Mow-kill regulation of winter cereals for spring no-till crop production

Field studies determined the influence of developmental stage on mow-killing of winter wheat and rye. Both crops were clipped at either three or four different growth stages in 1992 and 1993. When mowed at first node, wheat biomass was 4350 and 1970 kg/ha in 1992 and 1993, respectively. At this stage, primary tiller apices were below 10 cm and regrowth was vigorous. Mowing prior to 75% heading consistently yielded more than 1000 kg/ha regrowth 8 wk later. Wheat cut after flowering produced 15 460 and 9160 kg/ha dry matter in 1992 and 1993, respectively, but less than 30 kg/ha total regrowth. At first and second node, rye produced 4440 and 1800 kg/ha biomass in 1992 and 1993. When mowed before boot, more than 50% of the total rye biomass was due to regrowth. Rye mowed at boot yielded 6940 and 3740 kg/ha in 1992 and 1993 respectively, and regrowth measured 780 and 910 kg/ha 8 wk later. Mowing after flowering resulted in no measurable regrowth. Soil temperature and PAR were affected by mow-kill date and biomass. Biomass at first mowings (first and second node) in both wheat and rye reduced seasonal soil temperatures 3.5 C compared to bare soil temperatures; while biomass at kernal-filling lowered temperatures 6.0 C. Measured 8 wk after mowing, first node mowings absorbed between 55% and 70% PAR, while plants mowed at kernal-filling absorbed less than 5%. (author)