Atrazine [2-chloro-4(ethylamino)-6-(isopropylamino)-s-triazine] and propazine [2-chloro-4,6-bis(isopropylamino)-s-triazine] were applied to sorghum [Sorghum bicolor (L.) Moench] at 1.12 to 8,96 kg/ha on separate plots in 1960–63, 1965, and 1966 at 11 experimental locations across Nebraska. Winter wheat was seeded 15 months later. Atrazine, when applied to sorghum at recommended rates, did not affect subsequent winter wheat yields at North Platte on Holdrege loam and Holdrege silt loam. Occasionally, there was winter wheat stand reduction following atrazine and propazine at 4.48 and 8.96 kg/ha. At Alliance on Keith very fine sandy loam, winter wheat fall top growth was reduced by atrazine at 4.48 kg/ha in 1962 and 1963. Thinning of stand did not always reduce grain yields because of subsequent tillering. There was an increase in winter wheat grain yields in 1964 on plots treated with atrazine at 2.24 kg/ha in the sorghum in 1962. At Lincoln, on Sharpsburg silty clay loam, winter wheat yields were reduced from atrazine carryover in 1963 but not in 1964. Under most Nebraska conditions, atrazine applied to sorghum at recommended rates will not persist long enough to cause yield losses of winter wheat in a winter wheat-sorghum-fallow rotation.

Late spring tillage gave the most effective weed control in a winter wheat (Triticum aestivum L.)-fallow rotation. Downy brome (Bromus tectorum L.) populations in winter wheat on May 1 following plow, one-way, and sweep plow fallow treatments were 11, 22, and 24 plants per square meter, respectively. Tillages only in July or August with the sweep plow or one-way did not effectively control downy brome in the subsequent wheat crop. Yields of winter wheat were highest on the mold-board plow plots followed by one-way and sweep plow plots tilled in July and again in April. July tillages with the sweep plow or one-way resulted in the lowest winter wheat yields. During the fallow year, weed control in June was best on moldboard-plowed plots followed by May tillages with the sweep plow and the one-way. Quantities of plant residues on the soil surface prior to seeding winter wheat on sweep plow, one-way, and plot treatments were 896, 728, and 54 kg/ha, respectively.

Highly significant inverse yield-protein relationships in wheat grain were found at each level of applied N in an irrigation-N rate experiment on hard red winter wheat over a 3-year period at North Platte, Nebraska. The chief effect of applied N with adequate water was to increase yields, while the chief or entire effect with severe water deficits was to increase protein content. In intermediate situations, N increased both yield and protein content. In dryland experiments in 1966 and 1967 showing significant grain yield response to applied N, protein content also increased. Where little or no yield response occurred, N mainly increased protein content. Content of NO₃−N in the soil to a depth of 180 cm was also important in yield-protein relationships. Average protein contents of about 20 hard red winter wheat varieties at different locations in Nebraska in 1966 and 1967 were also negatively related to grain yields. Protein contents varied more widely among locations than among varieties at each location.

During the 2-week period before heading, a continuous growth record of irrigated winter wheat (Triticum aestivum) was obtained using a growth sensor attached to a leaf emerging from the whorl and a strip chart recorder. The growth rate was typically the greatest in the afternoon, with a maximum point usually occurring around sunset. The minimum growth rate usually occurred at the time of the minimum temperature, which on days without moisture condensation was around sunrise. The normal decrease in growth rate at night was arrested, or there was an increase in growth rate, when an increase in temperature or humidity occurred. A continuous growth record of a plant was obtained during a 6-day period that included a cold front passage followed by a late freeze and several days of subnormal temperatures. The temperature below which growth ceased was in the range 1 to 1.5C. On the day with the coldest morning, minimum temperature −0.5C (31F), considerable growth was made in the afternoon when the temperature rose to 23.5C (74F).