Effect of Mechanical Stress on Growth of Quackgrass (Agropyron repens (L.) Beauv.)

I. Effect of Treading Stress under Different Cutting Frequencies and Soil Compactions

Abstract

Growth of shoots from rhizome fragments of quackgrass was investigated in relation to cuttings and treadings during April to October, 1982, and growth of seedlings was also investigated in relation to cuttings, treadings and soil compaction in 1983. Cuttings or treadings with a small roller (80-kg weight) were conducted twice (60-day intervals) or six times (20-day intervals), respectively. Soil was compacted with the wheels of a large tractor (6.5-ton weight) before the experiment in 1983.
1) Penetration resistance in compacted soil increased three time as much as that in the control plot between 0 and 20cm depth. Treading effect was observed only between 0 and 5cm depth.
2) There was no difference between growth of shoots from rhizome fragments in 1982 and that of seedlings in 1983 for the above three treatments.
3) Total DM production per plant, mean distance of distributed shoots, and shoot number were decreased 49-65%, 72-81% and 42-87%, respectively, with increased treadings, and decreased 50-51%, 85-98% and 51-62%, respectively, with increased cuttings.
4) Mean distance decreased to 82%, while total DM production and shoot number increased to 127% and 114-459%, respectively, in compacted soil.
5) Depth of rhizomes in soil was 9.9cm in control soil, while 3.6-4.7cm in plots treated by treading or soil compaction.
6) It was suggested that rhizomes of quackgrass respond to treading stress by decreasing the breadth of their spreading and by increasing the number of shorter rhizomes produced.