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Soil hardness in no-tilled field with cover crop residue mulch and early growth of machine-planted soybeanHairy vetch and barley were cultivated for a cover crop at the University Farm of Niigata University, from October 1999. HV was killed by rotary mower (bush cutter) and roller, and barley was mowed by a reciprocal mower and flail mower on June 29, 2000. The soil hardness was reduced in the cover crop residue mulch field compared with the no-tilled field without the cover residue mulch, however, there was a difference in the amount of soil hardness reduction among cover crop residue mulches. In the field covered with rotary mower-killed HV, soil hardness was reduced most effectively. In the barley residue mulch field, some soybean seeds were not well settled in the planting furrows because the soil surface was hard. In HV residue mulch field, planting furrows were formed at the regular depth of 2-3cm, and the soybean seeds were well settled in the furrows. However, soil covering was insufficient in the HV residue mulch field. In addition, at the area with a large amount of HV residue, furrow formation was not complete. The frequency of stand establishment of soybeans in the cover crop residue mulch field was 50-60%, compared with the rotary tilled field without cover crop residue. The growth of soybeans in the field covered with rotary mower-killed HV residue was similar to that in the tilled field. It is necessary to establish the mechanical system in the soil covering after the seeds settle in the furrow when operating a sowing machine in a cover crop residue mulch field. |
