Influence of nitrogen on atrazine and 2, 4 dichlorophenoxyacetic acid mineralization in blackwater and redwater forested wetland soils

Abstract

Microcosms were used to determine the influence of N additions on active bacterial and fungal biomass, atrazine and dichlorophenoxyacetic acid (2,4-D) mineralization at 5, 10 and 15 weeks in soils from blackwater and redwater wetland forest ecosystems in the northern Florida Panhandle. Active bacterial and fungal biomass was determined by staining techniques combined with direct microscopy. Atrazine and 2,4-D mineralization were measured radiometrically. Treatments were: soil type, (blackwater or redwater forested wetland soils) and N additions (soils amended with the equivalent of 0, 200 or 400 kg N ha" as NH 4NO3). Redwater soils contained higher concentrations of C, total N, P, K, Ca, Mn, Fe, B and Zn than blackwater soils. After N addition and 15 weeks of incubation, active bacterial biomass in redwater soils was lower when N was added. Active bacterial biomass in blackwater soils was lower when 400 kg N ha-1 , but not when 200 kg N ha', was added. Active fungal biomass in blackwater soils was higher when 400 kg N ha-1 , but not when 200 kg N ha', was added. Active fungal biomass in redwater soils was lower when 200 kg N ha-1 , but not when 400 kg N ha', was added. After 15 weeks of incubation 2,4-D degradation was higher in redwater wetland soils than in blackwater soils. After 10 and 15 weeks of incubation the addition of 200 or 400 kg N ha' decreased both atrazine and 2,4-D degradation in redwater soils. The addition of 400 kg N ha' decreased 2,4-D degradation but not atrazine degradation in blackwater soils after 10 and 15 weeks of incubation. High concentrations of N in surface runoff and groundwater resulting from agricultural operations may have resulted in the accumulation of N in many wetland soils. Large amounts of N accumulating in wetlands may decrease mineralization of toxic agricultural pesticides.

Polyacrylamide in Agriculture and Environmental Land Management

“…To the extent they saw soil microbial biomass shifts, interpretation, especially in light of earlier literature, suggests this could be due to N enrichment resulting from the PAM addition rather than a direct effect of the PAM polymer chemistry itself. This has been seen in other studies where high soil N concentration reduced microbial biomass and mineralization of cellulose, lignin, and herbicides (Entry, 1999(Entry, , 2000 PAM IN AGRICULTURE AND ENVIRONMENTAL LAND 127 Entry and Backman, 1995;Entry et al, 1993). Thus if large amounts of PAM are applied to soil, it is reasonable to expect the additional N contained in PAM may slightly reduce microbial biomass.…”

The influence of high application rates of polyacrylamide on microbial metabolic potential in an agricultural soil

“…Intracellular and extracellular activity have been noted, and production and secretion of the enzyme appears to be dependent on C availability, as cells cannot derive C directly from PAM. Elevated soil N concentrations have been shown to reduce microbial biomass and mineralization of cellulose, lignin and herbicide (Entry, 1999(Entry, , 2000Entry et al, 1993;Entry and Backman, 1995). When large amounts of PAM are applied to soil, additional N contained in PAM may reduce microbial biomass.…”

Hexachlorobenzene dechlorination as affected by nitrogen application in acidic paddy soil

“…3a and b), and CH 4 production competed for electrons with HCB dechlorination. Secondly, it has been reported that excessive N addition could alter enzymatic systems of soil responsible for the degradation [12,13], and inhibit specific degraders' ability [14]. The application of NO 3 − -N decreased PeCB production rates significantly (Fig.…”

“…Some studies confirmed that N addition accelerated the degradation of organic contaminants owing to stimulating microbial activity [9][10][11]. Some studies showed that N addition inhibited the degradation of organic pollutants, because N sources could alter enzymatic systems responsible for the degradation and inhibit specific degrader's ability [12][13][14]. In addition, some other studies suggested an optimal C/N ratio for POPs biodegradation, and N sources were commonly added when carbon sources were excessive in the environment [15][16][17].…”