Mr Schier, you have been working in precision liming for 15 years. Is a highly variable pH typical for new customers?
There is always variability but it doesn’t always present in the same way. It can be towards a lower or a higher range, so from 4.5 to 5.5 or, for example, 5.3 to 6.5. But the gap can be much wider – even from 5 to 7. The starting points can be very different.
What factors lead to this variability?
The causes are the same as those which contribute to variable soil structure, nutrient availability and yield. On the one hand, the cause may lie in the history of the land. Parts of the field may have been cultivated differently. For example, some farmers may have used lime in the past where neighbors didn’t, and these fields have since been merged.
Another factor is the topography of the land. Nutrients accumulate in the dips and there will also be inconsistent water holding capacities across the field. In some areas this leads to greater yields and higher nutrient withdrawals which, in turn, increase the natural decline in the pH value due to the loss of basic cations.
If we assume that the average pH value is not too far out and that the variability isn’t too great, is it still worth investing in precision liming?
Let’s use a variability of between 5.5 and 6.5 as an example. Here, I would look to average about 4.5t/ha of lime if I spread consistently and calculated all pH values as an average. However, if I look closely, I will see that where the pH is 5.5 I need to spread 8t/ha, and where it is 6.5, 2t/ha would be required. The variation in the amount of lime needed then becomes clearer.
If I spread 4.5t/ha across the whole field, I wouldn’t be able to optimise the pH in the areas that need a lot of lime. And I would be adding lime to areas where the pH value is already good. So precision application makes sense. Based solely on the quantity of lime, the costs are the same. It’s only the application map that makes a price difference and then we are talking about €1.50/ha.
When do you class the pH value as uniform and how long does it take to get there?
It can take between five and six years, because we can’t change the pH value too abruptly. If a field has a value of between 5.8 and 6.5, we spread between 1.5 and 5t/ha, for example. After two or three years we will be seeing a more uniform result, possibly between 6.0 and 6.5pH. After another couple of years we will be getting closer to constant values.
That said, we also have farms which reached an optimal range five to six years ago but now see disparities, sometimes between 6.1 and 6.5. However, there is only a difference of 1.5-3t/ha in the quantity of lime applied.
So you can’t just standardise the pH and then go back to fixed application rates?
It does sometimes happen that a field reaches a really constant pH value. But this is very difficult to maintain over a long period because lots of factors work together. Leaching and yields are not the same in every spot and with those come a corresponding loss of nutrients.
The next point is organic fertiliser, particularly slurry. Even if applied by a contractor, it does not mean that every area receives the same amount of nutrients unless you are working with an NIR sensor. When you look at the values from these sensors the differences seen within slurry are crazy; sometimes 50% variation. This means we always need to adapt lime applications to the circumstances.
You are assuming that no other fertiliser is applied site specifically; this would be another way of balancing the soil parameters. So why rely on precision liming instead of precision fertiliser? Or do they complement each other?
Precision fertiliser is certainly not a bad choice and we offer it as for phosphate and potash. We have also been using a biomass sensor to variably apply nitrogen in real-time for several years now. But in my opinion, you need to follow a kind of ranking order. Every specialist will agree that you need to start with liming, followed by P&K before it’s finally time for nitrogen and micro-nutrients. I don’t want to start with things that can’t really do their job effectively when the pH value is too variable. The other measures don’t help much in this case.
You also need to think about the costs of liming vs phosphorus or potash fertiliser. My first port of call needs to be a method that is feasible using simple means and with manageable costs. If we were to find an area with bad pH, 5.2 for example, and apply phosphate to it, it won’t be absorbed at all because it immediately becomes fixed in the soil.
So in terms of yield, it is better to first ensure a constant pH than to compensate for nutrient deficiencies in certain areas?
At a pH of 5.2, the effect is so strong that the crop can only use 50-60% of nitrogen fertiliser applied, for example. With the current fertiliser regulations in Germany, and looking ahead to future regulations, farmers need to keep an eye on their nitrogen and phosphorus use. The fertiliser we use should be capable of 100% efficacy, but it only works if the pH is optimal across the board.
How many farms does AIS Schier carry out liming for, and what size do they tend to be?
More than 100 farms, both small and large in size. We have some farms that have around 20-30ha but our largest customer has over 8,000ha. Of course, that doesn’t mean that we lime all 8,000ha in one year. Last year we were spreading 15,000t of lime, which translates into an area of about 15,000ha. I would say that a quarter of our customers are now in the optimum pH range.
What is the economic gain of a tailored lime approach?
I expect it’s around €60/ha thanks to fertiliser savings, increased yields and grain quality. However, this figure does not come from a scientific study, but rather from our own assessment based on experiences with our customers.
How, in terms of agricultural technology, does precision lime spreading work?
The basic idea is to use GPS control and an ISOBUS connection that you’ll be familiar with from other applications. When it came to using maps, however, it took us a long time to find technology that we could always rely on. We had a lot of discussions with our current spreader manufacturer and they fine-tuned the machines until it worked. The challenge of variable lime application is keeping the speed of the spreading discs constant. In a new sub-area of the field, the weight on the spreading discs can change very quickly.
In the past we often had an issue with the speed dropping off, which led to a smaller working width and poor distribution. This problem was solved by improving the settings of the hydraulic motors and of the entire hydraulic system. The system has been designed so that the spreading discs can withstand this changeable load. The variable application rate is ensured by the feed rate of the scraper floor. The speed of the chain adjusts the rate of application.
Which variables go into the application maps?
We prepare the application maps ourselves using a fleet of five pick up trucks with GPS and computer technology. Soil sampling is done using a grid size of about 3ha. The maps then have grid cells of 24x24m which matches our typical working width of 12m. We currently only create application maps based on the pH value, but in the future we will also need to take differences in the soil into account. Before we start spreading lime application maps are discussed with the farmer or farm manager. During this conversations we take the final decision about application rates, timing and fields.
Up until now, it was assumed that every field contains just one type of soil, but this is rarely the case and it means you have to pinpoint your approach. That’s why we are now experimenting with a soil scanner which will allow us to find different soil zones. In areas where the soil is softer and sandier, we could set the pH value even lower. Where the soil is better quality, we can set it higher. All of this information could be added to the application map.
What customers say
“12 years ago we had very variable pH values. Since then, however, the values within a field only vary by a maximum of 0.5 and we only need to make small adjustments. The key factor is the GPS-controlled sampling. Only with this technology is it possible to accurately see how the conditions change. Everything is saved digitally and evaluated throughout the year. As well as liming, we have also started precision P&K applications. I think it’s really important to look after the soil over the long term to achieve even nutrition. That was our goal and it’s worked very well with this technology. In the medium term we saw a 10-20% increase in yield, so it clearly works. Also, I think that now, where we have a level pH, we’re spreading more cost effectively because we really only have to balance the pH in specific areas.”
Gerhard Zehnter, 800ha in Weißig, Nünchritz near Dresden, Germany.