Agronomy advice
30 October, 2021

A new way to manage iron deficiency in broadacre fruit

By: Giz Gaskin

Managing iron deficiency in broadacre fruit crops has always been tricky. Often the deficiency is caused by the low availability of iron rather than a lack of iron in the soil. Typically this is seen in high pH soils where the iron is locked up and unavailable to plant roots, so although there is plenty of iron in the soil, from previous applications of ferric iron, the actual uptake of iron by the crop is low.


Managing iron deficiency in broad acre fruit crops
Managing iron deficiency in broad acre fruit crops

Iron is critical to maintaining a healthy crop, even though it is considered a micronutrient. It is used by plants for the production of chlorophyll and as such has a direct effect on photosynthesis. In addition to the production of chlorophyll, iron is used to help crop enzyme functions. This means deficient crops can appear stunted or weak, even if where they are grown is abundant in macro minerals. Stunted or weakened plants inevitably fail to produce the desired yield & quality. This is why it is important to be sure that crops have a good supply of available iron.

Yara has developed a new iron solution for all growers, to bring the management of iron more in line with Yara’s other precision crop feeding solutions. YaraVita Ferritrac Pro is specially formulated to offer the crop 60 %w/w available iron straight to the crop root zone via injection. By being able to do this using a liquid product means that the process and cost of iron management is both simplified and more efficient than using current solutions. The new formulation guarantees that the crop can have a good supply of available iron, within the cropping year of application, to feed the crop in a preventative manner.

YaraVita Ferritrac Pro was recently launched in the UK and is now being trialled across a flotilla of UK fruit farms and crops, all with one thing in common -  a lack of iron availability in the plant. I say iron plant availability as not all the fields tested were deficient in iron. Some, according to soil sample results provided from Yara Analytical Services laboratories, show good levels of soil iron. So what’s the issue? The same fields have a very high pH which is locking up the iron availability to the plant roots. Therefore although soil iron is high from previous applications of ferric iron and similar products, the actual uptake of iron by the crop is very low.

The first trials on various broadacre fruit crops are very encouraging

The trials, located in the south of the UK from Sussex to Kent, cover wine grapes, apples and pears. As a consequence of the very strange year, we have had, the trials were amended due to late cropping on some sites. This amendment, however, proved fortuitous as it allows us to see a progression in the precision of applications. The progression further demonstrates how responsive YaraVita Ferritrac Pro is to precision applications. Reducing the overall input of the new product only goes to making it the best and most economical option for readily available iron products today.

Apples

In this trial on apples, a single large dosage of Ferritrac Pro at 60L/Ha was applied at the start of the season.

Below we can see the leaf content in parts per million of iron compared to the datum (pre any applications), and an arbitrary desirable figure for all crops and a measured control as a comparison. In this case, a late iron application was made to the control area.  

Leaf iron content in red windsor apples.PNG

The decline in iron according to the graph is not so much a sign of product loss, but of plant growth. As new leaves emerge long past application there is no new iron available for uptake, so the overall iron content across all leaves (young, med and old) drops.

Grapes

The next study trialled YaraVita Ferritrac Pro applied to wine grapes located in Sussex, 2021. The application was made in two doses of 30L/Ha, applied approximately one month apart. In this case, the control iron is a wettable powder iron @6% EDDHA (YaraVita Ferritrac Pro contains 7% EDDHA).

Leaf iron content in grape vines.PNG

The viticulture trial was very interesting in isolation from the other crops. What’s happening in this graph? The large drop in iron at the end of the graph is similar in crop yellowing to that of the apple data shown above. However, there is more activity going on in viticulture -  the site running the trial, like many other UK sites, de-leafs the older leaf surrounding the grapes as they swell. This shows in the graph as a massive reduction in iron midway through, due to the older leaf being full of iron, now removed. At the end of the season we see a small recovery in iron as a consequence of pruning the tops of the vine. The reduction in pale young leaves brings the overall iron score back up above the datum.

Based on these results and discussions with the grower, the application of YaraVita Ferritrac Pro in viticulture can now change. Given young leaves will be removed along with old leaves, the first applications of Ferritrac Pro can be moved past 6-8 true leaves. As the first 6-8 true leaves will be removed mid-season, this should shift the graph to the right, meaning more iron is present in mid leaf sections, though some will still reside in the old leaves. It should help mitigate the drop around de-leafing and pruning, so mid leaf can take the vine through the whole season. Given both lines are above target, there is a further argument that the total application of 60L/Ha can be further reduced to closer to 40L/Ha Total while still delivering a good result. This would further support the argument that YaraVita Ferritrac Pro is the best solution for readily available iron in viticulture.

Pears

Next, we look at Ferritrac Pro in pears. These trials were massively delayed by bad weather - in Kent, we had April and May back to front, April was warm and dry, May was cold and very wet. The pears were not impressed with the situation! That said it opened the opportunity to feed them their Ferritrac Pro iron in three parts. 60L/Ha total but applied as 10l/Ha, 20L/Ha and 30l/Ha. In this trial, we managed to match the foliage increase with the application increase. Thus a straight line balance of iron within the crop. The control, in this case, saw a paler crop receive a late dosage of iron, hence the step up at the end. Though the iron is not close to the target value, I believe the target value is high in pears, the crop leaf colour was good. This would suggest the target in future years should be closer to 100 ppm iron leaf content for pears.

Leaf iron content in conference pears.PNG

Fertigated Ferritrac Pro trial results are shown below. This trial was trailed down a preset T line by the grower as he was testing a competing iron product using the same application. The total rate, in this case, was less than 30L/Ha over the year. The grower was very happy with the outcome from YaraVita Ferritrac Pro, the green leaf colour though not as dark as he had seen in other non-deficient crops, was green enough not to know the crop was deficient in iron. The reduced total rate of Ferritrac Pro makes it economically and agronomically the very best option in this case. Again worth noting in pears that 100 ppm iron leaf content would be a better target than the all crop line at 150 ppm.

Leaf iron content in fertigated conference pears.PNG

The T-line results show that for this type of readily available iron product best results and savings can be made when using a precision method. Though the bulk of fertiliser is applied using prill product for NPK there is significant merit to using T-Lines to make precise adjustments to the program through the season. The low labour time required for these applications further saves money across broadacre fruit crops, something which likely will be of interest for the future. There will be a continuation of Ferritrac Pro trials with our trial growers next year, to fine-tune the precision application in their crops.

YaraVita Ferritrac Pro is as easy as to use as squeezy chocholate

YaraVita Ferritrac Pro is as easy as squeezy chocolate and has about the same consistency. The product is very easy to use, no splashing, no dust, just poor in and wash-in with water. Ferritrac Pro is a very soluble formulation as low as Yara’s well known Calcinit product. The flowability and formulation of the product ensure that it can be mixed in the tank with other products as required and that the product does not stick/stain the equipment as other iron products might.  The addition of water makes it a very flowable product from its more saturated consistency.

Ferritrac Pro has a very high ortho-ortho iron content of some 60% activity. It is this activity that is key to Ferritrac Pro’s ability to get iron into the leaf within as little as 2½ days after soil application. The EDDHA chelate content of our product is only 7%, it just goes to show that actually, the plants don’t need a lot of chelated iron, they just need the right amount of activated readily available ortho-ortho Iron.

 

Fruit agronomy advice

Apple fertiliser and crop nutrition advice
Apple fertiliser and crop nutrition advice

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