Weed competition is a limiting factor in warm‐season grass establishment often delaying the first forage harvest 2 or 3 years. Weed control with herbicides could reduce this competition resulting in more rapid grass establishment. Field experiments were conducted to evaluate the effect of atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] on weed control, warm‐season grass establishment, and forage yield during the seeding and following year. Several warm‐season grass species were spring seeded at locations having distinctly different soils. The soils involved were a Butler silty clay loam (Abruptic Argiaquoll) containing 3.8% organic matter and a pH of 5.2, a Crofton silty clay loam (Typic Ustorthent) containing 2.1% organic matter with a pH of 7.2 and a Nora silty clay loam (Udic Haplustoll) containing 2.8% organic matter and pH 5.8. Atrazine at various rates was applied preemergence shortly after grass seeding and at one site it was atso applied the preceding fall. Weed control, grass establishment, and forage yield were measured the year of seeding and the following year. Uncontrolled weeds during the year of seeding reduced stands and 1st year forage yields of big bluestem (Andropogon gerardi Vitman), indiangrass [Sorghastrum nutans (L.) Nash], sand lovegrass [Eragrostis trichodes (Nutt.) Wood], sideoats grama [Bouteloua curtipendula (Michx.) Torr.], and switchgrass (Panicum virgatum L.). Big bluestem and switchgrass tolerated preemergence atrazine applications of 3.4 kg/ha on the Butler soil. Big bluestem was less tolerant of atrazine than switchgrass on the Crofton soil. Some atrazine tolerance was present in indiangrass but not in sand lovegrass and sideoats grama. Seeding year forage yields of big bluestem and switchgrass were significantly increased by atrazine. Weed control during the seeding year sometimes resulted in higher forage yields the following year. Big bluestem and switchgrass can he readily established and produce substantial forage yields the year of seeding by using atrazine for weed control. This would make these grasses more attractive to farmers and ranchers.

Combinations of grass and legume mulches were planted in growing corn during the fall in 1985 and 1986, and the following spring no-till corn was planted into these living mulches. Mulch treatments consisted of a single species or grass plus legume mixtures. Fluazifop-P, 2,4-D, and atrazine were broadcast applied in late April to suppress the mulches and reduce their competition with corn. Chewings fescue and ladino clover competed least with dryland corn. Weed growth associated with chewings fescue and the ladino clover mulches was similar to that in the conventional disk-plant treatment, but corn yields were lower. Hairy vetch mulch was killed by 2,4-D. The winter rye mulch competed with corn and reduced yield.

An experiment was conducted at five locations in Nebraska to determine the extent of demise of weed seed in soil when seed production was eliminated from 1975 through 1979 in corn (Zea maysL.). Weed yields, weed seed production, and corn yields were determined under four weed management levels in 1980. Annual broadleaf weed seed were more prevalent than grass seed in cultivated soil throughout the study. The population of viable weed seed in soil declined 95% during the 5-yr period that weed seed production was eliminated. Weed seed buildup recovered to within 90% of the 1975 level during 1980 at Concord and Clay Center but remained low at Lincoln, North Platte, and Scottsbluff. Thus, seed longevity in soil was sometimes sufficient to withstand modern weed control methods and still reinfest a field after 5 yr of eliminating weed seed production. Corn yields were maintained 1 yr with minimum weed management effort following 5 yr of no weed seed production.

Relay intercropping soybean [Glycine max (L.) Merr.] into small grain has been suggested as a way to move multiple cropping further north, or as an alternative to conventional doublecropping in the lower Midwest. Our objective was to compare conventional monocrop soybean, grain sorghum [Sorghum bicolor (L.) Moench], and forage sorghum with relay intercropping and doublecropping in oat (Avena sativa L.) or winter wheat (Triticum aestivum L.). Field experiments were conducted from 1982 through 1986 in northeast Nebraska at 42.2° latitude, 97° longitude, further north and west than the usual multiple cropping regions. Skip‐row spacings every fourth drill row were left in the small grain where relay intercrops were later planted in 28‐ or 30‐in. spacings. All doublecropping followed removal of oat or winter wheat for forage, while with relay intercropping, cereals were harvested for grain. Weed control in a relay intercropping system also was investigated. Averaged over the eight location‐years, small grain yields with relay intercropping were reduced 34% compared to solid‐seeded monoculture yield because of wheel traffic damage and the skip‐row spacing effect. Average soybean yield with relay intercropping and doublecropping was 28% of conventional monoculture yield and relay intercropping was never superior to sequential doublecropping. Similar results were found with grain sorghum as relay intercropping and doublecrop yields averaged 15% of conventional grain sorghum. Relay intercrop and doublecrop forage sorghum yielded 37% and 54% of monoculture forage sorghum. Relay intercropping may make it possible at more northern latitudes to harvest cereal crops for grain rather than for forage as is usually done in a double‐crop system, which would be advantageous for cash grain producers. Satisfactory weed control was achieved in the relay intercrop system by applying herbicide on the green wheat or oats plus row banding herbicide at crop planting. Economic analyses indicated that monocrop systems generally provided greater returns than relay intercrop or doublecrop systems. Returns in the doublecrop system were more favorable than with relay intercropping, particularly with the wheat‐forage sorghum crops. Relay intercropping requires that many cultural practices be meshed for successful results.

Improved weed control systems in the absence of row cultivation were researched in order to take advantage of higher yields of soybeans [Glycine max (L.) Merr.] grown in narrow rows. Weed control systems, utilizing 13 pre‐emergence and two postemergence herbicides or herbicide combinations and the rotary hoe, were devised for the production of narrow‐row soybeans at two locations in eastern Nebraska during 1972–74. Experiments were conducted on a Sharpsburg silty clay loam (Typic Argiudoll) at Lincoln and on a Judson clay loam (Cumulic Hapludoll) at Concord, Neb. Research was undertaken to reduce labor, energy, and production costs while attempting to achieve better weed control, earlier ground cover, and higher soybean yields. Selective control of grass weeds in soybeans was more readily accomplished than the control of such large‐seeded broadleaf weeds as Pennsylvania smartweed (Polygonum pensylvanicum L.), sunflower (Helianthus annuus L.), and valvetleaf (Abutilon theophrasti Medic.). Reduced application rates of grass herbicides were used successfully in narrow‐row soybeans. Weeds were controlled in soybeans, with a number of herbicide treatments, with only minor early crop injury and no stand reduction. Average weed yields from all herbicide treatments were markedly lower than those on weedy check plots, but were not significantly different from the hand‐weeded plots. All herbicide treatments except one produced average soybean yields that were equivalent to those on the hand‐weeded plots. Available weed control systems can eliminate the need for cultivation in narrow‐row soybean production. Such systems of weed control should increase soybean yields, reduce production costs, require less labor and fuel, and improve ground cover needed to protect our soil from wind and water erosion.