EFFECTS OF BIOCHAR RESIDUAL AND NPS FERTILIZER ON MORPHOAGRONOMIC AND TUBER QUALITY TRAITS OF POTATO (Solanum tuberosum L.) AT HARAMAYA, EASTERN ETHIOPIA

Abstract

Potato is co-staple, food security and cash crop in East Hararghe, however, the productivity of the crop is constrained by low soil fertility as a result of soil degradation due to continuous cropping using inorganic fertilizers without incorporating organic matter. Biochar, an emerging agricultur al soil amendment, has long-lasting degradation resistance compared to conventional organics, but its long-term effects on soil fertility and sustainable crop productivity need evaluation. Thus, an experiment was conducted to evaluate the effects of biochar residual and NPS fertilizer on potato growth, yield, quality traits, soil physicochemical properties, and economic rate of return. Bubu potato variety was evaluated under plots treated with 0, 10, 20, and 30 t ha-1 residues of biochar that was incorporated in 2022 cropping season with the application of five rates of NPS fertilizer (0, 75, 150, 225, and 300 kg ha-1) in split-plot design and replicated three times per treatment same to the preexisting experiment. Urea fertilizer at rate of 100 kg ha-1 was applied to the plots. The soil samples analysis after one year indicated that sandy loam was changed to clay loam at plots where 10 and 20 t ha-1 biochar incorporated and changed to sand clay soil textural class in plot that received 30 t ha-1 biochar. The incorporated biochar also increased the pH, organic matter and organic carbon of the soil in the range between 0.93 and 1.61, 1.88 and 2.08% and 0.18 and 0.33%, respectively, while the soil total nitrogen, available Phosphorus and Sulphur increased from 0.094 to 0.104%, 0.61 to 13.46 (mg kg-1) and 1 to 9.78 (mg kg-1), respectively. Biochar residue and NPS fertilizer had significant effect on days to 50% flowering, plant height, average tuber number and average tuber weight. The interaction of biochar residue and NPS fertilizer significantly influenced the number of main stems per hill, leaf area index, marketable, unmarketable, total tuber yield, dry matter, specific gravity and starch content of tubers.The residue of biochar from the higher rates (20 and 30 t ha1) with the application of NPS fertilizerathigher rates (225 and 300 kg ha1) and the interaction of these rates much improved the performance of the potato for most of the traits. Bubu variety produced significantly the highest marketable tuber yield of 38.97 t ha1 from the combined application of 20 t ha-1 biochar residue and 300 kg NPS ha-1 fertilizer, however had nonsignificant difference with 38.43 t ha- marketable tuber yield produced by the interaction of 30 t ha-1 biochar residue and 300 kg ha1 NPS fertilizer. Moreover, the highest adjusted marketable tuber yield of 35 .07 t ha1, net benefit of 924923.3 Birr and benefit to cost ratio (7.27) with an acceptable marginal rate of return (1337.46%) were estimated for the interaction effect of 20 t ha-1 biochar residue and 300 kg ha-1 NPS fertilizer. Thus, it is concluded that the incorporation of 20 t ha-1 biochar in the soil during the preceded cropping season improved the soil physicochemical properties and with the application of 300 kg ha-1 NPS fertilizer increased the production of potato, ensure a higher net benefit and rate of economic return to the producers in the study area