Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability

Sennhenn, A and Njarui, D M G and Maass, B L and Whitbread, A M (2017) Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability. Frontiers in Plant Science, 8 (699). pp. 1-17. ISSN 1664-462X

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Climate variability is the major risk to agricultural production in semi-arid agroecosystems and the key challenge to sustain farm livelihoods for the 500 million people who inhabit these areas worldwide. Short-season grain legumes have great potential to address this challenge and help to design more resilient and productive farming systems. However, grain legumes display a great diversity and differ widely in growth, development, and resource use efficiency. Three contrasting short season grain legumes common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet] were selected to assess their agricultural potential with respect to climate variability and change along the Machakos-Makueni transect in semi-arid Eastern Kenya. This was undertaken using measured data [a water response trial conducted during 2012/13 and 2013/14 in Machakos, Kenya] and simulated data using the Agricultural Production System sIMulator (APSIM). The APSIM crop model was calibrated and validated to simulate growth and development of short-season grain legumes in semi-arid environments. Water use efficiency (WUE) was used as indicator to quantify the production potential. The major traits of adaptation include early flowering and pod and seed set before the onset of terminal drought. Early phenology together with adapted canopy architecture allowed more optimal water use and greater partitioning of dry matter into seed (higher harvest index). While common bean followed a comparatively conservative strategy of minimizing water loss through crop transpiration, the very short development time and compact growth habit limited grain yield to rarely exceed 1,000 kg ha−1. An advantage of this strategy was relatively stable yields independent of in-crop rainfall or season length across the Machakos-Makueni transect. The growth habit of cowpea in contrast minimized water loss through soil evaporation with rapid ground cover and dry matter production, reaching very high grain yields at high potential sites (3,000 kg ha−1) but being highly susceptible to in-season drought. Lablab seemed to be best adapted to dry environments. Its canopy architecture appeared to be best in compromising between the investment in biomass as a prerequisite to accumulate grain yield by minimizing water loss through soil evaporation and crop transpiration. This lead to grain yields of up to 2,000 kg ha−1 at high potential sites and >1,000 kg ha−1 at low potential sites. The variance of observed and simulated WUE was high and no clear dependency on total rainfall alone was observed for all three short-season grain legumes, highlighting that pattern of water use is also important in determining final WUEbiomass and WUEgrain. Mean WUEgrain was lowest for cowpea (1.5–3.5 kggrain ha−1 mm−1) and highest for lablab (5–7 kggrain ha−1 mm−1) reflecting the high susceptibility to drought of cowpea and the good adaptation to dry environments of lablab. Results highlight that, based on specific morphological, phonological, and physiological characteristics, the three short-season grain legumes follow different strategies to cope with climate variability. The climate-smart site-specific utilization of the three legumes offers promising options to design more resilient and productive farming systems in semi-arid Eastern Kenya.

Item Type: Article
Divisions: Research Program : Innovation Systems for the Drylands (ISD)
CRP: CGIAR Research Program on Dryland Systems
CGIAR Research Program on Water, Land and Ecosystems (WLE)
Uncontrolled Keywords: Grain Legumes, Kenya, Climate Variability, Climate Change
Subjects: Others > Climate Change
Others > Legume Crops
Others > Kenya
Depositing User: Mr Ramesh K
Date Deposited: 17 May 2017 06:37
Last Modified: 08 Aug 2017 06:31
URI: http://oar.icrisat.org/id/eprint/10010
Official URL: http://dx.doi.org/10.3389/fpls.2017.00699
Acknowledgement: We thank the technical staff of KALRO, Katumani Kenya for their continuous support and encouragement during the on-station field research to collect the comprehensive datasets for model calibration and validation. The German academic exchange service (DAAD) supported this research by providing a travel scholarship enabling the senior author to conduct field research in Kenya. Operational expenses were funded by the University of Göttingen via the department of Tropical Plant Production and Agricultural Systems Modelling. The CGIAR Research Programs (CRP) for Dryland Systems and Water, Land and Ecosystems (WLE) are acknowledged for partly funding the time of AW and CRP for Livestock and Fish for the time of BM to contribute to this study.This article is part of the research topic New Innovations for Sustainable Intensification of Smallholder Cropping Systems in Sub-Sahara Africa (SSA).
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