Published online by Cambridge University Press: 12 June 2017
Four herbicides were applied at 6-month intervals, and incorporated by disking, to desert cropland soils at two locations. Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was applied at 0.9 kg/ha; and 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) were applied at 1.8 kg/ha. Following treatment the soils remained fallow without irrigation for 24, 18, 12, 6, or 0 months before planting eight crops. Sugarbeet (Beta vulgaris L.) growth was affected 24 months after applications of trifluralin. Growth of two or three crops at each location was affected 18 months after application of prometryne. Residues of atrazine and diuron usually caused greater injury to most crops than did prometryne or trifluralin. Six months after the first planting four additional crops were planted. In plots planted 30 months after treatment diuron reduced sorghum (Sorghum bicolor (L.) Moench) stands by 70% and reduced fresh weights of three crops at Mesa. Trifluralin reduced fresh weight of sorghum by 80% at Yuma. Crops responded differently to herbicide residues at the two locations. Injury to crops was most severe at Mesa despite higher rainfall during the fallow period at this location.