Treatments Rehabilitate Saline/Sodic Soils to Produce High Rice Yields

This blog post was written by Michelle DeFreese, Innovative Agricultural Research Initiative (iAGRI), Tanzania.

Rice is an increasingly important commodity with rising rates of consumption throughout sub-Saharan Africa. In Northeastern Tanzania, where rice is the principal crop, soil salinity is of particular concern. Irrigation schemes have doubled rice production in areas with low precipitation by creating the ideal conditions in terms of water content for rice crops to flourish. However, on the long-term, traditional irrigation schemes in Tanzania are often suboptimal due to insufficient outlets and the re-use of water, resulting in soils with high salinity and sodicity if improperly managed. Due to a combination of low yields and increasing consumption, an estimated 10-25% of rice consumed in Tanzania is imported.  Roughly 90% of rice production in Tanzania is done by small-scale farmers. For these reasons, iAGRI funded a collaborative research project focused on management practices and improved varieties designed to increase agricultural production for small holder farmers in Ndungu, Tanzania.

The combination of poor infrastructure and inadequate water circulation through consecutive fields has aggravated existing high soil salinity areas, rendering farmland infertile, incapable of producing even minimal yields for most crops. For rice, this culminated in grains that failed to fill, producing empty husks. High soil salinity on irrigated land causes an estimated crop loss of 27.3 billion USD per year globally. As rates of irrigation increase, sustainable land management is needed to mitigate crop losses caused by salt-affected soils. As a result, the Innovative Agricultural Research Initiative (iAGRI) prioritized the research conducted by Sophia Kashenge-Killenga, Senior Researcher at Chollimo AGRO Scientific Research Center in Dakawa, Tanzania.  The research combines the use of the following to mitigate saline and sodic soils:

  • Soil treatment combining the use of gypsum and flushing plus farmyard manure to lower sodicity and improve soil structure
  • Experimental soil treatment infusing soils with rice husks and sawdust to improve filtration of compacted soils
  • Improved Tanzanian rice varieties developed for local markets through hybridization using  salt tolerant parents collected from International rice research institute (IRRI) 

The research has resulted in the reclamation of some of the fields within 680 hectares of Ndungu irrigation scheme. One field (0.45ha) that was previously abandoned for 20 years had produced 15 bags (of 80kg each) after Dr. Kashenge’s intervention.  The use of sawdust and rice husks improved soil conditions enough to be able to produce 3.0 t/ha on average. The combination of gypsum application and improved varieties raised rice yields from 0.5 t/ha to 6.0 t/ha. Today, the rehabilitated soils support rice production for 1,774 households in the semi-arid region of Ndungu, Tanzania. The project is applicable to a further 59 irrigation schemes in nine other regions in Tanzania similarly affected by saline and sodic soils. 

The views expressed here belong to the speaker and do not necessarily represent FAO’s views, positions, strategies or opinions.

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