By David Jones, CropNuts Broad Acre Agronomist

In Part 2 of the series ‘Setting Up For Top Yields in 2018 we take a look at Deep Nitrogen Testing, seed bed preparations and some thoughts on Dry Planting..should the weather change

deep nitrogen testing

Deep Nitrogen Crucial on high rainfall and high yield potential sites

The most expensive input we apply is most likely fertiliser, and the most expensive nutrient is most likely to be Nitrogen (N). Unfortunately Nitrogen is also a nutrient that behaves very unpredictably in the soil, but Deep Nitrogen Testing can help in many circumstances.

For Deep Nitrogen tests, sample to 60cm at least – ideally in two depths of 0-30 and 30-60cm – to understand the amount of mineralised nitrogen in the soil. Nitrogen is a tricky element to accurately calculate the optimum dose, but by looking at the trend and whether a season or field is above or below the average seen on a farm, it is a good basis for a more informed decision on the nitrogen dose rate.

Where you have double cropped and or experienced very heavy rain it is particularly important to understand the dynamics of N in the soil.

Too much applied Nitrogen is waste of money but also runs the serious risk of lodged crops which do not yield.

Deep Nitrogen TestingFor every season, every field and indeed soil type will have an optimum dose rate of Nitrogen, above which the cost of extra N applied is not returned in the value or yield of the crop.

It is my firm belief that it is not worth trying to be too precise on predicting this figure as it is highly variable. More money is lost from lost yield – through under applying nitrogen – than from lost expenditure from over applying.

Instead, I try to look for anomalies each year and store the data from previous years on every clients’ farm. If soil Nitrogen tests are particularly lower or higher than average, I adjust accordingly.

Although it is very variable, work consistently shows that there is a relationship. Data points at the extremes – either very low or very high – are extremely useful to highlight situations where more or less N is needed. Just don’t over obsess with the figures in the middle of the graph.

Deep N testing

In 2015, my colleague and friend Peter Cowlrick set the Milling Wheat Yield World Record with a 14.3 t/ha crop of Crusoe Wheat at 13.5% protein. The farm had previous used a lot of pig manure, but Deep Nitrogen tests that yield revealed only 50 kg/ha of N in the soil. This gave Peter the confidence to apply more top dressing N which he wouldn’t have otherwise done.

Seedbed preparation getting late

Areas of severe compaction or limited rooting should have been identified by now and rectified. Waiting for rain to help pull a subsoiler through is fine if the soil still shatters sufficiently, but if the soil is too wet this is likely to cause smearing and lead to further structural damage.

Rippers vs Subsoiler

A ripper is the tool of choice when the field needs to be levelled and moisture loss is not an issue. The clods pulled up by the ripper will need to be broken down at some point and may require sufficient rain beforehand, but will help to open up the seedbed especially if surface compaction is an issue.

A lower disturbance subsoiler is preferable however where the topsoil is in good condition and the field is level, and where you are in a no-till system. The closer you are to planting the less clods you want to create, so abandon the ripper and go to a subsoiler.

If you are ripping or subsoiling after several years of disc ploughing make sure you invest in an auto reset leg; nothing worse than spending all day jumping off the tractor replacing shear bolts!

Deep Nitrogen Testing

Dry planting

Beware of dry planting. It sounds great in principle but where seed sits in hot soil for long periods of time germination will be reduced, losses to predation are increased, and Blue Moulds can reduce germination.

I accept that there may be little option on large farms with acreages to cover, but even if rain does come quickly there is a reliance on having enough to penetrate and germinate all of the seeds.

Dry soil also massively reduces residual herbicide efficacy, not a good thing when we are reliant on pre emergence herbicides in many crops.

Dry planted seedbeds, unless very level, can also cause increased coulter bounce and reduce the evenness of depth placement, so be cautious.

When to dry plant:

  • Where the soil is DRY at and below seed depth
  • On soil types that you can’t travel on after serious rain
  • Where you have good quality seed with high vigour and germination
  • Where grassweeds are under control

When not to dry plant:

  • Where moisture is marginal and split germination is a risk
  • Where you have a serious grassweed problem and need the residual pre em herbicides to work effectively
  • High millipede pressure that has not been dealt with beforehand
  • Where seed quality is questionable
  • In crops where uneven germination will lead to difficulties at harvest (or anyone with C Series John Deere combines!)

And finally…

44 plots of wheat varieties, 44 plots of barleys, 12 plots of oats, 24 plots of peas, 24 plots of Chickpeas, 6 plots of Faba beans, some Lentils and Lupins were all planted over the weekend with help from the Agventure Centre of Excellence and my Cropnuts colleagues.

Growing the right varieties (and indeed the right crops!) is the basics of good farming. Within those trials I have also set some fertiliser treatments up to examine how hard we can push Robin wheat and an exciting new variety of barley which has been entered into National Performance Trials.

Deep Nitrogen Testing

Next week; I look at the yield effects of split germination and emergence in maize and why buying a good planter is money well spent.

See you then!


About David


David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.