mechanism of action
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CitationRalphs, M. H., Woolsey, L., & Bowns, J. E. (2003). Mechanism by which ammonium fertilizers kill tall larkspur. Journal of Range Management, 56(5), 524-528.
PublisherSociety for Range Management
JournalJournal of Range Management
AbstractEnvironmental concerns of using pesticides on public lands have greatly reduced the use of herbicides to control tall larkspur (Delphinium barbeyi Huth). An alternative method of control used ammonium sulfate placed at the base of individual plants. The objective of this study was to determine the mechanism by which fertilizers kill tall larkspur. We hypothesize the salt from the fertilizers kill the plant. We applied ammonium sulfate, ammonium nitrate and sodium chloride at equivalent salt concentrations and evaluated their effect on tall larkspur plants. There was no difference among treatments in larkspur mortality (P > 0.10). The high rate of all treatments (ammonium sulfate 400 g plant-1, ammonium nitrate 264 g, and sodium chloride 180 g, at equivalent salt concentrations) killed greater than 70% of larkspur plants. We conclude the salt in fertilizers kills tall larkspur, not the nitrogen. It is necessary to place the fertilizer or salt at the base of the plant to concentrate it in the root zone, rather than broadcast it. At the end of the study, bare areas left around the dead tall larkspur plants were only 13% of the original size of the tall larkspur plants at Yampa Colo. and Cedar Ut., and 46% at Emery Ut., indicating the surrounding vegetation was quickly filling in the vacated space. The relative cost of materials per plant for both ammonium sulfate and nitrate was 12.9 cents, and 2.6 cents for salt.
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Native forage quality, quantity, and profitability as affected by fertilization in northern MexicoRubio, H. O.; Wood, M. K.; Gomez, A.; Reyes, G. (Society for Range Management, 1996-07-01)Fourteen treatments of nitrogen (N) and phosphorus (P) fertilizers were applied in an overgrazed eight rangeland in northern Mexico, during 1990 and 1991. Eight treatments were applied using ammonium nitrate as a source of N (60-0-0, 60-30-0, 60-60-0, 80-40-0, 120-30-0, 120-60-0, 120-90-0 and 180-60-0 kg ha-1), 2 treatments with ammonium sulfate (60-30-0 and 120-60-0 kg ha-1), 2 with urea (60-30-0 and 120-60-0 kg ha-1), only P (0-30-0 kg ha-1), and the control (0-0-0 kg ha-1). Triple superphosphate was applied as a source for P. The 80-40-0 treatment was included because it was the commonly recommended rate for the area. Fertilizers were applied at the beginning of the rainfall season (July) and forage was harvested in late October (1990) and mid-November (1991). Dry matter production, crude protein (CP) content, and in situ digestibility were determined. An economic analysis was used to obtain the best economic treatment for forage production. In 1990 with a precipitation of 377 mm, dry matter production was significantly affected for both source and rate of N. The maximum amount of dry matter was obtained with a rate of 120-90-0 kg ha-1 using ammonium nitrate. However, the best treatment in terms of economic return was 120-30-0 kg ha-1 as ammonium nitrate. Urea did not produce as well as other N source treatments. Crude protein was highest in treatments with the higher N, but no significant trend was evident. In situ digestibility was not affected by rate or source of N fertilizer. During 1991, precipitation was higher than in 1990. Significant differences were determined among N rates but not in N source. In fact, urea produced greater in dry matter production than other N sources at the same rate. The maximum amount of dry matter was obtained with the 180-60-0 treatment using ammonium nitrate with 4,190 kg ha-1, but the best economic treatments were the 120-30-0 and 60-0-0 with a marginal return rate of 377% and 355%, respectively. Results of CP and in situ digestibility were similar to those of 1990.
Indiangrass and caucasian bluestem responses to different nitrogen sources and rates in the OzarksBrejda, J. J.; Brown, J. R.; Hoenshell, C. L. (Society for Range Management, 1995-03-01)Alternatives to cool-season grasses are needed for summer forage production on droughty, infertile soils in the Ozarks. The objective of this research was to compare nitrogen (N) sources and application rates for improving forage production, crude protein concentration, and apparent fertilizer N recovery by 'Rumsey' indiangrass [Sorghastrum nutans (L.) Nash] and caucasian bluestem [Bothriochloa caucasia (Trin.) C.E. Hubbard]. Pure stands of each species were treated with urea, NH4NO3, or (NH4)2SO4 at 0, 56, 112, and 168 kg N ha-1 from 1985-1987. In 1988 the (NH4)2SO4 treatment was discontinued and in 1990 the N rates were increased to 0, 78, 157, and 235 kg N ha-1. Forage yields, crude protein concentrations or both were greater with NH4NO3 compared to urea in 3 out of 6 years for indiangrass and 4 out of 6 years for caucasian bluestem. Indiangrass forage yields increased with increasing N rates up to 168 kg N ha-1. Caucasian bluestem forage yields peaked at 101 kg N ha-1 in 1985, 132 kg N ha-1 in 1986, 122 kg N ha-1 in 1987, 129 kg N ha-1 in 1989, and 161 kg N ha-1 in 1990. Crude protein concentrations of both species increased linearly with N rates in most years. At the lowest N rate (56 kg N ha-1) caucasian bluestem was more efficient than indiangrass in apparent fertilizer N recovery, but at greater N rates the 2 species were similar in fertilizer N recovery. Forage yield and crude protein concentration of both species responded similarly to (NH4)2SO4 and NH4NO3.