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Case Studies - Dairy

Nitrogen Needs Lime

Product Sector: Agriculture

Industry: Agriculture - Dairy and Dry Stock

Products: Aglime

Interviewees: Paddy Shannon M.Agr.s (Hons) MNZIAS - Farming Consultant

Location: Te Awamutu

Application of nitrogen will acidify a soil.

Without countering nitrogen induced acidity it is likely farmers will end up with poor responses to applied fertiliser as plants are less productive in acid soils.

How much Lime?

This graph shows the amount of lime required to neutralise the acidity released by different types on N on an applied basis.

Different forms of nitrogen have different levels of lime demand.

  • Applying nitrogen (N) fertiliser makes the soil more acidic. The change from ammonium or urea to nitrate leaves the hydrogen behind to acidify the soil. The amount of acidity depends on whether the applied N is leached as nitrate or taken up by plants and exported in produce.
  • The degree to which this occurs will vary depending on soil conditions and the form of N applied.
  • An average dairy farm applies around 90kg N/ha/year, but this can range from 0 to 150kg N/ha/year. Most nitrogen is applied as urea so at 90kg/N/ha/year the derived lime requirement is 160kg of pure lime, or 180kg/ha of Aglime (90% purity).
  • Farms at the high end of N applications are therefore likely to need 290-300kg of aglime to correct the N-induced acidity.
  • Di-Ammonium Phosphate (DAP) is usually applied as an effective way of getting a strategic seasonal N dressing on by teaming it with the autumn or spring P-fertiliser application. Given that a typical dairy farm will need around 35 to 40kg P/ha/year, the N applied in this way as part of the program will total 31 to 35kg N/ha-which equates to an aglime need of 125 to 160kg lime/ha/year.
  • Mono Ammonium Phosphate (MAP) and Sulphate of Ammonia (SOA) being ammonium-based fertilizers will always acidify the soil. A tonne of MAP needs 580kg lime per tonne applied, while SOA needs 1100kg per tonne applied, as shown in previous graph.

Why Nitrogen Needs Lime

  • Applying nitrogen (N) fertiliser results in the soil becoming more acidic. The degree or extent of acidification is determined by whether the applied N is leached as nitrate, or taken up by plants and exported in produce.
  • We can look at the extremes – all taken up, or all leached as nitrate. For urea, the two extremes are no acidity, or acidity requiring 3.5 kg of lime per kg of N applied to neutralise it. As we can’t reliably predict which is going to happen, we plan on the average: around 1.8 kg lime per kg of N added or, for every tonne of urea containing 460 kg of N, you will need 830 kg of lime.
  • Unlike urea, ammonium fertilisers will acidify even if all applied N is taken up. The lime requirement ranges between 3.5 and 7.0 kg (average 5.3/kg) of lime for every kg of N applied. Sulphate of ammonia with 210 kg N per tonne, or MAP with 200 kg of N per tonne, both need around 1.1 tonnes of lime per tonne applied.
  • DAP sits between sulphate of ammonia/MAP and urea needing an average of 3.6 kg lime per kg of N applied, because the P it contains uses up some soil acidity when it is absorbed by plant roots. With 180 kg N tonne, 650 kg of lime are needed per tonne of DAP applied. When planning N applications, you need to allow for the acidity created. This becomes more important if you use relatively large amounts of N. Without countering nitrogen-induced acidity, it is likely that you will end up with poor responses to N fertiliser, as plants are less productive in acid soils. Put another way, keeping your soils well limed with pH levels around 6.2 will guarantee the best possible response to nitrogen fertilisers whenever you need to use them.

Light Rate Annual Liming

Light rate annual liming is the best way to counter nitrogen induced acidity. Farms following this practise have seen some great results. They are also gaining all other benefits of maintaining a soil pH around 6.2, such as;

  • Improved soil structure and better nutrient recycling through greater microbial activity,
  • Greater drought resistance through increased root depth and soil moisture retention capacity,
  • Improved pasture palatability,
  • Increased clover content and overall better pasture composition giving higher total pasture ME.

Thoughts of the Farmers

  • “The paddocks that have been limed are a mass of clover and beautiful green grass. When we first came here the cows would pull the grass out of the ground as it was all just sitting on top. Now when I’m fencing, I see a lot of worms and the roots will be 200-250mm deep. In the last 4 years my baleage harvest has increased each year. The first year we got 56 bales out of three flat paddocks. This year we’re up to 72.” – Wayne Cederman, Otorohanga
  • “We have seen a marked turnaround in our farm since starting an annual liming programme three years ago. The regular application of lime has part in improving soil condition and pasture palatability. Since we started an annual liming regime, the farm is slower to dry out and quicker to respond when rain comes. We put on lime each spring and it has saved us a lot of money in fertiliser” – Ron Hamilton, Otorohanga

Dave Muggeridge

Dave Muggeridge 2015

Case Study: Lime and Farming

Product Sector: Agriculture-Dairy

Location: New Zealand

Products: Ag Lime, Calcimate and RaceFines

Source / Interviewee: Dave Muggeridge


Introducing Dave Muggeridge

  • Dave Muggeridge milks 280 cows on his 90-hectare farm in Tatuanui, in the Waikato.
  • He is one of 112 shareholder farmers who supply to the local Tatua Cooperative Dairy Company.
  • Dave employs a contract milker, leaving him to focus on the management of the pasture and stock.

The challenge: optimising farm production through growing more grass

  • Dave is passionate about boosting productivity through better pasture management.
  • “In this country we don’t grow enough grass to fulfil the potential of the New Zealand cow,” he says. “We don’t need to put more cows on – we just need to grow more grass!”
  • Dave uses three lime products on his farm – for pasture, Calcimate® for a feed supplement, and RaceFines™ for the tanker track.

“I use AgLime and 2-6 Chip to alter the pH, increase the microbial activity in the soil and hence improve soil structure. The lime makes the grass highly palatable. So while it doesn’t change the number of mouthfuls a cow is eating each day, it does mean there is more in each mouthful. It makes the grass thicker (a bit like a NZ Wool carpet!) and highly nutritious.”

Why McDonald’s?

Proven history

  • At his previous property, Dave used to apply lime to a quarter of the farm each year – and observed that it was the best-performing pasture.
  • “From this, we decided to apply Ag Lime at a lighter rate over the whole farm. Now we lime the whole farm every year.”


  • In a nutshell, the lime helps grow more grass – which is the cheapest form of dry matter, especially compared to supplements such as maize or palm kernel.
  • “You’re not writing out cheques for silage and you don’t need extras like a feed out wagon,” explains Dave. “Using a grass based system helps improve margins, and that’s especially valuable in low-margin periods.”

Better for the environment

“We’re growing a lot of grass and not leaving a footprint. And we’re not having a lot of nitrogen escaping out of the system.”

Quality product

“We have very active soil and lime is an integral part of soil fertility. McDonald’s (now Graymont's) is the best quality lime available.”


To sum up, Ag Lime has provided measurable improvements in pasture production; Calcimate® prevents Dave’s cows from becoming hypocalcaemic after calving; and the RaceFines™“compacts nicely, just like the road”.

“We’ve been working with McDonald’s (now Graymont) since 1996,” says Dave. “The cows are satisfied and the results are very encouraging. There’s always grass, even in a drought period.”


Mike Earwaker

Mike Earwaker 2015

Case Study: Lime and Farming

Product Sector: Agriculture-Dairy

Location: New Zealand

Products: AgLime

Source / Interviewee: Mike Earwaker


Hugh Chisholm

Hugh Chisholm 2015

Case Study: Lime and Farming

Product Sector: Agriculture-Dairy

Location: New Zealand

Products: AgLime

Source / Interviewee: Hugh Chisholm