Influence of nitrogen and potassium inputs on plant biomass and nitrogen use efficiency of Dioscorea alata

Abstract

Nitrogen (N) and potassium (K) are known to be important for root and tuber crops but their interactions have not yet been studied in Dioscorea spp. A field experiment was conducted on a Luvisol, in Sri Lanka, over two consecutive seasons in 2013/14 and 2014/15 with D. alata (cv. ‘Raja Ala’). The study was designed to assess the effects of combined N and K inputs added as mineral fertilizers on biomass production, leaf area index (LAI), tuber yield, N and K uptake, fertilizer N recovery in soil/plant system, and N and K input-output balances. The fertilizer N recovery was studied using ¹⁵N labeled urea. Increased N inputs increased the LAI, N and K uptake via increased biomass production, and tuber yield. Potassium input alone had no effect on LAI or tuber yield. After two seasons, 4 to 10% of the fertilizer N applied on yam, exported with the roots and tubers while 5 to 9% recovered in the senescent shoots, 29 to 62% of fertilizer N recovered in the first 50 cm of the soil and 25 to 58% of l fertilizer N had not been recovered in plant and soil system. Results suggest that nutrient management in yam should consider: (i) the amount of fertilizer N and K should cover the amount of N and K exported with the tuber harvest and (ii) yam should be followed by a crop with a long and fine root system to take up N in the soil profile.

Keywords:

• Yam
• N and K mineral fertilizers
• leaf area index
• fresh tuber yield
• N and K uptake
• ¹⁵N labeled urea
• N-fertilizer recovery

Acknowledgements

The authors dedicate this paper to the memory of Professor Upatissa Ravindranath Sangakkara from the University of Peradeniya, Sri Lanka, who contributed to develop and implement this project in Sri Lanka and collaboration with ETH Zurich and died in August 2014. Thanks are extended to Valery Hgaza and Lucien Diby for sharing their experiences on yam cultivation in West Africa and for the technical advices (Swiss Center for Scientific Research, Abidjan, Ivory Coast), Federica Tamburini for the mass spectrometer analyses (Group of Plant Nutrition, ETH, Zurich) and to all the members and co-workers in the Field Crops Research and Development Institute, Mahailluppallama, Sri Lanka and all the members in the Group of Plant Nutrition Eschikon (ETH) who helped in the field and in the laboratory. The Swiss Development and Cooperation Agency through the Research Fellowship Partnership Program (RFPP) managed by the North-South Centre of the ETH Zurich are acknowledged for supporting this project.

Disclosure statement

No potential conflict of interest was reported by the authors.