Watch: first of Yara’s new ALS2 nitrogen sensors in action in Kilkenny
Stephen Robb visited Kilkenny From the Tramlines farmer James O’Reilly, who recently took delivery of the first of Yara’s new ALS2 nitrogen sensors in Ireland.

When we caught up with James O'Reilly on a sunny morning in early April, he was top-dressing his Husky winter oats. The crop had come through the winter in great condition and the cool weather earlier in spring helped to slow down development. This was welcomed as he felt that the oats were a little too advanced.

He was applying round 260kg/ha of SulCAN, to finish the last of the crops nitrogen applications by GS32.

New ALS2 N sensor

He uses a Fendt 939 and trailed 10t Rauch Axent 100.1 spreader. Earlier in February, James took delivery of a new Yara ALS2 (active light sensor) nitrogen sensor, the first in the country.

The Yara N-Sensor is a real-time variable rate nitrogen sensor that allows growers to measure crop nitrogen requirement as the fertiliser spreader passes across the field and adjusts the fertiliser application rate accordingly.

It works by detecting the levels of light reflected from the crop and using this data to generate NDVI vegetation index maps, which are used to guide N applications.

The advantages of the new ALS2 over the previous sensors is that they are capable of working at night and can work when the crop is damp or has a heavy dew on it.

“To show how it worked, I went into a field at 4 o’clock in the evening and went to a number of points to see what nitrogen it [the sensor] was reading in the crop. I then went back in at 2 o’clock in the morning and went to the exact same spots and the readings were the same,” he says.

When spreading nitrogen using the sensors, he first puts in a minimum and maximum rate. The sensor then varies the rate of the spreader depending on the nitrogen present in the crop and working within the preset parameters.

The proof will be at harvest time

The idea of the sensor isn’t necessarily to save nitrogen, explains James, but to apply it where it’s needed and less of it where it’s not.

He expects to see more even crops closer to harvest time and hopes to see an increase in yield.

Ultimately, the proof that the sensor is worthwhile will be when he puts the combine through the field. To pay for itself, James estimates he would have to see 0.5% increase in yield.

“We have to try something, and we have to be seen to be a little more environmentally conscious about how were applying all of these inputs,” James concludes.

Watch the video below:

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Watch: spreading N on winter barley in Laois
Last week, Stephen Robb visited From the Tramlines farmer Paul O’Connell, who was spreading nitrogen on his winter barley.

Last week, we visited From the Tramlines farmer Paul O’Connell. Paul farms in Ballybrittas on the Laois/Kildare border.

Paul was busy applying 320kg N/ha on his winter barley this week.

So far, the crop has received 500kg/ha of 16:2.5:17 + S across two splits.

The crop also received an application of 0:10:20, which was incorporated into the seedbed in the autumn.

After a cold March, crops are at a normal growth stage for the time of year.

Watch the video below:

How to generate crop vegetation index maps using satellites for free
Stephen Robb explores how to use up-to-date satellite imagery to generate vegetation index maps for your crops for free.

Sensors capable of measuring crop reflectance to generate normalised difference vegetation index (NDVI) maps to guide nitrogen (N) applications have been around for some time now.

The most commonly known instruments include tractor-mounted active sensors and, to a lesser extent, drone-mounted passive sensors.

The sensors are able to detect the levels of light which are being reflected from the crop and correlate this to the crop N levels. This, in turn, can help to guide crop N requirements.

However, few growers are aware that they can access up-to-date vegetation index maps specific to their land for free.

Sentinel Hub playground

One of the sentinel satellites taking images of the earth.

The Sentinel Hub playground is an online engine for processing satellite data. It collates and processes thousands of high-resolution images taken daily by Sentinel, Landsat and other earth observation imagery and makes it easily accessible for browsing and analysis.

Depending on the satellites, they pass overhead every two to five days taking hundreds of thousands of multispectral images of the earth. The database on the Sentinel Hub playground can go back as far as 2015.

While the website offers a range of other uses which come at a charge, internet users can browse the satellite imagery free of charge.

As the satellites are multispectral, there are a number of layers to each map including natural colours, infrared, false colour and moisture index. However, the vegetation index is of most interest to us.

Areas and condition

Here, users can access up-to-date vegetation index maps quickly identifying vegetated areas and their condition. The images can detect different densities of vegetation, display variation within a field and can easily distinguish between grassland, stubble and cropped areas.

Sentinel Hub playground can be accessed here.

Satellite images taken last Monday

A satellite image taken this week.

Here, we have a satellite image taken from an area in Co Wexford yesterday, 18 March.

Vegetation index maps

The vegetation index map of the same satellite image.

Here, we have the vegetation index map of the same image. In this particular colour scheme, grassland is green, as are thick cereal crops. Stubble ground is yellow, while bare patches of soil are brown. Most fields of cereals, however, are blue in colour but contain variations in colour shades in each field indicating the areas of variation in crop performance.

Are these images useful?

While having free access to this data is interesting, it does not currently serve any practical use other than helping to identify variability within a field.

There are also a number of issues relating to the satellite imagery. Cloud cover can be a particular problem as the vegetation index maps can’t distinguish between clouds and land.

Furthermore, as the satellites use passive sensors which rely on sunlight, this can pose a number of issues with the readings. For example, the angle of the light coming off the sun can affect the levels of light reaching the sensor. This will have an effect on the accuracy of the readings.

A glimpse into the future?

Sentinel Hub playground does, however, serve to give us a glimpse into the future. The theory of satellites taking crop readings every number of days and presenting the data in a usable form for farmers is correct.

As satellite technology improves, this form of data collection is likely to play a much bigger role in crop and grass production.

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New guidelines may challenge use of poultry litter
New Department guidelines for the spreading of poultry litter may complicate its continued use on tillage farms.

New guidelines on the safe use of poultry litter have been published by the Department of Agriculture.

They are clearer on many issues and show the links to related guideline content.

They contain many elements of good practice that are very relevant. But they also contain elements that may make the continued use of poultry litter too cumbersome for some tillage farmers.

The poultry industry is highly relevant to the tillage sector as it is an all-year user of feed.

The sector is concentrated in areas that tend to be grassland orientated and so spread lands can be an issue.

In the past, the practice of acquiring map references for theoretical spread lands was common, but this is being tightened so genuine access to land is increasingly relevant. So tillage land is in demand for both chicken litter and pig manure as they can be incorporated to help structure and fertility while minimising smells.

One could be forgiven for thinking the risk of the spread of botulism is solely the fault and responsibility of those who use it.

If there are carcases in the litter that arrives, the risk is present, but the user may have no knowledge of the potential problem.

In the past, users could minimise the risk based on the poultry system used.

Layers’ litter has much lower risk because birds are unlikely to find their way to the litter. The guidelines do not differentiate between layers’ and broiler litter in terms of risk.

Challenges in the guidelines

One of the big challenges in using litter is its storage. The guidelines state that it cannot be tipped in a field and must be stored on a concrete pad away from rivers etc. This is not an option for some farmers.

A stack must be at least 500m from grazing or housed livestock and should be completely covered to prevent access by wildlife. This is a really big deterrent where loads are arriving on farm over a prolonged period.

The guidelines rightly state that the product should only be spread on tillage and not on grassland. However, who can define what any parcel of land will be used for in this era? Will this point cause landlords to prevent spreading on their land? Nowadays there is great uncertainty as to the future use of any land parcel, rented and owned.

The new guidelines specify a three-year interval between the spreading of litter on any field. For those who had been topping up soil test results annually, this may be a great inconvenience.

A grower applying 2t/ac/year would now have to apply 6t/ac every third year. This is a lot of nitrogen to put under most autumn crops for safe husbandry. It would work under rape but may be a deterrent for use at that rate on winter cereals, given the additional problems that it could help generate.

The guidelines rightly recommend that owners of neighbouring stock be notified of spreading so they can remove their stock from adjacent fields to keep them safe. But what happens if the stock owner chooses not to cooperate – where then might any liability lie?

Dust spread

One of the issues I have with the guidelines is there is relatively little reference to the risk posed by the possible movement of spores in dust. The only reference to dust is with regard to ploughing.

The suggestion that neighbours move their stock at least one field away from where litter is being spread is probably an indirect suggestion of this risk.

Most poultry litter is much drier than it used to be and it can be dusty. Being drier makes it easier to handle and transport but is this adding to the potential for the botulism organism to move in the absence of wildlife?

If the dry product contains botulism spores, the movement of dust is a real risk.

Dust can be created during tipping, loading and spreading. These are risk points for users and for neighbouring livestock.

While there is no direct reference to this avenue of spread in the guidelines, users might consider the possibility of wind-dispersed spores as a movement risk during all aspects of handling.

However, there is not that much one can do about this other than wait for the material to get wet or to try to spread during rain. Neither of these is totally satisfactory but they should help reduce dust movement.


Whether dust or carcases represent the greatest risk, there must be emphasis on getting immediately incorporation to close down both potential avenues of spread.

The guidelines clearly emphasise the need for immediate ploughing but not the difficulty in getting this done.

Where a user wants to stay safe, my recommendation would be to follow the spreaders immediately with aggressive discs to get the material off the surface and mixed in

While one cannot argue against the need for total incorporation to bury the danger, driving ploughs at a speed to keep up with the pace of spreaders makes good ploughing and complete burial virtually impossible.

Where a user wants to stay safe, my recommendation would be to follow the spreaders immediately with aggressive discs to get the material off the surface and mixed in. This would massively reduce the immediate risk of carcase movement (but not eliminate it) by wildlife but it would do nothing for the risk of movement as spores.

Ploughing should follow immediately and the initial discing should help slow the ploughing speed and give much more thorough trash burial.

For growers involved in min-till and no-till, these guidelines effectively prevent the use of poultry litter. And with reduced tillage being actively promoted, the safe use of litter in tillage fields may be increasingly difficult.

Prevent delivery

No farmer wants to endanger the health of his or his neighbours’ stock and these guidelines have a lot of elements that help in this regard. But perhaps the most important thing to remember is that one should not allow litter to be tipped on one’s farm that does or may contain dead birds. That is a basic starting point but difficult to guarantee.

It is important to know that the primary obligation to have carcase-free litter is with the poultry producer and then the transporter. Contaminated product should be rejected on arrival or where carcases are seen post-tipping, it should be reloaded and taken away.

In brief

  • New poultry litter use guidelines make it less attractive to some growers.
  • Problems include the prevention of land tipping and confining application to one in three years.
  • Litter arriving on farm should be free of bird carcasses.
  • Spread by dust and spores may be a transmission risk.