Explore the vast range of titles available.

Humic Substances (HS) sources of Sub-bituminous can be used as soil amandement. The purpose of this research was to examine the residual effects of HS combined with P-fertilizers and the method of incubation to improve Oxisols fertility and rice production. The experiment consisted of 2 factors, including: 1) incubation methods (i.e. I1 = HS incubated 1 week, then incubation of P fertilizers 1 week; I2 = HS and P- fertilizers directly incubated into the soil 2 weeks; and I3 = HS and P-fertilizers mixed 1 week, then incubated to soil 1 week), and 2) residual effect of HS with P-fertilizers combinations (i.e. H1 = 800 ppm + 100%; H2 = 800 ppm + 75% R; H3 = 400 ppm + 100% R; and H4 = 400 ppm + 75% R). All treatment was compared to the tradition of fertilization by the local farmers and control. The results showed that the combination of residual effects (HS and P-fertilizers) with the incubation method decreased exchangeable Al, as consequently increased the available P in Oxisols. The HS addition increased the efficiency of P fertilizers up to 25%, as well as increased rice production in averaged 3.9 t/ha (i.e. treatment H4).

Regosol, a suboptimal land, is rarely cultivated due to its low water retention and nutrient content. It is needed organic matter to improve the soil physical, chemical, and biological properties. A research conducted in glasshouse and soil laboratory was aimed to find out the best dosses of compost derived from rice straw and tithonia to improve soil chemical properties of Regosol as well as onion production. There were 9 levels of compost dosses (0; 2.5; 5.0; 7.5; 10.0; 12.5; 15.0; 17.5; and 20.0 tonha-1) applied to soil with three replications. The experimental units were allocated based on Completely Randomized Design (CRD). Crop data resulted were statistically analyzed using F-test and then continued using Least Significance Difference (LSD) at 5% level of significance if F-calculated > F-table. The result showed that compost application up to 20 ton ha-1 did not significantly affect chemical properties of Regosol as well as onion production. The highest weight of onion bulb was found at application of 7.5 t compost ha-1, however the highest N, P, and K uptake was found at dosses 20 t compost/ha-1. Therefore, it was needed further study to determine the appropriate compost dosses for optimal onion production in Regosol.

Volcanic eruptions affect land and humans globally. When a volcano erupts, tons of volcanic ash materials are ejected to the atmosphere and deposited on land. The hazard posed by volcanic ash is not limited to the area in proximity to the volcano, but can also affect a vast area. Ashes ejected from volcano’s affect people’s daily life and disrupts agricultural activities and damages crops. However, the positive outcome of this natural event is that it secures fertile soil for the future. This paper examines volcanic ash (tephra) from a soil security view-point, mainly its capability. This paper reviews the positive aspects of volcanic ash, which has a high capability to supply nutrients to plant, and can also sequester a large amount of carbon out of the atmosphere. We report some studies around the world, which evaluated soil organic carbon (SOC) accumulation since volcanic eruptions. The mechanisms of SOC protection in volcanic ash soil include organo-metallic complexes, chemical protection, and physical protection. Two case studies of volcanic ash from Mt. Talang and Sinabung in Sumatra, Indonesia showed the rapid accumulation of SOC through lichens and vascular plants. Volcanic ash plays an important role in the global carbon cycle and ensures soil security in volcanic regions of the world in terms of boosting its capability. However, there is also a human dimension, which does not go well with volcanic ash. Volcanic ash can severely destroy agricultural areas and farmers’ livelihoods. Connectivity and codification needs to ensure farming in the area to take into account of risk and build appropriate adaptation and resilient strategy.

Volcanic ash material (Vam) can cover the surface of the farming land post volcano eruption. The covering process could be advantageous for soil fertility if it is thin enough, but it can be destructive for the crops if it is thick. The purpose of this research was to study the effect of the application of Geo-organo granules from volcanic ash and Tithonia (Tt) for the production of Baby Corn in Oxisol. The pot experiments design with six treatments (1AV:1Tt; 1AV:2Tt; 1AV:3Tt; 1AV:4Tt; 1AV:0Tt; 0AV:1Tt)) three replications, and used Completely Randomized Design (CRD). The criteria test of compost standard used to test the benefit of these Geo-organo materials (PT Pusri, SNI, and Regulation from Agriculture Ministry, Republic of Indonesia). Corn growth was also measured for height and yield. Plant height and yield were analyzed using F-test and continued using HSD at a 5% level of significance. The results showed that Geo-organo granules be to improve soil chemical properties of Oxisol, and mass of cob of Baby corn.

Organic carbon in soil can be utilized to assess soil quality and aid to climate change mitigation. Soil organic carbon stock assessment in West Sumatra is still limited. This research focused on soil organic carbon stock distribution in various land-uses in Duku, Koto XI Tarusan, Pesisir Selatan Regency. Research area included secondary forest, scrubland, paddy field, and dryland agriculture. Soil samples were obtained by stratified sampling. Samples were taken at depths of 0-30 and 30-60 cm from each land-use type with the same slope and soil type. A soil unit polygon was randomly selected for sampling. 21 samples were collected and analyzed for bulk density, texture, soil respiration, total nitrogen content, and organic carbon. Secondary forest had the highest soil organic carbon storage (128.82 - 294.09 tons per hectare), followed by paddy fields (16.99 - 227.14 tons per hectare), dryland agriculture (10.40 - 65.43 tons per hectare), and scrubland (13.39 - 53.19 tons per hectare). Nitrogen content was higher in secondary forest>paddy soil>scrubland>dry land. Bulk density was found to be higher in scrubland than in dry land, paddy soils, and secondary forest. Soil pH was greater in paddy soil>scrubland>dryland>forest.

Volcanic soils in Indonesia cover an area of about 5.4 million ha and around 2.7 million ha in Sumatra. The prolonged eruptions of Mt. Sinabung in North Sumatra from 2013 to today eject pyroclastic materials, which blanketed and altered the soil surface. As a result, volcanic soil formed from these pyroclastic deposits. This study aims to map the chemical properties of volcanic soils after the prolonged eruption of Mt. Sinabung from 2013-2020. Thirty-four soil samples were collected at a depth of 0-20 cm according to the grid sampling system with an interval of 1x1 km covering an area of about 4,500 ha. Regression kriging (RK) was applied to predict the soil’s chemical properties and distribution spatially. The soil samples were air dried, sieved, and analyzed to determine soil pH (H2O and KCl), available, potential and retention P, organic carbon, total nitrogen, cation exchange capacity (CEC), and exchangeable basic cations. Soil pH (H2O) ranges from very acidic to neutral (4.14-6.52) and very acidic to acidic pH (KCl) (3.89-5.26), low to very high available-P (3.46-382.01 ppm), potential-P very low to very high (3.76-230.26 mg 100g-1), P-retention is categorized as very high (90-99%). The organic Carbon range from low to very high (1.73-13.05%), low to high total nitrogen (0.13-0.60%), low to high cation exchange capacity (11.78-97.71 cmolc kg-1), and exchangeable base cations are categorized as high with K values (1.60-2.98 cmolc kg-1). Na (3.72-7.45 cmolc kg-1) and Mg (5.79-12.15 cmolc kg-1) were categorized as high and Ca very low (0.039-0.157 cmolc kg-1). The estimated area of soils with pH between 4 and 5 is about 424.85 ha, and soils with pH between 5 and 6 covered an area of approximately 3,964.81 ha. Our findings suggest that persistent eruptions of Mt. Sinabung supply new plant nutrition, which can enrich and increase soil fertility in the future.

Volcanic activity produces pyroclastic deposits when erupted and cover the surrounding area. The minerals contained in these deposits are the source of plant nutrients. The volcanic deposits weathered, release nutrients to the environment, and improve soil chemical properties. The eruption of Mt. Sinabung in 2018 covered an area of 30, 320 ha, while in 2019 was 1, 371 ha. The study aims to investigate the status of nutrient content and the volcanic ash weathering level in 2020. There were 16 samples taken from ash deposits at various depths, with a total area of 1, 585.31 ha. Samples were analyzed to determine the total elemental composition using X-ray fluorescence (XRF) spectrometer, nutrient reserves, and weathering indices. The results showed that the total elemental composition of SiO 2 is 51.51-67.51% classified as mafic (basalt) to felsic (dacite) materials, Al 2 O 3 ; 15.54-23.41%, Fe 2 O 3 ; 2.84-10.02% and CaO; 3.94-6.46%. Mount Sinabung’s volcanic ash has a nutrient reserve capacity of MgO, CaO, P 2 O 5 , K 2 O, and SO 3 , respectively with the amount of 37, 384.17 kg/ha, 235, 794.99 kg/ha, 34, 293.12 kg/ha, 72, 357.39 kg/ha, and 70, 352.22 kg/ha. The weathering indices of volcanic ash of 2020 were determined with a value of 2.76-4.19 for Ruxton ratio and Product of Weathering Index (PWI) of 67.39-76.13, indicates the weathering rate of silicates from volcanic ash are still at initial stage and are still in the fresh condition.

Sulphur dioxide (SO 2 ) emissions from Mt. Sinabung eruption were quantified in time series for 2019. Both pyroclastic materials and gas or aerosol ejected during volcanic eruption contain sulphur as sulphate salt deposits coating volcanic ash grains or gasses. Sulphur dioxide from the eruption will directly impact the surrounding area. Spectral from satellite optical sensors can be used to monitor and measure SO 2 gas near real-time after an eruption. The distribution of SO 2 column density in the atmosphere was tracked using the Sentinel-5P satellite. Regression kriging (RK) is applied to predict the spatial distribution of sulphur. The area under study is located in a radius of 3 to 7 km from the eruptive center, covering an area of about 4,517 ha. A total of 51 soil samples and volcanic ash were collected from 0- 20 cm soil depth based on a 1x1 km grid interval. All samples were air- dried, sieved, and analyzed for pH, sulphate, and total SO3 using XRF. The Google Earth Engine (GEE) platform was also used to process Sentinel-5P satellite imagery to determine the number and distribution of SO 2 column density in the atmosphere during 2019. The pH of the ash is very acidic to neutral (3.56 - 6.55), while soils are considered acidic to neutral (4.67 - 6.52). The available sulphate content in soil ranges from 0 to 303.39 ppm and 0 to 142.47 ppm in volcanic ash samples. SO 2 content in ash ranges from 0 to 16.53% and 0 to 3.71% in soils. Sentinel-5P satellite image spectral data shows that SO 2 is concentrated mainly in the southern region, with the highest level occurring in August 2019. This study can serve as one of the volcanic mitigation programs and forecast the distribution of SO 2 in an active volcanic region of Indonesia.

The south-western slope of Anak Krakatau collapsed after the eruption on December 22 nd , 2018 and reshaped the volcanic island landscape. This work focused on determining the geomorphological features of Mt. Anak Krakatau before and after the eruption. A total of 71 lapilli and 17 volcanic ash samples were collected from Anak Krakatau and Panjang islands on February 23, 2019, and March 14, 2019. Sentinel-2 and Planet Scope images were utilized to monitor thermal activities and the changes of the coastlines. Google Earth Pro was capitalized to determine the rills and gullies formation. After the December 2018 eruption, the height of Anak Krakatau was reduced from 258 to 126 m and, about 76 x 10 6 m 3 of materials were eroded to the sea. The eruption caused Anak Krakatau to be covered by unconsolidated volcanic materials. About 214 of rills (dimension of 380 to 851 m and 30 to 100 cm) and 35 of the gully features (length from 150 to 841 m and width from 0.5 to 13 m) run from the highest peak to the coastline. This work can serve as a reference for predicting potentially disastrous events such as Anak Krakatau, which shows growth and destruction can be observed using remote sensing techniques.