Fine-Tuning Farming: Variable Rate Lime & PNM

Spreader for PNM & Variable Rate Lime

While New Zealand has a diverse range of soil types, only around 5% are fertile and versatile enough to support food production without significant manipulation. Variable rate lime and precision nutrient management are two important strategies in modern agriculture that can help farmers improve crop yields and reduce environmental impact. 

This approach is particularly important in today’s global economy, where farmers are under pressure to produce more food with fewer resources. By using these techniques, farmers can produce more food with fewer inputs, which is not only good for the environment, but also for the farmers’ bottom line. 

It is possible to have too much of a good thing.  

Accidification of soil occurs naturally, but can also be accelerated by fertilisation practices that decrease soil pH. Plants don’t tend to grow very well if the pH in your soil isn’t quite right. If you read last month’s edition you would have learnt about Yield Mapping and how you can use it to identify the high and low yield areas of your farm. So, how do you fix the low yield areas?  

This is where Variable Rate Lime comes in to play. We are sure you are all aware that Lime affects your PH. Variable rate lime is a technique that involves applying lime to paddocks at different rates based on soil test results. Lime is a valuable amendment for many soils, as it raises the pH and makes other nutrients more available to plants.  

If you have an acidic low pH soil you can add lime to raise pH levels, but lime is a very challenging material to spread due to its fine and non-uniform particle size. Applying too much can also waste product and damage the environment. Lime applied at a variable rate aims to reduce the variability of soil pH levels across the paddock by applying only what’s needed.  

So how do you figure out how much lime is required and where?  

Enter an important tool in your precision ag toolkit – Precision Nutrient Management.  

Precision Nutrient Management allows you to apply the right amount of nutrients only to the area that requires it, as determined by soil sampling. This process gives you a greater understanding of nutrient levels across your farm and the ability to correct any issues. 

Not all soil is the same. Your nutrients could be affected by the area you live in, your soil type, or you could have years of nutrient build-up in your soil from previous farming practices. Soil testing gives you an accurate map of nutrient levels within your paddock. Thanks to GPS technology, the data is accurate and the process is repeatable from the same points in the future. 

Using the soil test results, you can then use variable rate fertiliser allowing you to use fertilisers more efficiently and reduce the soils variability across a paddock. Through this method, both yields and environmental sustainability can be improved, while saving money on nutrients. 

So how does it work?  

We will take samples of soil from across your paddocks to determine their nutrient levels. We then work directly with the farmer or your preferred nutrient advisor team to ensure you are applying the right nutrients in the right places at the right time.  

Short term financial pain for long term gain. No two farms are alike, so until testing is done, you can’t tell what your nutrient levels are and what rates of fertiliser you need to apply to get your nutrient levels at optimum levels for plant growth. After performing tens of thousands of hectares of PNM across NZ, the general rule is that you will have to apply less lime in the first year (because the amount is already too high in most areas) and this will cover the soil sampling costs, with any additional nutrient (P, K etc.) savings being the cherry on top. 

If you don’t overapply or underapply nutrients, your range of nutrients will decrease year after year, and it is during this adjustment period (depending on how often you sample soil and apply lime and fertiliser) that you will achieve the greatest savings. Not only will you save money on fertiliser, but you will also enjoy increased plant growth and health as a result of reducing nutrient limitations. 

Trimble Ag Software and PNM

Using Trimble displays and Trimble Ag Software provides significant advantages in precision nutrient management. The integrated suite of tools and technologies offered by Trimble enables farmers to optimise the application of fertilisers with unmatched accuracy, enhancing crop yields and minimising environmental impact. The software’s advanced algorithms and real-time monitoring capabilities allow for precise variable-rate application, ensuring that nutrients are distributed precisely where and when they are needed most.


With Trimble Displays, Trimble Ag Software, AutoSync & Field_IQ, farmers can streamline their nutrient management workflows and record-keeping, reducing unnecessary paperwork and giving them more time back for doing what they’re best at – feeding NZ and the world.

Ready to take the guesswork out of farm nutrient management and stop blanket rate application? Talk to us today about precision nutrient management.  

Find out more at vantage-nz.com/precision-nutrient-management

Soil Testing in Mid Canterbury – Pye Group Case Study

Pye Group is an agricultural company owned by Leighton and Michelle Pye, operating 11 dairy farms and over 4,800 hectares of land across Temuka, Rangitata, Hinds, Rakaia, and Fairlie.

Their primary activities include dairy grazing for their own cows, substantial cropping (grains, wheat, barley, milling wheat, specialty grasses, and vegetables), and supplying turf grass to the US for golf courses. They also supply 25,000 tonnes of carrots and 15,000–18,000 tonnes of potatoes to McCains annually.

Working with Vantage NZ since 2012, the company has invested in soil testing, moisture probes, EM soil surveying, and yield mapping. This has helped them better understand soil quality and exactly what nutrients each piece of their land needs.

One of the biggest challenges for Pye Group is ensuring a balanced nutrient supply for optimal growth on their cropping farms and being able to provide proof of placement. Prior to working with Vantage, the group used blanket application of fertiliser, applying a standardised amount across the whole farm. 

The solution:

With Precision Nutrient Management, they are now able to apply variable rates of products such as Lime, Potassium Chloride, Superphosphate and Magnesium Oxide based on maps that outline the exact quantity each part of the paddock needs. They have found that in some paddocks, three quarters will receive no nutrients, and one corner will need four different rates. If they had blanket applied, they would have overloaded the majority of the soil.

Outcomes:

This approach has significantly increased their yield and allowed Pye Group to optimise fertiliser use and reduce waste.  The precision approach to fertilising has had numerous benefits for the Pye Group, including cost savings on transportation, time, effort, labour, fuel, and equipment wear and tear. Additionally, having guidance on equipment has resulted in savings of up to 10% on overlap. This translates into close to $50,000 in savings per percent of overlap in nutrients.

Soil testing has also been used on their dairy farms to ensure that there is no nutrient overload at the front of the paddock where the gate is located. The cows always return to the dairy shed through the gate, transferring all the concentrated nutrients from the back of the paddock to the front in their manure and urine. With this information, The Pye Group has implemented exclusion zones in the first 10% of the paddock, as nutrients are not required there.

Tony Gould, Operations and Transport Manager, has been implementing PNM strategies with the help of Vantage NZ and Ravensdown and has invested a lot of time and effort into data capture and quality.

“You can’t argue with data and can make long-term, data-driven plans that relate to real information; it’s not estimated. People either overestimate or underestimate, but when you have the data, you can actually see what you have done and what the result has been. Unless you get soil testing done and use variable rate application, you just can’t make targeted decisions,” said Tony.

Precision Agriculture Data on the computer at Pye Group

Precision agriculture has been a game-changer for the Pye Group, and they believe that it is a solution that can be implemented on any scale. You just need to start. 

To find out how precision ag could help you to reduce costs and maximise profits, contact Vantage NZ on 0800 482 682 or vantage-nz.com.