Soil Organic Carbon and Acid Phosphatase Enzyme Activity Response to Phosphate Rock and Organic Inputs in Acidic Soils of Central Highlands of Kenya in Maize

Aims: To evaluate the effects of phosphate rock and organic inputs on soil organic carbon and acid phosphatase activity.

Study Design: The experiment was laid in Randomized Complete Block Design with seven treatments replicated thrice.

Place and Duration of Study: The study was conducted at Kigogo Primary school in Meru South Sub-county, Tharaka Nithi County, Kenya. The experiment ran for two consecutive seasons the short rains of 2017 (October to December) and long rains of 2018 (March through June).

Methodology: There were seven treatments replicated thrice. The treatments included Tithonia diversifolia, Phosphate rock (PR), Goat manure, Tithonia diversifolia + Phosphate rock, Goat manure + Phosphate rock, Triple superphosphate + Calcium ammonium nitrate and a Control (no soil external inputs). The test crop was maize (Zea mays L.) H516 variety. Soil organic carbon followed modified Walkley and Black oxidation method while acid phosphatase enzyme activity was essayed following the method by Tabatabai and Bremner.

Results: Goat manure + phosphate rock, sole phosphate rock and use of goat manure significantly (P= .0001) increased soil organic carbon by 198, 100 and 71% compared to the control. Tithonia diversifolia reported a 3.4-fold increase in soil organic carbon compared to the control in short rains of 2017. Goat manure gave higher soil organic carbon by 135% compared to the control in the long rains of 2018. Goat manure + phosphate rock treatment significantly (P= .0002) increased the phosphatase activity by a difference of 1.12% compared with the control, with 2.14% decreases under TSP+CAN treatment compared to the control.

Conclusion: The results showed that integration of phosphate rock and manure could have a far-reaching influence on soil organic carbon and acid phosphatase activity thus could be recommended for improved soil productivity in humic nitisols in similar agro-ecological zones.