Multivariate Approach to Characterizing Soil Quality of Gabonese’s Ferralitic Soils

Assessing soil quality is essential for crop management and soil temporal changes. The present study aims to evaluate soil quality in the Ferralitic soils context countrywide. This assessment was done using multivariate soil quality indice (SQI) models, such as additive quality index (AQI), weighted quality indexes (WQIadd and WQIcom) and Nemoro quality index (NQI), applied to two approaches of indicator selection: total data set (TDS) and minimum data set (MDS). Physical and chemical soil indicators were extracted from the ORSTOM’s reports resulting from a sampling campaign in different provinces of Gabon. The TDS approach shows soil quality status according to eleven soil indicators extracted from the analysis of 1,059 samples from arable soil layer (0 - 30 cm depth). The results indicated that 87% of all provinces presented a very low soil quality (Q5) whatever the model. Among soil indicators, exchangeable K+ and Mg2+, bulk density and C/N ratio were retained in MDS, using principal component analysis (PCA). In the MDS approach, 50 to 63% of provinces had low soil quality grades with AQI, WQIadd and NQI, whereas the total was observed with WQIcom. Only 25% of provinces had medium soil quality grades with AQI and NQI models, while 12.5% (NQI) and 25% (AQI) presented high quality grades. Robust statistical analyses confirmed the accuracy and validation (0.80 r P ≤ 0.016) of AQI, WQIadd and NQI into the TDS and MDS approaches. The same sensitivity index value (1.53) was obtained with AQI and WQIadd. However, WQIadd was chosen as the best SQI model, according to its high linear regression value (R2 = 0.82) between TDS and MDS. This study has important implications in decision-making on monitoring, evaluation and sustainable management of Gabonese soils in a pedoclimatic context unfavorable to plant growth.

Characteristics of soil quality attributes under different agroecosystems and its implications for agriculture in the Choke Mountain watershed in Ethiopia

Awareness of how soil properties vary over agroecosystems(AES) is essential for understanding soil potentials and improving site-specific agricultural management strategies for a sustainable ecosystem. This study examined the characteristics of soil quality attributes and implications for agriculture in the Choke Mountain watershed in Ethiopia. Forty-seven composite soil samples(0–20 cm deep) were collected from lowland and valley fragmented(AES 1),midland plain with black soil(AES 2), midland plain with brown soil(AES 3),sloppy midland land(AES 4), and hilly and mountainous highlands(AES 5).Ten of 15 soil quality properties were significant(P < 0.05 or 0.01), including silt, exchangeable bases, cation exchange capacity, percent base saturation,p H, organic matter, total nitrogen and available phosphorous(P) across the five AES. However, all properties were variable with coefficients of variation from 7%(total porosity) to 169%(available P) across the AES. Although AES 2and 3 are affected by waterlogging and acidity, these two have better prospects for agriculture, but AES 1, 4, and 5 are unsuitable for agriculture because of soil erosion. Therefore, appropriate and applicable soil management strategies, particularly lime application and organic fertilizer, are fundamental to reversing soil acidity and improving soil fertility.

Changes in the Regulating Ecosystem Service on the Contaminated Site Used for Energy Purposes

Soil cleaning, the ability of the soil to immobilize the risk elements, belongs to important agroecosystem services in terms of protection of the hydrosphere and plant production from contamination. Dynamic monitoring of selected indicators of soil quality was realized in a special network of site on soil used for planting fast growing willow (Salix viminalis). Monitoring of the study site Kuchyňa (Mollic Fluvisol) is running since 2010 year. The fast-growing willow was planted on an area of about 43 hectares. Study site Kuchyňa belonged to the degraded contaminated sites, at the time of planting (the total contents of the risk elements were as follows: Cd 1.016 mg∙kg−1, Zn 199.000 mg∙kg−1, Ni 51.500 mg∙kg−1) There were positive changes in the total content of cadmium, zinc and nickel (in 2018 year), the zinc content decreased by 27% compared to 2010, the nickel content was lower by 23% and the Cd content by 57% in comparison to 2010 year, these elements have a declining trend during the monitored period. The remediation ability of the willow in relation to the risk elements was manifested by the accumulation of these elements in the wood mass and by their decrease in the soil below the limit value. The regulatory ecosystem service, the potential for the immobilisation of the risk elements, was evaluated based on the sum of the assessment of the contamination potential and the sorption potential of soil. The decrease of the total content of risk elements in the soil below the limit value was manifested in the increase of the potential of the agroecosystem regulatory service, the potential of risk element immobilisation, from very low category to medium category. If willow cultivation continued in the next decade, the value of risk element Zn would most likely reach the value 73 mg∙kg−1, which is less than 50% of the limit value, based on the results of the predictive model. In the case of Cd, the soil would be completely cleaned and in the case of Ni, its total content in the soil would fall to 23 mg∙kg−1, which is less than 40% of the limit value. The overall potential for contamination would fall into the category—very low (forecast for 2021 year). The higher potential of immobilisation reduces the risk of contaminants transport and thus prevents contamination of the other ecosystem components such as biota.