Da. Martens et Jm. Bremner, INFLUENCE OF HERBICIDES ON TRANSFORMATIONS OF UREA NITROGEN IN SOIL, Journal of environmental science and health. Part B. Pesticides, food contaminants, and agricultural wastes, 28(4), 1993, pp. 377-395
The influence of 28 formulated herbicides on transformations of urea n
itrogen in soil was studied by determining the effects of 5 and 50 mg
active ingredient kg-1 soil of each herbicide on the amounts of urea h
ydrolyzed and the amounts of nitrite and nitrate produced when samples
of two coarse-textured soils and two fine-textured soils were incubat
ed aerobically at 20-degrees-C for various times after treatment with
urea. The herbicides studied were alachlor, amitrole, atrazine, bentaz
on, bifenox, bromoxynil, chloramben, chlorpropham, 2,4-D amine, 2,4-D
ester, dalapon, dicamba, dinitramine, dinoseb, diuron, EPTC, glyphosat
e, linuron, monuron, paraquat, pendimethalin, picloram, prometryn, pro
panil, propham, simazine, trifluralin and vernolate. When the 28 herbi
cides studied were applied at the rate of 5 mg active ingredient kg-1
soil, they did not retard urea hydrolysis in the four soils used or ni
trification of urea nitrogen in the two fine-textured soils, but six o
f them (amitrole, chlorpropham, 2,4-D amine, dinoseb, propham and prop
anil) retarded nitrification of urea nitrogen in the twocoarse-texture
d soils. When the herbicides were applied at the rate of 50 mg active
ingredient kg-1 soil, two of them (alachor and dinoseb) retarded urea
hydrolysis in both of the coarse-textured soils, and six of them (brom
oxynil, 2,4-D ester, dicamba, linuron, diuron and glyphosate) retarded
urea hydrolysis in one of these soils. All of the herbicides tested r
etarded nitrification of urea nitrogen in one of the coarse-textured s
oils when they were applied at the rate of 50 mg active ingredient kg-
1 soil, but only four of them (propanil, propham, amitrole and dinoseb
) markedly retarded nitrification of urea nitrogen in all four of the
soils used when they were applied at this rate. ANOVA and correlation
analyses indicated that the effects of the herbicides tested on nitrif
ication of urea nitrogen in soils were significantly influenced by inc
ubation time, soil texture and soil organic-carbon content. The work r
eported indicates that the 28 herbicides studied are not likely to sub
stantially affect nitrification when they are applied to soils in conj
unction with. urea fertilizers.