A coffee biochar-mineral NP interaction: Boon for soil health

Abstract

Low soil fertility, attributed to a deficiency in multiple nutrients, is causing a decline in the productivity of potatoes (Solanum tuberosum) in the Gawata district of southwestern Ethiopia. To address this issue, a field experiment was conducted during the Belg season (February to May) and Meher season (June to October) of the year 2024. The objective was to assess the response of potatoes to the combined application of nitrogen, phosphorus, and coffee biochar (BC) in relation to specific soil physico chemical properties under rainfed conditions. The treatments comprised various combinations of biochar (2.5, 5, 7.5 t ha-1) and inorganic NP (25, 50, and 75%) of the recommended dose (165 kg N ha-1 + 60 kg P ha-1 = 100% recommended dose of fertilizer, RDF), along with 20 t ha-1 of biochar and 100% inorganic NP, with a no-fertilizer treatment serving as the control. In total, there were 12 treatments and a randomized complete block design with three replications was employed for the experiment. The results indicated that the combined application of 75% inorganic NP and 7.5 t ha-1 of biochar significantly increased pH, organic carbon, total nitrogen, available phosphorus, cation exchange capacity, and exchangeable calcium and magnesium. Additionally, it reduced bulk density, exchangeable acidity, exchangeable aluminum, and exchangeable potassium compared to the values obtained from the initial soil test. Consequently, it was concluded that the integrated use of 7.5 t ha-1 of biochar and 75% of inorganic NP during the Belg season, or 25% of it during the Meher season, represents an optimal nutrient management strategy for potato production in the study area.