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.
The south-western slope of Anak Krakatau collapsed after the eruption on December 22nd, 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 106 m3 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.
The research of Tithonia diversifolia utilization in the paddy soil that was fertilized P-starter on yield and N, P, K uptake on rice crop, has been conducted from August to December 2005. The objective of this research was to determine interaction between P-starter levels, and tithonia levels on production and N, P, K element uptake of rice crop. The research was pot experiment in the green house in factorial design 4 x 4. First factor was 4 levels of tithonia with reduce dosage fertilizer aplied (T0 = 0 t tithonia + 200 kgUrea ha-1 + 75 kg KCl ha-1; T1= 2,5 t tithonia ha-1 + 150 kg Urea ha-1, without KCl; T2 = 5,0 t tithonia ha-1 + 100 kg Urea ha-1, without KCl; dan T3 = 7,5 t tithonia ha-1 + 50 kg Urea ha-1, without KCl). The second factor was 4 levels of P-starter (0, 2, 4, and 6 kg P ha-1). The result showed that combination T3 treatment and 2-4 kg P-starter ha-1 increased the grain yield 20,51-21,08 g pot-1 (18,65-19,21%). Effect of T3 treatment was not significant with T2 treatment on the grain yield. The best interaction was T3 treatment on N and K uptake ((0,84 g pot-1 for N, dan 0,82 g pot-1 for K).
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