With regard to plant production drought and heat are limiting factors. As a result of the climate change extreme weather situations occur more and more frequently. To avoid negative consequences on the yields, methods like direct seeding are used.
Michael Horsch’s opinion with regard to direct seeding is clear: “Those who practice direct seeding as a religion forego profit and in the worst case can ruin their farms. We at HORSCH have been dealing with direct seeding for 40 years. With all ups and downs.” With regard to direct seeding there are quite a few things to consider. “In the first step direct seeding is not a question of technology. What is crucial is a good soil structure, a balanced rotation, a good soil covering and the sowing time.”
In Europe, direct seeding was mainly used as an argument for building up humus in the recent past. A mix of abandonment of tillage and catch crop cultivation can increase the share of organic substance in the soil. If you take a closer look at direct seeding all over the world, you will find the most different motivations for direct seeding: in the dry regions the focus is clearly on saving water. In the hot, partly subtropical regions the soil has to be covered so that the soil temperature does not rise into a range that is detrimental to the plant. The high-precipitation areas particularly need direct seeding and a soil cover to prevent erosion. And let’s not forget the markets with very low yields: Saving costs by sowing directly is another argument.
Direct seeding as a water-saving sowing method
Because of climate changes and the more extreme heat waves (35-40 %) of the past years which some farmers still worry about, farmers more and more think about the topic direct seeding and water-saving cultivation. The problem particularly affects for example parts of Hungary, Romania and Bulgaria. Why could direct seeding be a solution (at least partly)?
“Let’s take the above mentioned countries as an example. Maize, winter wheat, winter rape and sunflowers are the main crops. After rape/sunflower, when it still is very dry in September and October, sowing wheat with the Avatar after an ultra-shallow pass with the Cultro would be appropriate. After maize, too, you normally can quite well sow wheat with a single disc seed drill. Unless there is too much straw on the field. In this case you first have to incorporate the straw a little bit, for example with a disc harrow. If you want to sow maize in spring – this is done for example in Brazil, you have to decide from case to case. For if the soil temperature remains too low, it is a risk!”
The knife roller Cultro can actively stop a catch crop from growing.
A covered soil
Dark cultivated fields do not reflect solar radiation as well as uncultivated or covered fields. They absorb the sunrays and warm up faster. This, of course, depends on the type of soil. Thus, for example dark brown, almost black soils warm up considerably faster than light or even slightly red soils. “We assume that a soil cover consisting of plant residues improves soil protection. For it reduces evaporation, increases the water-holding capacity and reduces erosion.”
This is also advantageous for germination and root development, i.e. a crop can develop better if the soils do not tend to be overheated. “Especially in spring, there can be a fine line. For there are regions where in this case the soil does not reach the minimum temperature. What is good on the one hand can also be a disadvantage on the other hand if the soil does not warm up sufficiently.” If it is too hot in the soil, a safe germination and root development of the plant is no longer possible. Once the minimum temperature has been reached, the plant stops growing. If the temperature even is exceeded too such an extent that protein degenerates, plant development is completely finished. In some regions that have to struggle with extreme heat, this is a big challenge.
Another advantage of a soil cover is that it keeps the humidity that is transported to the surface in the upper layer of the soil. Thus, a kind of micro-climate is created where residual humidity accumulates in the topsoil and guarantees a good emergence. “You only have to go barefoot through a wheat population without any residues on the surface in June or July. Even if the population is dense, you burn your feet on the black clay soil – although the soil is covered with growing plants. This shows that there is a connection and that a population keeps up longer if there are residues on the surface.
According to Michael Horsch, we will have to give very much attention to the topic stubbles and stubble lengths to find an optimum way.
Another problem I noticed: if the straw stubbles are too long resp. if the straw remains on the field too long, among others mice feel very comfortable. I saw this only recently in Romania. The rape population did not look too bad but in the field, there was one mousehole beside the other! The same is true for slugs. If there is too long straw and too high humidity for a long period of time, the slugs devour the rape, wheat etc.”
Catch crop cultivation and direct seeding
Cultivating a catch crop before sowing directly is always better. But a prerequisite is that the catch crops fit in and that a sufficient water supply is guaranteed.
Catch crops can help to increase the humus content. Moreover, another rotation member always can separate the previous crop from the next crop phytosanitary. “In conventional farming this separation is done by tillage.”
If the total precipitations are low, farmers, of course, discuss the question if catch crops do not additionally require water. “It is obvious that this simply is not possible in some regions. For if it does not rain during the cultivation break in summer, the catch crops don’t grow either and, thus, it does not make sense to cultivate them.”
How can you actively stop the growth of a catch crop? This can either be done by frost, knife rollers or the use of glyphosate. “In this case, you have to check which method makes sense in which region. For in Europe, the use of glyphosate will soon no longer be an option. You then need other measures to stop the growth.”
Another question that always is asked when talking about direct seeding is if direct seeding and tillage are inconsistent. Not at all – quite the contrary. “I my opinion, a combination of both might even be the key for the future. The reasons are various. On the one hand, we see that direct seeding only involves high yields if the soil structure is very good. As I already mentioned, a good soil structure can be achieved resp. encouraged by growing catch crops. But there also are situations where there is no time to improve the soil with catch crops. In this case, it, of course, makes sense to loosen the soil so that the roots can grow deeply and reach water in the subsoil.
We notice that even in countries like for example Brazil where direct seeding has already been established for years the soil is loosened deeper at 30 – 40 cm as the soil, despite the catch crop, is compacted.“
But what direction will the topic direct seeding in Europe take? Does direct seeding have a future here? “We have to act on the assumption that weather extremes will increase and that we will get more hot, dry years. I don’t think that we will see a pure direct seeding, i.e. without any tillage, in our clime. In my opinion, farms will have to prepare in such a way that they prepare their soils to be able to sow directly in dry years if required. This means: always perfect straw distribution, cereals stubbles as short as possible, avoid resp. considerably reduce compaction/tracks during the harvest (e.g. by CTF harvest).”
Due to its individually controlled disc coulter SingleDisc, the Avatar 12.25 SD can be adapted to different sowing conditions and thus is also ideal for direct seeding.
This was about the general use of direct seeding. In the next terraHORSCH we will explain in detail which sowing method (discs, tines) fits where, how it is to be used, which preparatory work, if required, is suitable.
Moreover, we will provide tips with regard to the C:N ratio of residues, stubble lengths and how to handle them.
The angles of the closing wheel can be adjusted depending on the soil conditions. For direct seeding or on very heavy soils they can for example be set aggressively.