We investigated the influence of the placement and amount of the applied calcium superphosphate on the early growth of direct-sown onions (Allium cepa L.) on Andosols. The effect of localized fertilizer application was compared with broadcast application. The placement of calcium superphosphate below the onion seed may affect the early growth of onions, especially in the early growth stage. Fertilizer placed 0 to 4 cm below the seed was more effective than broadcast application. Seedling emergence based on the amount of calcium superphosphate 0 cm below the seed was not affected by the amount of calcium superphosphate in our experiment. The soil solution EC value of localized calcium superphosphate did not affect seedling emergence. These results suggest that the most effective placement of phosphatic fertilizer is directly below the seeds, and the effective amount to be applied is 30 or 45 kg・10 a

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We studied the germination and sprouting of onion seeds that had been immersed in a phosphorus solution from 0 to 5.0%. In cases of localized fertilization, we hypothesized that the phosphoric acid concentration in the soil would prevent or impede germination. Furthermore, we investigated the impact of fertilization with superphosphate on the emergence of onions. Fertilizing treatment with phosphorus of 4.66 g per pot decreased the emergence rate compared with no fertilization of 7 days after seeding, but afterwards it had no negative effect. The results suggest that the effects on germination and rooting of onion seeds immersed in a phosphorus solution are limited to just after germination. Therefore, even if seeds come into contact with superphosphate with localized fertilization, the effects on the emergence of onion decline over time. When superphosphate was locally applied, at a rate of 50 to 200 kg phosphate content per ha, the emergence rate 10 days after sowing was not affected. Key Words：local

The effects of interruption of alternating cropping of corn and Italian ryegrass with one or two years of soybean or white radish cropping or fallowing on the growth and yield of these crops in succeeding seasons were examined. Experiments were conducted in the fi eld of andosol in Ibaraki, Japan, where corn and Italian ryegrass were alternately cultivated for a long period. The effects of the interruption for one year and that for two years were not distinguishable. The corn yield in the first season after the interruption with soybean cropping was higher than that in continuous alternating corn / Italian ryegrass cropping. However, the corn yield after interruption with white radish cropping or fallowing was similar to that in continuous alternating cropping, although it depressed the early growth of corn and the colonization of arbuscular mycorrhizal fungi. Such effect of interruption was observed only in the fi rst season after the interruption. The interruption of sequential cropping did not affect the yield of Italian ryegrass in the second season; neither did it affect the yield of maize in the third season. Our results indicated that the effect of short-term interruption of sequential cropping of corn / Italian ryegrass was observed only in the fi rst season after the interruption.