2019 Volume 54 Issue 4 Pages 225-235
This study aimed to develop a technique for raising middle rice-seedlings under pooled conditions with application of organic fertilizer. We set up experimental plots in which rapeseed oil cake and ground fish were mixed with forest surface soil to prepare nursery soil in 2013 and 2014. Plots were kept fallow for 0, 1, 2 or 4 weeks. As fallow duration increased, the amount of mineralized nitrogen （N） within the nursery soil, which is mainly composed of ammonium-N, increased. The N contents of the seedlings, which were significantly （P<0.05） correlated with the mineralized N, showed a significant （P<0.05） positive correlation with rice seedling height, weight, and irregular seedling growth. All plots showed satisfactory growth for middle rice-seedlings based on leaf age. The plant height in the nursery boxes of the 4-weeks plot exceeded the standard value of 14 cm for representative middle rice-seedlings, although irregular seedling growth was observed. In contrast, the plant height in the 0-week plot was below 12 cm, the standard value for young rice-seedlings, and little irregular seedling growth was observed. It was concluded that rice seeding was the most appropriate in the 1-week plot, because leaf age was ranged from 3.4 to 4.5 of the standard value of middle-rice seedlings, the plant height exceeded 12 cm and there was little irregular growth. This indicated that the effect of fallow duration on the growth of organic middle rice-seedlings and mineralized N in organic fertilizer-amended soil could be used to set a guideline for the organic rice farmers in an Andosol area of Tochigi Prefecture.
