Studies on the development of a sloping greenhouse using scaffold materials and a new horticultural production system on sloping lands with it

Sloping-land agriculture comprises about 40% of the total farming area in Japan. Japanese agriculture faces a number of serious problems, including depopulation, aging farmers, and increasing abandonment of farmland. These problems are rapidly intensifying, particularly in sloping-land agriculture, most of which occurs in hilly or mountainous areas. In contrast, sloping-land agriculture offers potential due to its more versatile characteristics compared with those of flatland agriculture. Intensive horticulture is expected to play an important role in the development of hilly and mountainous areas. It is necessary to improve the low productivity of conventional vegetable and flower cultivation with rain shelters. To promote the development of mountainous areas, a new horticulture production system for sloping-land agriculture is needed. Accordingly, to establish a new horticultural production system on sloping land, a sloping greenhouse has been developed to replace the simple covered rain shelter. The objective of this thesis is to establish a new horticultural production system for the sustainable development of mountainous areas. Therefore, a sloping greenhouse, which is a greenhouse that can be constructed on a sloping field, was developed. The characteristics of the thermal environment in a sloping greenhouse were elucidated to establish techniques for its control. The adaptability of a sloping greenhouse for the horticultural production of vegetables and flowers was investigated and a production technique was developed. This thesis consists of 7 chapters. Chapter I is the introduction, and chapter VII consists of an all-inclusive discussion. In the introductory chapter, the outline and the background of the problems of sloping land agriculture in a mountainous area and the objectives of the studies are described as mentioned above. Chapter II describes the characteristics of the thermal environment in a sloping greenhouse, which was constructed as a high pipe tunnel on sloping land, in order to develop techniques for its control. The thermal environment in a sloping greenhouse was elucidated and internal temperature changes were investigated. The adaptability of a sloping greenhouse to vegetable and flower production in a sloping field was also investigated. At first, the changes in internal temperature were compared in high pipe tunnels on flat and sloping land. The ventilation of the sloping greenhouse was superior to that of a standard greenhouse constructed on flat land. When the sloping greenhouse was ventilated by opening both end walls, the internal temperature gradient along the slope was maintained. However, the internal temperature gradient was reasonably uniform in a sloping greenhouse ventilated with side openings. The changes in internal temperatures were compared by sending hot air from one end to the other. Temperature gradients were observed in a standard greenhouse. However, the temperature distribution in the sloping greenhouse was uniform, that is, the temperature difference along the slope was below 1.0 degrees. It was also affected by the attached circulation fan. These studies showed that the thermal environment in a sloping greenhouse, constructed as a high pipe tunnel, could be controlled and that a sloping greenhouse was proper for vegetable and flower production in sloping fields. However, some problems were found when the sloping greenhouse, constructed as a high pipe tunnel, was adapted to an actual sloping field where tomatoes were cultivated with a rain shelter. For example, unavailable space remained around the sloping greenhouse because its configuration was not fitted to the non-rectangular shape of the sloping field. Further, the surface of the field by the side of the sloping greenhouse was affected by rain shed from the roof. To solve these problems, a sloping greenhouse using scaffold materials was developed. Chapter III describes the characteristics of the developed sloping greenhouse. The developed sloping greenhouse was adaptable to various configurations of the sloping field because of its free construction. It could also be constructed at a low cost with mass-produced scaffold materials, which made a strong structure. The 3-m high eaves of the developed sloping greenhouse allowed ventilators to be placed on all sides for smooth ventilation. Its construction also increased the internal space for working and cultivation. The area usable for cultivation in the developed sloping greenhouse was about 30% greater than that in a conventional rain shelter. Rain drops on the roof were drained along the slope of the roof; therefore, surface erosion disappeared. Chapter IV describes the thermal environment in a developed sloping greenhouse and the development of control techniques to establish a new horticultural production system on sloping land. The investigations were conducted in a farmer's sloping field, in which tomatoes had been cultivated with a conventional covered rain shelter. The differences between the internal and external temperatures of a developed sloping greenhouse were smaller than those of the sloping greenhouse constructed as a high pipe tunnel. This was because the eaves of the developed sloping greenhouse were higher than those of the high pipe tunnel, creating a larger ventilation area. A ventilator was attached between the roofs of 2 developed sloping greenhouses constructed on a terraced field; this connected the roofs like a step. When the ventilator between the roofs was closed, the internal temperature increased in the upper part of the developed sloping greenhouse, and a temperature gradient was observed. On the other hand, when the ventilator between the roofs was opened, the internal temperature decreased and became equivalent to the external temperature, even in summer. In other words, the temperature distribution was uniform. Chapter V describes the development of heating techniques in a developed sloping greenhouse and the characteristics of the thermal environment of a few configuration patterns. At first, the internal temperature distribution in the developed sloping greenhouse whose length along the upward slope was greater than that along the contour was investigated. Hot air was generated by an air heater, with or without polyethylene tubes and circulation fans. When neither polyethylene tubes nor circulation fans were used, the hot air around the air heater at the lower part of the slope seemed to be moving in a vertical direction, and then upward along the roof. The directional pattern of hot airflow was changed by means of polyethylene tubes, and the downward airflow was made parallel to the slope using circulation fans. In the case of a developed sloping greenhouse whose length along the contour was greater than that along the upward slope, the internal temperature distribution was made reasonably uniform by using air heaters with polyethylene tubes set at the lower end of the slope. Chapter VI reports on the availability and utility of a developed sloping greenhouse in sloping land horticulture. Farmers benefited by producing vegetables and/ or flowers year-round with a developed sloping greenhouse, which was developed as an alternative to a simple rain shelter. An economic analysis was conducted using simple calculations of data from when the farmer cultivated tomatoes and a newly introduced crop, sweet peas, in a developed sloping greenhouse. An economic advantage was found with the new cropping system, which increased the total turnover by 30% compared to a conventional cropping system. These studies were conducted based on regional production needs and undertaken in a project entitled 'Developing an intensive vegetable and flower production system using sloping-land resources in Shikoku'. In the region where these studies were conducted, the horticultural turnover and production area increased by 73.9% and 73.7%, respectively. The new production system with a developed sloping greenhouse, developed in these studies, has been extended to other mountainous areas. These studies contribute to the sustainable development of mountainous areas based on a new intensive horticultural production system.