The effects of weed management under coffee trees on soil physical properties were investigated during four-years experiment in Lampung, South Sumatra, Indonesia. The treatments were as follows : coffee without cover crop (clean-weeded plot); coffee with Paspalum conjugatum as cover crop (Paspalum plot) ; and coffee with natural weeds which was dominated by Clibadia surinamense (natural weeds plot). Weed management was done every two weeks by clearing all the weeds in clean-weeded plots, and cutting the weeds around the coffee trees with diameter 1 m for the weedy plots (Paspalum plot and natural weeds plot). The results showed that a better soil physical condition was achieved when the soil surface under the coffee trees was covered with Paspalum conjugatum. The average soil organic-C in the soil profile of Paspalum and natural weeds plots were 32 g/kg and 27 g/kg respectively, which were higher than in clean-weeded plot which had 20 g/kg of organic carbon. A smooth horizon boundary was found in Paspalum plot due to the abundance of its roots which was also enhancing soil color more black, and the process of wetting and drying. A strong aggregate stability was found at the Paspalum plot as indicated by penetrometer readings as well as water stable aggregate index. Two centimeters thickness of hardpan which was developed at Paspalum plot made the water movement from upper layer inhibited during the dry season. The highest porosity was found at Paspalum plot (0.64 m3m-3) followed by natural weeds plot (0.62 m3m-3) and clean-weeded plot (0.60 m3m-3). However, the average available water content was not different between Paspalum plot and natural weeds plot, and only 0.15m3m 3 higher than that of clean-weeded plot. The permeabilities varied among the treatments, and this variance was biggest in the upper layer of Paspalum plot.
the effects of mixing tillage by rotor-bucket machine on improvement of subsoil under these fields. Some of the results obtained are as follows :
1. Thickness of both A and B horizon of the soil profile increased by mixing tillage by rotor-bucket machines.
2. The content ratio of soft-rocks decreased by this treatment and the hardness of soil also decreased.
3. Physical properties throughout the soil profile were improved especially in three-phase distribution.
4. Mixing tillage by rotor-bucket machine enhanced the growth of fine roots and yields of tea.
A prototype system for monitoring soil information was developed using a cellular phone. We named the system SIMS-CP (Soil Information Monitoring System using Cellular Phone). In the prototype system, soil water content and soil temperature at six depths in a field were monitored from a remote laboratory. The system will be quite promising as a tool that virtually converts a field experiment into a laboratory experiment. The present paper gives an outline of SIMS-CP and its potential applications in field science.
Acid sulfate soils are one of the problem soils worldwide, and are found mainly in the tropical mangrove forests and mangrove swamps of Southeast Asia and Africa. Together, these areas account for about 12 million hectares of acid sulfate soils. But there is a shortage of arable lands in these areas, hence, acid sulfate soils are studied for agricultural purposes. While many studies have already made clear the mechanism of soil acidification, it is still unclear how bacterial actions are influenced by soil physical conditions. Additionally, clarifying the mechanism of changes in iron formation, leading to the development of acid sulfate soils may contribute to the understanding of the phenomenon. Studies on changes in iron formation in paddy soils, for example, could become an interesting research area in soil physics. This research area requires interdisciplinary collaboration and has good possibilities of advancing. Likewise, other bacterial studies in croplands will greatly supplement studies in acid sulfate soils. In this paper, a number of studies on acid sulfate soils conducted in Japan and other countries are introduced and possible research areas in the future are identified.