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February '14 - Fruit Quality

February '14 - Fruit Quality

The last two months have seen a mixture of wet and dry conditions, throw in a couple of heat waves, some sub 10 degree mornings and you have a recipe for some fruit quality issues.

With tomatoes I have seen growers with a bit of crazing, this is possibly due to a combination of cool mornings followed by a rapid rise in temperature. If you do not have good air exchange in relation to the increasing temperature and climbing humidity, the result could be fruit sweats. If you have continued to heat and have had a pre morning ramp you will have better control (keeping up with the de-leafìng also makes a difference).

The "Delta EC" or conductivity (CF) under the dripper in the root zone is also important. For example, if you have had a large dry down over night the CF under the dripper will have increase. When you irrigate the next morning, you will have a rapid uptake (root tension). This rapid uptake will cause issues: Fruit splitting and crazing.

Different substrates will dry down differently at night, even under exactly the same conditions. When comparing the dry down with your neighbour, who is heating and irrigating the same but, has a different growing media, you are not comparing apples with apples. Hot pipes/low humidity will dry down your substrate a bit like a dryer does to your wet clothes. Different substrates and volume of substrate will have different dry down %. Night shots have been successfully used to help control fruit splitting and crazing in substrates that struggle to hold on to water and have dry down % which are too large.

True NFT systems are interesting because they run at a much higher CF and water is available 24/7, so when the plant requires water and fertilizer it is available (I do see some skin issues with this system but generally the fruit quality is good). Whereas with substrates we Often use weigh scales and water content readings to indicate when we should start irrigation. I know a substrate grower who starts irrigation at sunrise, to replace what is lost at night, therefore the root-zone does not have a high % change and at the moment of the day it is required, water and nutrition is available, exactly when the plant needs it. This does mean stopping irrigation earlier in the day to maintain the correct dry down % over night!

From my experience every crop and environment is different and even though the variety could be the same the substrate, the greenhouse structure, heating and irrigation systems could all be different. Even location makes a difference. So it is not possible to give precise advice, in one article, on fruit quality and hope that it improves. There are rules of thumb that should be followed but for the finer details one on one discussion is needed to best determine the correct direction for each grower's growing strategy.