Soft red winter wheat cultivars were evaluated in field experiments in Georgia for tolerance to dicamba alone and mixed with 2,4-D. Treatments reduced ‘Florida 302’ yield more than ‘Florida 301’ or ‘Coker 983’ at Tifton in 1986. Mid-tillering Florida 302 wheat was more sensitive to treatment than fully tillered wheat. In 1987, dicamba plus 2,4-D applied at mid-tillering reduced yields of all cultivars in Watkinsville. Injury and yield reductions occurred primarily when mid-tiller treatments were applied to wheat that was planted 10 or 21 days later than recommended at Tifton or Watkinsville, respectively. When applied according to labeling, dicamba or dicamba plus 2,4-D use in Georgia soft red winter wheat can reduce grain yield.

Bifra is an annual noxious broadleaf weed of winter-sown crops in the Central Anatolia and Middle Black Sea regions of Turkey. This species has become more prevalent in wheat fields in the past three decades because of poor chemical control. Field experiments were conducted in Havza and Kavak, Samsun, Turkey, to evaluate the effect of cultivar and seeding rate on the competitive interaction between bifra and wheat at four bifra densities. Wheat grain yield increased with seeding rate, either in the presence or in the absence of bifra in both locations. Decreasing the seeding rate from 250 to 200 kg/ha or 150 kg/ha decreased wheat yield in the presence of bifra in all cultivars. The percentage yield decreases were different according to cultivars, although yields decreased in all cultivars. On the basis of the analysis of yield variables, data suggest that the relative competitiveness was ‘Bezostaja’ > ‘Momtchill’ > ‘Kate A-1’ = ‘Panda’. Bifra biomass and seed numbers were reduced not only by an increase in the wheat seeding rate but also by cultivars. Bifra seed production in Bezostaja, Kate A-1, Momtchill, and Panda were diminished 60, 53, 54, and 46%, respectively, at the seeding rate of 250 kg/ha compared with bifra alone at a density of 350 plants/ m2.

The digestion of polysaccharides from the wheat cultivars Caphorn and Isengrain was investigated, and the efficiency of an enzyme preparation was tested using the TNO gastrointestinal model (TIM-1). The apparent digestibility (AD) of carbohydrates was determined based on the measurement of organic matter (OM), total monosaccharides, reducing ends (RE) and end products (EP: glucose, maltose and xylobiose). The AD of the OM from Caphorn and Isengrain measured using caecectomised cockerels did not differ from that measured using TIM-1: 72·0 (sd 2·6) v. 70·6 (sd 0·6) % for Caphorn (P = 0·580) and 73·0 (sd 2·3) v. 71·1 (sd 1·9) % for Isengrain (P = 0·252). After the 6 h TIM-1 digestion, 41·4–58·9 % of the OM, RE and EP were recovered from the jejunal compartment and 18·3–27·1 % from the ileal compartment, while ileal deliveries and digestive residues constituted the remainder. A commercial enzyme cocktail tested at 0·2 μl/g of wheat improved TIM-1 digestibility of Caphorn and Isengrain polysaccharides: 3·9 % (P = 0·0203) and 3·4 % (P = 0·0058) based on the OM; 9·7 % (P < 0·0001) and 3·1 % (P = 0·031) based on the total glucose; 47·2 % (P < 0·0001) and 14·2 % (P = 0·0004) based on the RE, respectively. The enzyme cocktail improved the release of the EP for Caphorn (3·8 %, P = 0·008) but not for Isengrain ( − 0·8 %, P = 0·561). The higher efficiency of the enzyme supplementation on the digestion of Caphorn polysaccharides compared with Isengrain seems to be linked to the higher soluble carbohydrate contents and/or less ramified arabinoxylan of Caphorn.