EURASIAN JOURNAL OF SOIL SCIENCE

203 - 212

Authors: Ali Bagherzadeh, Amin Gholizadeh, Ali Keshavarzi

Considering the important role of soil fertility and nutrient management in the modern agriculture seems to be a key step in appropriate site-specific fertilizers management for crop production. The present study was conducted to prepare a soil fertility zonation map based on soil nutrient elements including total nitrogen, available potassium and phosphorus, magnesium, manganese and iron and soil chemical parameters comprising cation exchange capacity, organic carbon, salinity and pH by integrated Fuzzy and AHP approaches for potato production in Rokh plain, northeast of Iran. In this regard the most important soil chemical parameters and nutrient elements in 0-30 cm depth of the soil was analyzed and mapped. The S-shaped fuzzy membership function was subsequently defined for each factor to fuzzify soil fertility parameters. The soil fertility map was prepared by weighing factor layers by the AHP approach and summation of factor layers by IDW interpolation function in GIS. The values of the soil fertility index in the scale of 0 to 1 ranged from 0.104 to 0.574, classified the study area in very low (922.90 km2), low (566.10 km2) and moderate fertility (14.86 km2) classes which comprises 61.37%, 37.64% and 0.99% of the surface area, respectively. A regression between soil fertility values and potato yield in the study area revealed a high correlation (R2 = 0.91) between the observed results which validate the zonation of the fertility classes in the region.

224 - 229

Authors: Abdel Wahab Ahmed Mohamed Ahmed, Mohammed Abdalla Elsheikh, Yousif El Gorashi El Mahi

A laboratory experiment was conducted to determine the extent and the importance of phosphorus (P) fractions of some agriculturally important Sudanese soils on P availability. The soils were gathered from different locations in Sudan, to represent three different orders: Aridisols (Um Dum soil, North Kordofan state), Alfisols (Hagu soil, Senar state), and Vertisols (Hosh soil, Gezira state). The soil P was fractionated using an authenticated procedure. The results showed that the soils had low total, organic and available P contents. Most of the inorganic soil P was present in the Fe-Al fraction in Um Dum soil (> 50%), and about 40% of this fraction in Hagu soil, but, only 20% in alkaline Hosh soil. The Ca-P fraction constituted > 60% in Hosh soil, about 40% in Hagu soil and 20 % in Um Dum soil. The available P in the top soils studied was positively related to the percent sum of Al+Fe -P of the total P, and was negatively related to the percent Ca-P fraction content of the total P. It has been proposed that the P sorption starts by exchange with singly coordinate Fe or Al- OH clay (OH− edge group) and quickly reorganizes into more stable and less soluble ring forms especially at pH more than 7.0, Alkaline pH more than 8.0 in soil like Hosh, will in presence of Ca, favour with time, the formation of inactive less soluble form like octacalcium phosphates and apatites at expense of the initial Al and Fe-P forms which are less stable at alkaline pH.

238 - 250

Authors: Justin George Kalambukattu, Suresh Kumar, Yogesh S. Ghotekar

Soil organic carbon (SOC) is a key component in maintaining soil quality. Mapping the local scale variations in the distribution and stratification of SOC and other soil quality parameters across different layers has always been a challenging task, in the current global scenario of changing climates. The study was aimed to investigate the spatial distribution of SOC and other soil quality parameters including SOC stratification ratio and CN ratio in a small hilly watershed (̴ 10 km2) located in the mid Himalayan region of Himachal Pradesh, India. Soil samples were collected in November 2015, from 75 points at two depths (0-15 cm and 15-30cm), along with their geographical coordinates using a Global Positioning System (GPS). The results revealed that SOC concentration (g kg-1) decreased with increasing soil depth, throughout the study area and differed significantly (P<0.01) between the two depths in vertical soil profile. The SOC stratification ratio values were greater than 1.2 in major portion of watershed indicating a spatial improvement in soil quality. C: N ratio, another important soil quality attribute values were found to be <12:1, indicating high degree of soil quality and increased rate of organic matter mineralization. The spatial distribution maps of SOC content (g kg-1), SOC stratification ratio as well as CN ratio of study area were generated using Inverse Distance Weighted (IDW) interpolation approach. Additionally soil quality index (SQI) was also computed using various soil quality parameters based on Analytical Hierarchy Process (AHP) and their spatial distribution was analyzed in the watershed. Nearly 76% of the study area had SQI values in the range of 60-75, whereas 22.16% of the area had SQI<60 and 2.59% had SQI>75. The overall results indicated that a higher degree of soil quality existed at the higher elevation regions of the watershed. Majority of the soils in the watershed accounted for only 60% of the maximum possible value of SQI, which necessitates the adoption of better management practices for improving the soil quality.

257 - 260

Authors: Abdelazim Mohammed Ali

This study examines the ability of different cropping sequence (including or not including alfalfa) to improve bean productivity in calcareous and alkaline soils of the old Nile (high) terraces in North of Sudan. The soil in the experimental site is sandy clay to sandy clay loom. Soil properties were examined before planting and after bean harvest. Salinity which was greater in non-reclaimed soil decreased regardless of the cropping sequence. Soil alkalinity remain higher than 8 in all cropping sequence after more than 6-7 cropping seasons. P (Olsen) and calcium carbonate showed inconsistent trends regardless of the cropping sequence. Organic carbon increased after bean cultivation in both cropping sequence. Change in growth parameters as affected by cropping sequence were significant in various levels, however, that determining yield were not. Presence of alfalfa in the cropping sequence increased seed yield, number of pods per plant, number of seeds per pods, pod length, plant length, leaf length, leaf width, fresh plant weight, nodule number. However seed weight was decreased.

273 - 283

Authors: Endalkachew Fekadu, Kibebew Kibret, Bobe Bedadi, Asmare Melese, Birru Yitaferu

Soil acidity is a critical issue necessitating urgent attention in most highlands of Ethiopia due to its impact on crop production productivity. Application of organic and inorganic amendments could effectively minimize the problem and improve the fertility level of the soil. Accordingly, a greenhouse experiment was conducted to evaluate the effects of sole and combined applications of lime, FYM, compost and P on soil chemical properties incubated at 20, 40 and 60 days. The treatments were arranged in a completely randomized design with three replications. The results indicated that various treatment combinations raised the soil pH at the 40 days of incubation. All treatments showed increased P availability consistently with increasing time of incubation. Maximum available P was observed at the 60 days of incubation due to application of 8 t FYM ha-1 + 30 kg P ha-1 + 5 t lime ha-1 followed by 8 t compost ha-1 + 30 kg P ha-1 + 5 t lime ha-1. Exchangeable acidity and Al were reduced at the 40 and 60 days of incubation with the application of 30 kg P ha-1 + 10 t lime ha-1 followed by 4 t FYM or compost ha-1 + 15 kg P ha-1 + 10 t lime ha-1. Highest exchangeable Ca was obtained at 20 days of incubation with the application of 30 kg P ha-1 + 10 t lime ha-1 followed by 4 t ha-1 FYM + 15 kg P ha-1 + 10 t lime ha-1. Sole addition of 10 t lime ha-1 elevated ECEC from 19.29 to 22.30 cmolc kg-1 at the 40 days of incubation. Likewise, combined applications of 30 kg P ha-1 + 10 t lime ha-1 improved ECEC of the soil from 19.53 to 24.27 cmolc kg-1 at the 40 days of incubation. Integrated applications of organic and inorganic amendments were found more effective to reduce soil acidity and Al3+ concentration with increasing the fertility of the soil.