Stem emergence of Dactylis glomerata L. and Rumex obtsifolis L. and total yield of grasses as affected by covering the seed-bed with a mixture of composts, fertilizers, seeds and soil in directly drilled pasture sward

This study was designed to examine stem emergence of Dactylis glomerata L. (abbreviated to Dg) and Rumex obtsifolis L. (abbreviated to Ro) and total yield of grasses as affected by covering the seed-bed with a mixture of composts, fertilizers, seeds and soil in directly drilled pasture sward. The objective was to examine a mechanism for stem emergence of Dg making a contribution to total yield of grasses by the ecological control of growth and germination of Ro in the renovation of degrading pastures. The experiment was carried out in the degrading pasture sods that had been covered with Ro since the establishment twenty and several years ago in the field at Kuju Agricultural Research Center of Kyushu University located at an altitude of 950 m in the middle of Kyushu highland area. Three experimental treatments were set up. The treatment No. 1 was drill seeding covering the seed-bed (3.45 cm wide and 3.53 cm deep) with a mixture of composts, fertilizers, seeds of Dg and commercial clay soil (5.45 cm wide and 6.55 cm thick) on October 1, 2001. The treatment No.2 was the drill seeding without covering the seed-bed, where there was a dressing of fertilizers and seeds without composts and commercial clay soil on October l, 2001. The treatment No.3, which was the control, was broadcasting the mixture of composts, fertilizers, seeds of Dg and commercial clay soil over the pasture sward on October 1, 2001 without drilling. In these experiments, measurements were made on May 2, 2003 for the number of stems of Dg in the area of 5.45 cm x 100 cm and total dry matter yield per m2 of grasses. The number of stems of Ro per m2 was measured on September 6, 2001 (about one month before drilling on October l), and then on May 2, 2003 (about two years and a half after the drilling on October l, 200l). The temperature and precipitation in the field were also measured during this experimental period. The number of stems of Dg in the area of 5.45 cm x 100 cm on May 2, 2003 increased significantly (p0.01) in the order of control (4.1) non-covering (7.63) covering (9.29). The percentage of Ro stems in total stems per m2 showed changes between September 6, 2001 (about one month before drilling) and May 2, 2003 (about two years and a half after the drilling), covering (86.6 %) non-covering (88.0 %) control (130.8 %) with 63 % lower (p0.01) in covering compared with control. The total dry matter yield of grasses per m2 on May 2, 2003 showed a significant increase (p0.01) in the order of control (261.5g) non-covering (448.9g) covering (655.3g), 250 % difference between covering and control. The results from this study suggested that the method of drill seeding covering the seed-bed with a mixture of composts, fertilizers. Dg seeds and soil increased the number of Dg stems and total dry matter yield of grasses by decreasing the number of Ro stems in the directly drilled pasture sward. The present method would make a contribution to simple methods of grassland renovation technology in terms of recovering vegetation by the ecological control of Rumex obtsifolis as weed in the middle of Kyushu highlands area.