Summer Irrigation – A Key Factor
The Australian 2017 French black truffle season, was by all accounts, extremely successful in terms of yield and quality. As an industry consultant, my research includes communicating with growers from a range of productive regions on a regular basis. This year, the feedback was overwhelmingly similar, reporting increases in yield of between 50 – 150% on the previous season. Quality issues, often related to rot and insect damage were quite variable, however, had generally also improved.
The Australian French black truffle industry has been on a steady growth trajectory since the first truffle was harvested in the winter of 1999. Seventeen years on, and this season, growers collectively harvested approx. 18 ton of Tuber melanosporum, the French black truffle. Not all this production was saleable, however, due to quality issues. In such a short history of truffle growing, remarkably, Australia now presides as the 4th largest producer in the world, and at this rate, could well become the most prolific producer on the globe within 20 years.
Why the dramatic increase in 2017?
Naturally, exponential growth and maturity in plantations tend to increase yield year on year, notwithstanding seasonal glitches due to unfavourable climatic conditions. My discussions with grower’s post-harvest were also centred around their individual thoughts on notable differences from the previous 2016 season.
Theories included cooler than average summer temperatures in many areas, intermittent heavy thunderstorm activity through the summer months, changes to irrigation regimes and seeing the benefits of annual cultivation around trees. There were only a few cases where yields were similar or slightly lower than the previous season.
Whilst we clearly can’t control the weather, keeping a close eye on the things we can control is vitally important in truffle growing, when striving for some form of consistency in production.
• Maintaining soil pH and preferred mineral ratios through lab testing at least every 3 years
• Considering installing moisture monitoring technology to improve irrigation accuracy
• Ensuring that annual cultivation around trees is carried out in the correct way
• Reinvesting in your plantation by returning 1st class truffle spore back to the soil annually
• Pruning at the right time and using the correct techniques for the host tree species
• Avoiding compaction of soil around trees
Without a doubt, the most important current maintenance consideration in southern hemisphere farms is summer irrigation. For established trees (4 years plus), the compelling evidence, gained through research, field trials and grower experience, is that deep watering at 2-3-week intervals (depending on soil type) through the summer months is critical. Summer heat intensity is variable from one region to the next, so basing your decisions on relative temperature will be more accurate for any given environment.
For example; daily high summer temperatures in the range of 22-28C (72-82F) may only require irrigation intervals of 3 weeks, and temperatures consistently above 28C (82F) may require intervals of 2 weeks. The other variable, of course, is rain events which must be taken into consideration.