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Biological Nitrogen Fixation of Pigeonpea and Groundnut: Quantifying Response Across 18 Farm Sites in Northern Malawi
Book chapter

Biological Nitrogen Fixation of Pigeonpea and Groundnut: Quantifying Response Across 18 Farm Sites in Northern Malawi

Wezi G. Mhango, Sieglinde Snapp and George Y. Kanyama-Phiri
Just Enough Nitrogen, pp.139-153
Springer International Publishing
2020
DOI: https://doi.org/10.1007/978-3-030-58065-0_10
url
https://doi.org/10.1007/978-3-030-58065-0_10View
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Abstract

Biological nitrogen fixation Groundnut Intercropping Pigeonpea Smallholder farms
The globalGlobal nitrogen (N) cycle is markedly, and increasingly, influenced by anthropogenic inputs. A large unknown remains the quantity of biological N fixation (BNF)Biological nitrogen fixation inputs derived from agriculture. This leads to major uncertainties in modelling reactive N interactions with climateClimatechangeClimate, and understanding N biogeochemical processes. Understanding N dynamics is central to enhancing productivity in croppingCropland systems. To fill this gap, we used measurements of natural abundance of the 15N isotopeIsotopeto quantify BNFBiological nitrogen fixation and yield of groundnutGroundnut and pigeonpeaPigeonpea at 18 on-farm sites in Ekwendeni, Northern MalawiMalawi. The study was conducted over the 2007/08 (2008) and 2008/09 (2009) croppingCropland seasons under farmerFarmersmanagementManagement, for a range of edaphic environments. Overall, the soilsSoils are largely sandy with low to moderate organicOrganic carbon (0.12–1.56%), pH (5.5–6.5), and very low to moderately high inorganicOrganicphosphorusPhosphorus (P) (3–85 mg kg−1). The main drivers of BNFBiological nitrogen fixation were plant density, inorganic P and interspecific competition. The proportion of N derived from the atmosphere (22–99%) was influenced by soilSoils P status across seasons and crop species, but not by croppingCropland system. The mean proportion of nitrogenNitrogen derived from atmosphere (Ndfa) was high in both groundnutGroundnut (75%) and pigeonpeaPigeonpea (76%). Total N fixedN fixed by groundnutGroundnut and pigeonpeaPigeonpea differed between croppingCropland system in the dry year, whereIntercroppingintercroppingCropland was associated with low levels of N fixedN fixed by pigeonpeaPigeonpea (15 kg N  ha−1) compared to sole pigeonpeaPigeonpea (32 kg N  ha−1). A short rainfall season could not support biomassBiomass production of pigeonpeaPigeonpea and this has negative implications for relying on BNFBiological nitrogen fixation to drive productivity on smallholder farms.

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