Tomato's reference:

"  The secret to obtaining very firm fruit with high flavor is to grow them at a very high CF value - UK growers are running from 70 to 95CF - (remember this are 7000 to 9500 µS/cm) the plants sometimes look quite stressed and the leaf cover sometimes looks less than healthy, however you don't eat the leaves!

    Most of the hybrids out of Holland and the UK
respond better to higher CF values - a few years ago the majority were growing at 25 -28 CF.

    Then 'Efford' research station, UK, (Dr Rachael Holder), did a lot of research at growing toms at 100 plus CF - terrible looking plants but great fruit.

    Most modern hybrids are now grown from 30CF up to the cherry type, which as I advised are being grown around the 90CF. In actual fact the trials showed that cherrys yielded the best fruit on plants running at 160CF however the high salts level seriously reduced the yield. This ultimately is the determining factor - run the CF as high as practical while maintain your required yield per M2. Yes you do have this ability to
control these factors - also the excessive uptake of water which leads to splitting (which is allowed with lower CF values) is inhibited by the higher CF values."

Rob Smith
Hydroponic Developments Ltd
rob@bopis.co.nz
7 Smiths Road
Matua
Tauranga - New Zealand

Tomato cherry's reference:

   " Just a comment in support of Rob about EC levels in cherry tomatoes.  We grew cherries for quite a few years and when we started out we based everything on guidelines from ABC of NFT as this was our only source of information (and inspiration).  As the years rolled by I guess our EC levels climbed gradually as we learned by experience that fruit quality and shelf life depends on sugar levels which are enhanced in a pretty linear way as EC rises.  However there are some points to make at the same time. In the first place it is still important to relate your EC to outside conditions.  We were growing in Western Australia where light levels and temps are high for most of the year.  It is essential to reduce EC in relation to light and temperature while our EC was high it was never and could never have been as high as levels used in UK.  I guess what happened to us was that the range of EC values increased over the years but it was still necessary IMO within that range to lower the EC during hot bright weather and lower it in cooler duller conditions. 

     I think at the end we ranged from 4mS to about 8mS.  Maybe if we were still growing we would be higher by now but I doubt it.

    As important as EC is constant attention to K levels.  Fruiting crop can strip out the K in a few days, whatever the EC. I have seen it happen. I believe that the K:N ratio for tomatos should be at least 2 and 1 also believe that the only way to be assured of that is to have a regular tank analysis or to buy an ion-specific meter for K.

    ... of people running their tanks for long periods without change or analysis and it needs to be pointed out that for commercial growers who have bills to pay and who depend upon regular harvest of consistent quality this is not an option. 

    ...I have seen the K be removed effectively from solution in a tank in which EC was maintained by controllers and I have seen the effect that this has on fruit quality. If I were growing now I would certainly plan on using the biggest possible tank and analyzing at the least on a weekly basis.

    ...Another  thing to point out is that a simple refractometer  can ... measure not the EC of the pulp but the sugar level reading it as BRIX.  I believe this to be an unsung and underused weapon in the growers armory.  It provides a quick simple measurement of that factor in the fruit (sugar) that has such a big bearing on both flavor and quality (shelf life). 

    ...We were able to demonstrate quite easily the following crucial points:

1.- fruit grown in high EC has higher º BRIX than fruit grown in lower EC PROVIDED K levels maintained.

2.- fruit with higher º BRIX keeps longer and looks good longer (much longer in fact.)

3.- taste testing clearly showed that there is a direct relationship between high  º BRIX and taster approval."


Giles W.Gunstone
giles@growthtechnology.com
Growth Technology
UK & Australia