Often intellectually disabled persons cannot engage in agriculture work because farming is a complex process composed of a combination of simple tasks. This study assesses whether a conventional farming method can be universalized by decomposing the tasks in each complex process into elementary ones. As a method, each process in the cultivation of Yamato Mana, a traditional leafy vegetable in the Nara prefecture, is performed by decomposing it into a process that can be executed by one operation or repetition, which is called elementary process decomposition in this paper. The germination number and harvest are compared with those from the conventional method. In addition, the data describing the state of each work process by high school students at Nara-nishi Special Needs School for Intellectual Disabilities are analyzed. Both the number of germinated seeds and the harvest in terms of weight and spread of foliage are significantly larger at 0.1, 0.1, and 1% level respectively in the cultivation via elementary process decomposition than those in the conventional method. Analysis reveals three findings. Elementary process decomposition and the use of assistance tools make it easier to understand the work content of each process. Repetition improves work accuracy. Sharing roles in the work process is easier for students. Consequently, elementary process decomposition increases the number of tasks that students with intellectual disability can do independently compared to the conventional method.

Cherry tomatoes require a longer harvesting time than large-sized tomatoes. Therefore, the labor and load of cherry tomato harvesting should be reduced. The characteristics of labor-saving harvesting procedures, such as the detachability of calyx and fruit stalk, differ with the cultivars of tomatoes for cherry tomatoes for table. In the present study, we investigated the time required for harvesting tomatoes with or without calyx. As a result, the time required for harvesting tomatoes without calyx was equivalent to or significantly shorter than that with calyx. The time required for harvesting tomatoes with calyx was longer for ‘Rosso Neapolitan’ and ‘Aiko’, with smaller aspect ratios. These results suggested that harvesting without calyx contribute to the reduction of labor and load in cherry tomato production.

Japan ranks 14^th on the list of total sweet corn production in the world; however, the ranking decreases to 24^th in terms of yield, which represents the amount of production per hectare. This low production efficiency might be due to the conventional Japanese cultivation method; therefore, we applied drip fertigation systems in open fields to increase the yield of sweet corn. Previous studies have shown that the yield of sweet corn can be increased through drip fertigation and that the key factor is nitrogen; however, information about how sweet corn reacts when receiving excessive nitrogen is limited. Therefore, the purpose of this study was to compare the performance of sweet corn using various levels of nitrogen fertilizer with drip fertigation and determine the optimum amount of nitrogen required to produce the maximum crop yield. Six different nitrogen application levels and three different fertigation frequencies were set: (i) 1.5 kg ha^-1 day^-1, fertigation four times per day (N1); (ii) 15 kg ha^-1 day^-1, fertigation four times per day (N2); (iii) 30 kg ha^-1 day^-1, fertigation four times per day (N3); (iv) 1.5 kg ha^-1 day^-1, fertigation once per day (N1-a); (v) 1.5 kg ha^-1 day^-1, fertigation once per three days (N1-b); (vi) no drip irrigation (rainfed), and 130 kg ha^-1 with local practices using granule fertilizers (Control). The results showed that the yield of sweet corn can be increased 2 to 2.5 times higher than that of conventional rain-fed cultivation practices if plenty of nitrogen fertilizer is applied through drip fertigation. The results also indicated that the yield reached a plateau between N2 and N3, so the N3 level of fertilization would cause more harm than good, especially for the environment. The frequency of irrigation was found to be an important factor for yield, especially during the dry season, and crops should be irrigated daily.

The downsized model of the sugarcane harvesting and transportation system in Kita Daitojima Island and Minami Daitojima Island was analyzed for its economic efficiency using a simulation method. To advance the replacement of aging machinery, it is advantageous to proceed mainly with large and medium model transportation trucks that also serve as escorting harvesters, or medium models using high-dump type escorting carrying machines. It is possible that the current operational costs can be maintained. Improvement of sugarcane yield and the rate of work would lead to cost reduction, and if there are technologies and mechanisms available that can control the crushing amount per day in the sugar mill, it is likely that a more flexible harvesting and transportation system can be constructed. It is important to increase the throughput of each machine throughout the sugarcane season and to take various countermeasures in the direction of reducing the idling time.

In order to elucidate the effects of soil compaction by machines such as sugarcane harvesters on the early growth of the sugarcane stalk and root system, an examination using a root box was conducted with soil density adjusted. As hypothesized, growth and dry weight of roots tended to be suppressed as soil density increased. However, there was no clear negative relationship between soil density and growth conditions with regard to the length and diameter of the stem, and different results were obtained in the underground and above ground parts. In addition to consolidated soil being prone to stagnant water in the upper part due to the low penetration capacity of irrigation water, the root system was also relatively concentrated in the upper part. This was thought to have the advantageous effect of absorbing moisture. Since research results have shown that soil compaction is not only a negative factor, it is necessary to continue research in the future, including reevaluation tests in the warm season.