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Solving Soil Quality Problems with Local Resources

In the graduate seminar Tropical Resources, visiting professor Pedro Sanchez emphasizes the relationships between food security, poverty, and environmental protection.

High-tech solutions like genetically engineered crops can help hunger-ravaged Africans after we invest in development programs that resolve basic soil fertility issues, he said. Sanchez has just returned to the states after 10 years as Director of the International Center for Research in Agroforestry in Nairobi.

“The potential of genetically improved crops cannot be realized when soils are depleted of nitrogen and phosphorus,” he said. Small-scale farmers in Africa have removed nutrients equivalent to US $4 billion in fertilizer. Traditionally, farmers elsewhere replace these nutrients with mineral fertilizers. But at a cost two to six times higher than in Europe or the U.S., Africans can’t afford them.

Working with farmers, Sanchez helped develop a new program for restoring soil fertility. The key is using naturally available resources.

The farmer-designed program uses leguminous trees as a rotation crop to fix nitrogen into the soil. Indigenous phosphate rocks are incorporated that break down in the mildly acidic soil to provide phosphorus. . These techniques increase maize yield two- to four-fold. And for high-value crops, farmers till leaves and biomass into the soil from the nutrient-accumulating roadside shrub, Tithonia diversifolia.

“This works because we involved the farmers from the beginning,” Sanchez said. The goal now is to increase participation from tens of thousands to tens of millions of African farmers.

For the seminar program, Sanchez uses his experiences in Africa to demonstrate the trade-offs between conservation and development in the tropics. A soil scientist by training, Sanchez is also using his time at Berkeley to revise his classic book, Properties and Management of Soils in the Tropics. Though accepted as the standard, Sanchez said it is out of date and he has received a grant from the Kearney Foundation of Soil Science to update it.

For his work, Sanchez has recently received recognition from opposite ends of the academic spectrum. He was awarded an honorary doctorate degree from the prestigious Catholic University of Leuven, Belgium, and he was adopted as an elder into the Kenyan Luo community. “That’s a very rare honor for a non-Luo, non-Kenyan,” he said. But the Luo said Sanchez was not an appropriate name for one of their elders. They renamed him Odera Kang’o, after one of their prior kings who was very concerned about the environment.


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