In Hokkaido, a f our-crop rotation system consisting of wheat, potato, sugar beet, and beans was executed for vegetable production. The number of farm households has decreased, whereas the area of farmland per farmer is rapidly increasing. Under these circumstances, introduction of new technologies for avoiding farm work competition and working time are important for maintaining crop rotation. In the present study, we first presented an outline of the farm work competition in field crop rotation and farm work involved in the production of each major crop, and provided information of the techniques corresponding to the farming problems in crop rotation. In next, we gave the information of spreading novel technologies, e.g., the use of highperformance harvester, automatic steering tractors, and precision farming, and developing support systems. Finally, we discussed the new subjects of farm work and farming awaiting solution in the future in Hokkaido.

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Lack of management and years of conflict have resulted substantial stress over natural and seminatural ecosystem in Bamyan, Afghanistan. In this study, we evaluated the spatio-temporal changes in land cover in Bamyan from 1990 to 2015 and lack of land management issues. To achieve the objective a comprehensive field work survey was conducted with 97 local people and farmars with a framed questionnaire. 88 local people and farmars stated that land cover has changed with 30 years. Both respondent groups specified the reasons as population increase, overuse of resources, overgrazing, shrub collection, drought and mismanagement. The result of interview with governmental organizations and NGOs demonstrated, land degradation is acute problem due to vegetation cover removal, overgrazing, dependency on natural resources, fodder collection and cultivations on steep slopes. Moreover, we applied the Maximum Likelihood Classification method to produce land-cover maps using Landsat images of 1990, 1999, 2008, and 2015. Defining grid cells with unique cell IDs allowed us to quantify spatio-temporal changes in land-cover classes. Rangeland decreased from 60.2% to 37.9%, accompanied by rapid increases in bare soil and built-up classes. This suggests the extension of anthropogenic influence into surrounding natural and semi-natural ecosystems. Statistical comparison of the land-cover changes in 0.81 km2 grid square cells showed that the decrease in rangeland was strongly negatively correlated with that of bare soil. Furthermore, around Bamyan city, the expansion of builtup areas was strongly positively correlated with that of plantation areas, and negatively correlated with bare soil increases. This is due to the rapid socio-economic changes between 1999 and 2015. The result indicates that years of conflict, absence of management, and socio-economic change caused land cover change in Bamyan between 1990 and 2015.

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The mechanical har vesting of spinach for processing use is becoming common in Japan. We investigated the effects of cultivars and cultivation conditions, including the supplemental application of fertilizer after first harvesting and the time of first harvesting, on leaf yield and appearance quality in ratoon cropping, which utilizes regrowth of spinach foliage, in Miyazaki Prefecture, which is the largest spinach producing center in Japan. Regarding whole plant weight at harvest, there was no significant difference between cultivars, but the ratio of foliage weight cut at harvest to whole plant weight was consistently higher in the upright cultivar‘ Kuronosu’ than in‘ Sapuraizu7’ in both the first and second cropping (ratoon cropping) with supplemental fertilizer application. In‘ Kuronosu’ cropping, the supplemental fertilizer application after first harvesting increased the foliage weight at the second harvest and percentage of good leaves for products. In addition, the longer growing period increased the foliage weight at the second harvest. Therefore, in a mechanical harvesting system with ratoon cropping, the following measures are recommended: upright cultivars should be grown; when the plant length reaches approximately 40 cm, spinach should be initially harvested to ensure adequate growth period for the second harvesting; and supplemental fertilizer should be applied after first harvesting.

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Gramineae and Leguminosae are used as summer cover crops in monoculture; however, their biculture system has not been studied well. This study compared the effects of biculture of summer cover crops on biomass production and nitrogen leaching in the fields of the Field Science Education Center, Ibaraki University. The fields were seeded using different seeding ratios of guinea grass ( Panicum maximum Jacq. cv. Natsukaze) and crotalaria (Crotalaria spectabilis Roth. cv. Nemaclean). We prepared six combinations of the biculture in the following seeding ratios: 100:0 ( guinea grass monoculture) , 75:25, 50:50, 25:75, 0:100 ( crotalaria monoculture) , and 0:0 ( bare). In 2016, the aboveground biomass of the cover crop, the C / N ratio, and the amount of absorbed carbon were highest in the harvested guinea grass monoculture crop compared with the other seeding ratios. In 2017, the aboveground biomass in the guinea grass monoculture crop and in the 75:25 biculture crops were almost similar, while it was lowest for crotalaria monoculture crop. On the other hand, the C / N ratio was the highest in the crotalaria monoculture crop. The concentration of nitrate in the soil decreased significantly due to the cover crop uptake in the both years. The results of these two years showed that it is possible to increase the decomposability of the residue and promote the supply of organic matter necessary for agricultural productivity of the land, securing biomass production, by lowering the C / N ratio.

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