Harvest and crop residue management

All previously described preparations and agrotechnical operations lead to the climax of crop production – harvest. Every farmer certainly dreams that harvest time brings joy, satisfaction, and profit. Of course, just like at all earlier stages, harvesting requires proper agronomic practices and consideration of weather and field conditions. It is also necessary to decide how to manage residues and smoothly move into post-harvest tillage – as mentioned at the beginning of this e-book, the season simultaneously ends and begins again.

Optimal harvest timing

When deciding on harvest, you should be guided not only by the calendar, but also by grain moisture. For cereals such as wheat, barley, or rye, optimal grain moisture at harvest is around 13–14.5%.
- Harvesting too early at higher moisture means greater threshing losses and the need for costly grain drying, as well as a risk of mould development during storage.
- Excessive delay, on the other hand, leads to grain shattering, yield and quality losses, and a higher risk of disease infection (especially if rainfall occurs during delayed harvest).

Important! In practice, farmers use handheld moisture meters, which are fast and sufficiently accurate to determine the right harvest moment.

Combine harvester settings and working technique

During harvest, care must be taken to ensure even feeding of crop material into the threshing system – the operator should drive in such a way that the header cuts evenly across its full width and delivers a constant flow of straw and ears. Otherwise, losses may occur: too little material causes grain cracking and damage, while overload leads to unthreshed grain reaching the straw walkers.
Important! Driving speed and threshing settings (concave clearance, drum/rotor speed, airflow, sieves) must be adjusted to conditions. Modern combines often support the operator with automatic adjustment systems.

Below are the key machine components that require adjustment.

Threshing drum speed

It is set to achieve clean threshing with minimal grain damage – usually starting from values given in the manual and then fine-tuned in the field.
- Too high → grain cracking and damage.
- Too low → unthreshed ears.

Concave clearance (drum–concave gap)

Adjusted depending on crop species and maturity stage.
- Too narrow → excessive straw shredding and grain damage.
- Too wide → unthreshed ears and higher losses.

Sieve settingst

Upper and lower sieves must be set to effectively separate grain from chaff and residues without causing grain losses. For small seeds (e.g. rapeseed), gaps are narrower; for large seeds (e.g. maize), wider.

Fan speed

Adjusted gradually while observing grain samples.
Too much airflow → grain blown out.
Too little → impurities in the grain tank.

Header cutting height

Should be as low as possible to collect all ears, but without unnecessarily taking in excessive straw and weeds. In rapeseed, side knives are often used to reduce shattering losses.

Straw chopper and spreader

In simplified and no-till systems, even chopping and spreading of straw across the full working width of the combine is crucial. Good distribution requires short straw cutting (usually 4–8 cm segments) and uniform spreading over the field surface. Uneven distribution creates residue bands that hinder subsequent sowing.

Distribution of chaff and residues from straw walkers

Chaff and fine residues should also be spread evenly – this improves organic matter decomposition.

Straw and crop residues: plough in, leave, or manage differently?

Straw represents a valuable by-product crop—it is a treasure trove of macro- and microelements as well as organic matter. On average, 5 tons of cereal straw contains about 30 kg of nitrogen, 12 kg of phosphorus (P₂O₅), 62 kg of potassium (K₂O), and significant amounts of calcium, magnesium, and micronutrients. Rapeseed straw is even richer—5 tons contains about 35 kg N, 15 kg P₂O₅, 104 kg K₂O, 112 kg CaO, and 11 kg MgO. It's no wonder that incorporating straw into the soil is considered a practice that enriches it with humus and nutrients.

Important! The value of well-managed straw in the field can correspond to as much as 12–16 tonnes of manure per hectare – organic matter from straw is difficult to replace with mineral fertilisers alone.

For smooth decomposition without problems for the next crop, several rules should be followed:

- Chop and spread straw evenly.
- Mix with soil shallowly – about 8–12 cm is sufficient.
- Supply nitrogen – 6–8 kg N per tonne of incorporated straw (urea, UAN, slurry, or another nitrogen fertiliser). This nitrogen feeds cellulose-decomposing bacteria andprevents nitrogen immobilisation and temporary nutrient deficiency for the next crop.

Leaving straw on the surface (mulching) is an alternative to immediate incorporation. Straw chaff remains as a mulch layer on stubble, often for several weeks, and is mixed with soil or ploughed later. Straw mulch protects soil from erosion and excessive water evaporation – such cover can retain moisture until late autumn. In hot summers, leaving straw acts as thermal insulation, reducing soil heating and drying. After initial decomposition (2–4 weeks), mulch is usually shallowly mixed with soil using a cultivator or disc harrow.

Important! Leaving straw as mulch should be combined with good chopping, thin and even spreading, and timely sowing of subsequent crops with strong root systems capable of penetrating residues.

Other ways of managing straw include removing it from the field and:
Using it as bedding for animals or roughage,
Industrial and energy use – more companies purchase straw to produce briquettes or pellets for biofuel; straw bales are used in construction (wall insulation in eco-houses), horticulture mulching, and as substrate for mushroom cultivation.

Important! Any removal of straw from the field reduces organic matter and nutrient resources. Farmers should weigh short-term profit from straw sales against long-term loss of soil fertility.

Cover crop sowing after harvesting the main crop

After harvesting the main crop, fields should not be left idle. Sowing cover crops (catch crops) immediately after harvest is an excellent way to regenerate soil, supply fresh organic matter, and maintain living plant cover until the next season. Cover crops are often called green manure – they are sown between two main crops not for market yield, but to improve soil and suppress weeds. Entire Chapter 5 is dedicated to cover crop sowing.