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Improvement of the chemical properties and buffering capacity of coastal sandy soil as affected by clays and organic by-product application | Fibrianty Minhal, Azwar Ma'as, Eko Hanudin, Putu Sudira | Agricultural Journals

Sugarcane is a strategic commodity in Indonesia. It is usually raised in a monoculture system. There is a lack of information about the effects of extended sugarcane monoculture on the soil carbon fraction. The aim of this study was to determine the relative changes in the soil organic C fractions in response to the duration of sugarcane monoculture on Entisols, Inceptisols, and Vertisols. The measured variables were the percentages of sand, silt, and clay, organic matter (OM), total nitrogen (TN), pH (H₂O), cation exchange capacity (CEC), NH₄⁺, NO₃^-, labile carbon fraction (soil carbon mineralization (C-Min), soil microbial carbon (C-Mic), and carbon particulate organic matter (C-POM)), and stable carbon fraction (humic and fulvic acids). Soil type with sugarcane monoculture period had significant influences on the percentages of clay, sand, silt, CEC, and pH (H₂O). Soil type and sugarcane monoculture period had no apparent significant effect on C-Min or C-POM but did significantly influence C-Mic. The humic and fulvic acid levels in all three soil types were affected by the duration of sugarcane monoculture. To establish the impact of long-term sugarcane monoculture on the physicochemical properties of soils with various textures, it is more appropriate to measure the soil stable carbon fractions such as humic and fulvic acid rather than the soil labile carbon fractions such as C-Min, C-POM, or C-Mic.

Today’s agricultural development is expected to be able to optimize the utilization of agricultural waste resources to improve soil fertility and nutrient for plants, such as the utilization of shrimp waste. This research was conducted to test the level of improvement of the soil fertility and the efficiency of N uptake of corn by application of shrimp waste. The study was conducted using a randomized block design, consisting of five treatments divided as control and the addition of biochar, shrimp waste, urea, and biochar+shrimp waste. Analysis using orthogonal contrast with biochar and shrimp waste was classified as ameliorant, while urea, and biochar+S as fertilizer. The results showed that the application of biochar+S was able to increase soil pH (4.9 out of 4.3), N-total is 85%, OC is 66.2%, CEC is 1.5 times the initial CEC, plant height and number of leaves at 56 days respectively 225 cm and 13 sheets, and Nitrogen uptake efficiency around 24,8% with a dry shell yield of around 10.6 t ha⁻¹. Biochar and biochar+S both increased P-available (4.8 out of 3.4 mg kg⁻¹), whereas K-available increased in shrimp waste applications (88 of 46.1 mg kg⁻¹)

Andisol is a soil with high P adsorption, this is due to high content in reactive amorphous materials. The present study was conducted to compare humic acid and silicate acid in blocking the P adsorption on amorphous minerals. The results indicated that the old and young formation of parent materials were not different in reactivity of the amorphous minerals and able to adsorb P > 98% and fit with the Freundlich equation. Application of humic acid and silicate acid with rate of 100mg/l, respectively, was not effective in decreasing P adsorption. However, silicate acid was a little bit better than humic acid in decreasing P adsorption, in case of pH 4 either pH 6. Infrared spectral characteristics of the amorphous material indicated that the absorption bands of the first region appeared at a range of 3440-3510 cm-1, the band due to stretching vibration of hydroxyl (OH) groups either as structural OH or as adsorbed water. The absorption bands of HOH from adsorbed water appeared ranging from 1639-1655 cm-1. The maximum adsorption bands were observed appeared ranging from 910-972 cm-1, the bands are due stretching vibration of Si- O-Al for allophane with low Si/Al ratio, whereas allophane with high Si/Al ratio appeared at 1033 - 1030 cm-1. In general, the addition of humic acid and silicate acid caused the peak OH, Si-O-Al and Si-O adsorption move to the right and increase the adsorption intensity

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