Effect of nitrogen rates and irrigation regimes on nitrogen use efficiency of potato (Solanum tuberosum L.) in southwest Ethiopia

Abstract

Despite the high production potential of potato in Ethiopia, the national average yield is low mainly due to poor fertilizer and irrigation water management. Various scholars have indicated existence of knowledge gap among potato growers with regard to nitrogen application rates and irrigation regimes that could potentially enhance efficient use of both water and nitrogen in relation to variety. This work therefore was initiated to assess effects of nitrogen rates and irrigation regimes on nitrogen use efficiency of selected potato varieties in south western Ethiopia. The experiment was 3³ factorial with three replication managed by Randomized Complete Block Design using Jalene, Guassa and Degemegn potato varieties; 130, 110, 90 kg/ha nitrogen rates, and 100%, 80% and 60% irrigations. Nitrogen content, uptake and utilization efficiency data collected were subjected to analysis of SAS Software version 9.2 and the mean separation was done by list significant difference (LSD). Irrigation and variety significantly affected the nitrogen utilization efficiency while only irrigation highly significantly influenced the nitrogen up take efficiency, nitrogen up take and shoot nitrogen content. Decreasing irrigation water from 20-40% decreased average nitrogen up take efficiency by 20.1- 38.86% and average nitrogen up take by 20.2-38.89%. The interaction of variety and irrigation significantly affected the average tuber nitrogen content.  Reducing irrigation water by 40% caused tuber nitrogen content reduction of 51.7 and 56.6% in case of Jalenie and Guassa varieties, respectively. It can be concluded that irrigation regimes and variety significantly affected nitrogen use efficiency of the potato varieties while the nitrogen rates did not influence the nitrogen use efficiency of the potato varieties significantly. Guassa and Jalenie varieties were more efficient than Degemegn variety.