Effect of biochar and inorganic fertilizer on growth, yield, and quality of beetroot (beta vulgaris l.) in Kenya

Abstract

Beetroot (Beta vulgaris L.) is crop grown for its antioxidant properties. It also contributes to the improvement of livelihoods of stakeholders in its value chain. However, beetroot farming has faced various challenges that negate the root yields in Kenya. The high cost of inorganic fertilizers has resulted in the continuous use of ineffective combinations of synthetic fertilizers and soil amendments resulting in low soil fertility. This study aimed at determining the effect of biochar and NPK on the growth, yield, and quality of beetroot. A 2- seasons experiment was conducted at Egerton University’s Field 3. The experiment was laid out in a randomized complete block design (RCBD) in a factorial arrangement with 3 replications. Each replicate had twelve (12) treatments. Biochar was applied at three levels (0, 5, and 10 t ha-1), while inorganic fertilizer (NPK) was applied at four levels (0, 200, 300, and 400 kg ha-1). Initial characterization of soil and biochar for macro and micronutrients were done, before planting. Data was collected for plant height, leaf area and the number of leaves at two weeks intervals starting from two weeks after emergence. Data on yield and quality parameters were collected after harvesting. Folin Denis reagent was used to analyse beetroot’s total phenolic content, A hand-held refractometer (RHB; Shanghai Precision and Scientific Instrument Co. China) was used to measure total soluble solids (TSS). The spectrophotometric and complexometric method were used to analyse phosphorus and calcium content. Atomic Absorption Spectrophotometry used to analyse iron content. The Shapiro-Wilk test was used to ascertain the normality of data and analysis of variance using Proc GLM in Statistical Analysis Software (SAS). Tukey’s Honestly Significant Difference was used to compare the means. Application of all rates of biochar (0, 5 and 10 t ha-1) did not increase significantly beetroot growth, while NPK at 200, 300 and 400kg ha-1 significantly increased beetroot growth in seasons one and two. Moreover, biochar combined with NPK significantly increased beetroot growth in terms of height at 75 and 90 days and leaf area 45, 60, 75 and 90 days in season two. Biochar at 5 t ha-1 (B5) resulted in 61.1 t ha-1 of marketable yield. Treatment B5 showed iron content of 713.4mg kg-1 in the beetroot in season one. However, in season two was 720.7mg kg-1. Additionally, biochar at 5 t ha-1 also had the highest concentration of total soluble solids (10.8 oBrix), compared with the other treatments. Therefore, biochar at 5 and 10 t ha-1 combined with NPK at (200, 300 and 400kg ha-1) were not statistically different from each other to increasing beetroot growth, yield and quality. Based on findings of this study, B5N200 can be recommended for beetroot production in Kenya.