Root nodulation and yield of French bean (Phaseolus vulgaris) are altered by fallow length in slash-and-burn agriculture

ABSTRACT

Shifting cultivation (Jhum) involves the conversion of forest land to agricultural land, and two successive Jhum cultivations in a patch of land make a Jhum cycle. Shortening of the cycle to meet population needs is a challenge, and one potential solution is to use N₂-fixing, trees in fallow-phase and crops in cropping-phase. A pot experiment was conducted with soil from 2-, 4-, and 8-years fallows of alder-based (N₂-fixed) and traditional Jhum agroecosystems, grown with surface-sterilized local French beans (design: CRD). A factorial micro-plot field experiment was also set up in alder-based Jhum sites in 2-, 4-, and 8-years fallow. In both, soil physico-chemical and biological properties, root nodulation and yield attributes of French beans were studied. Root nodulation and biomass yield attributes were higher in alder-based systems compared to traditional, with comparable improvements seen in shorter fallows. At harvest, yield parameters were in the order of 4->2->8-years in alder-based and 8->4->2-years in traditional Jhum soil. Rhizobium populations may decrease with longer fallow lengths without a host and fire stress of Jhum. Fallow length effect on all soil parameters, with increased values as length increased in both Jhum. Combination of soil-fertility and nodulation led to higher grain yield in 4-year-fallows of alder-based Jhum.

KEYWORDS:

• Alder-based and traditional Jhum
• nodule index
• nutrient uptake
• potential mineralizable nitrogen
• soil enzyme activity

Acknowledgments

The researchers are thankful to Dr. R.C.S. Jayaraj, Director, and Dr. Indrani P Borah, Scientist-C, of Rain Forest Research Institute, Jorhat, Assam, India, and acknowledge them for facilitating the research. The authors are grateful to Mr. Ashini Karam, Jiten Akoijam, Jotin Takhelambam and Premjit Athokpam from Manipur for all their help and support during field trips and Jhum cycle identification.

Disclosure statement

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

Additional information

Funding

We gratefully acknowledge the funding provided by the Department of Biotechnology, Ministry of Science and Technology, Government of India, through sanction order number DBT-NER/Agri/14/2012 dated October 31, 2021 and the Forest Research Institute, Dehradun, India, in support of PhD research (registration number 14/PHD/350)