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Large parts of Germany have struggled for years with very erratic rainfall patterns. Some farmers are now tending to
question the usefulness of cover cropping in dry and even semiarid regions largely on the basis of their experience in
the dry summer and autumn of 2015. Does cover cropping conserve water or squander it?

Written by Markus Scheller ∙ Dettelbach-Euerfeld

The benefits of cover crops are undisputed: They help to increase biological activity in the soil and improve the soil structure. Cover crops also prevent soil erosion caused by wind or heavy rainfall and reduce nutrient leaching. Some species even have the ability to unlock nutrients bound in the soil, making them available to the crops. Despite this, cover crops are frequently accused of consuming water that is badly needed for the follow-on crop. Long term practical experience and scientific studies, especially in dry regions such as Austria‘s Burgenland, have clearly shown that this is not the case. Cover crops do not consume any more water than fallow land.

Water evaporation on uncultivated land is significant

The table below shows that water loss is large due to evaporation from the uncultivated soil surface. By contrast, the sum of transpiration for cover crop growth and evaporation from the cover crop canopy – evapotranspiration – in dry years is lower than that of evaporation from the bare soil. In winter in particular, the canopy cover reduces non-productive water evaporation from the soil.

Winter rainfall is normally sufficient to make up for the increased water consumption of cover crops in the autumn. Cover crops have not been shown to have any negative effects on the subsequent crop either. Quite the reverse, in fact; carefully chosen cover crop mixtures can prepare the soil specifically to meet the requirements of the follow-on crop. This has been demonstrated by comparison trials at Kraichgau in Baden-Württemberg (South-West of Germany) in which cover crop mixes were found to be superior to the standard single crop mustard both in terms of nutrient fixation and the productivity of the follow-on crop grain maize.

Moreover, the productivity of the follow-on crop depends far more on the rainfall pattern in the crop year than rainfall events during the cover crop growing season. Experiences on my own farm in Lower Franconia, Bavaria (Central-South Germany) with wheat/sugar beet rotations demonstrate the importance of establishing the cover crop. It is not always easy to use the residual moisture in the soil to germinate the cover crop seed, especially in the dry conditions typically found in Lower Franconia.

Strategies for preserving soil moisture are the key

This begins right from the point of harvesting the previous crop. It is important to pay careful attention to your combining operation. For example, check the settings on the combine harvester (low losses), make sure the knives on the straw chopper are sharp, select a short chop length and uniform straw distribution. The timely use of a mulcher to shred the straw may even be worthwhile to reduce the ‘chimney effect’ of the stubble, i.e. loss of water via the hollow stalk, especially with large quantities of straw. Control of volunteer cereals is also critical for the successful establishment of the cover crop.

If the straw is harvested, pay particular attention to the area underneath the swath as the proportion of shed seed, chaff and weed seeds will be particularly high here. The main thing is to prevent the volunteer cereals swelling or germinating ahead of the cover crops seeds. If volunteers from cereals that are harvested early in the season, such as winter barley, are encouraged to germinate, it is very important to shallow till immediately after the cereal harvest to break the capillary action. In later crops such as winter wheat, farmers are often left with no choice but to till at the same time as sowing the cover crop, as sowing ought to take place by the end of August at the atest to ensure reliable establishment of the cover crop. Plan to sow as early as possible to prevent non-productive evaporation from bare soil during summer when temperatures are high.

The aim is to make productive use of the residual moisture to form biomass and absorb nutrients. By cultivating a mixture of crops it is possible to exploit the benefits of cover crops even under unfavourable climate conditions and to minimise risks. Cover crop mixes containing a variety of components promote diversity and provide herbage growth even when individual species fail – often ensuring that adequate soil functioning can still be achieved.  

Sowing methods that conserve water

Direct seeding and shallow mulch seeding are effective means of conserving moisture. Since good reconsolidation is important with these techniques, it can be helpful to make an additional pass with a roller.

The right tillage for the followon crop

The way in which soil is prepared for the follow-on crop and therefore how the cover crop is managed also has an important impact on the soil water balance. Leaving the cover crop in situ until just before the following crop is sown maximises water conservation. A rolling pass in autumn or winter when the soil is trafficable can encourage the cover crop to die off over winter, if this is the intention. This has proved particularly helpful in the mild winters of recent years. For early sown summer crops, e.g. oats, spring barley and sugar beet, a shallow cultivation pass in winter when there is a ground frost is a good idea, depending on the location, to speed up the drying of the soil prior to sowing.

If the cover crop is followed by maize, the cultivation pass may either be carried out to incorporate manure or immediately before drilling. Even cover crop plantings that are not needed to satisfy greening requirements should under no circumstances be ploughed up in autumn or early spring. Such action would have a negative impact on the water balance and reduce the performance potential of the cover crop.

Conclusion

Cover crops are an important part of the crop rotation system, even under difficult conditions. They benefit the soil in many ways, often giving more back to it than they took from it in the first place in the form of water or nutrients. The positive effects of growing cover crop mixes are numerous; they support soil organisms, increase aggregate stability, reduce the risk of nitrate leaching and erosion etc. The key to success, however, is to pay as much attention to the cover crop as to the main crop. The farmer‘s job is to find the right timing, prepare the seedbed optimally, and select a cover crop mix that is appropriate for the region and the crop rotation system.

Cover crops for nitrogen fixation

After the cereal harvest there is an opportunity to produce and fix nitrogen for follow-on crops. Special cover crop mixes with good nitrogen fixing capabilities are available for this purpose. N-Fixx is a good choice for winter cereal crop rotations. It comprises nine different components, including 80 % legumes. According to Deutsche Saatveredelung AG (DSV), this mix is not only good at fixing nitrogen, it also enriches the soil humus and promotes soil health to boost the performance of subsequent food and forage crops.

Think “soil quality” rather than “new drill” when planning your change to zero-tilling.

Min till and no till are quickly becoming part of everyday agriculture. Whether used to increase soil health and the productivity of soils, or as part of a Black Grass strategy, or both, we are seeing this type of tillage being accepted as a bona fide method of farming. And, where it is done correctly the rewards can be a healthier soil and a lower input growing system. However, a word of caution needs to be put into the tillage conversation as many farmers are rushing to the machinery depot to pick up the new drill.

That word of caution should be ‘air’. A soil without air is a soil that will not sustain a healthy growing crop to a profitable yield. The air allows moisture to percolate into the root zone. It allows roots to grow in-between soil particles and allows gaseous exchange. We need air to supply the Nitrogen that is available from the atmosphere, and we need air spaces to allow CO2 to escape from the soil so that it may enter the stoma on the leaves.

Why do you think most stoma are on the bottom of the leaf? If a farmer on a heavier soil starts reduced tillage with no soil life, including bacteria, fungi, algae together with earthworms, who are the main workers of the soil, there is a good chance that growth and yields will drop, sometimes significantly. At a farmer meeting recently when no-till farmers were asked ‘how many farmers saw a yield drop’ after starting no-till, around half of them raised their hand. This wouldn’t happen if the health of the soil was examined and worked on before the new drill arrived.

Compost application, cover crops (with the right species), fertiliser and chemical control are all contributing factors to soil health and need close examination before setting out on this journey. I often hear the phrase, ‘Cover crops are a waste of time’ but then on farms that use them, I hear, ‘We saw a difference after the first crop’. When on farm the first question I am asked is ‘Where do I start?’ The answer will never be ‘Buy a new drill’. We need to look at soil type and then decide what can be done to make it suitable to use a no-till farming system. If you are lucky enough to have an open, aerated soil with a good structure then off you can go.

If, on the other hand, you have a heavier soil that is more clay, then we really have to work out how we can increase the Organic Matter content so that the soil can breathe, and breathe is the correct word, as the soil is a living entity that requires air (oxygen) to operate at peak efficiency. A soil that is lacking air will rely on high inputs of fertilisers and agrochemicals. By far the best way to achieve this goal would be to obtain hundreds of tonnes of organic matter, compost them correctly and then apply to the soil. Anybody who has listened to Simon Cowell will know that this works, and perhaps it may be the start of a journey for you to be a future soil farmer of the year. Unfortunately, this system is not available to many so other ways of farming must be found.

Cover crops are undoubtably a great idea to everyone who has the interest to try them. They will not increase organic matter levels in the soil anywhere near as quickly as applying compost, but it is a fantastic second place. We have seen heavy soils lifted and aerated after only one or two sowings and you can really feel the spring in the soil as you walk the fields. The roots grow large and deep in comparison to stunted and on the surface. To start to accomplish this, work has to be done on the best potential seed mix for your soil. You need to also consider the best way to get rid of them, which is generally by sheep or crimping, but herbicides are also needed (we are able to limit herbicide impact and help to repair the bacterial damage the herbicide does to soil life).

A good cover crop can give you a huge boost in plant available nutrients plus the rooting will open the soil and allow new roots to penetrate deep into the ground. Another part of getting a soil ready for a new tillage system is to increase microbiology and the rest of the soil food web. This can be achieved by reducing the amount of nitrogen applied by using a Humate to sequester the nitrogen making its uptake far more efficient. The Humate will also complex phosphorous which stops it locking onto the Cations in the soil.

This means you can put on considerably less and still get more into the plant. Remember, that for every kilogramme of nitrogen that is applied to the soil and is not utilised by the plant you could stand to lose 100kg of organic carbon, which slumps the soil. This explains why so many fields are lower than their surrounding roads. A soil that slumps, put simply, contains no air, which leads to poor rooting, which in turn leads to higher fertiliser and agrochemical use as the plant’s resistance to pest and disease drops.

We have seen that, by supplying a large amount of the required nutrients to the plant as a foliar programme, we can further lighten the load on the soil leading to even better rooting. A reduction in fertiliser and especially agrochemicals will lead to increased yields, so there is no need to accept the drop that we are told to expect. No one system will suit everyone but by having an open mind, looking at the tools at your disposal, and taking well worked out steps you will get a superb soil that works away below your feet providing the nutrients that your plant needs to produce the crop/yield that you want.

Interested in hearing a little more? Visit us online on www.aivafertiliser.co.uk, call us via 01235 834 997 or email office@aivafertiliser.co.uk.

How can you keep weeds and disease at bay this spring? As warmer weather arrives and the season gets underway, we explore here the role of adjuvants in boosting the performance of herbicides and fungicides on farm to optimise weed and disease control.

Right time, right place

Bumper harvests are made in spring. Where every kilo counts, optimising a fit and healthy crop free from weed and disease competition is absolutely essential. Of course, this is easier said than done. As certain species become resistant to herbicides and fungicides, restrictions tighten and active ingredients disappear from the crop protection toolbox, the job certainly isn’t getting any easier for farmers. If conditions are challenging during application, as they so often are these days, things become even more stressful. Plants struggle, workloads rise and yields fall.

There isn’t much we can do about the weather. What we can do is make sure that crop protection products are delivered to the right place, at the right time – and that the tools we have are working as hard as possible. This is where adjuvants are worth their weight in gold. E m p l o y i n g a suitable a d j u v a n t e n s u r e s herbicides and fungicides are delivered exactly where needed, m a x i m i s i n g effectiveness and protecting yield. For those looking to get the most out of rotational weed control this spring, they are practically a secret weapon.

Kick-start your weed control programmes

We know that spring crops are limited in their post-emergence armoury. To give your plants the best start in life, it’s a matter of control. While the majority of black-grass germinates in autumn, the startling truth is it only takes 12 plants/ m² to reduce yield by as much as 5% and power seed return of an eye-watering 144m seeds per hectare. Pre-emergence residual herbicides need to be applied with precision in problem fields to protect yield, keep on top of populations and prevent issues in the next crop. Working in lighter soils, getting rid of spring germinators early – like knotgrass, black bindweed and redshank – defends sugar beet, potatoes and the like – crops where early establishment, free from weed competition is vital to protect yield. During the pre/peri-emergence spray timing your aim is to get maximum coverage with the spray and retain the herbicide in the top 5cm of the soil to control new flushes of germinating weeds that may appear over time.

This can be challenging for three reasons:

1. Coverage can be compromised by drift, reducing the applied dose, missing parts of the soil altogether and allowing weeds to germinate and outstay their welcome.

2. The dry soils typically seen in spring have an impact on performance.

3. Levels of moisture in the soil can affect retention and therefore leach the potential of the herbicide.

Designed to reduce drift, a low-drift nozzle produces bigger droplets but reduces coverage –meaning we still have problems two and three to deal with. This is where a residual herbicide adjuvant like our Backrow product can help. Adding Backrow to spray water both reduces drift and improves coverage. The product helps soil retain herbicide and moisture in the top 5cm of soil for up to eight weeks and prevents herbicides leaching to groundwater or the roots of the crop itself. Used in this way, Backrow improves the efficacy and longevity of weed control and general crop safety, particularly in light soils. Field-scale research on onions has shown that where Backrow was applied pre-emergence, the leaching of all subsequent crop protection products was dramatically reduced. Follow-up work using lysimeters in a controlled environment revealed that the product upped water retention by 33% and diminished leaching by an incredible 62%.

Four ways Backrow can help increase overall weed control

Adding Backrow to your weed control has four central benefits:

• Increases contact between the herbicide and the weed

• Increases effectiveness of herbicide in dry conditions

•Increases longevity of weed control

• Improves crop safety

Over the past nine years, replicated trials have been carried out with a range of herbicides applied both pre and periemergence. The results of these trials have shown conclusively that Backrow advances the performance of herbicides by an average of 9%. Let’s crunch the numbers; for a black-grass population of 500 heads per m², 9% means a yield benefit of 0.45 t/ha, or to put it in financial terms, a margin of roughly £80/ ha. Importantly, it also means a reduction in black-grass seed return to the tune of 270,000 seeds per hectare (based on seed viability of 60%), protecting future crops from competition.

Broadleaf weed control in cereals: +13%

Broadleaf weed control in combining peas: +13%

Broadleaf weed control in spring beans: +10%

Broadleaf and grass-weed control in potatoes: +8%

Enhancing weed control post-emergence

Once weeds have surfaced, we are dealing with an entirely new target; aiming to get herbicide into a small established weed, rather than sufficient coverage of the bare soil. If the weed gets particularly big, hairy, or waxy in texture, things become even more tricky. What then if applications are delayed due to weather or workload? … If you find yourself with an out-ofcontrol weed situation, choose your solution wisely. A good adjuvant should reduce drift and improve retention on the leaf, rather than allowing the herbicide to simply bounce or run off the surface.

It will aid spreading across the leaf to optimise entry points, improve penetration and increase uptake. Sulfonylurea (SU) herbicides in particular benefit greatly from the addition of an adjuvant; on a molecular level, the very small nature of the active ingredient makes it hard to wet in formulations. Adjuvants like Arma and Kantor are ideal in this situation. Kantor would be the better choice to reduce drift and/or when using hefty tank mixtures. It has the ability to keep complex mixtures stable within the solution; a notable benefit with Basagran in spring beans which can be “hot” on the crop.

Pushing the performance of fungicides

While SDHI/azole mixtures have proven effective in controlling Septoria in cereals, monitoring data shows there has been another slide in sensitivity to SDHIs and azole chemistry. At present, we’re also experiencing disease control challenges in controlling Cercospera in sugar beet and Ramularia in barley, to name a few vicious examples. We’re not saying that adjuvants are the holy grail, but there’s no denying resistance poses a significant threat to the ongoing performance of fungicides. By optimising the application process, we can not only increase efficacy and yield, but importantly also reduce negative genetic effects and slow resistance.

During fungicide application the aim is to get as much of the active ingredient inside leaves as is possible. The surface area to hit is large and we need to protect it all. While multi-sites act as a protectant, they don’t move on the leaf. This means they can only protect the portion of the leaf they actually cover. If the base of the leaf doesn’t receive adequate coverage, the fungicide will be prevented from moving downwards, leaving that part of the leaf either completely unprotected or having received a sub-lethal dose of the active ingredient.

Although they work slightly differently, both the Arma and Kantor products will improve spreading and uptake to protect the whole crop. Prothioconazole-based mixtures will benefit in particular as it is a large molecule which needs to be converted to desthiocolnazole inside the leaf for it to be “activated” – so the quicker it gets inside, the faster it starts working. Extensive trials over the past seven years have also shown that where Kantor is added to prothioconazolebased sprays with chlorothalonil, antagnosism is reduced and yield is improved. 

Over 6 years of trials, 44 comparisons, average yield benefit in winter wheat across all timings: +0.28 t/ha

+14% improvement in Cercospera control in sugar beet with epoxiconazole + thiphanate-methyl

Up to 18% improvement in Downey mildew control in onions with Invader

Our top tips

So how to get the best out of your herbicides and fungicides this spring?

• Choose your crop protection carefully and make sure it is applied in the right place, at the right time.

• Incorporate a suitable adjuvant to ensure your herbicides and fungicides are working as hard as possible.

• Aim for the highest levels of control when applying pre-emergence residual herbicides to give crops the best possible start in life.

• A good offence is the best defence. Use pre-emergence herbicides in problem fields in the spring to keep on top of weeds and safeguard against issues in the next crop.

• Rid lighter soils of spring germinators like knotgrass, black bindweed and redshank as early as possible. In crops like sugar beet and potatoes, doing so is crucial to protect yield.

• Employ crop rotation where necessary to crowd out weeds via competition.

• Pre/peri-emergence, choose a low-drift nozzle and aim for max coverage. Adding a residual herbicide adjuvant like Backrow can help optimise soil coverage and retain herbicide and moisture in the top 5cm of soil for up to 8 weeks.

• Post-emergence, aim to get as much of the active ingredient in the weed leaf as possible. Adjuvants Arma and Kantor improve coverage and uptake to control as many weeds as possible.

• To boost the performance of fungicides, apply an adjuvant like Arma or Kantor to boost spray coverage and uptake to protect the whole crop. 

Adjuvants like Backrow, Arma and Kantor are a valuable tool, pushing performance of herbicides and fungicides and helping you get the most from your crop in health and yield. To discuss individual scenarios or to request product guides, please feel free to get in contact with us at info@interagro.co.uk.

Soil health is one of the government’s main concerns relating to the future of agriculture, and with many farmers
now turning towards conservation and biological farming, it is important to get soil heath, the cornerstone of these
principles, right.

George Hepburn, biological soils expert at QLF Agronomy, gives his six practical steps for improving soil health, no
matter what farming system.

Analysis

When looking to increase soil health, the first thing I look at is the soil itself. Go out with a spade, or in extreme cases a digger, and physically look at the soil. The presence of deep rooting systems, good soil aggregation and abundance of visible soil life are all key indicators of a healthy soil structure. To test this, look at how far rooting is going down and whether or not there are any fine hair roots. It’s also useful to smell the soil – healthy soil smells almost like dark chocolate, whereas anaerobic soils have an unpleasant smell.

Assess the aggregation of the soil to see if it’s crumbly or compacted, and check for soil life, such as millipedes, beetles and worms. You should see around 10 to 20 worms per spade in a healthy soil. It’s also useful to compare soil in the field with that from under the hedgerow, where soil health and structure won’t have been affected by cultivations or compaction.

Once you’ve assessed the look and feel of the soil, taking a soil test is the next step, because if you don’t measure it, you can’t manage it. However, it’s important to note that a standard UK test only provides N, P, K, Mg and pH measurements, which isn’t enough to accurately determine the level of soil health. I recommend a full spectrum test, which costs around £30 per sample. This will provide a more accurate picture of the soil make-up, by measuring calcium, boron and organic matter (OM) levels, pH, and the cation-exchange capacity (CEC) of your soil. It doesn’t really matter which lab you use, but once you have chosen one stick with it for consistency, as methods of analysis do vary. Once you’ve assessed the condition of your soil, you can then start to make changes.

Soil structure

Before you can affect the biology of the soil, the structure needs to be right. The soil micro flora and fauna need air to breathe, and food and water in the right proportions. The ideal soil structural makeup to provide this is 45% minerals, 5% OM, 25% air and 25% water. Calcium and magnesium are extremely important minerals as they help to define soil structure. Calcium deflocculates the soil, allowing air in and water out, and magnesium does the opposite, making the soil tight and sticky. Therefore, it’s essential to get this balance right. If there’s an imbalance you may need to apply gypsum (calcium sulphate) to help lower magnesium levels or apply calcium lime or magnesium lime. It may be the case that simple cultivation techniques such as subsoiling, ploughing or getting a tine in to aerate the soil, could be what you need to improve the structure.

Soil fertility plan

After creating the right conditions for the soil biology to thrive, you can now concentrate on providing the right inputs to make the soil more fertile. Traditional fertilisers, although necessary, generally do not improve the fertility of the soil itself. For example, as much as 40% of nitrogen can be lost to leaching, immobilisation by soil microbes, denitrification and volatilisation. This can leave you out of pocket due to wasted resources and can potentially reduce yields. Through experience, I would apply a new organically based input each year on each field to feed the soil. This could be FYM, compost, chopped straw, cover crops, lime, seaweed, gypsum, liquid carbon-based fertilisers or biologicals. These will all encourage the soil biology either by improving its habitat or directly feeding it.

Use quality inputs

When implementing a soil fertility plan, make sure you’re using the best fertiliser for your soil. This could simply mean switching from muriate of potash (MOP) to sulphate of potash (SOP), however there are also many other considerations when choosing inputs. We tend to focus on N, P and K but, although they are important, they’re a small part of the picture. Micro nutrients such as boron, zinc and manganese, are also important to soil fertility and include inputs that contain a range of nutrients can be much better for the soil, for example, Limex, P grow.

Ensure you’re using the right type of Nitrogen for your crop, establish if there is enough sulphur or phosphate, if the phosphate reserves are available to the plant and most importantly if you’re getting the most out of your applied fertiliser. There are a wide range of phosphate sources available, for example TSP is the most popular but the poorest efficiency of around 20%. Ironically some of the most efficient sources such as sewage sludge, fibrophos, FYM and digestate, are some of the cheapest. The added value of including organic sources of P, is that they also contain a mixture of other nutrients, such as sulphur and trace elements. Using a liquid carbon-based fertiliser, such as L-CBF BOOST™, can improve uptake efficiencies by stimulating the soil biology and providing an energy source which aids the breakdown of nutrients into a more readily available format for the plant.

Carbon

Although nitrogen is essential for plant growth, don’t overlook carbon, and especially the carbon to nitrogen ratio. This is vital because when the carbon to nitrogen ratio isn’t balanced and high nitrogen inputs or amendments are used, microbes then feed on the soil organic matter for their carbon, respiring carbon dioxide back into the atmosphere, depleting carbon and causing long term soil fertility and environmental problems. Including a carbon source with any applied nutrient will help to stabilise and buffer the nutrient.

This is because the carbon binds to the nutrients, chelating and complexing them, which improves plant uptake. Applying a carbon source such as carbon-based liquid fertiliser, L-CBF BOOST™, seaweed extracts, organic acids, compost teas, compost or manure, can improve nutrient cycling and reduce losses, meaning you’re getting the most out of the input. Wherever you can, keep the soil covered with a carbon residue to protect the soil from the elements, and help reduce the risk of OM burning off into the atmosphere. This can be achieved with cover and companion crops.

Evaluate

Finally, evaluation is crucial. Testing the soil and the plant itself will help you to determine if your work has been successful. Tissue testing can give an indication of the uptake of nutrients by the plant and help to determine if any additional remedial work and fertiliser applications have been effective. This is even more important on land where you’ve cut back on nutrients. Take the first test when crops begin to grow in spring and repeat on a fieldby-field basis two to three times per growing season, as a deficiency in just one trace mineral could limit yields. If deficiencies are seen, consider foliar applications of micro and macro nutrients to address this. After six months, go out with a spade to check soil structure and compaction where you’ve made changes. Analyse the results of soil samples and tissue tests and continue to take them regularly. Yield is important, but what we should be aiming for is long-term soil fertility so that we can continue to use the land for generations to come. For more information on improving your soil health contact George at george@qlf.co.uk.

Written by James Warne of Soil First Farming

Ever measured the brix levels of your crops? Been told that if you achieve the magic figure of ~15% brix then you won’t
have an issue with pest and disease?

I have spent the last couple of years testing brix (during the spring) of most crops I visit and have never managed to get anywhere near to 15%. For a while I blamed my refractometer so got that tested against another one, no problem there. I then decided I must be measuring the sap from the wrong part of the plant. My understanding is that the sap should be taken from the newest ‘sink’, i.e. the newest emerging leaf. So I tried this as well with little success. However with another approaching growing season I intend to try again.

So what does brix measure? The general consensus is it measures the sucrose content of the plant sap, but this is only part of the story. It turns out that brix is actually a measure of all dissolved solids within the sap. So when measuring brix you are also measuring other solids contained within the plant sap although the largest proportion of these should be sucrose. These solids could be other sugars such as glucose and fructose although these are usually converted to sucrose for phloem transport; it could be amino acids, proteins and minerals also be found within the sap. Brix levels should be measured between 12pm and 4pm on bright days to get a meaningful result. The bris should then drop overnight as the sucrose has been delivered to the sink. If the brix does not fall by a considerable amount this may indicate a shortage of boron.

Why should you be worried at all about brix, after all its principally just a measure of the plant sugar? Well if your desire is to lower inputs and to get off the high input farming treadmill then creating an healthy plant community is essential to achieving a lower-input crop without reducing the output. Essentially it’s a simple measure of our abilities as crop managers at light capture and chlorophyll production. 

So what can affect brix levels? Brix can be negatively affected by most pesticide applications and some fertilizer applications such as ammonium nitrate as both place undue stress upon the crop. So how do we positively affect the concentration of sucose within the sap? As previously mentioned sucrose is the plants transport sugar and is made from the condensation of glucose and fructose, the primary products of photosynthesis. Plants produces glucose as the product of photosynthesis. Plants can also manufacture fructose, which is chemically very similar to glucose. It then combines these two monosaccharides into the disaccharide sucrose for transport from the source around the plant to the sink. The process of combining glucose and fructose into sucrose is known as condensation and is controlled by the enzyme sucrase-p-synthase. Potassium is well known to enable the sucrose to enter the phloem transport system. Once the sucrose has reached its sink the plant hydrolyses the sucrose into glucose and fructose to provide energy via the enzyme sucrase.

Photosynthesis is carried out in the chloroplasts by chlorophyll molecules. Magnesium and nitrogen are central to the chlorophyll molecule. We can assume that the crop is able to access sufficient nitrogen as most crops receive more than they can utilize and very rarely show any signs of deficiency, more likely than not most crops actually reveal an excess of nitrate. It is also worth noting that excess nitrate within the plant can actually depress brix as the crop uses more energy to assimilate nitrate than it does using ammonium. Can we ensure the crop receives all the magnesium it requires, especially in high pH soils or soils with excess potassium or low magnesium?

Of equal importance is manganese. Manganese is central to over 35 enzyme functions; it’s critical to chloroplast production, photosynthesis and the photosystem II process; nitrogen metabolism and nitrogen assimilation. Manganese is also believed to be essential to sucrose synthase. Manganese is also shown to be central to the plant ability to synthesis hydrogen peroxide which helps the plant defend against pathogens. Manganese is important for the process of lignification which give the plants strength to stand and resist pathogens within the roots.

Manganese deficiency is a common sight in cereals in the UK. The plant may be suffering from a shortage of manganese before we see physical symptoms. By the time we see the classic yellowing of the crop we are already two weeks too late, consequently yield will have been compromised. It takes around two weeks for the shortage of manganese to reveal itself with leaf symptoms so from that point on we are fire-fighting the deficiency. Over 95% of all the soil analysis we undertake shows very low levels of available soil manganese. While the obvious solution is to re-mineralise the soil using manganese sulphate or similar, in reality this proves expensive and doesn’t help with some of the underlying causes of deficiency such as soil pH.

Manganese deficiency is typical associated with high pH soils, loose well aerated (cultivated soils) and lighter textured soils. Soils high in iron can also reduce manganese availability. Manganese has low phloem mobility in the plant therefore regular foliar applications are necessary in situations where deficiency has been previously seen or maybe expected. Where the deficiency has already expressed itself in the form of visible symptoms a minimum of 750g of manganese as foliar manganese sulphate is required per application if you are using a straight un-chelated product. This can be reduced to 150g per application if using a quality chelated product. As with all foliar applications you always need to ask yourself the vital question; how does the positively charged metal pass through the negatively charged leaf surface? If your product or supplier cannot answer this question it probably means the product hasn’t addressed this fundamental question.

References.

Mineral nutrition of higher plants. Marschner. 2012

Principles of plant nutrition. Mengel & Kirkby. 2001

Applied soil trace elements. Davies. 1980.