Precision seeding, an engineering challenge

Many manufacturers are dedicating themselves to creating seeding systems able to optimize crop operations and to manage with maximum precision the placement of seeds in the ground. ISOBUS technologies and the new generation of electronic systems allow an effective control of all the fundamental parameters, such as the processing speed, the quantity of seed used and the seeding density

In the context of open field crops (but not only), seeding is undoubtedly one of the operations that demand great attention. The diligence in adjusting the machine and the precision in the execution phase are fundamental for the optimal growth of the crop and to facilitate some subsequent processes, such as weeding, earthing up, fertilization with granular fertilizers, as well as the harvesting.

The market for seeders is very large and offers many options, to meet any crop and management need, from row seeders for autumn-winter cereals (known as “universal” models) to precision seeders for corn and soy, mechanical or pneumatic, or even for sod seeding, or with the optional laying of mulching film.

In the field of so-called “precision” seeders (i.e. for crops in which both the inter-row distance and the row distance must be as constant as possible) the offerings are broad. The manufacturers have recently embarked on an increase in the operating quality of the new models, starting from the assumption that, at least in flat and large plots, it seems appropriate to work with machines of no less than 8-12 rows, in order to reduce working time, with the full benefit of timely interventions.

 

Precision

The essential characteristic of these machines is the precision of the seed placement in the ground. This is a decisive feature to ensure a regular growth of the plant, i.e. without mechanical damage due to post-seeding operations. In particular, the distance on the row can often be altered either due to a more or less temporary malfunction, or due to construction problems which inevitably lead to unsatisfactory performance.

It is particularly important to avoid this non-uniform seeding, because the subsequent passes in the field can cause significant and more or less irreversible damage if any seedlings emerge in incorrect positions.

The manufacturing industries are engaged in the development of systems to optimize seeding operations. Among the innovations proposed by the engineering of the sector we should note, for example, the Sigma 5 model by Sfoggia, and the Azurit 9 model by Lemken, which are characterized by the good ability to control the placement of the seed on the row, as well as setting the seeding depth. Sfoggia allows for the adjustment of the position of the side wheels on the axis of the fall point of the seed, which is conveyed through a fall tube inside the seeding discs.

The process is completed by a coulter to improve the furrow and by a pair of rear wheels for earthing up.

This combination is particularly useful for working with non-uniform soil profiles, therefore it is also suitable for minimal processing, when there are still abundant crop residues on the surface. The depth wheels are independent and mounted on a rocker arm, so as to ensure effective contact with the ground even in the presence of stubble, stalks and stones.

As with almost all models of precision seeders, the shifter for varying the distance on the row uses several combinations (20-40) by arranging the available gears in various ways. To guarantee a sufficient air flow necessary for optimum adhesion of the seeds to the holes of the disc, the fan is driven by the PTO at 540 rpm; usually, the speed of execution of the operation is 6-8 km/h, although some seeding machines are available that perform quality work at much higher speeds, with the benefit of a high work capacity.

An example of this is the Maxima range by Kuhn, which according to the manufacturer allows a productivity of up to 7 ha/h, a value that however can only be reached with 9-12 row models (or 6.75-9 m working width for the classic 75 cm corn inter-row) and with high capacity hoppers (those for seeds are 52 l), in order to reduce the impact of filling times. Considering also its very stable structure, the Maxima range proves effective in seeding after minimal processing, ensuring the regularity of the planting. Obviously, there is no lack of PVC tanks for the distribution of plant protection products (insecticide, snail killer, herbicide, etc.) and of course for the distribution of fertilizers, often performed with a special fertilizer spreader with a front hopper.

 

Electronic monitoring

ISOBUS, the established technology aimed at facilitating direct “dialogue” between the tractor and the operator, has now reached a certain maturity, and is also fruitfully applied to seeding. Several manufacturers (and in particular all the market leaders) have developed ISOBUS-based strategies in order to offer the operator on board the tractor complete control of the seeding operation.

This includes the partial and total count of the worked surface area, the planted seed counter, detection of feed rate and calculation of seeding density, and these are just some of the large amount of information provided. In addition to all this, the adoption of GPS with the precise geolocation of the work site has made it possible to minimize errors in aligning the passes, benefiting the homogeneity of growth of the plants and more regular harvesting.

It is precisely the devices for interrupting the seeding on certain rows, used effectively in irregularly shaped plots and/or when it is important to avoid overlapping, that take advantage automatically of both GPS and ISOBUS, in order to relieve the operator from this tedious (but important) task.

An additional solution that can facilitate the farmer’s work is the automatic calibration based on the type of seed. In this case, the main advantages obviously lie in being free from manual calibration when the seeding conditions change, but also a reduction in seed losses and, above all, a lower exposure of the operator to the harmful dust of seed preparation.

 

Main versatility features

The large working capacity of modern precision seeders (up to 18-24 rows and more) inevitably entails a considerable size, which become a problem for transport in normal traffic conditions on public roads, where the total external width of all vehicles has to be limited to 2.55 m. For this reason, machines with many seeding elements are equipped with folding frames (with different mechanical-hydraulic solutions) or are towed in line by the tractor.

The masses of the various models obviously vary according to the working width from 400 to 3000 kg, reaching even 7-8000 kg (and more) at full load in the larger versions. In this case, also for work in the field they use one or more ground support wheels.

The power of the tractor to be coupled varies accordingly, from a minimum of 50-60 kW for models with 4 rows up to 170-220 kW for larger complete models, the prerogative especially of farming equipment companies, where the availability of high power tractors is undoubtedly easier compared to traditional farms.