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Effect of early stop time on substrate EC. Example illustrates a cluster tomato crop but which ever crop you grow the principles for EC control with an adjusted stop time are the same.
Focus now on the stop time to help you control substrate EC, particularly on brighter days as at 14:30 hrs the light intensity can still be high. It is best practice to let the irrigation run on light a setting until 250-200 W/m2 outside light remains to keep the EC stable as illustrated from practice in Figure 2. In this example, taken from a commercial glasshouse the stop time can be seen to vary by +1.5 hrs on a bright versus darker day, yet EC and the decrease in WC overnight remain stable despite the widely fluctuating light levels.
Optimal start and stop times and irrigation gift maintain stable root zone conditions in variable weather. Example illustrates a cluster tomato crop but which ever crop you grow the principles for EC control with an adjusted stop time are the same.
There should be no reason to lower the dripping EC too far i.e. for cluster tomatoes less than 3.0mS with sufficient irrigation in line with crop activity towards the end of the day. With a targeted stop time on a bright day, EC can remain 3.0-3.5mS to help the balance in the crop. Stopping too early on bright days will result in an uncontrolled increase in the substrate EC. This has been the case at several growers this year where irrigation is stopped approximately 14:30 hrs with outside light levels still around 400-600 W/m2. Lowering the drip EC too far at this time of year can have a negative impact on plant development making harder to achieve the correct balance in the crop for maximum summer production. For further guidance on how to structure the start and stops in the climate computer please refer to the relevant Grodan 6 phase reference tables for you slab/crop.
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