Absorption spectrometric macronutrients review of soil health during taro crop production

Abstract

The purpose of this study was absorption spectrometric assessment the soil health of the soil from the taro growing areas of Taveuni, Fiji. The soil samples were collected in four cycles during taro cultivation period. The soil samples were analyzed for macronutrients (Ca, Mg, K, P and NO 3-N), soil organic matter (SOM) and soil pH. In general, the soil pH at all sites showed lower than the ideal pH (5.6-6.6) for taro planting throughout the cropping cycle. The results showed the significant loss in SOM from taro planting (15.41%) till harvesting (5.63%). Pronounced decrease in levels NO 3-_ N (18.29 to 13.86 mg kg À1), P (45.97 to 25.71 mg kg À1), K (77.90 to 22.96 mg kg À1), Ca (62.20 to 27.59 mg kg À1) and Mg (316.10 to 121.48 mg kg À1) were recorded from planting till harvesting for different sites. There was significant reduction in the soil macronutrients and SOM in all the four study sites and some sites showed below critical level and critical to medium levels of these nutrients in the soil at the end of the harvesting period of taro. The statistical analysis of the soil test data confirmed the declining trend of the soil health on the island of Taveuni, Fiji.

Impacts of Tropical Rainforest Conversion on Soil Nutrient Pools in Viti Levu, Fiji

“…Mean soil exchangeable calcium was low in this study (483.83 mg/kg) (Blakemore et al 1987). Similar low soil calcium concentrations have also been reported in soils of Fiji by Curtin et al (1991), Waterloo (1994), Morrison (2019) and Nisha and Prasad (2020). Acid soils are commonly associated with calcium deficiencies (Nisha and Prasad 2020).…”

“…Similar low soil calcium concentrations have also been reported in soils of Fiji by Curtin et al (1991), Waterloo (1994), Morrison (2019) and Nisha and Prasad (2020). Acid soils are commonly associated with calcium deficiencies (Nisha and Prasad 2020). Calcium is also considered one of the limiting nutrients in tropical forests (Bizuti et al 2018).…”

“…Relatively low pH values may also be attributed to the acidic nature of the parent material (Garrison-Johnston et al 2007, Oshunsanya 2019, Zhang et al 2019. Low soil pH has been reported by several other workers in Fiji (Curtin et al 1991, Waterloo 1994, Goundar et al 2014, Morrison 2019, Nisha and Prasad 2020, Vessel and Simonson (1958) in Palau and Reverchon (2015) in Solomon Islands. Soil pH was highest in plantation followed by primary forest while secondary forest had the lowest soil pH.…”

“…The mean Olsen available phosphorous was 0.87 mg/kg; classified very low as per Blakemore et al (1987). Low phosphorous levels have also been detected by Curtin et al (1991), Naidu et al (1991), Goundar et al (2014) and Nisha and Prasad (2020) in soils of Fiji. The paradigm of phosphorous limitation (Dalling et al 2016) suggests that phosphorus is the most important limiting nutrient in lowland tropical rainforests with the largest pool of plant available phosphorous actually present in biomass (Turner and Engelbrecht 2011, Yang et al 2016, Nasto et al 2017.…”

Soil Phosphorus Test Using a Low-Cost Spectrophotometer and Machine Learning

“…Research has shown that analysis of the spectral signature of the soil enables the estimation of texture, water and organic matter content, cation exchange capacity, and soil chemical attributes, such as total carbon, pH, and concentrations of nitrate, calcium, potassium, magnesium, and phosphorus (Jiang et al, 2017;Soriano-Disla et al, 2017;Mayrink et al, 2019;Nisha & Prasad, 2020;Pätzold et al, 2020). However, it is necessary to use appropriate spectral signature analysis techniques to estimate soil attributes from spectroscopic data (Pinheiro et al, 2017).…”