Effect of Organic and Inorganic Fertilizer on the Soil Chemical Properties of the Rhizosphere in Kiambu County, Kenya

The experiment was carried out at Kenyatta university farm using 2×3×3 factorial plan in a randomized complete block design. The experiment was carried out for two seasons. Pre cropping soil analsyis was carried out before and after the study to assess soil pH, macro and micro nutrients in the soil. Pre cropping analyses showed that the study site soil pH was 5.2, slightly acidic, Calcium amount was 1.7 me%, nitrogen was 0.07% and phosphorous was 6 ppm, iron recorded 59.3 ppm and magnesium 0.73 me%. The soil was low in macro and micro nutrients. The organic quail manure used was also analysed and showed that it was high in phosphorus that recorded 9.748 ppm, magnesium was 0.29%, calcium of 3.2 me%, total nitrogen was 4.5% and Zn was 9.00 ppm and pH was 6.4. Two Amaranth species (A. cruentus and A. tricolor) were used in the investigation. To determine significant differences among treatments, analysis of variance (ANOVA) was done using SAS computer software and least significant difference (LSD) at 5% was used for mean separation. Chemical properties of the soil were significantly (P≤0.05) influenced during the second season. The result after the experiment showed that macro nutrients increased except for phosphorus. Nitrogen increased in the soil from 0.07% to 2.17%, potassium from 0.9% to 1.34%, the pH increased from 5.2 to 6.2, iron increased from 59.3 ppm to 167 ppm when 250 kg/ha of NPK + 8.45 t/ha, at 500 kg/h+16.9t/h calcium increased from 1.7 to 3.97 me% and manganese from 0.16 me% to 2.61 me%. Sole NPK which is inorganic fertilizer slightly increased magnesium from 0.73 me% to 1.49 me% in the first season to 1.52 me% in the second season, manganese was raised from 0.16 me% to 0.37 me% in the first season and to 0.46m% in the second season. Intergration of poultly manure and NPK was more effective in increasing soil nutrients than sole application of fertilizer materials.