Positive results of coconut/acacia intercropping for nitrogen, potassium and magnesium restoration.

Abstract

In trial plots set up in 1986 in Côte d'Ivoire, the coconut hybrid PB 121 was intercropped with Acacia mangium or A. auriculiformis. The coconuts were planted at 108 palms/ha in the intercropped plots and at 160 palms/ha in monoculture controls. The Acacia trees were cut back to 1.5 m in height every 4 years; trunks were removed but leaves and small branches were left on the ground. It was estimated that after a year, A. mangium restored 80% of the K, 25% of the Mg and 20% of the N originally immobilized to the soil, while A. auriculiformis restored 95% of the K, 60% of the Mg and 35% of the N. Although A. mangium produced more biomass than A. auriculiformis, residues of the latter seemed to decompose more readily and restored nutrients to the soil more rapidly. Coconut yields/palm in 1993-94 were significantly higher with either of the intercrops than in coconut-only plots supplied with N fertilizer. Yields per ha in the same year were increased from 3500 nuts in coconut monoculture without additional fertilizer to ∼8000 nuts in the intercropped plots. It was concluded that these woody legumes provide a sustainable alternative to N fertilizer application and also provide a supply of wood for domestic use.