Sowing plays a key role, particularly in maize. It is hardly possible to compensate for problems in germination and the development of young plants during the vegetation period. This is particularly true in the light of increasingly difficult weather conditions. New technologies and cultivation methods offer potential for optimisations.
Increased efficiency is the latest buzzword when talking about the continued development of precision seeders. Today, the most important objectives are the conservation of soil moisture, the improvement of nutrient availability and simplified operability thanks to digital electronic aids. Prof. Hans W. Griepentrog of the University of Hohenheim believes that the requirements for sowing machinery have increased in general: variably adjustable row spacings, simultaneous fertiliser incorporation, seed counting sensors and the possibility of integration into the tractor and information system are just some of the things that modern sowing machines have to offer today. Improved sensor systems, electric drives and the related electronics are constantly opening up new possibilities for optimising the quality of work.
The inter plant distribution is critically important for crops with little scope for spatial compensation, like maize. However, longitudinal distribution with precision seeding offers barely any scope for improvement, leaving only the row spacing as a potential influencing factor. Some agricultural machinery manufacturers are now offering solutions for flexible tramlines and row spacings.
New systems offer the option of precision longitudinal fertilisation for maize; this is coordinated with the sowing machine and its seed placement. Studies have shown that the spatial concentration of the nutrients ensures easier accessibility and that the quantities of fertiliser needed for the entire crop can actually be reduced.
According to Prof. Till Meinel of Cologne University of Applied Sciences, several manufacturers have been offering actively controlled systems for improving the quality of embedding in maize sowing for some time now; these are based on measuring the contact pressure of the depth control rollers on the sowing units.
Alongside electric drives, sensors for registering specific soil characteristics will gain in importance in the near future. The soil is always opened up during sowing. This offers the opportunity of registering the characteristics in the soil, not just at its surface. However, the high driving dynamics prove to be a difficulty, says Prof. Griepentrog. A system that automatically controls the seed planting depth depending on the soil's moisture was presented at Agritechnica back in 2019. In this system, the sensor measures various soil parameters directly in the furrow (including the soil temperature, soil moisture, cation exchange capacity and the organic matter content).
Variable seed rates
Variable seed rates that are adapted to the location reduce the pressure of competition for water, nutrients and light, and therefore influence the yield and quality of crops. Today, this is made possible by partial site-specific sowing maps based on satellite data in combination with modern sowing machinery. Particularly during periods of drought, many farmers are noticing with increasing frequency that some plants are no longer developing any cobs. However, having the courage to plant e. g. two seeds fewer in the ground in weak areas can result in four cobs more. Maize is outstandingly suitable for adjusted seed spacings. It is not cultivated like cereals. With a little finesse and experience, farmers are therefore entirely capable of assessing what effects the various seed rates will have on the individual partial areas.
Implementing this requires digital application maps based on satellite images, soil samples and/or biomass data as well as a seeder that can automatically vary seed planting with the aid of electrically or hydraulically driven sowing units.
The farmer usually determines the extent to which the seeding quantities are to vary per unit of area either by himself or together with an advisor, a contractor or the seed producer.
However, there is no clear-cut answer as to whether this approach is profitable in the individual case. The conditions at the specific field site and the preferences of the operations manager, in particular, play a key role in this. Variable maize sowing offers a number of potential advantages, especially in the case of variable soil conditions and in difficult weather conditions. It offers farmers a comparatively simple and inexpensive inroad into partial area-specific cultivation.
Combining partial site-specific sowing and fertilisation would be beneficial to improve nutrient efficiency even further. Wherever there are more plants, more fertilisation should be undertaken and vice versa. This is entirely possible from a technical perspective. The crux of the matter is that sowing is often carried out by a contractor whereas the farmer himself undertakes fertilisation.
New cultivation systems
The cultivation of maize using the ridge method offers promising perspectives, particularly in view of the increasing number of extreme weather events. During the wet autumn of 2017, maize fields using ridge cultivation were significantly easier to harvest than conventionally cultivated areas because the soil was more load-bearing. Saaten-Union's Paul Steinberg reports that in the particularly dry years of 2018 and 2019, ridge cultivation yielded up to 14 % more dry mass in field trials.
Deep loosening beneath the row of maize, the heaping of the top layer of soil using ridging bodies and subsequent re-compaction of the ridges using V-shaped rollers are carried out in a single operation. The trailing seeder plants the seed in the ridge. Steinberg explains that in this process it is crucial for the support wheels to run 12 to 18 cm deeper than the sowing units between the ridges in order to enable specific seed placement.
With a row spacing of 75 cm, no tillage is carried out between the rows, with the result that the capillarity is not disturbed here. Deep loosening in the row can be carried out down to a maximum depth of 50 cm to break through possible ploughing pans. At the same time, this method enables the maize roots to penetrate into deeper layers. Thanks to this technique, the seed is planted as usual for the location or up to 5 cm deeper. As a result of this, it is also supplied with water from below thanks to the undisturbed capillarity in addition to moisture from above.
According to Steinberg, ridge cultivation also offers further advantages: the seed is surrounded by the well-ventilated, nutrient-rich topsoil layer. The ridge also warms up faster, which fosters the development of the young maize. The raised position of the plants on the ridge ensures less competition for light. The maize's growth outstrips that of weeds even better, because the latter only have access to the lower-nutrient soil on the flanks. Nutrient bundling in the ridge and its faster conversion thanks to the heat significantly increase the efficiency with which the available nutrients are exploited. Deep loosening directly beneath the maize plant leads to the formation of considerably more root mass.
However, extremely heavy or very stony soils can push the technique to its limits. In the case of heavy soils, farmers should switch from one pass in the spring, during which ridge formation and sowing are carried out, to two separate passes (ridge formation before the winter and sowing in the spring). GPS-supported sowing is then required for precision placement of the seeds in the ridge. To form the ridges, the soil must have a certain degree of moisture, as the ridge otherwise quickly collapses again. It is also advisable to talk to the respective manufacturer before purchasing such a machine, because the optimum equipment for each farm and the right setting for each location have to be determined.
Mixed maize cultivation also offers good approaches in terms of the arable farming strategy and species or insect protection programmes. It fosters biodiversity, enables the use of combined chemical and mechanical measures for controlling weeds, reduces the amount of nitrogen fertiliser required on deficient soils and may possibly ensure a more balanced nutrient composition in the silage due to increased protein contents. Additional blossoming plants enrich the landscape, especially in the summer when few blooms are seen. Climbing beans have proved to be a particularly suitable partner both in various trials and in practice. While this mixed crop was only cultivated on around 400 ha in Germany in 2018, this figure had already increased to around 15,000 ha in 2020, a trend that looks set to continue.