Performance of an Improved Fallow System in the Peruvian Amazon—Modelling Approach

background

This research compares the ecological and economic potential of an improved leguminous tree fallow (using Inga edulis) to the traditional grass fallow (dominated by Imperata brasiliensis) in central Peru.

Research Goals & Methods

For the study, two plots were compared: 1) four year rotation consisting of 3 years of I. brasiliensis fallow and 1 cassava crop, and 2) 5 year rotation consisting of 3 years of I. edulis fallow and 2 subsequent cassava crops. A computer model (SCUAF) was used to predict how the differing rotations would change soil conditions and how these changes would affect plant growth and plant yields over the long-term.

Conclusions & Takeaways

Soil fertility was found to decrease over the longterm in the I. brasiliensis plot; however, nitrogen levels increased, soil organic matter slightly increased, and phosphorus levels were maintained in the I. edulis plot. Yields of cassava decreased over time in the I. brasiliensis fallow system while yields increased at the beginning and then remained stable in the I. edulis fallow system. Over a 30 year period, the I. edulis system is predicted to produce a larger surplus due to higher crop yields and the additional benefit of firewood extraction even though costs are about 10% higher for the I. edulis fallow system. If a higher discount rate is used (25%), the cost-benefit ratios of both systems is roughly equal suggesting that smallholders may be less likely to adopt the I. edulis system. The authors conclude that there are significant benefits of converting to the I. edulis fallow system, seen in improved soil fertility and higher crop yields, but suggest that adoption might be difficult for smallholders due to initial establishment costs.