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Publikasi 13: The Benefits of Biochar on Rice Growth and Yield in Tropical Riparian Wetland, South Sumatra, Indonesia


Abstract
Biochar improves soil quality. However, most biochar research has focused on aerobic soil conditions. The objective of this research was to evaluate the agronomic benefits of applying biochar on unfertilized rice crop, cultivated under transitional anaerobic soil conditions during early vegetative growth phase, and gradually drying out to fully aerobic at harvest time. This transitional condition is typical during the rice growing season of the tropical riparian wetlands in Indonesia. Biochar was applied in the form of fine powder at rates of 0, 0.4, 0.8, and 1.2 Mg.ha-1; no inorganic fertilizer was applied. The research was conducted on a farmer’s paddy field at Pemulutan Ulu Village, South Sumatra, Indonesia from July to November 2016. Results indicated that applying biochar at rates up to 1.2 Mg.ha-1 increased rice yield, but restrained shoot elongation rate and plant height. During the vegetative growth phase, applying biochar significantly increased the number of tillers, leaves, shoot dry weight, and root dry weight. Biochar significantly affected the following yield components: number of tillers, percentage of productive tiller, number of grains per panicle, panicle density, percentage of filled grain, and weight of 1,000 grains.

Full article can be downloaded here: 2018 CMUJ Natural Sciences 17(2)_111-126 Benefits on rice

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Publikasi 12: Steady shallow water table did not decrease leaf expansion rate, specific leaf weight, and specific leaf water content in tomato plants


Abstract
It was presumed that shallow water table restricted leaf growth and some water-related parameters; therefore, they can be used as indicators of plant stress due to the water table condition. Objective of this research was to evaluate morphological stress indicators in tomato plants exposed to shallow water table. The research was conducted in two stages: (1) developing reliable LA estimation model from June to September 2016; as pre-requisite for (2) calculating and evaluating the morphological indicators for stress due to shallow water table treatments, conducted from February to May 2017. Treated plants were placed inside experimental pools. Each treatment was done by partially submerging growing substrate to the targeted water tables at 5 cm and 10 cm below surface of the substrate. Untreated control plants were kept outside the pools. Zero-intercept linear model was the selected model for leaf area estimation after evaluating 15 combinations of five regression models and three predictors. Results of this study indicated that steady water table at 5-cm and 10-cm depth did not restrain relative leaf expansion rate (RLER) and there was no significant difference in specific leaf fresh weight (SLFW) and specific leaf water content (SLWC) between treated and untreated plants, measured prior to, during, and after recovery from shallow water table treatments. In conclusion, if position of water table was steady, the shallow water table at 5-cm depth or deeper did not affect tomato growth.

Full article can be downloaded here: 2017 AJCS Shallow water table in tomato plants

Publikasi 11: Relative leaf expansion rate and other leaf-related indicators for detection of drought stress in chili pepper (Capsicum annuum L.)


Abstract
Leaf is a sensitive plant organ in responding to abiotic stresses, especially drought stress. Objective of this research was to evaluate changes of relative leaf expansion rate (RLER) and other leaf-related indicators as affected by gradual drought stress. The stress was induced by withholding water supply to chili pepper (Capsicum annum L.) for up to 12 days. Afterward, the crops were allowed to recover. The research was conducted in two stages. The first stage was for finding a reliable leaf area (LA) estimation model. The second stage was for evaluating relevance of RLER, specific leaf fresh weight (SLFW), specific leaf water content (SLWC), and total leaf area (TLA) as indicators for drought stress in chili pepper. Combinations of five regression models (linear, zero-intercept linear, quadratic, zero-intercept quadratic, and power) and three predictors, i.e. leaf length (L), leaf width (W), and LW were evaluated as candidates of LA estimation model. Selection of the models were based on coefficient of determination (R2) and geometrical principles. The selected model was used for calculating RLER, SLFW, SLWC and TLA. Results of this study indicated that dynamic changes of RLER were mainly driven by daily day-night cycle rather than long-term gradual drought stress. SLFW and SLWC did not significantly decrease during drought stress period. However, drought stress significantly inhibited TLA in chili pepper. Chili pepper was able to recover from short-term (4 days) exposure to drought stress; yet, this crop was unable to recover after 8 days exposure to drought stress or longer.

Full article can be downloaded 2017 AJCS Drought stress in chili pepper

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