Sustainable quality herbage production is related with defoliation management of the dwarf variety of late heading type (DL) of napiergrass (Pennisetum purpureum Schum.) in northern Kyushu, Japan. The optimal closing date in autumn for sustainable use and the optimal defoliation stage for maximizing quality herbage production with silage processing were ascertained for DL napiergrass transplanted in Shimabara, Nagasaki Prefecture in late May in 2004, 2005, and 2006. Closing dates were set at two levels in mid-late October and mid-late November for plants established in 2004 and 2005, showing higher winter survival for mid-late November closing-cut. Nutritive values and fermentation quality of round-bale silage were examined at three growth stages based on plant length in 2008 for plants established in 2004 : at or below 110cm, 120cm, and above 130cm. Results show that harvest at the 150cm of plant length is the optimal for making good quality silage processing, with maintaining high dry matter yield and good plant quality. Suitability for two sites on Kyushu’s main island and two sites on remote islands was examined for June or July transplanting in 2007, showing high winter survival at 95%.

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The forage paddy rice (Leaf Star, Oryza sativa L.) fertilized with different applications of nitrogen fertilizer and/or cattle manure compost was ensiled with or without lactic acid bacteria, and their chemical composition and fermentation quality of silage were investigated. Nitrogen fertilizer was applied at 0, 12, 24kg/10a, respectively. Additionally manure was applied at 0, 2 or 6t/10a. Strain Chikuso-1 (Lactobacillus plantarum) was used as the lactic acid bacteria inoculant for silage preparation. Nitrogen application increased moisture and crude protein contents of forage rice silage, promoting volatile basic nitrogen and butyrate production during silage fermentation. In contrast, manure application had no effect on silage fermentation although crude protein content was increased. The addition of lactic acid bacteria did not inhibit the butyric acid production of silage treated with nitrogen application and the fermentation quality did not improve under high fertilization condition. However, in the case of supply of fertilizer up to nitrogen application 12kg/10a and manure application 2t/10a, when the silage prepared with lactic acid bacteria, the lactic acid content was increased and the fermentation quality was improved.

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We investigated the effects of applying composted cattle manure on the leaching of nitrogen, phosphorus, and potassium from lysimeter paddies （W0.5×D1.0×h0.5m）, where forage rice （Oryza sativa L.）was cultivated from 2003to 2009. In 2007, we did not cultivate rice. In the years when rice was cultivated, nitrogen leaching increased with amount of the manure applied when adequate rainfall occurred between the application of manure and the commencement of irrigation. The amounts of nitrogen leaching from paddies during winter were equal or smaller than during the cultivation period. The amount of nitrogen leaching from the paddy to which 6kg/m² （6M-plot） manure was applied was the highest. The amount of nitrogen leaching in the year without cultivation was significantly high. The effects of cultivation on phosphorus and potassium leaching were smaller than on nitrogen. Although the rice yield increased in the 6M-plot, the nutrients loss and the accumulation in the soil were the greatest. In the 2M-plot, the yield was higher than that in the 0M-plot, and nutrients loss and accumulation in the soil were as high as those in the 0M-plot. These results suggested that annual manure application at 2kg/m² was preferable.

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Earthworms can convert the organic phosphate compounds into ones available for plants. The arbuscular mycorrhizal fungi (AMF), which are symbionts that colonize plant roots, can promote the growth of host plants by absorbing and then providing phosphorus to plants. To investigate the effects of AMF and earthworms on pasture growth, with bahiagrass (Paspalum notatum) as the host plant, the earthworm Eisenia fetida, and two AMF species, Gigaspora margarita (Experiment 1) and Rhizophagus irregularis (Experiment 2), were used. There were four experimental treatments: control (C), earthworm addition (E), inoculation with AMF (M), and both AMF inoculation and earthworm addition (M+E). In the case of G. margarita, at 9 weeks, the dry weight, phosphate absorption, and nitrogen absorption of the bahiagrass were significantly larger with M treatment than with E or C treatments; it was largest with M+E treatment. In the case of R. irregularis, they were significantly larger with AMF inoculation. On the whole, the plant growth tended to be larger in the order: C, E, M, M+E. These results suggest that the growth of the grasses were promoted by AMF and earthworms coexisting in the soil rather than by AMF or earthworms alone, although the size of the effects were different, depending on the AMF species.

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