Da. Martens et Jm. Bremner, EFFECTS OF PREEMERGENCE AND POSTEMERGENCE HERBICIDES ON UREA HYDROLYSIS AND NITRIFICATION OF UREA NITROGEN IN SOIL, Biology and fertility of soils, 17(4), 1994, pp. 309-313
The influence of 5 and 50 mg active ingredient kg-1 soil of nine preem
ergence and nine postemergence herbicides on transformations of urea N
in soil was studied in samples of two coarse-textured and two fine-te
xtured soils incubated aerobically at 20-degrees-C. The effects of eac
h herbicide on soil urea transformations was measured by determining t
he amounts of urea hydrolyzed and the amounts of NO3- and NO2- produce
d at various times after treatment with urea. Applied at the rate of 5
mg active ingredient kg-1 soil, none of the herbicides retarded urea
hydrolysis in the four soils used, but four of the postemergence herbi
cides (acifluorfen, diclofop methyl, fenoxaprop ethyl, and tridiphane)
retarded nitrification of urea N in the two coarse-textured soils. At
50 mg active ingredient kg-1 soil, four of the postemergence herbicid
es (acifluorfen, diclofop methyl, DPX-6202, and fenoxaprop ethyl) reta
rded urea hydrolysis in the two coarse-textured soils. All the herbici
des tested except siduron retarded nitrification in the two coarse-tex
tured soils when applied at 50 mg of urea N active ingredient kg-1 soi
l, and fenoxaprop ethyl and tridiphane markedly retarded nitrification
of urea N in all four of the soils when applied at this rate. One-way
analysis of variance and correlation analyses indicated that the inhi
bitory effects of the 18 herbicides tested on nitrification of urea N
in soil increased with a decrease in the organic-matter content and an
increase in the sand content of the soil.