Fast-growing trees support water management

| Enviromental Protection |

Plantations of fast-growing trees have turned out to provide support in water management of the areas where droughts are common. At the same time, they constitute a deposit of a resource which might be used for production of bioenergy.

Trouble with watering dryland farms

In dryland farming systems, it is common practice to remove the deep-rooted native vegetation and replace it with shallow-rooted annual plants. In the long term, this leads to the accumulation of excess groundwater. Annual plants are notorious for not making full use of the rainwater, which can cause the water to accumulate in the soil.

A natural way to combat soil salinity

Professor Richard Harper, a lecturer at Murdoch University in Australia, believes that PFT or phase-farming with trees, is a method to counteract soil salinisation and reduce the excessive amount of groundwater. In the case of dryland farming systems, this strategy enables to improve the quality and quality of yield.

According to Professor Harper, a recommended method of coping with soil salinity is to plant fast-growing, deep-rooted, native trees. A few years later, the return to agricultural use of the land is possible. The presence of trees makes it possible to dry up the soil adequately, even up to a few meters’ depth.

In order to test the idea, the scientists conducted a 5-year test in the fields outside Corrigin in the Wheatbelt region. The test aimed at analyzing how various species of trees and their density may help reduce the quantity of water in the soil. Three species (Eucalyptus globulus, Eukaliptus occidentalis, Pinus radiata) were planted at various density (500, 1000, 2000 or 4000 trees per hectare) and in three landscape locations. The team found that E. occidentalis planted at 4000 stems per hectare was the most efficient at extracting water. It absorbed 443-771 mm more water than on land without vegetation. Professor Harper thinks that the experiment indicates that three-to-four-year tree rotations followed by 11–20 years of agriculture appear to be the best option.

What makes plantations successful

However, the detailed results of the experiment were very variable, which suggests that preparing a selective sowing and irrigation scheme would be useful. What matters is that the differences in soil salinity, including highs and lows, may be managed using the diversification of the species of plants grown on the land and the reorganization of the plantation, for example by the modification of the density of plant placement.

“Careful adjustment of the genus of the plant to the local conditions is going to be an important element of implementing phase-farming with trees” – said Professor Richard Harper.