Weed seed return and seedbank composition, with particular reference to common lambsquarters, were studied in four tillage systems established on a site near Fingal, Ontario. The tillage treatments were moldboard plow, chisel plow, ridge-till, and no-till. The cropping system was a cornsoybean rotation. Tillage effects on weed population composition were assessed after all weed control measures had been implemented. More than 60% of the weed seedbank was concentrated in the upper 5 cm of soil in chisel plow and no-till. The seedbank of the moldboard plow system was more uniformly distributed over depth and larger than the other systems. Common lambsquarters comprised more than 50% of the seedbank in all systems except ridge-till, but only dominated the aboveground weed population in chisel plow. Seedbank populations of common lambsquarters with moldboard plowing were greater than those with ridge-till and no-till, and chisel plow seedbank populations were greater than those in ridge-till. Chisel and moldboard plow systems generally had higher aboveground plant populations of common lambsquarters than the other two systems. Seed production per plant by common lambsquarters was equivalent among the four systems, but estimated seed production per unit area was higher in moldboard plow and chisel plow systems than in the other systems. Populations of common lambsquarters and similar species may produce more seeds and persist in moldboard plow and chisel plow systems; these weeds may produce fewer seeds per unit area and be easier to manage in no-till and ridge-till systems.

Experiments were conducted to determine the energy requirements and the most effective rotary tiller configuration for incorporating cyanazine {2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl] amino]-2-methylpropanenitrile} on an 18-cm band centered on top of the previous year's corn (Zea mays L.) ridge. When the rotary tiller was operated full width at a 10-cm depth, the least cyanazine concentration was found in the center of the ridge, and the greatest concentration was found between ridges. The treatment having the greatest cyanazine concentrations in the center of the ridge and the least in the inter-row between ridges consisted of a ridge cleaner, a cyanazine application, and the rotary tiller configured to till a. 30-cm strip on the center of the ridge with a rotor enclosure. Energy requirements for operating the rotary tiller increased as the depth of operation increased, and the 10-cm depth of operation required less energy than two passes with a tandem disk.

Atrazine detection in drinking water has raised questions about how to reduce levels of this herbicide. Field experiments were conducted near Ottawa, KS, to determine atrazine levels in runoff from grain sorghum grown under three tillage systems in three growing seasons. Atrazine at 1.12 kg ai/ha was applied several weeks before planting to areas where no-till (NT), ridge-till (RT), and chisel-disk (CD) systems were used, followed by an additional 0.56 kg ai/ha applied at planting. Surface-water runoff was collected from enclosed metal frames within each tillage system, and total water runoff and atrazine concentration were determined and used to compute total atrazine loss. Atrazine loss was less from CD than from the other tillage systems in years when atrazine was soil incorporated. Atrazine loss was highly variable among years and tillage systems. This suggests that other factors besides till systems influenced atrazine runoff.

Triazine-resistant (TR) kochia control with herbicides was evaluated in the greenhouse and in the field on ridge-till and ecofallow corn. In the greenhouse, bromoxynil, dicamba, linuron, and paraquat applied POST controlled TR kochia > 86%. Control of TR kochia with 2,4-D ester at 0.3 kg ae ha−1 varied with kochia biotype. In three ridge-till fields in 1985, atrazine plus fluorochloridone at 2.2 plus 0.6 kg ai ha−1 applied before planting plus a layby cultivation was the only treatment that reduced TR kochia biomass to < 750 kg ha−1. In 1986, atrazine plus dicamba at 2.2 plus 0.3 kg ha−1, atrazine plus fluorochloridone at 2.2 plus 0.3 or 0.6 kg ha−1 applied EPOST; atrazine at 2.2 kg ha−1 applied EPOST followed by an MPOST application of bromoxynil at 0.3 or 0.4 kg ha−1, or dicamba plus 2,4-D ester at 0.3 plus 0.3 kg ha−1; and an MPOST application of atrazine plus dicamba at 1.3 plus 0.5 kg ha−1, atrazine plus pyridate at 1.1 plus 1.0 kg ai ha−1, or pyridate plus cyanazine at 1.0 plus 1.7 kg ai ha−1 followed by a layby cultivation reduced kochia biomass to < 400 kg ha−1. In ecofallow corn, the only herbicide treatment that consistently controlled TR kochia > 95% 21 to 30 d after application was pyridate plus fluorochloridone at 1.0 plus 0.6 kg ha−1. Other treatments were less effective because kochia was too large or additional kochia emerged after application. When added to atrazine plus cyanazine, paraquat at 0.3 kg ai ha−1 plus dicamba was more effective than paraquat plus 2,4-D ester or paraquat alone in controlling TR kochia.