Use of biological agents such as earthworms and mycorrhizal fungi to improve or maintain soil health. Recently five of us from the Pacific made a trip to Cuba to learn about their urban/organic agricultural practices. The trip was organised by POETCom and funded by the UNDP Small Grants Program (SGP). Mr Johnson Ladota and I represented the Solomon Islands in this trip.

The trip included a mixture of lectures and field visits to various farms, including a nursery. We learned a lot of things during this trip. However, one thing that impressed me most is their use of biological agents to improve and/or maintain soil health and therefore plant health. In particular, the use of earthworms or vermi-culture in the production of nutrient-rich composts, and the use of mycorrhizal or root fungi to increase the roots’ capacity to absorb nutrients and water.

The Cubans use two species of earthworms in composting animal manure, especially cow manure. These are the African crawler and Californian worm. These two species are said to adapt well to the warm climatic conditions of Cuba.

They raise these worms in specially made cement wells. Vermi-composting can be carried out under a roof or under shade, such as under a grove of neem trees. This is because the worms want a dark, cool and moist environment. Vermi-composting involves introducing about 1 kg of worms into a layer of manure, and adding a fresh layer of cow manure each time until you reach the level of the tank or well about 05 -1.0m high. The vermi-compost is ready for use after three months. The vermi-compost is then mixed with 25% rice husk and 25% soil or compost from aerobic composting before use in a nursery or applied to the field.

Mycorrhizal fungi is used in one particular farm we visited. The fungi are cultured in shallow cement wells shown in. This involves adding a layer of clayey soils to a well then pouring hotwater into the soil layer to sterilise the soil. Then a commercial culture of mycorrhizal fungi is introduced into the well by spraying the inoculant onto the soil. Then a grass (or any fast growing fibrous root plant) is planted into the soil to allow the fungi to colonise its roots. After some time watering was withdrawn from the well resulting in the soil drying up and the plant undergoing water stress. This condition stimulated the mycorrhizal fungi to multiply and produce spores. When this happens the soil including the roots are harvested and used as the inoculant on crops. The soil/root mix would be made into a very watery slurry and seedling roots would be dipped into the slurry before planting out in the field. Inoculating crops with mycorrhizal fungi has been said to increase yields by 3-4 times.

Since one of our trip’s main objective is to identify technologies that can be transferred to the Pacific, I believe these two technologies will have a great impact on organic and urban agriculture in the Pacific. The Cubans recommended identifying suitable earthworm species in the islands as a first step. Introducing foreign earthworms would be a last resort they said. Commercial cultures of mycorrhizal fungi are easy to obtain and cultured using the technique we saw in Cuba.