Title : Optimized shrub-intercropping system: A novel rhizosphere alliance to increase crop production and mitigate drought in the Sahel
Abstract:
The Sahel is facing severe soil degradation and chronic food insecurity. An overlooked solution are the shrubs, Guiera senegalensis or Piliostigma reticulatum. Although these are found in farmers’ fields throughout the Sahel; shrub density is low and the current management of coppicing and residue burning prior to cropping deprives soils of much needed organic matter. In contrast, our team over 20 years has shown that non-thermal management is feasible, and ecologically and agronomically very beneficial. Research in farmers’ fields and two long-term factorial experiments (each intercropped with G. senegalensis or P. reticulatum) of an optimized shrub-intercropping system (OSS) (~1500 shrubs ha-1 with coppiced residue returned to soils) compared to sole-cropping (under varying NPK rates of 0 to 1.5 times the recommended rate) relative to edaphic and agronomic performance of the staple crops pearl millet and groundnut in Senegal. After 10 years, OSS showed great potential to sequester C with 3700 more kg ha-1 of total C than the –shrub plots (6667 compared to 2952 kg ha-1 total C) with G. senegalensis. G. Senegalensis on the more sandy soil and drier northern site had more dramatic effects on C properties. Overall, OSS is increasing soil quality and harbors a more diverse/beneficial microbiome for crop production. Significantly, both shrubs perform hydraulic lift (HL) (movement of water via deep roots from wet sub- to dry surface-soil at night) with the profound discovery with G. senegalensis that it transferred isotopically labeled HLed water to adjacent millet plants - meaning shrubs are “bioirrigating” crops. Shrubs reduce time to harvest by ~15 days further buffering against low rainfall. Notably both millet and peanut yields have been dramatically increased with OSS. OSS is advantageous for subsistence Sahelian farmers, because it is a local, familiar resource that does not require any new infrastructure nor even external inputs – thus overcoming Green Revolution technologies shortcomings. Twenty years research has shown that OSS regenerates degraded soils, increases crop productivity, resists drought, and sequesters C; all of which is critical to address a changing climate – thus providing a sound scientific basis for piloting, demonstrating and ultimately scaling OSS across the Sahel to increase food security and regenerate degraded landscapes.
Audience Take Away Notes:
Applicable to West Africa:
- The Optimized Shrub-intercropping System (OSS) remediates degraded soils
- OSS harbors beneficial microorganisms known to promote plant growth
- Two native shrubs bioirrigate adjacent crops, reducing drought stress
- OSS dramatically increase crop yields
- OSS is an appropriate biotechnology for subsistence farmer that is expected to reduce food insecurity
