AN IDEA FOR TRENCH HOUSE TO PROTECT CROPS FROM HOT AND STRONG WIND

Abstract

In the holes under the ground, temperature is low and soil is humid even in summer, and wind is soft. Aiming to use these phenomena to protect crops from hot and strong wind, experiments were conducted in Okinawa located in a subtropical region in Japan in 2000 summer. Trenches of north-south and east-west directions, deep (1.0 m) and shallow (0.5 m), with 1.2 m wide, were constructed. Cultural beds were prepared both sides of trench bottoms. Kidney bean (Phaseolus vulgaris L.) and turnip (Brassica Rapa L.) were sown on beds in trench and a conventional flat bed mid summer. Trench beds were superior in germination and growth to the conventional bed. Deep trench beds were superior in germination and growth to shallow ones. In beds of the north-south direction trenches, the east sides and the west sides were superior in germination and growth, respectively. In beds of the east west direction trenches, the south sides were superior in germination and growth. The kidney bean yield was remarkable high in the west sides of the north-south direction trenches, and the south and north sides in the 1.0 m deep trench of east-west direction. The air temperature difference was not found between trenches and the conventional. However, the soil temperature was lower and soil water was more in the trenches than in the conventional. In beds of the north-south direction trenches, soil temperature in the west side was hastened to increase, and that in the east side delayed increasing. In beds of the east-west direction trenches, soil temperature in the south side were lower than in the north side. The soil water contents were higher in the trenches than in the conventional, in the deep trenches than in the shallow ones. In the trenches of the same depth, soil water contents were as following, the east-west direction south sides > the east-west direction north sides > the north-south direction east sides = the north-south direction west sides. Trenches soften wind velocities. Soil temperatures increasing in trenches were suppressed by shading and water evaporation. Soil water, the cooling source, was transferred from soil beside the trench to the trench bottom. Using and improving the heterogeneous environment in trenches, crop would be protected from hat and strong wind without energy use and with less money. We propose a trench house equipping a movable roof to protect crops from heavy rain and extra strong wind.