For substrate-grown crops , moisture dynamics in the root zone can be a useful tool to steer crop development , ensure high levels of oxygenation , and act as a reservoir of water and nutrients between irrigations . Fortunately , these days we have such a wealth of high-quality hydroponic substrates to choose from that crops can be matched to a growing medium and moisture levels precisely controlled .
Why are Moisture Dynamics Important ?
Within the root zone of a substrate-based hydroponic system , there should exist a gradient in moisture levels from the top to the base of the growing container / bag / bed / slab . This is due to the effect of gravity but is modified by the size and shape of the growing container and the physical properties of the substrate . This means there is a reserve of moisture in the lower layers of the substrate and a higher percentage of larger air-filled pores towards the surface . Both are essential for plant growth and development , however , matching these properties to plant species and growing conditions is worth investing a little time . A water-holding capacity of 45-65 percent is considered optimum for most soilless growing media in hydroponics . Water-holding capacity is the portion of container pore space that retains water after drainage is complete and this can be easily measured : A container filled with the substrate is fully saturated with water and then permitted to drain . Once draining is complete the damp medium is weighed , dried at 110 ° C ( until all moisture has been removed , then re-weighed ). The difference between the wet and dry weight is the water holding capacity of that substrate . This can be a particularly useful exercise for determining the water-holding capacity of substrates that are a blend of different materials to determine if they fall within the optimal range .
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For substrate-grown crops ,
MOISTURE DYNAMICS IN THE ROOT ZONE CAN BE A USEFUL TOOL TO STEER CROP DEVELOPMENT .”
The root system must not only maintain its own growth and development , but provide supplies for the upper regions of the plant .
Different Crops , Different Tolerances
Some plant species are highly prone to problems with overwatering , while others are more tolerant . Strawberries are one plant that has no tolerance for a saturated substrate and crop losses have resulted from overwatering the crown and the root rot that often follows . Many cacti and succulents will also rot when overirrigated and prefer a coarse , freedraining substrate such as perlite or coarse sand . Other plants , more notably those that are grown under warm , high-light conditions , have large leaves and a rapid rate of growth that are better suited to highly moisture retentive mediums that will hold sufficient water between irrigations . Cucumbers , tomatoes , squash , and similar crops perform well in a medium that has a high water-holding capacity and also a good rate of air-filled porosity to provide oxygenation . These often include substrates such as coconut fibre , which has a blend of both moisture retentive ‘ fines ’ or finer coir particles , mixed with longer , coarser fibres that retain the open structure of the medium and provide a suitable level of aeration and drainage .
Fruit cracking can be caused by uneven watering of the root zone .
Maximum Yield 37