Abstract
This long term research is being carried out in degraded lands of low fertility conditions in the humid tropics of the Peruvian Amazon. The objective is to recover degraded lands for sustainable agriculture that was affected by shifting agriculture and overgrazed pastures. The recovering trials in three farms are fertilized cover crops with the legume Centrosema (Centrosema macrocarpum), and the establishment of th prototype agroforestry systems are based on a) woody trees with Swietenia macrophylla, Guazuma crinita (GC), Calycophylum spruceanum (CS) and Simarouba amara (SA), b) woody-fruit trees with Cedrelinga cateniformis, GC, SA, Inga edulis and Bactris gasipaes, and a c) silvopastoral system with Centrosema and woody trees with GC, SA and CS. Initial degraded compacted soils were covered with degraded grass (Brachiaria brizantha) and weeds, and the soil were very acid (80% of Al saturation) with 4 ppm of P and low soil organic matter and cation exchange capacity. Soil was weeded and fertilized with a combined fertilizer based on rock phosphate (40 kg/ha), and then Centrosema was planted followed by the plantation of trees with localized fertilization application. In three months we had 100% cover and weeds were controlled. Average Centrosema biomass in 8 months was 8.12 T/ha, and while the different trees were growing with 55 to 89 percentage of survival due to water stress, Centrosema recovered the soil compaction up to 20 cm depth. Biomass can be used as forage for small animals and to enrich soil. Mean total nitrogen accumulation in biomass was 232 kg/ha.
Highlights
The Peruvian amazon had a reserve of 78.9 million hectares of natural forest, comprising 58.8% of the total Peruvian territory
Some high and low input technologies in long term trials have been tested in the humid acid tropical soil of Yurimaguas, Peru and one of the main options was the agroforestry systems (Palm, 1995; Alegre, 2015)
Crops can force associated trees to take up a great part of nutrient from deep or laterally distant soils, and can deplete these nutrients when they are released from decomposing tree litter (Schroth et al, 2001)
Summary
The Peruvian amazon had a reserve of 78.9 million hectares of natural forest, comprising 58.8% of the total Peruvian territory. Several other causes affect the degradation of the Amazon; the main driving forces of deforestation are the selective extraction of wood, new roads and land tenure (Kaimowitz and Angelsen, 1998). Several technical options to recover degraded land have been studied to recover compacted soils by overgrazed pastures or intensive mechanization (Alegre et al, 1986; Lal, 2015). The potential of trees and cover crops to contribute to the maintenance and rehabilitation of the soil’s physical characteristics such as better bulk density, mechanical resistance and soil aggregation has been well established, including an improvement on productivity (Alegre and Rao, 1996; Rao et al, 1998; Alegre et al, 2005). Crops can force associated trees to take up a great part of nutrient from deep or laterally distant soils, and can deplete these nutrients when they are released from decomposing tree litter (Schroth et al, 2001)
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