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The cultivation of maize gets more and more important, not only for silage use. The cultivation of grain maize is very interesting, especially for breaking-up the crop-orientated rotation on heavy soils. Strip tillage with a row spacing of 75 centimetres is a very interesting alternative for maize cultivation. The Focus CS is extremely suitable for light and medium soils. On heavy and very heavy soils this system comes to its limits. During the test years the yields on heavy soils have not been worse than those for the conventionally grown maize, but it was not possible to realise a yield increase. If you look at the regions where strip till for maize originates (35. latitude) and compare it to Central Europe, you will see that the most significant difference lies in the temperature during the vegetation period. The temperatures in the typical maize growing areas in the USA during the crucial months July / August / September are considerably higher than in Central Europe. These considerably higher temperatures also lead to considerably higher soil temperatures. High soil temperatures are necessary for the mineralisation of the nitrogen supplies so that the maize has enough nitrate nitrogen for the plant at its disposal in the crucial stages (tasseling out, graining). Maize does not need constantly high nitrogen quantities during the growing period, but rather real nitrogen explosions in July / August. This is the crux of classical strip till. With the strip cultivation method organic material is only removed from the loosened strip. The space between the rows, however, remains covered. This “mulch cover“ acts as an insulating layer for the soil and sees to it that the unloosened soil between the maize rows remains cooler – too cool for the Central European locations. The modification from nitrogen to nitrate, and thus the nitrate supply, is too slow. An additional disadvantage of this retarded nitrogen dynamics is that even when the ripening of the maize is finished nitrogen is still supplied and, thus, the ripening off of the plant is retarded. This fact limits strip tillage with the HORSCH Focus CS on light and medium soils.

Especially on heavy, loamy sites maize growers are facing the challenge to find the optimal moment for seedbed preparation in spring. If they cultivate too early, the soils often are still too wet – the results are smeared layers and compaction. If cultivation is carried out too late, important vegetation days and thus yield potential are lost.

The challenge for heavy soil sites is the possibility to realise drying and soil warming without seedbed preparation in spring.

The simplest method to generate drying and soil warming is a large, cultivated soil surface. Maize cultivation on ridges provides these conditions. The ridges have to be formed on heavy sites in autumn and, due to the large surface, allow for an intensive frost mellowness. With heavy soils, the forming of ridges like for example for potatoes is not possible or only with a considerable input of energy, another solution for cultivation combined with ridge forming has been developed. The resulting machine, the HORSCH Tiger DT is a 4-bar cultivator with a tine spacing of 37.5 centimetres.

The tine geometry has been chosen in such a way that it is cultivating the soil ridges with a centre spacing of 75 centimetres. The first two tine rows loosen the area below the future maize row, the rear two tine rows loosen the area between the rows. Loosening is carried out at a depth of 20 to 35 centimetres depending on the site and the moisture content of the soil. The soil coming from the loosening between the rows is used for forming the ridges which consist of loose soil and larger clods. Due to the large surface of the ridges there is an intensive frost impact and settling of the ridges. Immediately after the cultivation the height of the ridges is between 20 and 40 centimetres depending on the type of soil. Come the spring they have settled to about 10 to 20 centimetres.

Experience shows: The rougher the ridge is left in the autumn, the more intensive is the frost mellowness.

For loosening with the Tiger DT two different point types are available. The MulchMix point, known from the Terrano and Tiger series, is 80 millimetres wide and is recommended for light and medium soils in order to get enough soil for a safe ridge forming. For the heavy and very heavy soils only a 40 millimetre wide chisel point is available. Due to the narrower design the horsepower requirement for this point version and the mixing effect are lower.

The TerraGrip tine with hydraulic trip system serves as an overload protection for the tines. Even when loosening deeply up to 35 centimetres this system with a release force of 800 kilogramme guarantees a safe control of the coulters in the soil. If it collides with a foreign object, each tine can trip to a height up to 30 centimetres.

The depth control of the Tiger DT is made via the central chassis which is integrated in the 4-bar frame. The advantage of this arrangement is that the wheels of the chassis do not roll over soil that has already been cultivated. Thus, they do not leave any tracks.

The currently developed machine has a working width of 6 meter and with its 17 tines prepares 8 maize rows with spacing of 75 centimetres.

For forming and sowing a ridge culture it is important to have exact straight ridges with an equal spacing also in the join area of two working widths. The ridges of the adjoining passes have to be in a tolerance range of plus/minus five centimetres, especially if machines with different working widths are used.

When cultivating, an exact joining pass in the lower centimetre range may cause problems, particularly with trailed cultivators and on hillsides. The Tiger DT is no exception to this rule and also is exposed to lateral forces. The most considerable deviations from the “optimum line“ are caused by tracks or compaction in the soil. However, to get neat, straight ridges, the Tiger DT has been equipped with two steering discs per side. This active machinery control (also called Implement Steer) is supplied by the hydraulic system of the tractor and is able to keep the cultivator in the tractor track by means of hydraulic cylinders. The disc control is made via a GPS-control system with a RTKcorrection signal (Real Time Kinematik). This device has an accuracy of plus/minus two centimetres. The control system used does not only allow for controlling the tractor, but also for simultaneously keeping the machine on a preset line. Both machines are operated centrally from a control unit on the tractor. In practice, this means that a GPS-receiver is mounted on both the tractor and the machine.

For the RTK-correction signal a stationary unit on the respective farm as well as a mobile reference unit on the field boundaries can be used.

The ridges and tracks that are made in autumn are recorded by this system and can be retrieved in spring when sowing.

The experiences of the past four years with the cultivation of maize on ridges have shown various advantages – starting with cultivation in autumn that can be carried out over a very long time frame. If maize is grown after cereals, deep loosening and the forming of ridges will have been carried out at the end of August/beginning of September, preferably in dry conditions. Cultivation is performed directly into the stubble or after a shallow stubble cultivation pass for example with a short disc rotary harrow. The advantage of the second variant is that the germination of volunteer crops, weed and grass weeds are stimulated, after that they are fought mechanically by carrying out deep cultivation. There is a much longer cultivation time frame for the Tiger DT if maize is to be grown again after maize for silage or grain maize. An intensive further treatment of maize straw with a flail mulcher along with a shallow mixing with a cultivator has proven to be advantageous for the cultivation of grain maize. If the grain maize harvest is delayed too long and the cultivation conditions get worse, it is also possible to cultivate the soil with the Tiger DT even if there has already been slight frost.

As already mentioned at the beginning, the loose ridges consisting of fine earth and clods are intensively “treated” during the winter months by the climatic conditions. They are well settled in spring and the fine surface structure guarantees a safe sowing of maize.

There are even more interesting advantages if the soil surface is undulated when forming the ridges. The heating of the soil in the seed range of the maize is a crucial criterion for the beginning of sowing maize. Most maize growers presume that 8° C is the minimum soil temperature for a safe emergence of the maize. So the aim is to reach the desired soil temperature as soon as possible in order to get as many vegetation days as possible. The increase in soil temperature is closely connected to the size of the soil surface, the degree of coverage and the air volume (loosening condition) in the soil. Exactly this parameter is the approach for cultivation with the Tiger DT – large soil surface due to forming of ridges, low degree of coverage and high air volume in the soil due to systematic, intensive cultivation.

Considering the drying behaviour of the soil, another advantage of the ridge structure is obvious. The large, uncovered surface of the ridge allows for quick drying. The drying in the ridge takes place from top to bottom, thus the area dries in such a way that the sowing of maize can start early.

The water supply in the soil is interesting for ridge cultivation as the capillaries always transport humidity to the highest point. At this highest point, the peak of the ridge is the maize plant and it, thus, is integrated in the water supply in the most ideal way.

The experiences made in the Czech Republic from the development and test stage of the Tiger DT have proven that, depending on the weather pattern, the sowing of maize on the ridges in spring could start seven to ten days earlier compared to conventional sowing. On the one hand this head start is of considerable importance for the yield output of the maize and on the other hand it results in a significant increase of the area output of the maize seed drill.

Maize on ridges is sown with a conventional mulch-seed precision seed drill. The seed drill, a HORSCH Maestro SW / CC or Maistro RC/CC, is also equipped with the control system that is used in the Tiger DT. This active machinery control system sees to it that the precision seed drill places the seed exactly in the middle of the ridge. For a smooth sowing the track records of the loosening in autumn are necessary in order to be able to drive correctly in the ridge area. If the recorded tracks do no longer exist, you have to drive again along the course of the ridges and record that course “manually”.

The track widths of the tractor and the seed wagon of the maize seed drill have to be aligned with the ridge system. The seed wagon has a track width of three metres. The tractor track width is 1.5/2.25 or 3 metres depending on the model. The disadvantage of a 2.25 meter track width is that the seed drill has to mount to the tractor with an offset of 37.5 centimetres. A tyre width of not more than 540 millimetres has proven to be ideal.

The well settled ridges that have been “cultivated” intensely by frost mellowness and the weather are an ideal seedbed for maize. As soon as a soil temperature of 8° C has been reached and the ridge peaks have dried, you can start sowing. Maize is always sown in combination with underground fertilisation to encourage the early growth in the best possible way. The fertilisation planning for underground fertilisation should not be directed mainly to a mere nitrogen fertilisation. Maize as a cultivated plant does not take up any important nitrogen quantities within the first 45 days. The nutrients phosphor and potassium and on certain sites also magnesium are more important for optimum early growth. Tests showed that nitrogen quantity between 25 and 35 kg/ha as underground fertilisation are sufficient. Concerning the form of nitrogen you should pay attention to the fact that fertilisation is carried out with the lowest possible amount of nitrogen nitrate, so that the young plant will not be “pumped up“ with nitrate and that the ratio between sprout and root growth will not be changed.

The remaining nitrogen for the maize can be given before sowing for example in the form of urea or into the existing population from the four-leaf stage onwards.

The necessary phosphate and potassium amounts depend on the supply of the respective site. On well-supplied sites additional phosphate fertilisation of 20 to 30 kg/P2O5/ha is advantageous during the early growth, especially if the growth conditions are unfavourable.

The fertiliser band of the underground fertilisation is placed in an even spacing of six centimetres beside the row and about five centimetres below the seed. A direct seed-fertiliser contact has to be avoided to prevent damages from chemical burns at the young maize seedling.

The placement depth of the maize seed depends on the humidity of the soil and ranges from 3.5 to 6 centimetres. A crucial criteria is the safe supply of the maize grain with germination water to stimulate a quick pre-germination. If a maize grain remains in the soil too long without germinating, it is prone to fungal attacks or it can lose its germination capacity.

The maize seed has to be covered with enough earth and has to be pressed efficiently so that the area around the seed grain does not run dry and is supplied with humidity due to the seed-soil contact. Two press wheels of Maestro SW / CC and Maistro RC / CC that are arranged in a V-shape press the seed down. They can be adjusted according to the intensity of the consolidation.

Like for any new cultivation method the benchmark for the ridge till system for maize finally is the yield. The harvest results of the last four years were throughout positive. In the average of three years, the harvest quantities – compared to dry goods – were ten percent higher than those of the conventional cultivation variant. This yield increase surely is due to various factors. The largest factor for the increase is the fact that you can do without any seedbed preparation in spring. The additional advantage of sowing earlier along with having an earlier sowing window for maize is another reason for the increased yield that has been realised.

Fertilisation, especially deep fertilising, is another interesting aspect of the tests with ridge maize. The placement of the basic nutrients phosphate and potassium directly below the maize row is a practicable possibility to take the fertiliser even closer to the plant and to take it systematically into the root area. Due to the continuously rising prices especially for phosphate but also for potash the focus of the development of this system will be an even more important topic of nutrient placement.

The regulation of weed and grass weed coverage can be carried out with the same combination of agents as for conventional cultivation. The advantage of cultivation in ridges is that loose ridges consisting of fine earth and clods provide an extremely unfavourable germination environment for weed seeds, grass weed seeds and volunteer crops. This phenomenon is also evident on roughly ploughed fields. It takes a very long time till this field is “green“ again. The main reason for both systems surely is that there is no consolidation.

In spring a treatment with glyphosate before sowing or directly after sowing on soils with many weeds and grass weeds might be expected.

To further develop the experiences for the ridge till method for maize, about 200 hectares of ridges on twelve sites have been set up in Hungary in autumn 2010. A lot of sites have very heavy soils. Cultivation was carried out in mid-October under partly rather wet conditions.

In spring 2011 maize will be sown on these prepared fields with a HORSCH Maestro 8 CC. This precision seed drill is equipped with an active machinery control to guarantee a safe sowing of maize on the ridges.