Range, Wildlife and Fisheries Management
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Effect of Multiple Rates of Municipal Biosolids Applied
Twice-a-Year for Four Consecutive Years on Tobosagrass
by Pedro Jurado, David B. Wester, Ronald E. Sosebee, and Ernest B. Fish
Biosolids were applied to tobosagrass experimental plots twice-a-year in winter-and-summer, or spring-and-summer at rates of 0, 3, 8, or 15 dry tons/acre/season. Biosolids were applied for one year only (1994), two (1994 and 1995), three (1994 through 1996), or four consecutive years (1994 through 1997). Supplemental irrigation was provided to half of the plots throughout the summer in case of low rainfall. Aboveground standing crop was harvested by clipping tobosagrass at the end of the growing season (middle October).
During the four years of the study (1994 through 1997), twice-a-year application of biosolids either increased or maintained tobosagrass standing crop, but never decreased it compared to no application of biosolids. Only the first year of the study, winter-and-summer application showed a better response than spring-and-summer application. Low rates of biosolids (3 and 8 tons/acre) increased tobosagrass standing crop when applied for 2, 3, or 4 consecutive years. The high biosolids rate (15 tons/acre) increased tobosagrass standing crop when applied for one or two consecutive years, and maintained tobosagrass standing crop when applied three or four consecutive years compared to control rate.
Supplemental irrigation increased tobosagrass standing crop during the four years of the study. Residual effects from one year application of biosolids in 1994 on tobosagrass standing crop were detected from 1995 through 1997, especially at 8 and 15 tons/acre rates.