Bioirrigation and Hydrology

Shrubs BioIrrigate - here's how it works

It starts with the shrubs' deep roots that grow 10 meters or more down into the wet subsoil.

Deep Tap Roots                  Tap Root

The roots suck up water from the wet deep sub-soil and deposit this small amount of water in the dry upper soil layers at night when photosynthesis stops. Surrounding crops take advantage of some of this water that is drawn up. This is called hydraulic lift or hydraulic redistribution. We call it bioirrigation.

Bioirrigation

To test they hypothesis of water transfer, we set up a simulated drought experiment in Senegal during the dry season using irrigation to manipulate the amount and timing of water delivery.

  • We attached bottles with labelled water (deuterium) tracer to the deep roots of the shrub. Then, we collected aboveground leaf samples of the shrub, and adjacent millet plants growing over a period of five days which were analyzed for the tracer.

  • We found evidence of the tracer in a shrub on the first day after injecting the labelled water, and then a day later we found it in the millet growing nearby.

Deuterium Tracking

This finding confirms for the first time that hydraulically lifted water by shrubs can be transferred to the adjacent millet crop.

Simulated Drought Experiment During the Dry season - April to June 19, 2014

  • Millet was irrigated with adequate water until flowering

  • 41 day cessation of additional water through harvest

  • The plot without shrubs had a failed crop. The plus shrub plot produced a yield

This is of major significance in a region with recurring in-season drought. For the majority subsistence farming faimlies crop failure can quickly lead to famine.

drought experiment

In 2013, we also found greater soil moisture before rains started in late July and into planting season with shrubs.

Soil Moisture

In plots with shrubs and zero fertilizer, there was an 87% increase in millet Water Use Efficiency (WUE).

WUE

Bogie, N., Bayala, R., Diedhiou, I., Conklin, M., Fogel, M., Dick, R., and Ghezzehei, T. 2018. Hydraulic redistribution by native sahelian shrubs : bioirrigation to resis in-season drought. Frontiers in Environmental Science  https://doi.org/10.3389/fenvs.2018.00098.

Bogie, N.A., R. Bayala, I. Diedhiou, R. P. Dick andl T. A. Ghezzehei. 2018. Intercropping with two native woody shrubs improves water status and development of interplanted groundnut and pearl millet in the Sahel. Plant Soil. https://doi.org/10.1007/s11104-018-3882-4.

Kizito, F., M. Senè, M. I. Dragila, A. Lufafa, I. Diedhiou, E. Dossa, R. Cuenca, J. Selker, R. P. Dick. 2007. Soil water balance of annual crop-native shrub systems in Senegal’s Peanut Basin. Ag. Water Management 90:137 – 148.

Kizito, F.; Dragila, M.; Sene, M.; Lufafa, A.; Diedhiou, I.; Dick, R.P.; Selker, J.S., Dossa, E. 2006. Seasonal soil water variation and root patterns between two semi-arid shrubs co-existing with Pearl millet in Senegal, West Africa. Journal of Arid Environments. 67:436-455.

Kizito, F., M. I. Dragila, M. Senè, R. J. Brooks, F. C. Meinzer, I. Diedhiou, M. Diouf,, A. Lufafa, R.P. Dick, J. Selker, R. H Cuenca. 2012. Hydraulic Redistribution by Two Semi-arid Shrub Species: Implications for Sahelian Agro-ecosystems. J. Aird Environments. 83:69-77.