EURASIAN JOURNAL OF SOIL SCIENCE

295-306

Authors: Dinesh Khadka, Sushil Lamichhane, Shukra R. Shrestha, Buddhi B. Pant

Soil fertility evaluation of an area or region is most basic decision making tool for the sustainable soil nutrient management. In order to evaluate the soil fertility status of the Regional Agricultural Research Station (RARS), Tarahara, Susari, Nepal. Using soil sampling auger 81 soil samples (0-20 cm) were collected based on the variability of land. The collected samples were analyzed for their texture, structure, colour, pH, OM, N, P2O5, K2O, Ca, Mg, S, B, Fe, Zn, Cu and Mn status. The Arc-GIS 10.1 software was used for the preparation of soil fertility maps. The soil structure was granular to sub-angular blocky and varied between brown- dark grayish brown and dark gray in colour. The sand, silt and clay content were 30.32±1.4%, 48.92±0.89% and 20.76±0.92%, respectively and categorized as loam, clay loam, sandy loam, silt loam and silty clay loam in texture. The soil was moderately acidic in pH (5.98±0.08). The available sulphur (2.15±0.21 ppm), available boron (0.08±0.01 ppm) and available zinc (0.35±0.03 ppm) status were very low, whereas extractable magnesium (44.33±6.03 ppm) showed low status. Similarly, organic matter (2.80±0.07%), total nitrogen (0.09±0.004 %), extractable calcium (1827.90±45.80 ppm) and available copper (1.15±0.04 ppm) were medium in content. The available phosphorus (39.77±5.27 ppm), extractable potassium (134.12±4.91 ppm), and available manganese (18.15±1.15 ppm) exhibits high status, while available iron (244.7±19.70 ppm) was very high. The fertilizer recommendation can be done based on determined soil fertility status to economize crop production. Furthermore, research farm should develop future research strategy accordance with the prepared soil data base.

312-318

Authors: Kofi Agyarko , Kwame Agyei Frimpong , Akwasi Adutwum Abunyewa

This study was undertaken to assess the release pattern of available phosphorus in a Togo phosphate rock and ammonium sulphate soil amendment. Treatments were prepared through the combinations of soil, phosphate rock (PR) and ammonium sulphate (AS) fertilizer. The treatments were; Control, 12.5g PR, 25g PR, 12.5g PR+1g AS, 12.5g PR+2g AS, 25.0g PR+1g AS and 25.0g PR+2g AS kg-1 soil. Standard laboratory methods were used to assess pH, available phosphorus (P) and total phosphorus (P). Generally, the pH of treatments decreased to the lowest levels between the 4th and 6th weeks after amendment. The AS fertilizer treatments had significantly (p≤0.05) lower pH values than those without. Amendments with the 2gAS kg-1 soil had significantly (p≤0.05) lower mean pH values than those with the 1gAS kg-1 soil. The AS fertilizer treatments also had significantly (p ≤ 0.05) higher levels of the available P than those without. The higher the amount of the AS in the amendment, the higher the level of the available P concentration. Increase in the level of AS in the amendment also increased the mean value of the available P released. The peaks of available P released were observed between the 6th and the 8th weeks, after the lowest pH values had been attained. Decreased soil pH relatively increased the amount of phosphorus released (y = -12.47x + 111.4; R2=0.53). Addition of PR in the treatments increased the total P levels. In conclusion, combined application of AS and PR has the potential to increase soil P availability, which is beneficial to crop farmers.

327-336

Authors: Sayed Roholla Mousavi , Feraidon Sarmadian , Somayeh Dehghani , Mahmood Reza Sadikhani , Abass Taati

Today, the presence of accurate information about variability of soil properties been considered more than ever to apply this information in economic modeling, environmental predictions, accurate farming and natural resources management. The present research was conducted in some lands of Qazvin plain to study variability of some chemical and physical properties of soil by sampling 62 observational points in depth of 20 cm above soil surface. Initial statistical study of data indicated that the studied properties follow normal distribution in the region. Spatial variations of the studied properties showed that spherical model was the best fitted model to semivariogramin other properties than silt percent and bulk densityand total porosity. The highest radius for the studied properties was 21100 m related to bulk density, total porosity and electric conductivity and pH. Spatial dependence class was observed medium to strong in all physcial and chemcial properties. To validate intrapolation methods, three indices of evaluation, R2, MBE, MAE which indicate accuracy of each of the intrapolation methods were used and results showed that the studied properties had spatial structure, their impact range had good variability and kriging estimator better can show variability of the studied properties in the region in comparison to IDW method. At the end, considering the best interpolation method, spatial variability map of each of the properties was prepared in ArcGIS software.

350-356

Authors: Olufemi Emmanuel AyanfeOluwa , Olugbenga Oluseyi AdeOluwa , Vincent Oluwatomisin Aduramigba-Modupe

Acceleration of composting process could influence fertilizer-efficiency of the accelerated composts. This study therefore evaluated the nutrient release dynamics of different rates of a commercial accelerated compost (OBD-plus ) in two soils described as Alfisol and Ultisol, under laboratory incubation study, in order to generate information for simulation under field conditions. Accelerated compost (AC) at the rates of 30, 60, 90, 120, 150 kg N ha-1, mineral fertilizer (NPK 15-15-15) and conventional compost (CC) at 60 kg N ha-1, were each mixed with 2 mm sieved soil (Alfisol and Ultisol) in cups, and arranged in a completely randomised design with three replications. Soils without amendment served as control. The treated soils were retrieved at 2, 4, 6, 8, 10 and 12 weeks of incubation (WOI), air dried and analysed for pH, organic C, N, P and K, and data analysed using regression test. The results revealed that the 60 kg N ha-1 AC improved the pH, OC, N. P, K by -2%, 11%, 3%, 141% and 4% respectively, across the WOI, on the average of performance in the two soils, comparable with mineral fertilizer (-5%, 8%, -1%, 76%, 4% respectively) and CC (11%, 40%, 3%, 773%, 10% respectively). The 60 kg N ha-1 AC significantly correlated (p<0.05) with time of incubation only with respect to P (0.934) and gave a similar nutrient release pattern compared with mineral fertilizer and CC, in terms of C, N, P and K in both soils. It therefore showed that the accelerated compost evaluated could mineralize in a way similar to conventional compost and mineral fertilizers, despite its shorter composting duration to maturity.

365-373

Authors: Boško Miloš , Aleksandra Bensa

The objectives of this research were: (i) to assess the accuracy of diffuse reflectance spectroscopy (DRS) in predicting the soil organic carbon (SOC) content, and (ii) determine the importance of wavelength ranges and specific wavelengths in the SOC prediction model. The reflectance spectra of a total of 424 topsoils (0-25 cm) samples were measured in a laboratory using a portable Terra Spec 4 Hi-Res Mineral Spectrometer with a wavelength range 350-2500 nm. Partial least squares regression (PLSR) with leave-one-out cross validation was used to develop calibration models for SOC prediction. The accuracy of the estimate determined by the coefficient of determination (R2), the concordance correlation coefficient (ρc), the ratio of performance to deviation (RPD), the range error ratio (RER) and the root mean square error (RMSE) values of 0.83, 0.90, 2.22, 14.2 and 2.47 g C kg-1 respectively, indicated good model for SOC prediction. The near infrared (NIR) and the short-wave infrared (SWIR) spectrums were more accurate than those in the visible (VIS) and short-wave near-infrared (SWNIR) spectral regions. The wavelengths contributing most to the prediction of SOC were at: 1925, 1915, 2170, 2315, 1875, 2260, 1910, 2380, 435, 1960, 2200, 1050, 1420, 1425 and 500 nm. This study has shown that VIS-NIR reflectance spectroscopy can be used as a rapid method for determining organic carbon content in the Red Mediterranean soils that can be sufficient for a rough screening.