New patented hybrid arid-adapted nitrogen fixing mesquite trees for ornamentals and carbon sequestration.
Two new hybrid, arid-adapted nitrogen fixing mesquite trees for ornamentals and carbon sequestration have just been patented (See links here: Sonoran Patent and Mojave Patent.) Other patented thornless mesquite trees are available, but this is a hybrid between a freeze-hardy thornless Texas native mesquite, and an Argentine mesquite with lovely feathery leaves, is adaptable to much more severe freezing weather in southwestern US.
Due to the low moisture content of arid soils, with intense solar radiation, they heat up quickly, stimulate microbial respiration, and rapidly consume organic matter and organic nitrogen. As a result, arid soils have ten times lower soil carbon and nitrogen than midwestern farm soils. Only 1-2 kg/ha-yr of nitrogen comes into arid ecosystems from rainfall and blue green algae. At steady state equilibrium, no more nitrogen can leave the ecosystem than enters it. At 1% nitrogen in dry matter, 1-2 kg/ha-yr N will only support 100- 200 kg dry matter per year. Plants in arid zones lose considerable precipitation to runoff and evaporation, and often only transpire 150 mm out of the 500 mm they receive. With sorghum transpiration water use efficiencies of 2.96 kg dry matter per cubic meter of water, a dry matter production of 4440 kg ha-1 would result from 150 mm of transpiration. At 1% N of dry matter, 44 kg of N would be required. These N fixing trees can fix 50 kg N ha-yr which would allow other plants to take advantage of their water use efficiency.
As a plant’s C/N ratio is minimally 12. For every kg of N fixed, the plant needs to take up 12 kg of C which for 50 kg N ha-yr from nitrogen fixation, is 600 kg C per ha per year. As arid lands comprise approximately 25% of the earths land mass, they are an enormous sink for carbon. At 600 kg C fixed /ha-yr over the worlds arid lands, approximately 20% of the goal for annual reduction in carbon would be achieved.
A spiny, multi stemmed tropical mesquite, with not very palatable pods, from the Caribbean was introduced into Africa and now covers tens of millions of ha in arid Somalia, Ethiopia, Kenya, Yemen and India-much to the consternation of pastoralists- however the same trees do provide needed charcoal, pods for livestock food and biomass for electrical generation plants. My collaborators and I have planted replicated field trials comparing the thorny, multi stemmed Mesquite now naturalized to Africa, against Peruvian mesquites that are noted for their sweet pods and found erect thornless Peruvian mesquites with greater biomass than the undesirable Caribbean species. As such these Peruvian mesquites could be most helpful in poor arid lands of East Africa. The calculations above are described in detail in a forthcoming Elsevier book edited by Cecilia Puppo of the National University of La Plata, Argentina and myself titled “Prosopis: one of the most heat tolerant, nitrogen fixing food legumes of the world. Prospects for economic development in arid lands”.
The lovely thornless erect Prosopis in the attached patents are available from Altman Plants, the largest US wholesale grower, through Chris Scott (CScott@Altmanplants.com) out of the San Antonio location. Contracts can be arranged to provide trees throughout the south and southwest.