Integration of biochar and inorganic fertiliser on soil biochemical properties, nutrient use efficiency and yield of potato (solanum tuberosum l.) in Njoro Sub County, Nakuru County, Kenya

Abstract

Declining soil fertility is a major hindrance to potato farming in Kenya. The objective of the study was to determine the effects of biochar and Diammonium Phosphate (DAP) on growth, yield, nutrient use efficiency and selected soil properties in potato farming. A 2-season study was conducted at Egerton University agricultural field and in a farmer’s field in Mau Narok using a split plot design in a randomized complete block (RCBD) arrangement. Biochar and DAP were applied at three levels (0, 5 and 10 t ha-1) and (0, 250, 500 kg ha-1), respectively resulting in 9 treatment combinations. Two potato varieties (Shangi and Destiny) were used in the study. The high number of potato stems was observed in plots that received B0D500, B5D500 and B10D500 at (P≤0.001). These results were consistent for both varieties in the two sites and seasons. Application of B5D500 resulted in the tallest plants that were not significantly different from plants in plots fertilised with B0D500 and B10D500 at (P≤0.001). Plots that received only biochar produced the shortest potatoes plants, that were not significantly different from the control. The highest number of tubers per plant, total tuber yield and marketable yield was obtained from plots treated with B0D500, B5D500 and B10D500 with B5D500 producing the highest marketable tuber yield of 39.9 t ha-1 and the lowest was from control and plots that received sole biochar application at (P≤0.001). The highest pH of 7.54 and 7.39 were obtained after applying B5D0 and B5D500 respectively. Sole application of DAP acidified the soils while soil pH became alkaline with biochar application at (P≤0.001). The highest soil phosphorus of 136 mg kg-1 was observed in B5D250 plots at (P≤0.001). Soils amended with B5D250, B10D250, B5D500 and B5D0 gave the highest soil nitrate and ammonium at (P≤0.001). Soils amended with B5D500, B10D500 and B10D250 gave the highest (P≤0.001) alkaline phosphomonoesterases while the highest acid phosphomonoesterases were observed under B0D500. Plots amended with B5D500, B10D500, B5D0, B10D0 gave the highest potato dry matter (P≤0.001). Highest N uptake was from plots with B0D500, B5D500, B10D500 and B5D250. The greatest P uptake was from plots treated with B0D500, B10D500 and sole use of biochar (P≤0.001). Treatment B5D0 gave the highest nitrogen use efficiency of 560.38 kg ha-1. Biochar application of B5D0 significantly affected (P≤0.001) gave the highest phosphorus use efficiency of 2451.67 kgP ha-1. These results confirm that use of biochar especially its integration with inorganic fertiliser is a sustainable strategy that increases potato growth, yield and nutrient use efficiency and improves soil properties.