Here in England we are finding ourselves short of water. That will come as a big surprise to growers from warmer countries.
Having said that I note the following ‘facts’ from Wikipedia at http://en.wikipedia.org/wiki/List_of_weather_records
Highest amount of rain in one year = 26,470mm (Cherrapunji, India)
Average annual total rainfall = 11,872 (Mawsynram, India)
Most rain in 12 hours = 1,144 (Foc-Foc, Reunion)
Most rain in 1 hour = 305mm (Holt, Missouri)
However much people complain about British weather, we appear to be pleasantly dry by world international standards and now un-pleasantly dry for strawberry growers!
At our British Haygrove Open Days we discussed water conservation and erosion control. We based our calculations on an average rainfall of 792mm (for Ross-on-Wye, Herefordshire) but also presented calculations based on provisional data for 2011. I was shocked when speaking to a leading grower and nurseryman from the East of England, to find that he had recorded only 100mm of summer rain. I have subsequently discovered that the April-August total for Ross was actually a similarly low figure (97mm).
||Annual rain fall
||April – August (incl.)
|Watsonville, California (average)
Average = 1971 – 2000
We were demonstrating a mobile steel gutter forming system and calculating how much the water collected from guttered fields, during the covered season, could contribute to the total need of the crop. Allowing for the fact that, due to evaporation, only about half of the rain landing on a tunnel would be collected by the gutters we calculated that in a relatively dry year like 2011 we could collect 25 -30% of crop need. In a normal year the number would between 45 and 75% of need.
Haygrove Guttering System
In the UK ‘mains’ water can cost commercial farmers £1.30 per m3. Water from the gutters could therefore save £1,300 and £2,000/ha. The collected water is also largely free of salts – great for salt sensitive crops and for diluting saline water supplies.
Statistics from Mark Else at East Malling Research (http://www.emr.ac.uk/) show that a commercial crop of soil grown strawberries requires around 70 m3 irrigation water per tonne of harvested fruit. With some sophisticated sensor equipment it is possible to make substantial reductions in irrigation requirement. East Malling has suggested a target of 10m3 per tonne although the industry has yet to see whether this will sustain the consistently high yields it requires to remain competitive.
Even though table top and glasshouse systems are completely dependent on a ready supply of water the high yields achieved tend to bring the water use per tonne significantly below the 70m3 average.
For me it is clear that growers will be investing more in soil moisture sensors and decision support systems but I also foresee a big increase in gutter installations both to collect water from the roof and to collect drain-water from soil-less growing systems. It is likely that many growers will also be forced to re-cycle/re-circulate that water.