Undersow or sow this year?

Due to the cold spring and the slow initial development of the maize, the question is whether all maize that was intended to be harvested before October 1 will be sufficiently ripe by that time.

This may mean that, contrary to what was intended, the catch crop must still be undersown. This is to comply with the obligation to sow the catch crop before the stated date. The question is what is the best decision. The text below provides more clarity on this.

Cold spring: slow initial development of maize
Last spring was cold with an average temperature of 8,1°C compared to the long-term average of 9,9°C. The last time the temperature was this low in spring was in 2013, with an average temperature of 7,4°C. The 3 months of spring were all colder than usual. Not a single summer day was counted in De Bilt this spring. This has had an impact on the initial development of sown maize. This may mean that not all maize can be harvested in time ripe for October 1. The regulations indicate that on parcels of sandy and loess soil where maize is harvested as silage maize, the catch crop must be sown by 1 October at the latest. For the legislator, just sowing a catch crop is not enough. There must also be a result, which is visible in the form of a covered bottom (result obligation). In addition, the legislator prescribes that there must be a best efforts obligation. This means that the grower must have made the necessary effort to make the catch crop a success by using sufficient seed and using the right machine.

Timely ripe corn based on the kernel makes all the difference this year!
From an agricultural point of view, the point is that the catch crop captures nutrients in the autumn and winter that have not been absorbed by the main crop, in this case maize. This is to reduce the nitrate load in the groundwater, as described in the Nitrates Directive. Depending on the type of catch crop, timely sowing is a precondition for this. Timely sowing of the catch crop does not conflict with the harvest of the maize if it can be harvested early due to timely ripening. This is the system for now and the future. A combination of a maize variety that has been proven to be really early in the grain with the sowing of a catch crop that can still develop well in early autumn due to the relatively high soil temperature. KWS has been working with precocious genetics for years, with a view to preventing that one less positive point that comes with maize cultivation, namely the chance of nitrogen leaching. Due to the great financial efforts in research and development of maize varieties that mature on time, genetic progress is relatively rapid, especially in the ultra-early and early group of maize varieties.

An additional advantage of using varieties that ripen in time in the grain is that maize can also be harvested earlier and earlier as MKS and harvest before 15 October will no longer be an exception. The late October or even November harvesting of silage maize is behind us. There are trial fields where researchers are looking at the silage maize varieties to determine the harvest date, while the trial with maize varieties for the grain on the same plot could have been harvested long ago as silage maize. That's the reality right now!

undersow
Undersowing normally takes place shortly before the close of the maize rows. Sowing the catch crop during the growing season has the advantage that:

• The grower is flexible to determine the right harvest time in consultation with the contractor. The contracting company can thus also plan the spreading of the harvest and thus the deployment of personnel and machines.
• The harvest can take place at the ideal moment for the maize variety, which means that this will be in October instead of September.

However, there are also points for attention that have come to the fore after the experiences with underseeding in the past 2 years:

• The chance of the success of the catch crop is much smaller if the rest of the growing season is (too) dry. The so-called best efforts obligation has in fact been met by sowing the catch crop. In the event of a drought, however, the question is whether the catch crop meets the requirements of the inspection authority after the maize harvest in October. This may mean that, as happened last year, a second sowing has to be done, which entails additional unforeseen costs.
• There is a risk of loss of maize yield due to competition with the catch crop for moisture and nutrients. This is especially a problem on plots where the available amount of moisture and nutrients is already limiting.
• The moment of undersowing of the catch crop is quite close and therefore requires precise planning.
• A later harvest in October automatically also means that the risk of structure or crop damage increases. The undersown catch crop is then destroyed.
• If ruts have been driven in October, then good tillage cannot take place with undersowing.
• Weed control is more difficult, especially when smooth-fingered grass is present in the plot.
• When swapping land with arable farmers, it is not possible to use catch crops that propagate nematodes.
• There is some evidence that grass catch crops, which are commonly used for underseeding, increase wireworm damage in the subsequent maize growing season.

Seed
Due to the advantages of the catch crop, which is sown after the maize harvest, but also as a result of disappointing results from under-sowing, post-sowing has grown considerably in recent years.  

• Because the conditions during the maize harvest are normally better in September than in October, there is less chance of structural damage. Contractors can also work more smoothly, which prevents unnecessary wear on machines, saves fuel and prevents employees from working too long.
• The combination with the (intermediate) cultivation of Fast Spring Rye for more protein and dry matter yield from own soil is very well possible.
• Adequate weed control can be carried out very well, because there is no restriction on the permitted choice of agents.
• The aftercare of the plot is very well possible, such as remedying structural damage and improving the pH by means of liming.
• Because there is simply no catch crop yet, there is no competition with the maize in terms of moisture and nutrients.

However, there are also a number of points to note when applying this system:

• Harvest at the ideal time of maize is at risk due to bad weather in September and limiting the harvesting capacity of all contracting companies.
• In years with a less favorable growing season, there is a chance that many maize varieties will not be harvested sufficiently ripe. This applies in particular to maize varieties that, due to its genetics, do not ripen in time in the cob.

If it is decided to harvest the maize as MKS, for example, then the latest sowing date for the catch crop is 31 October. That could be an extra argument this year, also in view of the somewhat wider roughage position with grass, to opt for the maize harvest in the form of MKS. This post-sowing can still be done with a suitable hardy crop as Fast Spring Rye.

Make the right choice!
Several options are therefore possible, although every system has 1 or more points to take seriously. It is up to you to determine what is the best choice for your situation. You may need a maize variety that can achieve a higher yield every year or if you live in the north of the Netherlands, so it is more desirable to use under-sowing. Or do you decide to sow a variety that is so early in the grain that it can be harvested ripe in September, even in growing seasons with a lower spring temperature, such as this year. This year, when an early harvest is chosen, the wheat will be separated from the chaff. Good agreements with the contractor are always of great importance, regardless of the choice that is made!

Still not sure what to choose? Sow or just sow? Then ask for advice your own regional KWS advisor. 

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