Enhancing nitrogen and rainwater use efficiency through rainwater harvesting in semi-arid smallholder sorghum (Sorghum bicolor) farming systems

Abstract

Nitrogen and rainwater use efficiency in semi-arid smallholder farming systems is low due to low soil fertility and unreliable rainfall. The objective of this study was to evaluate the effect of rainwater harvesting and mineral nitrogen fertilizer on nitrogen and rainwater use efficiency under two sorghum (Sorghum bicolor) varieties. A split-split plot experiment, replicated three times, was conducted in Mt Zonwe smallholder farming area from 2016/17 to 2018/19. The results showed that water content under tied contour (TC) and infiltration pits (IP) had significantly higher water content compared to standard contour (SC) and moisture content significantly decreased with an increase in distance from RWH practices. TC and IP had higher agronomic efficiency than SC across all nitrogen applications, distance from RWH practice, and seasons. Sorghum variety Macia had higher nitrogen use efficiency indices than Sc Sila at nitrogen application of 50 and 70 kg N/ha while nitrogen application >100 kg N/ha had no difference in nitrogen use in both varieties. A decreasing trend in nitrogen productivity with an increase in nitrogen application was shown in both varieties. Mineral nitrogen fertilizer application increased rainwater productivity up to 100 kg N/ha beyond which there was no significant difference. Regardless of sorghum variety and season, TC and IP had higher rainwater use efficiency than SC at each distance from RWH practice. This study recommends the integrated use of TC and IP rainwater harvesting practices and mineral nitrogen fertilizer sustainably to improve N and rainwater productivity in semi-arid smallholder sorghum farming systems.

Keywords:

• Sorghum
• agronomic efficiency
• rain-fed
• rainwater harvesting
• rainwater use efficiency

Acknowledgments

We acknowledge partial funding from International Foundation for Science (IFS) grant number C4569-2.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the International Foundation for Science [C4569-2].

Notes on contributors

Friday Nguvayasvika Mudondo Kubiku

Friday Nguvayasvika Mudondo Kubiku is a Lecturer in the Department of Agricultural Economics at Manicaland State University of Applied Sciences, Zimbabwe. He is a PhD student in Agricultural Sciences at Bindura University of Science Education in the Department of Environmental Science and holds a Master of Science in Agroforestry, Bindura University of Science Education. His research interest is in exploring sustainable agriculture farming systems.

Ronald Mandumbu

Ronald Mandumbu is an Associate Professor in the Department of Crop Science, Bindura University of Science Education, Zimbabwe. His research interest is in biology, ecology, and management of weeds and his current research is on the Ecology of strigolactone production in Sorghum arundinaceaum and Sorghum bicolour.

George Nyamadzawo

George Nyamadzawo is a Professor of Soil Science and Environmental Science and Research Consultant at the Swedish University of Agricultural Science - Productive Sands Project in Climate Smart Agriculture Options. His research interest is in climate change adaptation and promoting marginalised crops through their cultivation, use and value addition.