Truffle irrigation on variable soil types

The question of how much water, how often and how quickly it should be applied, is one of the most debated aspects of truffle farming.

The answer to how much and how often to water truffle, usually involves a combination of soil characteristics, drainage, weather and the age of the trees. How fast to apply water is generally based on the soil type.

Soil types differ from paddock to paddock and weather differs from region to region, so there is clearly no ‘one size fits all’ answer. Added to the confusion, is the fact that there’s been great variation of soil types used throughout the evolution of the truffle industry in non-traditional environments, at times, without any meaningful soil preparation.

Soil types

To explain more clearly, its helpful to highlight some extremes in soil characteristics, in relation to general irrigation.
Clay-based soils have small, flat, compact particles with large surface to volume ratios. Water is absorbed and moves slowly through clay soils, but once wet, they retain significant amounts of moisture. This means water applied quickly to clay soil tends to run off rather than move into the soil. Therefore, when irrigating clay based soils, water should be applied slowly over a long period.
Sand-based, or very stony, gravelly soils are at the other end of the spectrum, having comparatively larger particles with small surface to volume ratios. Water is absorbed and moves quickly through sandy and stony soils, but they retain very little. Irrigation times on sites with these soil types, should be shorter and more frequent, otherwise water moves beyond the root zone, becoming unavailable to the mycorrhizae/plant and contributing to soil leaching. Quick water application on sandy and stony or gravelly soils will contribute to a broader wetting area, providing more soil volume for the mycorrhizae to exploit.

Existing farms

For existing growers, its important to fully understand your soil type and its characteristics. This will make it easier to make informed decisions about truffle irrigation. It’s also important to gain an understanding of the truffle life-cycle, and so be able to meet its specific needs at different times. The developing truffle spends a long time underground during its growth phase. It’s subject to constant changes in soil moisture, humidity, temperature and in some cases movement, so managing irrigation events well, is important to successful outcomes.

New farms

New farms being established are at a distinct advantage in many ways. The knowledge base we now have in relation to site selection for truffle growing and soil preparation, if adhered to, allows for much better irrigation management practices, among many other benefits.

New trees and established trees

In coming posts I’ll explain the critical water requirements and irrigation techniques for new trees (up to year 4) and the dynamic and increasing irrigation, required for more established trees.

Till next post…

Noel Fitzpatrick