Harvest
Maize is a highly versatile crop, and with increasing diversification of its uses, the demands on harvesting technology are growing, too. On most farms today, silage maize is harvested using self-propelled maize choppers. Modern machines ensure the best possible quality in terms of chop length and processing of the harvested crop. The chop length is influenced by the dry matter content of the plant: as the maize matures, the dry matter content increases, which in turn reduces the chop length because of the poorer compaction in the silo. The chop length typically ranges from about 15 mm to 6 mm. Furthermore, modern technologies such as NIR sensors (Near-Infrared Sensors) have been integrated into these machines, allowing real-time quality analysis of the harvested material and offering a level of convenience to the driver. This technology helps improve the coordination of harvest planning, especially when dealing with different varieties and ripeness stages.
Estimating the correct harvest time is crucial, and this relies on accurately determining the dry matter content of the plant at maturity. For silage maize, the ideal dry matter content should be between 30% and 33%, with a minimum of 28% and a maximum of 35%. If the silage is too wet, leachate losses occur, which can deplete nutrients and pollute the environment. If the dry matter content is too high, it becomes difficult to adequately compact the silage in the silo. This compromises the ensiling process, increasing the risk of aerobic respiration by microorganisms (which causes reheating), leading to mold growth. As a result, the silage becomes unsuitable for feeding.
In addition to harvesting silage maize, the maize chopper can be used to harvest CCM (Corn-Cob-Mix). For this method, the silage maize header is replaced with a row-dependent picker. This way, only the cobs and their leaves are harvested, while the remaining plant material is left chopped in the field. This method is especially popular for feeding pigs.
Grain maize is traditionally harvested with a combine harvester once it has reached physiological maturity. Alongside the classic maize header, the threshing unit is modified, and coarse-mesh sieves are installed to accommodate the relatively large maize grains. The key factor for harvesting grain maize is achieving the highest possible dry matter content in the grains. The rest of the plant is left chopped in the field. Harvesting can begin when the dry matter content of the grains reaches about 65%. However, maize is susceptible to fungal attacks and may begin germinating relatively quickly when stored in damp conditions, so it must be dried to over 85% dry matter as early as possible for safe storage. With rising energy costs, drying maize has become an increasingly important consideration in assessing profitability. Therefore, it makes sense to leave the maize to dry in the field as long as possible. However, this comes with the risk of missing the optimal harvest window and having to thresh the maize under more humid conditions.
There are various methods that can be easily performed without special tools to estimate the right harvest time:
The wringing test provides an indication of the moisture content in the remaining plant. Select five plants in a row that are as representative as possible of the surrounding crop. Repeat this in several locations to get a good overview of the field. Cut the plants as close to the ground as possible. Then, wring the plant about 30 to 40 cm above the cut between the nodes with both hands. The dry matter content can be roughly estimated by the amount of sap that is released:
The harvested crop should also be continually monitored during the harvest and at the silage heap. In addition to all the modern technologies used for monitoring dry matter content on forage harvesters or in laboratories, manual sampling by the farmer remains essential. It can be done quickly, and the more samples taken, the more the farmer will learn about silage quality.
