As leaders on the topic of catch/cover crops, we send you even more detailed explanations of possible cases you may encounter this spring in the field. This is our second circular this year on the topic of catch crops, we hope there are no unresolved issues.
AGAIN ON CATCH CROPS, SPRING AFTERCARE AND SOME OTHER TIPS
As the winter was mild, but out of the blue the last week of February and the beginning of March brought Siberian frost, the picture in the catch crop / cover crop fields is not quite clear yet, even after the cold there needs to be a period of decay after the frost, so I give some OPTIONS FOR ACTION according to the respective field situation:
1. If there are only annual non-wintering catch crops in the field - e.g. turnips, mustard, phacelia, etc.:
a/ in a normal winter they freeze completely and nothing needs to be done, everyone can sow or cultivate as they wish. Maybe it will happen with a delay this year;
b/ until the last frosts only mustard was frosted, turnips and other species were green or just scalded. In such fields we have the following options:
- If there is vegetating green above-ground mass, it should be treated with glyphosate - the plants would not interfere with direct drilling with direct drills, but according to my science it is not good to mix green plant mass with the soil, it should be rotten, and direct drills and Strip-till units have real tillers;
- With No-Till technology with suitable drills you can sow directly on them, they don't mix the soil significantly, but you have to judge the C/N ratio of the stand and in most cases I would recommend treating with glyphosate here too;
- If there is no green above-ground mass but there are unfrosted roots, glyphosate treatment is pointless. Sow according to all technologies and then deal with the herbicide in the main crop if there are shoots and volunteers;
- Instead of a total herbicide at grass stands above 30 cm, mulching is also practiced and then sown directly into mulch that slowly composts. Some colleagues deny this practice, but it has its merits and is widely applied in Europe. In some species, just knocking down the stand with beams or rollers can also be applied;
- Conventional technologies - the usual spring treatments are carried out. If there are live roots and new shoots appear after sowing the main crop, all vegetative herbicides in maize and process sunflower will deal with them.
2. If there are also winter cereals in the field, whether sown for the purpose or from volunteers, whether or not there are living green broadleaved plants among them - glyphosate treatment is mandatory for all technologies, because with the spring vegetation the cereals will pick more, will suck up nutrients intended for the main crop and grow in height, thereby competing with and compromising the main crop. This is why we do not recommend winter cereals for catch crops in the classic version. They may do well with mulching or mowing for a green conveyor in combination with strip-till seeding the main crop.
3. If the field has only winter broadleaves - this is the least likely option anyone has implemented, but should be mentioned as there are differences:
- If it is winter rapeseed, it should absolutely be killed with a total herbicide. Even if it is mulched for direct or semi-direct seeding, rapeseed always recovers the cut above-ground parts in spring;
- If it is a winter legume, it is optional:
a/ be treated with glyphosate or
b/ mulch and sow in mulch and
c/ can only be knocked down with light rollers or beams and sown with Strip-till equipment. However, if there is winter wheat in the mix, the choice is again glyphosate, the other measures will have no effect.
You may notice that nowhere is there any mention of over-fertilizing, tilling, etc. It goes against the concept of cover crops and the term "green manuring" is in the sense that the plants leave organic matter and nutrients behind, not that the greens have to be tilled into the soil. Those who are very keen to plough should do so after the crop residues have rotted, but isn't the aim to optimise the treatments and the catch crops to do some of the work of the 'irons' which, if overused, permanently destroy the soil structure.
It is important to assess the situation on the ground, in any case, and if there is a little struggle after winter in the fields with catch crops, it will not erase their merits.
Do soil samples and compare with fallow fields that have been bare over winter or with dead stubble, ploughed, etc. You will see that after the catch crops you have in the top layer, besides organic nitrogen, much more phosphorus which they have pumped up from depth and accumulated in the layer accessible to the main crop. Also potassium and magnesium and some trace elements are increased. There will be fewer weeds and a better water regime. As for the soil reaction, it will not change significantly, but the higher organic content will dampen the negative effects of a low pH, for example. Soil reaction is not an isolated abstract quantity, it should always be considered in relation to the humus content. Observe the fields and draw your own conclusions.
In 2017, heavy floods carried away large layers of soil in many areas, along with the sown crops. We have particularly revealing pictures from the area of Svishtov. I highly recommend starting catch crop samples on the sloping ground, which is constantly eroded by water and wind, and in more extreme rainfall simply shifted and stripped. This is the only way to save your high slope cropland by providing continuous vegetative cover, a primary means of combating erosion. It is very surprising to me that, in spite of everything, many of these fields are now being sown again in the direction of the slope, which is absolutely the wrong practice. Your yield will increase by about 15% just from working and sowing perpendicular to the slope. Modern machines allow trouble-free working on the slope as well. I am not referring to cases that require terracing. In addition, proper crop rotation and catch crops will have a really appreciable jump in results on farms with a high proportion of arable land with significant slope.
All of these measures are aimed at maintaining and improving soil fertility and are a route to yield stability and reducing the risks of crop failure due to various natural events or phenomena.
Ing. Evelina Marinova
05.03.2018
Catch crops in winter
Stop the erosion!