite has been the competitive advantage of nitrogen fixing woody legumes on sites that have become impoverished in nitrogen. Measurements of tree spacing versus tree diameter over a range of 10,000 to 20 stems/ha revealed a highly significant logarithmic relationship (Felker et al. 1988). This suggested the presence of substantial intraspecific genetic variation and the possibility of preventing the spread of dense stands of young mesquites by competition from large mature mesquites.
Agroforestry experiments indicate that the growth of the trees was maximal in intercropped situations. Diameter growth rates of 1.25 cm/year were recorded over a three year period that are equal or greater to hardwood growth in more temperate regions of the United States (Cornejo-Oveido et al. 1991).
Given the fact that there are over 20 million ha of Prosopis just in Texas, it became important to convert what was viewed as a liability into an asset. Extensive anthropological data on human food uses of Prosopis pods and food technological experiments have demonstrated conclusively the potential of mesquite pods in human food preparation. The limitation to food use is the cost of hand labor to gather the pods. Presumably equipment could be devised for use in managed orchards to economically harvest the pods, but without this equipment and orchards of mesquite in rows, this aspect of mesquite pod utilization is not economically possible.
The three main uses of Prosopis wood are (1) as a source of energy and/or chemical feedstock, (2) as barbecue chips and chunks, and (3) as lumber or flooring. Assuming a value of $2 per million BTU delivered to a power plant for fuel, mesquite wood has a delivered value of $34/t for fuel. Current wholesale prices for mesquite packaged in 2 kg plastic bags for the grocery trade are about $400/t. If mesquite lumber is priced equivalent to cherry, walnut, and premium oak at $3,000/thousand board ft, then mesquite is worth about $1700/t. It is then clear that the highest and best use of mesquite is in solid wood applications.
A 300 hp mesquite combine has been under development for nearly 10 years to harvest small diameter mesquite and related brush for industrial fuel and/or chemical feedstock (McLauchlan et al. 1994). While great improvements have been made, this equipment is not yet commercially viable. The goal of this machine will be to harvest woody brush for about $9/t (green) in the field.
Fortunately there is a good demand for smaller pieces (15 to 25 cm in diameter and 1 m long) by the barbecue industry that could result from thinning overstocked stands. Prices of about $25/m3 ($90/cord) are being paid by mesquite barbecue processors for these small diameter logs. The hauling costs dictate that at $25/cubic meter these logs can be hauled a maximum of about 150 km (100 miles).
The mesquite barbecue industry is experiencing rapid growth with the two top processors having product in over 8,000 retail outlets in all 50 states (J. Lawson and G. Wartsbaugh pers. commun.). In 1995, the volume of mesquite processed by the three largest mesquite barbecue manufacturers was about 14,000,000 kg which at $0.44/kg is a $6 million industry. Since there are about 600 kg/m3 (5,000 lb/cord) and since the volume of mesquite ranges from 9 to 90 m3/ha (1 to 10 cords/acre), the area harvested can be calculated to range from 250 to 2500 ha. As there are 20 million hectares in Texas and as raw material for the barbecue plants can only be economically hauled 150 km, there is obviously a need to greatly expand the demand for mesquite wood for barbecue uses. Fortunately the charcoal briquette industry is a $400 million/year industry so there is great opportunity to increase the market share of this product.
As it is to the benefit of Texas cattlemen to create a market for beef and mesquite, mesquite wood barbecue producers of the trade organization, Los Amigos del Mesquite, conducted a beef/mesquite co-marketing program with the Texas Beef Council. Two mesquite processors contributed $5,000 that was matched with $20,000 by the Texas Beef Council to produce color displays with beef and mesquite in the meat section of 1700 grocery stores in Texas.
Los Amigos del Mesquite also worked with the National Hardwood Lumber Association to establish a new grading system applicable to mesquites short and narrow lengths. In 1996, Los Amigos del Mesquite began working with the Lumbermans Association of Texas which have many retail chains that sell wood products for joint marketing efforts. These latter 3 joint activities clearly point to the advantages of developing professional societies to work together in win-win situations.
In 1981, when Los Amigos del Mesquite was formed, there were only 3 mesquite sawmills in Texas and these sawmills only operated part time to produce end-grain flooring and rough, non-kiln dried lumber. In 1996, there were at least three full time companies producing mesquite flooring and lumber, one of which has developed into a million dollar per year business. Detailed information on the mesquite program can be obtained from Los Amigos del Mesquite through Texas A&M University-Kingsville. Worldwide information of mesquite is also available in the Prosopis email network. To subscribe to the network, mail to Listserv@taiu.edu and type subscribe Prosopis and mail the message.
It is significant that alfalfa cannot be grown in much of Texas due to susceptibility to cotton root and that Leucaena is 100% resistant to this pathogen (S. Lyda pers. commun.). In a 4 year trial, on two sites with four large (12 m by 36 m) replicates per site, we demonstrated that one-row commercial equipment could be used to plant, cultivate and harvest leucaena (Felker et al. 1991). The annual forage production ranged from 1.5 t/ha to 9 t/ha and the crude protein content ranged from 11.8 to 23.9% (Felker et al. 1991).
As a follow-on to this research, Mr. Edwin Singer and associates of Corpus Christi, Texas have established a 200 ha pivot-irrigated leucaena plantation and developed mechanized planting, harvesting, drying, and pelletizing operations. The largest demand for the pelletized product is in feed for wildlife operations. Mr. Singer has also held organizational meetings of scientists, growers, and ranchers. For further information contact Mr. Singer at Suite 2020, Mercantile Bank Tower, Corpus Christi, Texas 78477.
In Texas the primary use of cactus has been in times of drought when the spines have been burned off the cactus to feed cattle. In thick stands of native Opuntia lindheimerii, it has been reported that one man can burn enough cactus for 100 cattle. It has been estimated that 1 liter of propane is sufficient for one mature cow and when propane is purchased in bulk for $0.10/liter, the daily feeding propane cost is about $0.10/animal. A daily ration of 40 kg of cactus, 0.5 kg of mineral salts, and 0.5 kg of protein supplement is sufficient to permit excellent liveweight gain, reproduction, and lactation from nursing cattle (Maltsberger 1991).
While the young tender spring vegetative growth of wild cactus (nopalitos) has been extensively consumed by Hispanics during Lent (Russell and Felker 1987), only recently have plantations of spineless cacti been established in Texas for nopalito production. An improved nopalito cultivar with greater year round production, lack of spines, lack of glochids (nearly microscopic spines), and low mucilage is available as `Texas A&M 1308'. In contrast, spineless Opuntia plantations for nopalito production have been common in central Mexico (Milpa Alta) for many years (Russell and Felker 1987).
The fruit of native Opuntias weigh about 30 g and have a sugar content of about 9%. In contrast commercial cactus fruit varieties from Mexico weigh about 110 g with a sugar content from 13%-15% (Pimienta-Barrios 1991). There is great diversity in colors, seediness, and date of ripening of the Mexican cactus fruits. The fruits may be lime green, orange, pink, red, or purple. Typically the lime-green fruits are the sweetest and most desirable in Mexico, but the red fruits are in most demand for export to northeastern United States and Canada.
A commercial cactus fruit orchard, operated by the D'Arrigo Bros, has been in existence for nearly 50 years near Salinas, California. This orchard produces red fruits that are sold to people primarily of Italian descent in northeastern United States (R. Bunch pers. commun.).
An Opuntia genetic improvement program is underway at Texas A&M University-Kingsville to find fruit producing cactus clones that are adaptable to Texas. The primary limitation to cactus fruit production in Texas is the presence of Arctic cold fronts about every 10 years in which temperatures may remain below freezing for several days with minimum temperatures of -12°C. Opuntia fruit cultivars have been collected in high elevation sites in Mexico's cold deserts with the goal of finding cultivars with good fruit quality and cold hardiness. In 1996 over 130 clones were being evaluated in field trials at the Texas A&M University-Kingsville field station.
The cactus new crop effort at Texas A&M University-Kingsville is about equally divided between development of new clones/cultural practices and working with all aspects of the commercial cactus industry to stimulate awareness and market demand.
The private/federal investiment of about $150,000/year into new crops R&D at Texas A&M University-Kingville from 1981 through 1995, has been closely associated with the development of the mesquite industry which grew from 0 to $5 million/year over the same time period. We believe in the medium term both cactus and leucaena will also develop into multimillion dollar per year industries. While these industries are very small by industrial standards, these revenues are being generated in poor rural areas in desperate need of economic development. In the case of mesquite, this industry has converted what was previously a weedy-liability into an asset. The university R&D effort facilitated creation of organizations of diversified users (i.e. chefs, brokers, barbecue manufacturers, farmers, physicians) that were critical to the development of the entire industry. Both from a financial and sociological perspective these R&D funds into new crop development in Texas were a sound investment. We believe that each state in the United States has similar valuable indigenous resources that could be developed into commercially viable new crops. It is our hope that proactive New Crop policies will change to obtain financial resources to create similar programs throughout the United States and the world.