Maize heading, or simply heading, is one of the most important technological operations in the production of maize hybrid seed, involving the manual or mechanical removal of the male inflorescences of certain maize plants. It is usually carried out by students with appropriate supervision and guidance. The term ‘heading’ is derived from the male flowers of the maize, since it is necessary to remove them during the operation. The actual labelling is preceded by a number of specific technical operations which are not found in conventional maize cultivation, but which are also part of maize labelling in a broad sense. Hybrid maize has now completely replaced conventional varieties in commercial maize production in Hungary, so there is a need for a continuous supply of hybrid seed. The high price of seed makes it possible to carry out labelling, as the process is relatively expensive and would not be feasible at a lower production value.

Biological basis

Maize is a monoecious, monocotyledonous plant, with the fruits and stamens in separate inflorescences (panicle, stalk inflorescence). This unique feature makes the castration of maize a very simple task. It is used only when crossing two breeding lines or ‘varieties’ with different characteristics. In fact, hybrid seed is never produced using varieties, but rather so-called breeding lines, which are subjected to lengthy and detailed breeding trials in the nursery or small plot. Detasseling, i.e. the removal of the label blossom, prevents the plant from pollinating itself, so that the seed of that plant can easily be fertilized by another type of maize (which has not been detasseled).

Pre-titling operations

The detasseling of maize is preceded by various specific and non-specific operations. Non-specialised operations which do not exclusively precede the management of maize crops for seed production. These include soil operations (ploughing, soil preparation), sowing, crop protection, etc. In addition, maize heading is preceded by a number of operations that do not take place in maize crops.

Sowing

Although sowing is a process that is also present in commodity maize stands, the operation is different in seed production fields due to the specific sowing structure. In seed production, the two different types of maize are sown in separate rows, known as the father and mother rows. It is the maize in the mother rows that will be harvested, and it is these plants that need to be germinated. The maize in the father rows is only for pollination, and the crop of these plants is not harvested. The most common field design is a 4:2 (4 mother rows:2 father rows) seeding structure, but there are also different solutions. As with the parent rows, the sub-rows can be sown at a standard row spacing or at a narrowed spacing, which increases the area of the field occupied by the parent rows and thus the amount of seed harvested.

Scraping

The hybrid maize must be kept clean by repeated manual hoeing until the end of the field (20 August). We will be hoeing several times during the camp. Heavy weeds may be a reason for exclusion from seed production and may result in exclusion from the field. Weediness must be kept below the weed level throughout the area when the board is closed.

Access

Alienation is the removal from the field of plants which, because of some abnormal characteristic (height, leaf structure, colour, etc.), are presumed to be genetically different from the predominant plant population on the field. This operation is necessary because, if alien plants remaining in the sire lines pollinate the maize of the parent lines, the genetics of the progeny will not be as they should be. When harvested, the yield of the aliens left in the mother rows will contaminate the seed lot. In the process of alienation, the alien maize should be removed preferably at the root, it is not sufficient to discard them. If a small stump is left above the soil, it can resprout in a few days under favourable weather conditions, and fully regenerate after 1-2 weeks.
Staking, levelling

The so-called stover shoots of the maize are removed during the basting process. These are shoots that grow out of the bottom of the plant for various reasons (damage, excess nutrients) and do not produce an economically valuable crop, so their presence in the stand is undesirable because they deprive the stand of nutrients, compete for light and water and, by increasing the stand density, significantly reduce the clarity of the rows. The removal of such bastions should be carried out in such a way that no stumps are left behind, so as to avoid the resprouting of the bastions. The susceptibility of maize to bastardisation is strongly dependent on its genetic characteristics and the nutrient supply of the field.

Levelling is the removal of individuals (usually lower) that are significantly different from the height of the maize stand (higher maize is removed during the ginning process). It is necessary because during ginning, the ginner’s eye and the ginning machine pass over low-lying maize without removing the label. However, such small cobs are just as capable of producing pollen as larger ones, so they can contaminate the crop with their pollen after heading.

Picking and levelling are usually carried out at the same time, as the workers are both inspecting the lower level of the vegetation.