Tuesday, May 22, 2012

How sustainable are intensive irrigated rice cropping systems?

The sustainability of highly intensive irrigated rice cropping systems is of great importance worldwide, particularly in the context of Rio+20.

With German support, long-term fertility experiments (LTFEs) for intensive rice-based irrigated systems in the Senegal River valley were established at AfricaRice’s research farms in the Senegal River delta and middle valley in 1991 and these trials continue today.

These trials are without doubt unique in Africa. The LTFEs contain six fertilizer treatments and rice is grown twice a year. As of December 2010, some 40 crops had been grown in succession on both research farms (Senegal River delta and middle valley).

The main aim of this research is to analyze the effect of intensive irrigated rice cropping on rice yield and the soil resource base by studying the changes of soil characteristics over time and by comparing soil nitrogen, phosphorus and potassium supply in different fertilizer treatments.

The results over 40 consecutive seasons showed that the best treatments at both sites yielded on average 7.1 to 7.5 tons per hectare. Soil organic carbon remained stable or increased irrespective of fertilizer application. The LTFEs have shown that intensive monocropping of irrigated rice is sustainable in the Sahel.

Yields remained stable at around 3 to 4 tons per hectare without the application of any fertilizer. Higher yields could be obtained by applying nitrogen every season, and phosphorus and potassium once a year.