KAJIAN SIFAT TANAH PENENTU STABILITAS BEDENG PERMANEN SAWAH TADAH HUJAN PADA VERTISOL LOMBOK

• Main Authors: , Gusti Made Kusnarta, , Prof. Dr. Ir. Bambang Djadmo Kertonegoro, M.Sc.
• Format: Theses and Dissertations NonPeerReviewed
• Published: [Yogyakarta] : Universitas Gadjah Mada 2013
• Subjects: ETD
• Online Access: https://repository.ugm.ac.id/118763/; http://etd.ugm.ac.id/index.php?mod=penelitian_detail&sub=PenelitianDetail&act=view&typ=html&buku_id=58739
• Institution: Universitas Gadjah Mada

Permanent raised beds system has been proved to be superior in rainfed Vertisol of Lombok, compared to gogorancah system, but still needs improvement, especially in terms of the bed stability. This study aimed to assess the vertisol�s stability problems in order to establish stable permanent raised beds. To achieve the objectives a series of experiments was conducted, which consisted of four phases of experiments. The first experiment tested some dominant factors determining aggregate stability of rainfed Vertisol of Lombok. This first experiment was carried out using a method of semi-detailed survey, in which each sampling point represented an area of 50 ha. The second experiment tested three kinds of soil amendments: sand, cattle manure, and gypsum, to find out their effects on stability of soil structure. The third experiment tested design of beds to find out a suitable bed dimension for rainfed vertisol of Lombok. Finally, the fourth experiment was a field trial to test best results obtained from the second and third experiments. The results showed that the stability of soil structure, indicated by soil aggregate stability is determined by soil organic matter content, the COLE (coefficient of linear extensibility) value, clay content and lime content of Vertisols, but it is not significantly affected by exchangeable sodium percentage, ESP. The soil amendments sand and cattle manure, each at the rate of 20% and 15 ton ha-1 showed a good effect in improving soil aggregate stability. A good bed design for Vertisol of Lombok is bed with 20 or 30 cm height with an angle of edge of the bed is 60o. The results of the second and third experiments were examined further in the fourth experiment, i.e. a field experiment with rice grown on it. It was revealed that 6.38 ton ha-1 of rice was obtained from the treatment of the addition of 20% sand along with cattle manure at the rate of 15 ton ha-1 in beds with a height of 20 cm. The calculation of rice yield was obtained by considering the area reduction due to the presence of furrows. A good rice yeld under such treatments was followed by better soil conditions, such as an increase in soil aggregate stability, a reduction in COLE value, an increase in soil organic matter content, as well as a better rate of capillary rise. The most stable bed was also obtained under treatment of the addition of 20% sand and 15 tons ha-1 of cattle manure in beds with a height of 20 cm and the slope of bed edge of 60o. The reduction of width and height of bed in the treatment was 1.9 cm and 1.1 cm, each.