Biosolids play an important role in rehabilitation of deteriorated rangeland soils but data regarding their effects on seed germination of Sonoran desert shrubs does not exist. The study was conducted at the National Service of Seed Inspection and Certification (SNICS-SAGARPA) at Ciudad Obregon, Sonora, Mexico. The objective was to test the effect of domestic biosolids extracts upon seed germination. Seeds of fairy duster (Calliandra eriophylla), mesquite (Prosopis juliflora), tree morning glory (Ipomoea arborescens), Ironwood (Olneya tesota), palo verde (Cercidium microphyllum), piojito (Caesalpinia pumila), and Rosary Babybonnets (Coursetia glandulosa) were germinated with biosolid extracts and distilled water. One hundred seeds were set on triplicated petri dishes In a germinator chamber at two temperatures 15 and 28 ºC. Evaluated variables were seed germination and viability. The tetrazolium test was used for viability. A randomized complete block design and analyses of variance were used for plot distribution and data analyses. The greatest (P<0.05) germination for all species was obtained with 28 ºC. Biosolid extracts did not (P>0.05) significantly increase seed germination in most species, except palo verde and mesquite. Germination of palo verde and mesquite averaged 52 and 74% in the controls and 85 and 88% in the biosolids extraction treatment. Biosolid extracts negatively affected seed germination in fairy duster, tree morning glory, piojito and Rosary Babybonnets. Average germination declined from 17 to 26% among these species, and germination was consistently greater (P<0.05) in the controls. Seed germination of Ironwood was not affected by biosolids extracts. Seed viability was 80.0, 91.6, 98.7, 98.0, 77.0, 99.0 and 98.0 for fairy duster, mesquite, tree morning glory, ironwood, Palo verde, piojito and Rosary Babybonnets, respectively. We conclude that since biosolids-treated soils may reduce seed germination of browse species, range managers need to take that under consideration to adjust seeding rates for proper plant establishment.
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