Farm Ireland

Thursday 22 March 2018

Beware of the risks strong early growth can pose to winter crops


Richard Hackett

The unseasonably warm spell we have enjoyed over the winter months has encouraged enthusiasm for the upcoming growing season.

A lot of winter crops have been sown and established very well. Most have also had their herbicides applied.

A lot of crops have begun growing in the last few weeks and are sporting a dark, lush, green colour. It's not unusual in recent years for crops to begin to grow very early like this, but subsequent weather conditions have balanced out this early growth with no long-term negative effects.

However, strong early growth does pose very real risks to crops and we must remain aware of these risks. The first risk is disease development and spread. Septoria in particular is a disease which we have not gotten fully under control.

Weather patterns over the last few years have been very kind to us in terms of helping control disease but the fundamentals remain that strong, lush canopies in early spring increase the risk in terms of disease development later in the season.

The second risk associated with strong early growth is increased lodging risk. Variety selection is the most important management tool to control lodging.

All recommended list varieties will be well assessed for lodging risk, it's one of the most important reasons to restrict variety selection to recommended list varieties. The second most important mechanism for controlling lodging risk is the rate of applied nitrogen and timing of the applied nitrogen.

Minimise as much as possible the amount of nitrogen in the first split, right up to no nitrogen at all in the first split in some circumstances. Given the amount of organic manures applied and the amount of catch crops sown this year, coupled with the kind autumn/winter we have come through, we can expect a lot of nitrogen to be released from these sources.

Also Read

This nitrogen tends to come available late in the season, with increasing soil temperature and moisture, so design the nitrogen programme to take this extra nitrogen into consideration.

The third and final control mechanism for lodging is the correct use of plant growth regulators.

Be aware of the low income projections when planning to control disease and lodging risk.

More expenditure is not the answer here, better use of timings, use of the wide range of available chemistry options and frequent monitoring is what is required.

For example, in most instances a well-timed application of chlormequat with adjuvant if necessary will have as much benefit to shortening a wheat crop than the most complex and expensive PGR programme. Thick, lush crops have higher yield potential if managed correctly.

Don't waste this extra potential on spending more on the crop than it actually needs.

One action that has to be taken soon is management of overwintered catch crops. This is a new crop to many and is actually the third biggest crop grown in Ireland this year. The season has been kind to these crops as well, and in general they have been very successfully cultivated.

This has resulted in huge canopies grown in some situations and these strong covers have to be carefully managed if they are to be of any benefit to the soil and subsequent commercial crop. Soil bacteria are required to break down these covers, who in turn require time and a huge amount of nutrients on a temporary basis to do their job.

While these nutrients are being temporarily tied up, don't have an establishing commercial crop equally on the hunt for nutrients at this time - there won't be any available and the establishing commercial crop will come off second best.

The way to overcome this is to maximise the time between catch crop destruction and sowing the subsequent commercial crop.

Ideally, catch crops should be sprayed with glyphosate or else topped/mulched/flailed or shallow incorporated for a few weeks before ploughing or sowing the subsequent crop.

This will give the soil bacteria a chance to break down the catch crop, well in time before the establishing crop has a requirement for nutrients.

When the catch crop has been broken down sufficiently, it releases nutrients to the soil so the subsequent commercial crop has more nutrients available to it than it otherwise would have, so will it respond in kind with better establishment and hopefully better yield.

Richard Hackett is an Agronomist based in north Co Dublin and is a member of the ITCA and ACA

Indo Farming

More in Tillage