HORSCH Live
In December 2022, HORSCH Live entered the third round. This time, the event series was not limited to one week but provided interesting professional speeches of different speakers until mid-February 2023. The focus was mainly on the entity of soil and plant. This article will summarise the speeches about catch crops, leaf fertilisation and liming.
You missed a speech or a discussion? They are still available after the event.
Catch crops
In his HORSCH Live speech “Catch crops – successful cultivation regarding nutrient and water management” (date: 5th December 2022) Christoph Amslinger, crop production consultant of the Hanse Agro GmbH, explained that catch crop cultivation accomplishes so much more than just the compliance with the greening and that the correct cultivation and the integration into the rotation are crucial for the success of catch crops.
Crop production objectives
One crop production objective of catch crop cultivation is the improvement of soil fertility. To have food for the macro- and micro-organisms in the soil, we try to get a larger pore volume but also a better infiltration as well as to include organic matter. Nutrient transformation also improves groundwater protection and nutrient efficiency.
Erosion protection, too, plays a major role. “The soil is the capital of every farmer”, Amslinger says. Therefore, when growing catch crops, we try to reduce the soil loss caused by wind and water. To prevent grass and weeds from emerging, we use the shadowing and the competition of the catch crops but also the segregation of the root exudates. To build up humus, a second objective of catch crop cultivation, surface and subsurface plant biomass is integrated into the soil. “To what extent this biomass is used resp. into which humus pool it will be included, mainly depends on the C/N ratio.” To fight nematodes, phytosanitary aspects are important, too.
Establishment
When establishing catch crops, many farmers among others wonder how to determine the right time for sowing. According to Amslinger one important factor is the time when the previous crop was harvested. “There is for example a difference if you grow GPS cereals which normally are harvested at the beginning of July or if we talk about late wheat that in the North of Germany will be harvested in August.” But also the choice of the catch crop components, the site characteristics and how the catch crop is to be used are decisive factors. You have to ask yourself what you want to achieve – just a little covering of the soil to reduce erosion or if you try to create a huge biomass growth which is to build up humus in the soil or which will be used for cuttings.
To establish a catch crop, you can use different sowing methods. On the one hand ploughing allows for sowing the following crop directly or in mulch seed, provides a homogeneous catch crop population and allows for using soil water from deeper layers. “The disadvantage is that there is no time to incorporate harvest residues […] and you, thus, produce a straw mat. Moreover, the risk of erosion increases.” And so does the risk of desiccation.
Mulch seed is another option. It allows for incorporating organic fertiliser, repairing compaction and using the straw mulch as an erosion protection. For this method you should allow some extra time to guarantee a safe emergence of volunteer crops.
In case of direct seed, you sow directly into the stubble after the harvest of the previous crop has been finished. “Thus, we achieve a head start for the catch crop compared to the volunteer crops or the weed seeds. Moreover, it is a very water-saving method. Especially in seasons with dry summers like in 2022 this is an important argument.” In Amslinger’s opinion the disadvantage of this method is the special technology that is required to achieve an appropriate emergence.
Consequences on the water balance
The germination water requirement depends on the seed size, husks, seed coats as well as on the seed ingredients. “The higher the germination water requirement, the higher the requirements on the seedbed.” Oil radish for example requires less germination water and can thus also be established if the seedbed is bad. The germination water requirement of a field bean is very high, the requirements on the seedbed are correspondingly high.
Catch crops are often said to withdraw water that later on lacks elsewhere. An Austrian study shows that especially in dry years (2004) the loss of water in complete fallow is higher than with catch crops. “Moreover, catch crops build up biomass in a very water-efficient way. In autumn, it first needs water. The soil water content decreases considerably compared to complete fallow. Already in December/January the tide turns and there is constantly more water available with catch crops. This is due to a higher infiltration output which helps to refill the soil supplies during the winter. The mulch layer prevents a non-productive evaporation in spring.”
Nutrient management
When talking about nutrients, farmers often wonder whether or not they should fertilise the catch crops. “We tried to classify this on the basis of different scenarios resp. sowing methods.” When sowing after a plough or if the straw is removed, often no fertilisation is required. If the straw remains on the field, you possibly might have to fertilise an additional 30 to 60 kg N/ha within the scope of the statutory rules.
For mulch seed, we examined two different scenarios for stubble cultivation. In the first case it was very dry at the time of stubble cultivation or the stubbles had not yet been touched. “If the straw was removed, there is no additional N requirement. If the straw remains on the field, the nitrogen requirement of the catch crop coincides with the nitrogen requirement for the straw degradation and a straw compensation fertilisation is required.” In the second scenario, it was very wet during stubble cultivation. Thus, the rotting process started earlier and the course of the N dynamics in the soil was more regular. Thus, the catch crop does not suffer from an extreme nitrogen loss. In this case, an additional fertilisation is not necessary says Amslinger. With the direct seed method, the straw is on top, but as there is no tillage the mineralisation potential is lower, and you have to consider the N values in the soil. “If they are significantly beyond 50 kg, you do not have to fertilise. If they are considerably lower, a compensating fertilisation should be carried out.“
Yield consequences on the following crop
“In years with high yields without any weather extremes especially sugar beet on fallow land (without catch crop cultivation) reacts with better yields. The higher the yield potential, the better was the yield result for sugar beet in optimum conditions after complete fallow compared to catch crops. For maize or spring crops there are no significant differences.” In summary, it became evident that in stress years higher yields were achieved more reliably with catch crop cultivation than without the cultivation of catch crops.
In Amslinger’s opinion it is obvious that the climate changes will require stable cultivation systems in the future. To make sure that the catch crops can do their bit in this respect, their establishment has to be successful. A special focus has to be on the right sowing systems to guarantee the water supply and the associated safe emergence of the catch crop. With regard to nutrients, too, farmers should keep an eye on the catch crop to make sure it helps to keep the nutrients in the system and with the right management place it at the disposal of the following crop at the right time. Catch crops do not always lead to higher yields in sugar beet as a following crop but they can contribute significantly to a climate-resilient and stable cultivation system. Thus, catch crops can be a building block in an economically interesting rotation with stable yields. “Catch crops are part of the solution and not the problem.”
Liming
Max Schmidt is an independent lime and soil specialist. Moreover, he is a lecturer at the University of Applied Sciences Weihenstephan-Triesdorf in Triesdorf as well as a consultant of the DLG (German Agricultural Society) academy. In his HORSCH Live speech “Liming – the first step towards safe yields” (date: 12th December 2022) he talks about the role of lime for soil functionality and stability and about the resulting yield effect in farming.
According to Schmidt, an important question is what the plant needs from the soil. There are four important factors: enough root area, water and nutrients as well as oxygen for root respiration. “In summary, the plant needs a well rooted soil with a balanced water nutrient and air supply.”
“The predominantly young soils which developed after the last ice age contain a lot of valuable minerals like for example quarz, but also primary and secondary silicates like mica, feldspars and clay minerals which have an important function with regards to the storage of nutrients”, Schmidt explains. In Germany, the arable land mainly consists of mineral soils the biggest part of which consists of the mineral components sand, silt and clay as well as humus which among others contains carbon and nitrogen. The humus content of our soils ranges between 1 and 4%. Moreover, another important part are the colloids, also called exchanger. These are clay minerals and humic substances which are smaller than 0.002 mm. Their ratio in the soil is between 5 and 50%. Colloids are negatively charged and, thus, can store basic cations in an exchangeable way.
But what makes up an optimum soil? According to Schmidt, our best soils are the luvisol soils consisting of loess with a lime content of approx. 20 to 30%. Loess is a limey fine soil material which developed from stones that were grinded by glaciers. “These soils are base- and nutrient-rich, they are deep, and the air and water circuit is optimum.” They consist of 50 to 55% inherent parts and of 45 to 50% pore volume. The soil pores are very important for the functionality of the soil, for they deviate water, make it available to the plant and aerate the soil.
If the lime disappears from the soil, this quickly results in acidification processes. This leads to negative consequences like for example clay shifting. I.e. with pH values below 6.8 the clay minerals in the soil become instable, are shifted to deeper layers with the seepage water, and the result is a dwindling mellowness of the soils. The clay shifting can lead to compactions of the subsoil leading to a waterlogged site. Thus, the soil deteriorates and worse forms of humus like rotting humus and raw humus develop which partly are hydrophobic. “If the soils more or less are in the process of self-destruction, clay minerals are destroyed, too. And the result are completely different soil structures.“ According to Schmidt, all this leads to a degradation of the soil.
“All these processes essentially are related to the decalcification of the soils and to the concomitant acidification processes. On light soils, these acidification processes take place faster than on heavy soils as heavy soils are more intensely buffered.” These processes are something natural and take place without human help. Fertilisation influences the base content of the soils. The consequence of high fertiliser inputs of nitrates and chlorides is that the soils become over-fertilised. Or if potash is used as a fertiliser, the anions in the soil are washed out as they cannot be bonded.
If exchangers resp. humus are degraded or washed out, the plant quickly shows deficiency symptoms and thus shoot und root damages. “The plant cannot develop any root mass in an acid soil und suffers from a lack of calcium. Calcium is an essential nutrient for the development of fine roots, shoots and young sprouts.” If the pH value differs too much from the site optimum, the nutrient availability for the plant is limited in case of stressful conditions. Toxic elements can become available to the plant and can then be absorbed. The pH value is one of the first parameters which should be considered for a safe yield.
With regard to lime supply, the situation in Germany is alarming.
What do we have to optimise to achieve soils that provide safe yields? We have to take measures to improve the lime supply. Moreover, we have to build up a supply especially of bivalent cations to maintain the soil structure resp. the soil stability. There is one basic principle: “An optimum lime supply is indispensable for a sustainable use of the land in a humid climate.”
When asked if it makes sense to react with liming to an intensive rainfall event, Schmidt answers: “Yes. In certain crops it may definitely make sense.” But experience also showed that on some sites the soils have become more stable by reducing the extreme potash fertilisation. In case of rape, it might be helpful to optimise the environment and to stabilise the soil to get the silting problem under control at short notice.
Surveys with regard to the conditions of the soil in Germany show that a large-scale recovery liming would be necessary in the country. “We simply have to rethink. Analyses about liming in Bavaria show that farmers invest less than an average of 25.00 € per year in liming. […] Humus alone will not sort the problem and a humus enrichment of the soil will only work if there are sound lime conditions in the soil. This is the only way to generate stable humus in the soil. So we have to push both. We need the humus, and we need the calcium to bring on an aggregation in the soils. Therefore, we have to optimise the base saturation of the soils. This is a measure that is affordable and very economic.”
Leaf fertilisation
In his speech “Leaf fertilisation” (date: 30th January 2023), Henning Jaworski (head of the technical management department at Lebosol Dünger GmbH) deals with the question how it can contribute in view of the occuring weather extremes and what role the element silicon can play in this respect.
There always have been plants and weather extremes. Over millions of years, plants learned to adapt to weather extremes, to conserve their species and to develop further. Within the scope of the climate change, crops get damaged among others because of extreme temperatures combined with dry periods and unforeseen frost events but also with radiation, i.e. a sunburn of the plant. According to Jaworski, we can also observe that the winters become more rain-laden und significantly more humid. “For the crops, this means that they probably only gain momentum rather late in spring as the soils are too wet and as a consequence heat up more slowly.” Another trend that can be observed are more frequent and more secular heat waves in summer. The consequence of a distinct drought is that the nutrient availability for the plant is limited. Moreover, a quick temperature increase accelerates the plant development what in turn results in a postponement and a significant shortening of the development phases. The timespan for a sufficiently good root development is shortened extremely. In such a situation, the plant with its not sufficiently developed roots can take up nutrients via the soil only to a limited extent. In this case, there has to be a little boost via the leaf to supply the plant sufficiently with the required nutrients.
Nutrient supply of the plants
A good phosphate supply of the plant is crucial for a good root development. Phosphor provides the energy for the root growth and encourages the regeneration of roots. Thus, the water and nutrient supplies in the soil can be used much better. “After a wet winter, a cold spring and a subsequent slow heating of the soil you could, at the start of the vegetation, carry out the first measure as a leaf fertilisation with phosphor and amino acids.” Thus, the basic supply of the plant is guaranteed, and it is encouraged to develop roots so that it can access water and nutrients even in difficult times.
Jaworski explains that potassium is another element for the drought regulation of the plant. “Potassium is the element that keeps up the turgor. The result is that the transpiration coefficient resp. the non-productive water consumption decreases.” Thus, the plant can better deal with droughts. Trials showed that the plants require a regular potassium flow over the whole season. Thus, the plants better cope with stressful situations.
But boron, too, plays an important role with regard to the water supply of the plants and the root development. We noticed that the potassium uptake of plants that were supplied with enough boron was better. Cereals for example do not require much boron. “The requirement amounts to 50 to 150 g for a yield target of 8 to 9 tons of wheat.” In the trial, an input of a total of 130 g boron in cereals in 2022 achieved a surplus of 7 decitons. The third element that demonstrably plays an important role with regard to the regulation of the water supply of a plant is manganese. Plants with a good manganese supply also consume less water than plants with a lack of manganese.
Radiation stress
The second part of the speech was not only about plant stress caused by heat and drought but also about abiotic radiation stress. Sensitive crops are damaged by solar radiation, the plant virtually gets a sunburn. Within the scope of this too high energy radiation, the plants react in such a way that they produce to many radical oxygen products. These are for example hydrogen peroxide and/or ozone. As more is produced than degraded, cells are destroyed.
So according to Jaworski, you have to find out how to avoid oxidative stress. Among others, antioxidants (radical scavengers) protect plants from radiation stress by giving one of their electrons to the free radicals. Thus, the plant cell remains protected. In this process, the element manganese plays an important role again as well as for example zinc. For the latter sort of detoxicates the oxygen radicals. A third protection option is provided by amino acids which help to build up sinapin acid esters which in turn form a protection inside the plant that does not let the sunlight pass to such a high extent.
Silicium
Silicon is no essential nutrient and thus is not classified as a plant nutrient but as a useful element. It is not considered to be a bio stimulant. The question, of course, is: Where does it fit in? What can we do with this element and especially how can it be useful? Silicon strengthens the tissue and reinforces the cell wall of the plant. It also supports the plant with regard to the regulation of the water supply. Moreover, it encourages the formation of sugar and thus increases root activity. The plant becomes more resistant to mycosis and unalluring to insects. In some crops, for example salad, it also increases the transport and storage stability. “Silicon encourages the phosphor, potassium and calcium uptake. This also leads to a balance of the elements, i.e. no element is taken up excessively.”
If silicon is applied as a leaf fertiliser, the formulation is crucial. For only stabilised ortho silicic acids can be taken up via the leaf.
Jaworskis summary is that plants inevitably are at the mercy of stress phases like cold, heat, drought or radiation. Even if every year is different, we have to create a balanced and good nutritional condition for the plants by means of an early, targeted and repeated application of leaf fertilisers to help them survive possible stress phases without major damage. With regard to the dosage, it is the requirement of the crop that is crucial. The characteristics of the soil (e.g. pH value, nutrient content, water-holding capacity etc.) and things like the susceptibility of the cultivated crop to a lack of nutrients should also be taken into account. To make sure that plants can accomplish an extra performance in relation to their adaptability to different stress factors, you have to be prepared to fertilise more than is required.
You missed a speech or a discussion? They are still available after the event.