Variations in Soil Properties and Forms of Inorganic Phosphorus within the Rhizosphere of Annual Crops
Variations in Soil Properties and Forms of Inorganic Phosphorus within the Rhizosphere of Annual Crops
Stanley Uchenna Onwudike* and Vivian Chizoba Edoziem
ABSTRACT
Phosphorus deficiency is one of the soil factors affecting crop production in Southern part of Nigeria and understanding its distributions in rhizosphere soils will help in its management. This investigation examined some variations in soil properties and inorganic phosphorus forms within the rhizosphere of three annual crops, viz groundnut (Arachis hypogea), bean (Phaseolus vulgaris) and okra (Abelmoschus esculentus) on a loamy sand, typic haplustult soil. The work was sited at the research farm of the University during 2016 planting season and the region lies within the latitude of 5° 38¹N and longitude 6° 97¹ E. At 10 weeks after planting, both the rhizosphere soil (soils within 2 mm region of the test crops) and bulk soil or control (soils away from the root zone) from the experimental plots that were planted with bean, groundnut and okra were sampled, air dried and analyzed in the laboratory. Results showed significant effect (p = 5%) on soil moisture content, soil pH, organic carbon and exchangeable bases between the bulk soil and the rhizosphere. The highest value of saloid bound P (7.77 mg/kg) was found within the bean root zone while the highest value of phosphorus bound to Al (Al - P) (13.27 mg/kg) was found in okra root zone. Highest value of occluded – phosphorus (46.07 mg/kg), Fe -Al–P (40.62 mg/kg) and Ca-P (6.77 mg/kg) were recorded in groundnut root zones. Significant relation occurred between occluded–P with bulk density, exchangeable Ca and ECEC (effective cation exchange capacity), saloid bound P with BS (base saturation), moisture content as well as organic carbon, Al–P with available phosphorus and moisture content while Ca–P and Fe-Al–P had significant relation with available phosphorus and effective cation exchange capacity. As a result of different concentrations of inorganic phosphorus forms within these roots zones, appropriate agronomic management practices such as crop rotation, mixed cropping and shifting cultivation is recommended for sustainable phosphorus management in the studied soil.
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