Sowing of winter wheat and barley is behind us in most regions, but the field’s season is really only starting now. The job in November is to look at emergence: to count how much of the seed has turned into plants and to find the cause wherever the stand is thin. The second check comes in spring: working out which plants have survived the winter. In this article we explain how both checks are done, what happens in the field over winter, why barley is more sensitive than wheat and how many plants per square metre are considered enough.
Counting emergence: seed sown versus plants up
For a count to mean anything, you first need to know how many seeds went into the field. The calculation is simple: multiply the kilograms sown per decare by one thousand and divide by the lot’s thousand-kernel weight, and you get the number of seeds per square metre. For example, if 25 kg per decare was sown from a lot with a thousand-kernel weight of 40 grams, 625 seeds fell on each square metre. If the thousand-kernel weight is not known, it can be found by counting out a thousand random seeds from the seed and weighing them. We covered how much seed to sow per decare in detail in our article on how many kilos of seed per decare.
The count is made once emergence is complete, when most plants have one or two leaves. A 50 × 50 cm frame of wood or wire, a quarter of a square metre, makes the job easier. The frame is thrown at different spots in the field, and the plants inside are counted and multiplied by four. Headlands where the drill turned are not representative of the field, so the count should be made further in.
The number of plants is then compared with the seed sown. Germination in certified seed is 97-98 per cent; in the field a loss of 5 to 10 per cent comes on top of that. In other words, under good conditions most of the seed sown should be visible as plants. If the count falls clearly short of this, or part of the field is full and part is bare, the cause needs to be found. Recording this first count matters: the difference between it and a second count at the same spots in spring will show what the winter has cost the field.
The cause of thin emergence lies below the surface
Looking down at an empty row does not reveal the cause; you have to dig down to the depth where the seed lies. If the seed sits unchanged in dry soil, there was not enough moisture for it to germinate; the problem is water, not the seed, and emergence is waiting for rain. If the seed has germinated but the shoot has curled and yellowed below the surface, it was either sown too deep or there is a crust above it. A crust forms when rain after sowing rearranges the soil particles at the surface and they harden into a shell; it lets neither water nor air through and stands in the shoot’s way as a mechanical barrier. It is more common on fine-textured soils with poor structure. To prevent crusting, we recommend applying a sulphur-containing fertiliser before sowing. We explained the effect of deep sowing and the 3-5 cm rule in our article on winter barley sowing time.
Plants with their leaves pulled down into the soil and patchy gaps point to the cereal ground beetle (Zabrus). According to the technical instructions of Türkiye’s Ministry of Agriculture and Forestry, its larvae feed in autumn by pulling the leaves of the young crop into the soil, spend the winter in the soil and continue the damage in spring; with three or four larvae per square metre, open rows and gaps appear in the field. Growing cereals on the same field year after year increases the damage, so the first measure is crop rotation. Open holes, runs between the holes and gnawed plants, on the other hand, are signs of field voles. Vole control does not work unless it is carried out at the same time as on neighbouring fields, which is why provincial agriculture directorates recommend collective control. In both cases the first step is to inform the district agriculture directorate.
Winter hardiness is gained in autumn
How a plant gets through the winter is largely decided in autumn. According to a review on cool-season cereals by researchers from the Bahri Dağdaş International Agricultural Research Institute and Selçuk University, wheat adapts to winter by building up sugars in its cells during cool autumn days just above zero; this lowers the temperature it can withstand from minus 5 to minus 10 degrees, and the light frosts that follow increase its hardiness further. This resistance is not permanent. It is lost when the weather warms, and a sudden cold snap after mild days catches the plant unprepared. According to the same review, warm weather before a frost together with plenty of nitrogen and water increases the plant’s sensitivity to cold, and deep-sown plants are also hit harder by cold.
Snow is the best protection in winter. In one measurement cited in the review, under 52 cm of snow the soil surface was minus 1.6 degrees while the air was minus 17; under field conditions a snow cover of 8-10 cm is reported to be enough to protect wheat from cold and winter damage. The real danger is a hard frost without snow. In the early stage in which it goes through winter, the plant’s growing point is close to the soil, so it is still hardy; according to the table in the review, two hours at minus 11 degrees at this stage leaves yellowing leaves, burnt tips and a bluish look across the field, but the plant can recover once the weather warms. Because ridges where the wind sweeps the snow away are left bare, winter damage usually appears in patches across the field.
Frost heave, ice and snow mould
Part of winter damage comes not directly from the cold but from the soil. In wet soil that thaws by day and freezes again at night, the volume of the freezing water increases by 9 per cent and the soil heaves upwards; as this repeats, the roots break. This is called frost heave, and the breaking of the roots is known as frost cutting. When the soil water freezes, the plant cannot take up water either; this condition, called physiological drought, makes the damage worse. A layer of ice forming over the plants can also cause damage.
In winters when snow lies for a long time without a break, the damage seen after the snow melts is not always caused by cold. Snow mould first appears as white and pink spots; within a few days the plants die completely and the field looks as if it has suffered cold damage. Looking at the field as soon as the snow has gone therefore makes it possible to read the cause of the damage correctly.
Barley does not withstand winter as well as wheat
Barley and wheat do not come out of the same winter in the same way. The University of Minnesota’s publication on winter barley states that winter barley is less hardy than rye and wheat. In a cold-hardiness project in Eskişehir cited in the review, white-grained wheats also proved more cold-tolerant than barleys, and red-grained wheats more tolerant than white-grained ones. The review lists the main factors that determine the degree of damage as the duration of the cold, how quickly the temperature drops, the plant’s growth stage and the position of the field. This is why a plant sown at the right time and going into winter with three to five leaves is better prepared.
Even so, in cold regions the choice of variety matters more in barley than in wheat. In the registration trials in Thrace, Manava’s cold damage scores were among the lowest of the standard varieties; we described this in detail in our article on Manava barley yield. Because the six-row Ramata has good cold tolerance, it can also be sown as a winter crop where winters are harsh, and Sinanbey, chosen for fully dry land, also withstands cold well. In wheat, Renan has very good cold tolerance; because it has a vernalisation requirement, it does not head without going through winter, and it is recommended for Central Anatolia, the transition zones and Eastern Anatolia.
Telling dead plants from live ones in spring
At the end of winter a yellowed, browned field can look dead at first sight, but leaf colour on its own says nothing. According to a publication by the agriculture department of the Canadian province of Manitoba, brown leaves do not always mean winter injury, and leaves that come out of winter green are not a sure sign that the plant has survived either. The place to look is the crown, the part of the plant close to the soil surface from which the roots and tillers emerge. In a healthy plant the crown looks white and firm. In our own field checks at the end of winter, we too first look at root development in yellowed plants or count the seeds that never made it above ground.
If a decision has to be made before the weather warms up, a simple test helps. A few plants are dug out with their soil from different parts of the field using a spade and kept in a warm room with the soil kept moist. According to the same publication, if new roots sprout from the crown within five to seven days the plant is alive; if no new roots appear, it has not survived the winter. When a second count is made at the spots counted in autumn, the difference between the two counts shows the winter loss.
The decision to replough and plants per square metre
Reading the result of a count requires a yardstick. According to our field observations, yield stays low if there are not around 450-500 plants per square metre at the end of winter. In a field that falls short of this number but has an evenly distributed stand, new tillers partly make up for the losses; even so, because tillers yield less than the main stem, the yield is not fully recovered.
We leave the decision whether to replough the field to the farmer, and recommend consulting an expert who can see the field on site before it is made. If spring sowing comes into question because most of the field has been lost, the choice should not be varieties that do not head without going through winter, but varieties of alternative type that can be left until spring, such as Ramata.
The count in November and the second one in spring also guide the seed rate and the choice of variety for the next season. If you would like to assess the emergence in your field or the condition of your plants after winter, you can share your region and your observations with our agricultural engineer: +90 506 101 01 50.