To improve uniformity of growth of cabbage plug seedlings, we investigated the effects of seed size and sowing depth on the growth of seedlings.
1) Cabbage seeds divided by size (2-7mg by every 1mg) were sowed in plug tray at 10mm depth, and germination rate and shoot growth at cotyledon expanded stage were investigated.
(a) The germination rate of 100% did not obtained in each size. (b) Growth of shoot differed depending on the seed size. (c) The difference in seed size did not influence the uniformity of the shoot growth. The result of (b) and (c) clearly shows that uneven of the shoot growth in a tray is caused by not seed size but coexistence of different size of seeds.
2) We sowed cabbage seeds (5.0-5.9mg) into the sowing hole set in three depth of 5mm, 10mm, and 20mm, and growth of seedlings at cotyledon expanded stage were investigated. (a) The ratio of defective seedlings was decreased when sowed more than 10mm depth. (b) Growth of the shoot was inferior when sowed at 5mm or 20mm depth compared to 10mm because of the smaller root growth in the former, and because of the delay of emergence and increased dry matter partitioning to hypocotyl in the latter. These results indicates that the desirable sowing depth to be 10mm in plug nursery system in cabbage.
In concluding, we should note that it is possible to get the uniform growth of cabbage seedlings in plug nursery system by the seed selection of high accuracy of about 1mg and then sowing in the depth of 10mm.
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