|Ares, Adrian - OREGON STATE|
Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 19, 2009
Publication Date: June 1, 2009
Citation: Ares, A., Burner, D.M., Brauer, D.K. 2009. Soil phosphorus and water effects on growth, nutrient and carbohydrate concentrations, d13C, and nodulation of mimosa (Albizia julibrissin Durz.) on a highly weathered soil. Agroforestry Systems. 76(2):317-325. Interpretive Summary: There is growing interest in southeast United States in the use of mimosa trees as browsed forage for raising meat goats, as a means of overcoming the low abundance and low quality of forages typically found during the late summer period. Growth and physiological performance of plants can be severely constrained by shortages of soil phosphorus (P) and summer drought. ARS scientists from Booneville AR examined P fertilization and irrigation effects on growth and physiology of mimosa. Biomass of mimosa increased five-fold when irrigated with 10 inches of supplemental water during the growing season. Phosphorus fertilization also increased mimosa growth; however, phosphorus fertilization decreased water use efficiency. These results indicate that even native pioneer plant species, like mimosa, respond to increases in soil fertility and irrigation, and management protocols for the use of mimosa as a browse for meat goats should include adequate soil fertility and possibly irrigation.
Technical Abstract: Growth and physiological performance of multipurpose tree species can be severely constrained by nutrient shortages such as of phosphorus (P) in highly-weathered soils. Limitations to plant growth are accentuated by seasonal dry periods. We examined P fertilization and irrigation effects on growth, foliar nutrients, intrinsic water-use efficiency by carbon isotope 13 abundance, nodulation and carbohydrate content of mimosa (Albizia julibrissin Durz.), a N-fixing tree species being tested for browse in agroforestry practices in central-southern United States of America. In a field experiment carried out during two growing seasons, mimosa had a strong growth response to irrigation. Mean total plant aboveground biomass at the end of the second growing season was 9.8 g for the rainfed treatment and 44.1 g for the rainfed treatment plus 300 mm of irrigation water. Placed applications of 90 kg P per year also increased mean aboveground biomass from 19 g for the 0 P treatment to 69 g in the 90 kg P per year treatment. Similarly, irrigation consistently increased stem basal diameter, total height, survival, root biomass, stem biomass, foliar biomass, total aboveground biomass and number of nodules per plant. Phosphorus addition increased stem basal diameter, root biomass and stem biomass in both irrigation treatments. The addition of P decreased both foliar and root carbon 13 isotope abundance, suggesting decreased water use efficiency with P fertilization. Foliar P concentration to obtain 90% of the maximum total plant biomass was estimated at 0.16 %. Total nonstructural and water soluble carbohydrate, and starch concentrations increased non-linearly with irrigation and P addition suggesting impaired re-growth potential after defoliation of seedlings with reduced water supply and at low soil P levels.