How to technologically support the quality potential of high protein wheats
1. What dependencies exist between grain quality indicators
The main difference of wheat from other cereals is its gluten content. The higher it is, the bulkier the bread becomes. But gluten also has its own constituent parts - glutenins, which bind the dough together, and gliadins, which allow the dough to be weighed - the latter being provided only by certain wheat varieties that are of interest for special needs and quality flours for the domestic and foreign markets.
Gluten correlates with crude protein and its quality is reflected in both protein content and sediment value. High protein content and low sedimentation are a sure sign of poor gluten quality.
We will not dwell here on precise baking analyses of wheat grain. The aim is to fulfil the potential genetic merits of premium varieties by some measures in the cultivation technology and to protect farmers from mistakes when growing such varieties.
2. Low falling number - poor quality
A stable falling number is of utmost importance. While by physically mixing different batches of wheat the gluten content can be regulated, mixing varieties with a low falling number and those with a high falling number does not give a positive result! The higher amylase activity of the high falling number wheat affects the low falling number wheat less favourably than the latter is profited by the former. It is therefore absolutely essential for quality wheats to have a consistently high falling number and a minimum tendency to sprout - especially when the weather deteriorates during harvest.
3. What the falling number is affected by
The premature enhancement of amylase activity that collapses the falling number is controlled by the phytohormones gibberellins, and abscisic acid maintains germ dormancy. All processes that stimulate gibberellins and lower abscisic acid levels in ripening grain increase the risk for falling number.
Apart from the genotype of the variety, meteorological conditions have the greatest influence on these processes. If temperatures drop during the first 2 weeks after flowering, the plant self-selects that "winter is coming". This reduces the flow of abscisic acid, which should actually stop premature germination. If cool weather persists, the resistance to sprouting is already compromised and good fall numbers cannot be expected either.
Sunshine is also important. Even at high temperatures under diffuse radiation or in other words in cloudy weather during milky and waxy maturity the hormonal activity is increased and with it the risk for the falling number. Bright sunshine has a beneficial effect. Rainfall, especially prolonged rain during waxing and full maturity lowers the fatal falling numbers.
4. Important for crops
Avoid uneven crops! In order to have the prerequisite for premium quality we must first of all achieve homogeneous crops. This starts with soil tillage as a condition for friendly uniform germination, placing the seeds in an even soil bed under uniform conditions and also densities that are appropriate to the sowing period - all to avoid the share of minor classes and to ensure a crop with equivalent brothers or classes. A moderate, not excessive, starting nitrogen dose in spring also contributes to this.
Excessive amounts of nitrate nitrogen can negatively affect fall numbers. Nitrate fertilizer should be limited to the spring starter rate. With sufficient soil moisture, amide and ammonium fertilizers are preferable, especially for late rates. Also bear in mind the control of voles - vole damage is also a cause of uneven crops and stretched tillering.
From a phytosanitary point of view, a very important point is to avoid fusarium. The most appropriate is the application of so-called azoles (fungicides with active substances of the -azole type). Apart from being a good remedy against fusarium, azoles directly suppress gibberellins and thus stabilize the dropping number.
Strobilurins should be avoided as they increase the risk of sprouting in the grain.
5. Protein is not produced with nitrogen alone
Protein accumulation in the grain ends at milk maturity. Thereafter the grain as a reserve accumulates mainly starch. As the weight of the grain increases, the relative/percentage protein content decreases, it is 'diluted', although in absolute value the amount increases.
In addition to varietal characteristics and nitrogen supply, environmental influences and other nutrients involved in protein synthesis are important for protein content.
With low sunshine, less protein is formed during stalk growth and later during grain formation, as the supply of assimilates for amino acid formation is lower. Drought is also limiting as it blocks the uptake of potassium, manganese and boron.
On poorly stocked and heavy soils, a pre-sowing application of potassium at a greater depth is recommended. In this way, even when drought occurs in the topsoil, the wheat will be able to obtain potassium from a greater depth. The potassium fertiliser will also be sufficient for the next crop. Potassium can also be applied vegetatively at the time of stem elongation in solid mineral form - this is recommended for light soils, and in a pinch a foliar treatment with a potassium-saturated liquid fertiliser is beneficial.
The need for pre-sowing phosphorus stockpiling is undeniable and is already practised in this country; it is also advisable to have phosphorus as a stockpiling element in the rotation and as a result of soil analysis.
Nitrogen fertiliser rates cannot be universally determined and fixed. They depend on the yield objective according to the potential of the variety and the soil fertility and structure, on the precursor and the corresponding mineralization and mobilization of nitrogen, on the sowing period, on the density of the crop, its development, etc.
As a rough fertilisation scheme, the following can be recommended: the starting rate should be moderate, a second fertilisation at stem growth and a third/fourth fertilisation with small doses of nitrogen in the flag leaf and/or at emergence.
The nitrogen fertiliser rate after taking all conditions into account is only about 0.3 points or about 10% higher than normal bread wheat, so there is almost no difference in the amount of nitrogen fertiliser. What matters more is that it is calculated correctly in principle, that the right products are used, that they are applied at the optimum times and that the other subtleties of the technology are observed.
6. Provision of trace elements
Foliar fertilisation with manganese should be completed at the moment when stem growth begins. Even an autumn-only application would be advisable. The aim is not to prolong the budding process in spring, which would result in unequal brothers, respectively unequal spikes. Only when there are visible symptoms of deficiency is a late application of manganese justified. On soils with high soil reaction values, where manganese and boron are blocked, their uptake is stimulated by acidifying the soil reaction - this is best achieved with ammonium sulphate.
Cereals, especially quality wheats, also need boron. Of course the amounts are far below the needs of rapeseed, for example, but they are a must. Particularly on alkaline, heavy soils and in drought there can be supply difficulties, so an application of 3-5 g/dcaa of B is appropriate at the most appropriate stages of stem growth or flag leaf and can be combined with a fungicide.
A common cause of low grain protein levels is the difficulty in converting nitrate to nitrite and amide. With drought as a first response, the plant limits its nitrate reduction. Even short-term deficiencies of molybdenum and copper can cause the same reaction. Especially on humus soils, copper application is a must. The period from flag leaf to full emergence is recommended as the phase for copper application.
7. Without a lot of nitrates in the class
Between 50 and 80% of the protein in the spike comes from the leaves. The leaf protein is broken down by the enzyme protease to water-soluble amino acids, which are transported directly into the grain infuser. This process is slowed by high levels of cytokinins in the leaves, which in turn are caused by high nitrate levels. The golden rule is therefore that late doses of nitrogen should not be in nitrate form.
Excessive amounts of nitrate are deposited in cell vacuoles, which serve as "waste containers" and are released after leaf death. It is then too late for protein formation. And yet: crucial for the protein content of the grain and the quality of the gluten is a sufficient supply of nitrogen. Until the end of stem growth, we aim to give the basic doses to pump up the leaves with protein, without, however, causing nitrate excesses.
For smooth movement of assimilates we need to have healthy plants and conducting pathways. Especially diseases such as basal rot and other infections at the base of the stems must not be allowed. Also lodging should be avoided.
The new selection offered by Leader Consulting is significantly resistant to lodging, but sometimes, depending on the conditions, the introduction of growth regulators is justified to reduce excessive vegetative growth. Bear in mind that if a prolonged drought is imminent growth regulation can have a negative effect on yield! Also, in quality wheats, growth regulation should be completed before flag leaf. An ethephon is preferable as it aids the runoff of assimilates from the leaves.
8. What affects the sedimentation value
The quality of gluten depends mainly on the variety, the ripening period and the supply of nutrients, in particular sulphur. Early flowering and prolonged ripening are positive. Conversely, with late flowering and subsequent heat which shortens ripening, gluten quality is reduced and sediment values are low.
When there is a high proportion of late tillers in the crop or a fusarium infestation - sedimentation values are doomed. This is also why gibberellin inhibitors should not be used as growth regulators - especially at later stages, as they slow down emergence.
Sulphur is an important constituent of aminoacids, and is also necessary for building 'bridges' between glutenin molecules. Approximately 3-4 kg/dcaa of sulphur is required. Sulphur is mobile and washable and cannot be relied upon to be stored. It is recommended that half of the sulphur required be supplied as a sulphur-containing nitrogen fertiliser for the start in spring, or as kieserite - magnesium sulphate, also in early spring, and the other half in later feeding at the end of stem growth.
9. Suitable conditions for growing premium quality
- areas with sufficient sunshine
- areas with dry harvest weather without risk to falling numbers
- sufficient moisture supply from flag leaf to milk maturity
- soils with sufficient absorbable potassium in the deep soil layer
- soils with good nitrogen mineralisation
10. Summary
a/ variety selection
- stable falling number
- high sedimentation value
- high protein
b/ soil preparation
- removal of compaction
- aligned seedbed
- good settlement to stimulate fine roots
c/ sowing
- jointly germination
- in early sowing, do not reduce the density excessively so as not to provoke incomplete tillers and spikes by heavy tillering
- for late sowing, rely on a large number of central tillers
d/ nitrogen and sulphur
- moderate starting rate of nitrogen
- strong dose at stem growth
- late dose preferably with urea
- double application of sulphur 3-4 kg/ha
e/ basic fertilisation
- ensure available potassium
- phosphorus according to crop rotation and soil
f/ trace elements
- boron and manganese - mandatory in drought and high pH
- copper on humus soils and soil deficiency
- Molybdenum on acid soils
- Magnesium according to soil analysis - often underestimated
e/ growth regulators
- Prefer lodging resistant varieties
- protect against and treat plant root diseases
- apply regulators early if necessary, not late
f/ fungicides
- control of basal rot
- keep the top 3 leaves healthy until milk maturity
- azoles against fusarium and sprouting
- avoiding strobilurins
g/ pests
- mice and slugs make heterogeneous crops
- aphids and cicadas carry viruses that clog the vascular tissues
- lice also carry amylases which increase the risk of overgrowth
- bedbugs reduce gluten quality by transferring proteases when sucked from the grain.
As a conclusion, we can say that in order to reach the quality genetically set through selection in a variety, apart from the importance of weather conditions, which we cannot actively influence, we have a lot of levers in our hands that we could use and, by observing important regularities and analytically concretising the technology for growing this type of wheat, successfully produce a truly valuable product that would also receive an adequate market price and sales.
Compiled on the basis of research and materials from foreign specialized publications:
Eng. Evelina Marinova, Leader Consulting EOOD