EFFECT OF TILLAGE, CROP ROTATION AND NITROGEN FERTILIZATION ON SOIL MICROBIAL DIVERSITY IN NIGERIAN SAVANNA ALFISOLS

Abstract

ABSTRACT The study assessed tillage practices, crop rotation and N-fertilizer on soil microbial diversity in Nigerian Alfisols. The aim of the research was to evaluate the influence of long-term tillage practices, cereal/legumes rotation and N-fertilizerrates on soil microbial diversity and its effect on soil quality. The trial was a split split-plot experiment laid in a randomized complete block design replicated three times; with tillage as main plot, crop rotation as sub-plot and N-fertilizer rates as sub sub-plot. Soil properties were analyzed using standard procedures while serial dilution and molecular techniques (16S rRNA genes for bacteria) were used to study soil microbial dynamics. Results revealed soil texture as sandy loam, soil pH, exchangeable Ca and Mg, CEC and available P were moderate, bacterial and fungal populations were high. Phylogenetic diversity depicted Bacillus as the dominant genera studied; others are Rhizobiale, Rhodobacter and Sinorhizobiumobserved in cowpea/maize rotation. The influence of cropping systems on both bacterial population and clustering of microbial sequences were significance (P<0.05); tillage and N-fertilizer rates (T*NR) and crop rotation and N-fertilizer rates (CR*NR) on bacteria and fungi loads were significance (P<0.05). Shannon Index for bacteria negatively correlated with available P. (P<0.01) and silt but positively correlated with sand (P<0.01). ABSTRACT The study assessed tillage practices, crop rotation and N-fertilizer on soil microbial diversity in Nigerian Alfisols. The aim of the research was to evaluate the influence of long-term tillage practices, cereal/legumes rotation and N-fertilizerrates on soil microbial diversity and its effect on soil quality. The trial was a split split-plot experiment laid in a randomized complete block design replicated three times; with tillage as main plot, crop rotation as sub-plot and N-fertilizer rates as sub sub-plot. Soil properties were analyzed using standard procedures while serial dilution and molecular techniques (16S rRNA genes for bacteria) were used to study soil microbial dynamics. Results revealed soil texture as sandy loam, soil pH, exchangeable Ca and Mg, CEC and available P were moderate, bacterial and fungal populations were high. Phylogenetic diversity depicted Bacillus as the dominant genera studied; others are Rhizobiale, Rhodobacter and Sinorhizobiumobserved in cowpea/maize rotation. The influence of cropping systems on both bacterial population and clustering of microbial sequences were significance (P<0.05); tillage and N-fertilizer rates (T*NR) and crop rotation and N-fertilizer rates (CR*NR) on bacteria and fungi loads were significance (P<0.05). Shannon Index for bacteria negatively correlated with available P. (P<0.01) and silt but positively correlated with sand (P<0.01).