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Case Studies - Dry Stock

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

Lime, Low-rate Application, On North Island Hill Country

Product Sector: Agriculture - Dry Stock

Products: Aglime

Source: Farm Production and Practice-Ministry of Agriculture and Fisheries (AgLink) 

  • Low soil fertility is still a major factor restricting production on North Island hill country. Many properties still have a low phosphorus status and low soil pH.
  • Although information is available on the phosphorus requirements of many of our hill soils, less is known about lime. This AgLink presents findings of preliminary research on lime, and discusses its value on hill country.
  • The research is being carried out at Te Kuiti on Mahoenui steep land soils (Mudstone soil), with a pH of 5.5. This soil is typical of approximately 400 00 ha of North Island hill country. Research investigated the production responses to low application rate of lime (1.12 t/ha).

Ewe live weight and pasture availability

The main research features are:

  • Lime increased pasture production.
  • The main response appeared 15 months after application
  • The response to lime continued and increased over time and was still present 3 years after application.
  • The delayed response to lime is probably due to a combination of two factors: the low rate of application and low solubility of the limestone.
  • Even with a high rate of lime (5t/ha), it can take up to a year for ground limestone to have its maximum effect on soil pH and Calcium levels.

Wool production

  • Fleece weights of both ewes and lambs show a response to lime. Additional 0.5-0.6 kg greasy wool per ewe and up to 0.13kg per lamb was obtained-due to the better overall plane of nutrition of the animals grazed on limed pasture.
  • The effect of lime on wool characteristics, in particular fibre diameter, confirms the benefits of an improved nutritional regime.

Lamb performance

  • No valid comparisons can be made between lime and no lime treatments on lambing percentage, because of low ewe numbers.
  • The lambs from pastures receiving lime were, however, superior in live weight at weaning. ‘Lime’ lambs were on average 3kg heavier, mainly due to a better level of feeding.

Reasons for improved stock performance with AgLime

  • AgLime increases animal production through an increase in pasture production.
  • In addition there is some evidence to suggest lime also improves the legume component and decreases the amount of pasture litter. Earthworm numbers on the lime treated land also tended to increase.

Conclusion

  • A low rate of lime on a steep hill country soil increases pasture and animal production.
  • There is no response for 15 months, but thereafter lime increases ewe live weights by approximately 5kg/ewe, ewe fleece weight by 0.5-0.6 kg/ewe and lamb live weight at weaning by at least 6%.
  • The response appears to be due to an increased total pasture production rather than any improvement in pasture quality.
  • An economic appraisal of the results suggests lime usage is very profitable.

John Girvan

Johnny Girvan 2015

Case Study: Lime and Farming

Product Sector: Agriculture-Dry Stock

Location: New Zealand

Products: AgLime

Source / Interviewee: John Girvan