Impacto Economico De Los Biosolidos En La Rehabilitación De Praderas Viejas De Zacate Boer En El Norte De Sonora, Mexico

Boer lovegrass (Eragrostis curvula var. conferta) is an introduced species planted to increase productivity on deteriorated rangelands on arid and semiarid areas. Forage production with Boer lovegrass following biosolids increases two to three flod as compared to native grasses but productivity declines as stands became old. This study was conducted at Cananea, Sonora, Mexico to evaluate forage responses of old Boer lovegrass stands fol application and to evaluate the economic impact of biosolid application to restore productivity on these rangelands. Biosolids were hand-applied during 2006 on triplicated 5 x 5 m plots. Variables evaluated were plant density, plant height, basal cover, forage production, changes in animal increases two to three-fold as compared to native grasses but productivity declines as stands become old. This study was conducted at Cananea, Sonora, México to evaluate forage responses of old Boer lovegrass stands following biosolids applications and to evaluate the economic impact of biosolids applications to restore carrying capacity and net income. All variables were measured three growing seasons after biosolids application. A randomized complete block design was used. Data was analyzed by ANOVA (P<0.05). Results show that all heavy metals were within the limits allowed by the Official Mexican Standard of the SEMARNAT so they are considered of good quality and can be used in the rehabilitation of deteriorated soils without risk of contamination or danger for humans and animals. Plant density, height, and basal cover were significantly increased (P≤0.05) by biosolids. Boer lovegrass density increased from 43.2 to 67.6%; plant height increased from 36.7 to 41.6%; and basal cover increased from 37.0 to 52.4 % in plots treated with biosolids at rates of 25 and 50 t/ha, respectively. Total forage production averaged 0.96 t/ha dry matter basis in the checks and increased 69.8 and 113.3% on plots treated with 25 and 50 t/ha of biosolids, respectively. Biosolids significantly increased Boer lovegrass plant density, height, basal cover and forage production even three growing seasons after application at rates of 25 and 50 t/ha in a semiarid rangeland. The uses of these nutrient-rich organic materials play an important role in the improvement of deteriorated rangelands in northern México. The areas treated with biosolids increased U.A. in 71.6 and 135.8% with the application of 25 and 50 t/ha, respectively, of organic sludge. Ranchers using biosolids may almost double forage standing biomass, the grazing capacity and the production potential of their rangelands. The use of biosolids to restore productivity in old Boer lovegrass stands may increase income from $127.30 to 245.20 pesos/ha/year.