Field experiments were conducted in Oklahoma to determine the effects of row spacing, cultivar, seeding rate, and water or ammonium polyphosphate fertilizer injection in the row at seeding, on the competitiveness of hard red winter wheat with cheat. Decreasing row spacing from 23 to 8 cm increased yield of weed-free wheat at two of three locations and cheat-infested wheat in six of ten experiments. Increasing seeding rate from 265 to 530 seeds m-2 increased wheat yield. Injecting water at 20 ml m-1 of row at seeding did not increase wheat emergence or yield. Cheat seed production was not consistently suppressed by any one cultivar. Juvenile growth habit was unrelated to wheat competitiveness.

In field experiments, wheat row spacing, seeding rate, and herbicide treatment affected cheat seed content of harvested wheat, wheat yield, and net returns. No individual practice or combination of practices consistently increased net returns from cheat-infested wheat. Net returns frequently were increased and never decreased by applying metribuzin at 420 g ha−1 or chlorsulfuron + metsulfuron at 21.9 + 4.4 g ha−1 or by increasing the seeding rate compared to baseline inputs. The data indicate that herbicide rates should not be reduced when row spacing is decreased and/or seeding rates increased.

Experiments were conducted near Duke and Forgan, OK, on land enrolled in the Conservation Reserve program (CRP) that had been seeded to Old World bluestem (OWB) to evaluate tillage systems for returning CRP grassland to winter wheat production. Glyphosate controlled OWB 72% or less in no-till (NT) wheat. Disk tillage (DT) and moldboard plow tillage (MPT) for wheat seedbed preparation controlled OWB 87 and 99%, respectively, at Forgan and 96 and 100%, respectively, at Duke. At Forgan, OWB control in NT was higher when glyphosate was applied in July than when applied in May. Soil water content to a depth of 120 cm at planting was as high in DT and MPT without herbicide as in NT with 1,680 g ae/ha glyphosate. Within NT and MPT, glyphosate did not consistently increase soil water content compared to the respective nontreated checks. In DT, soil water content to a depth of 120 cm was greater following glyphosate at 1,680 g/ ha than without glyphosate. Wheat density was greater in DT and MPT than in NT. Compared to the NT no herbicide treatment, tillage tripled wheat yields. Wheat yields were often greater where glyphosate was applied before tillage. No-till wheat production immediately after CPR in Oklahoma without prior destruction of accumulated OWB residue does not appear feasible.

Field experiments were conducted in Oklahoma to determine the effects of winter wheat seeding date and cheat infestation level on cultural cheat control obtained by increasing winter wheat seeding rates and decreasing row spacing. Seeding rate and row spacing interactions influenced cheat density, biomass, or seed in harvested wheat (dockage) at two of three locations. Suppressive effects on cheat of increasing wheat seeding rates and reduced row spacings were greater in wheat seeded in September than later. At two other locations, increasing seeding rate from 67 to 101 kg ha–1 or reducing row spacings from 22.5 to 15 cm increased winter wheat yield over a range of cheat infestation levels.

In field experiments at three locations, wheat row spacing, seeding rate, and herbicide treatment affected Italian ryegrass control, wheat yield, dockage in the grain, and net returns. Diclofop at 560 or 840 g ai/ha controlled Italian ryegrass better than chlorsulfuron at 18 or 26 g ai/ha. Net returns were increased at all locations by diclofop POST at either rate and at two locations by chlorsulfuron PRE at either rate. Although increasing the wheat seeding rate reduced dockage at two of three locations, net returns were maximized by herbicide application alone without increased seeding rates or reduced row spacing.

A hammer mill removed most of the lemmas, paleas, and pericarps from cheat florets. Typically, the cuticular layer of the testa was the only remaining intact layer, and damage to the embryos and endosperm was severe. A roller mill disrupted tissue organization of lemmas, paleas, and outer layers of the caryopses primarily at the cuts. Large gaps between the aleurone layer and testa, between testa and pericarp, and between the scutellum and endosperm were created. In the field, germination of mill-damaged florets was reduced, and florets exhibited progressive degradation the longer they were buried. Nematodes and fungi penetrated the cuticular layer of mill-damaged seed. Attaching a hammer mill or a roller mill to a grain combine to treat cheat seed before it is returned to the field could provide a novel method of cheat control.

Several herbicides were evaluated as seed-applied treatments to determine the feasibility of controlling cheat by applying herbicide directly onto the cheat seeds during the wheat harvesting process and returning the treated seeds to the field. Seed-applied trifluralin reduced cheat emergence 80% in exploratory evaluations. In herbicide-seed mixing time and spray volume experiments, short mixing times were adequate, and spray volumes from 113 to 227 ml/kg seeds did not affect results. Herbicides applied with a sprayer-equipped auger reduced cheat emergence >90% and were as effective as herbicides applied with a rotary drum seed-treater. Increasing spray volume increased the efficacy of auger-applied treatments. Adjuvants did not improve the efficacy of seed-applied trifluralin.

This study assessed the tolerance of ‘Midlawn’ (Cynodon dactylon × C. transvaalensis) and ‘OKS 91-11’ (C. dactylon) bermudagrass to commonly used postemergence herbicides and compared visual assessment with vehicle-mounted optical sensing (V-MOS) for evaluating herbicide phytotoxicity. Two postemergence herbicides were applied to mature stands of Midlawn and OKS 91-11 at two and four times label rates, and seven postemergence herbicides were applied at standard and two times label rates. Visual evaluation and spectral assessments were made for turf color 2, 7, 14, and 21 d after treatment (DAT). Triclopyr and triclopyr plus clopyralid at 2× and 4× label rates caused significant damage on OKS 91-11 and Midlawn bermudagrass in both July and September experiments. MSMA at 2× rate and MSMA + metribuzin at 1× and 2× rate caused up to 73% color reductions that disappeared within 21 DAT in both cultivars. During July, 2,4-D plus mecoprop plus dicamba at the 2× rate caused at least 18% injury to Midlawn bermudagrass for 21 d. Metribuzin was safe at the 1× rate but caused significant injury for up to 7 d at the 2× rate. Imazaquin and halosulfuron-methyl each caused significant damage on one rating date. Pronamide caused no change in color regardless of rate or time of application. OKS 91-11 tolerated 2× rates of 2,4-D plus mecoprop plus dicamba better than Midlawn, but cultivar responses to other herbicide treatments were similar. V-MOS was effective for measuring green color reduction on bermudagrass turf. V-MOS and visual evaluation were linearly related (P < 0.01) at a strength of r = 0.58. Statistical results obtained using visual rating and V-MOS were the same in 86% of all cases.

Two field experiments were conducted in Oklahoma to determine whether changing wheat row spacing, seeding rate, and cultivar would reduce interference from rye. Wheat row spacing did not affect rye seed production. Averaged over row spacing, increasing wheat seeding rate from 67 to 134 kg/ha reduced rye seed production 21 and 25% in two experiments. At one site, grain yield of rye-infested wheat was increased 27 and 23% by doubling wheat seeding rate in 10- and 20-cm rows. Doubling the seeding rate of rye-infested wheat in 30-cm rows did not increase wheat yield. At a second site when data were pooled over row spacings, increasing the wheat seeding rate from 67 to 101 kg/ha increased yield of rye-infested wheat 21%, but yield was still 36% less than for rye-free wheat. In two additional experiments, rye seeds in harvested wheat were reduced 36% by increasing the wheat seeding rate from 60 to 162 kg/ha, whereas yield of rye-infested wheat was increased 82%. Nine cultivars were compared for competitive ability against rye in four experiments. Of 32 possible cultivar location situations, the rye-induced yield loss of ‘Jagger’ wheat was less than 16 other cultivar location situations, whereas the yield loss of ‘Triumph 64’ wheat was less than 10 other cultivar location situations. Mature wheat height, wheat yield, and wheat maturity classification were each negatively correlated to rye yield in infested wheat at two of four sites. Wheat plant density, head density, sunlight interception, and fall cover capability classification were each negatively correlated to rye yield at one of four sites.