Abstract
We examined the effect of the number of soybean seeds dibbled per hole on the seedling emergence and establishment on crust-forming soil in order to improve the unstable emergence and establishment caused by the soil crust formed by drying after rainfall. The rate of hill establishment was markedly increased by dibbling over 3 seeds per hole compared with dibbling 1 or 2 seeds per hole, and the final rate of hill establishment was increased to 96—100% by dibbling over 3 seeds. Using an unbonded strain gauge transducer and null balancing, we measured the emerging force of the seedlings. The emerging force was doubled by dibbling 3 seeds per hole compared with dibbling 1 or 2 seeds. The maximum emerging force when 3 seeds were dibbled was 378g, which was 3.5 times as strong as that when 1 seed was dibbled, and 1.6 times as strong as that when 2 seeds were dibbled. Thus, the emerging force of the seedlings was increased rapidly by dibblig 3 or more seeds per hole. This may be why the rate of seedling establishment on the soil with a crust formed was high increased by dibbling over 3 seeds per hole.
