Effect of nitrogen and phosphorus on yield and yield components of potato (Solanum tuberosum L.) AT masha woreda, southwestern ethiopia

Abstract

A study was conducted to determine the response of potato (Solanum tuberosum L.) to different rates of N (0, 55, 110 and 165 kg ha-1) and P (0, 20, 40 and 60 kg ha-1) fertilization at Masha in southwestern Ethiopia from November 2010 to February 2011 main cropping season using randomized complete block design with factorial arrangement (4x4) replicated three times. The plot size was four rows of 3m length each with a spacing of 75 cm between rows and 30 cm between plants. Data collected was on growth yield and quality parameters and analyzed using SAS 9.2 software. The result of the experiment showed that application of 165 kg N /ha highly significantly increased days to flowering by six days, days to physiological maturity by 13 days, above ground biomass by 36%, underground biomass by 29.79%, total tuber yield by 60.33%, marketable tuber number by 56.36% and total tuber number by 31.7% and reduced significantly dry matter content by 21.2%, specific gravity by 1.84% over the control and average tuber weight by 22.43%. Specific gravity and dry matter content showed a highly significant (P<0.01) reduction with the increased application of nitrogen and phosphorus over the control. However, N or P did not influence days to emergence, stem number, unmarketable tuber yield and number. Application of P significantly (P<0.05) increased days to flowering by three days, above ground and underground biomass by 8.78% and 61.4%, respectively and marketable tuber number by 19.72%, and reduced significantly dry matter content by 10.66%, specific gravity by 0.99%. The interaction effect of 165kg of N with 60 kg P increased marketable tuber yield (36 t/ha) by 122% as compared to control (16.2 t/ha). Application of 165 kg of N and 20 kg P (75.27) increased plant height by 24cm as compared to control (51cm). The phosphorus critical and requirement factors for the site were 12and12.5ppm, respectively. The highest total tuber yield (38.07 t/ ha) was recorded with the maximum N rate of 165 kg N/ ha. The lowest total tuber yield (23.75 t/ ha) on the other hand was recorded with no application of N (control treatment). Correlation analysis showed that total yield per hectare was highly and positively correlated with marketable yield per hectare (r =0.91**) total tuber number per hectare (r =0.81**) and number of marketable tuber ha-1 (r =0.77**). Average tuber weight (r =0.94**). Partial budget analysis also revealed that application of 165with 60 kg N and P gave the highest return followed by 165 with 40 and 20 kg N and P. The result of this study verified that yield and yield components of potato are influenced by different Nitrogen and Phosphorus rating. From this study, it can be concluded that the higher rating (165 kg Nitrogen and 20Kg Phosphorus) produced higher yield and marketable yield per hectare than other ratings. Thus, potato (Jalenie variety) growers in the study area (Masha) can be benefited if they use these higher rating levels (165 and 60 kg Nitrogen and Phosphorus). However, more such studies need to be conducted at various soils, at different agro climatic conditions and extra rate of nitrogen and phosphorus to generate more reliable information.