- Farming on hills and mountain slopes plays a crucial role in global food security. However, agriculture in these regions faces significant challenges. That’s why it is essential to develop suitable methods to manage the land effectively, says Huu Thuong Pham.
He is soon to present his dissertation on how agriculture in such areas can be improved. His study sites are located in the mountainous regions of northwestern Vietnam.
Pham has investigated a method known as agroforestry, where trees and grasses are integrated with crops to reduce erosion. In these farming systems, trees, crops and grasses are planted in rows along the contour lines. Crops such as maize or coffee are grown in the alleys between the tree rows. In this way, all land is utilized: trees may produce fruit, grasses provide fodder for livestock, and crops both offer food and income for farmers.
- The hope is that this land-use approach will lead to higher yields while also reducing erosion, preventing nutrient loss, and optimising the use of sunlight and rainwater, says Pham.
In his study, he examines how the plants’ access to light, water, and nutrients varies across steep agroforestry fields, and how these systems can be optimised. Trees, crops and grasses compete for resources, especially downslope from the tree and grass rows. However, the combination of different plant species results in more efficient use of sunlight and water, potentially increasing overall productivity. These systems can become even more effective if competition is reduced through targeted cultivation measures.
- With the right tree species selection, agroforestry can retain more water, which is vital for crops during dry periods. These effects can be further enhanced by introducing measures to reduce evaporation and perhaps complementary irrigation, says Pham.
Legumes Improve Soil Organic Matter
He also explores what happens when legumes are planted between the rows of trees and grasses and beneath coffee shrubs. Legumes increase the soil's carbon and nitrogen content. However, they also compete with other plants for phosphorus and potassium, and nutrient deficiencies proved to be the main limiting factor for plant growth in the studied systems. To remain sustainable in the future, all system components will need adequate fertilisation.
Model simulations show that resource-use efficiency improves significantly when legumes such as peanuts and mung beans are grown alongside maize. This practice extends the growing season and increases the duration of living soil cover, leading to better utilisation of light and water.
- This study gives hope that sloping lands can be managed sustainably while also increasing income for smallholder farmers. Fruit tree-based agroforestry systems make farming on sloping lands more beneficial for both farmers and ecosystems, says Pham.
