Aj. Cessna et al., TRANSPORT OF NUTRIENTS AND POSTEMERGENCE-APPLIED HERBICIDES DURING CORRUGATION IRRIGATION OF WHEAT, Journal of environmental quality, 23(5), 1994, pp. 1038-1045
The nutrient and pesticide content in runoff water from surface irriga
tions can adversely affect the quality of receiving waters, and can al
so determine the suitability of the water for reuse in the subsequent
downstream irrigation of other crops. In order to assess the magnitude
of loss under normal corrugation irrigation practices, the transport
of plant nutrients and postemergence-applied herbicides was monitored
in runoff water from two irrigations of a 12.6-ha wheat (Triticum aest
ivum L. cv. Owens) field. Cumulative P and N losses in runoff water fr
om both irrigations were 1007 and 2487 g, respectively, which correspo
nded to 0.29 and 0.13% of the amounts applied through fertilization. L
oss of either nutrient in the first irrigation was approximately twice
that in the second irrigation. Total losses of dicamba (3,6-dichloro-
2-methoxybenzoic acid), MCPA [(4-chloro-2-methylphenoxy)acetic acid] a
nd {(+/-)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid} from the e
xperimental site were 3.0, 9.3, and 22.8 g, respectively, which corres
ponded to approximately 0.2% of the amount of each herbicide applied t
o the wheat. Of these losses, the majority (almost-equal-to 97%) was t
ransported during the first irrigation. Irrigation efficiency was 70%
for the first irrigation and mean nutrient fluxes in the resulting run
off were 0.79 and 1.92 g ha-1 h-1 for P and N, respectively, with corr
esponding weighted concentration means of 253 and 617 mug L-1. Herbici
de fluxes were 3.1, 9.8, and 23.3 mg ha-1 h-1 for dicamba, MCPA, and d
iclofop, respectively. Corresponding weighted concentration means were
1.0, 3.2, and 7.7 mug L-1. Nutrient and herbicide weighted concentrat
ion means were below Canadian Water Quality Guidelines for both drinki
ng and irrigation water. Maximum P and diclofop concentrations exceede
d drinking water guidelines, whereas those for dicamba and MCPA exceed
ed interim guidelines for irrigation water.