Abstract
In this experiment carried out in 1957, using concrete pots of 90 cm square, it was shown that emergence of Alopeculus aequalis differed in number according to the degree of fineness in harrowing (i. e. the size of soil clods) and of packing of soil, and its mechanism was clarified. In the coarsely harrowed plot (clod size 1-5 cm) the number of seedlings was reduced to approximately 60 % of that of the finely harrowed plot (clod size smaller than 1 cm) (Fig. 1). In the former plot, average emergence depth (Fig. 2) was shallower and more viable buried seeds remained than in other plots. Most of these viable seeds were placed in the inner portion of the soil clods and in the lower layer of soil. Also, the number of seedlings was decreased by soil-packing to abbut 80 % of that of the non-packing plot (Fig. 1). The packing was effective to suppress the emergence from the lower layer of soil in the finely harrowed plot and from the upper layer in the coarsely harrowed plot (Fig. 3). In the inner portion of the large clods or under the packed soil, air porosity of soil was low and then it was proved that there was the high correlation between air porosity and number of seedlings or average emergence depth (Fig. 4).
