Potato (Solanum tuberosum L.) growth and tuber quality, soil nitrogen and phosphorus content as affected by different rates of nitrogen and phosphorus at Masha district in southwestern Ethiopia

Abstract

Background: Potato (Solanum tuberosum L.) was introduced to Ethiopia in 1858 and 70% of Ethiopian land, mainly in the highland is suitable for potato growing. Despite this the national average yield is only 8.2 t ha-1. Low soil fertility especially N and P deficiency is the major constraint limiting potato yield in Ethiopia in general and Southwestern part in particular. Concomitantly, there is insufficient site specific information on how much fertilizer to apply on different soil types with patch of high and low fertility. Therefore, this study was conducted to determine area specific N and P rates for optimum potato growth, quality tuber production and improved N and P content of the soils of the study area. Materials and Methods: Four rates of N at 0, 55, 110 and 165 kg ha-1 and P at 0, 20, 40 and 60 kg ha-1 combined in factorial arrangement and laid out in RCBD with three replications. Data collected on potato growth, tuber quality, TN and available P content of the soil after potato harvest were analyzed using SAS version 9.2. Results: The interaction of 165 kg N ha-1 and 20 kg P ha-1 increased plant height by 51% over the control. Besides, 165 kg N ha-1 increased TN contents of the soil by 95% and available P by 42%. Plant height was positively and significantly correlated with soil TN (r = 0.55) and available P content (r = 0.68). Similarly, tuber dry matter content was positively and significantly correlated with tuber specific gravity (r = 0.94) verifying tuber dry matter is an indicator of tuber specific gravity. Conclusion: The present results indicated potato growth, tuber quality, TN and available P content of the soil were affected by N and P rates. The lower and medium N and P rates were favoring potato tuber quality parameters while, the higher N and P rates were favoring potato growth, TN and available P content of the soil. Therefore, the combined application of 165 kg N and 60 kg P ha-1 is required for optimum growth of Jalene potato variety and improved TN and available P content of the soils of Masha district.