Soil Compaction Trials Boost Pasture Production on Canterbury Dairy Farms, Dr Gordon Rajendram with Agraforum New Zealand


Left to right: Agraforum Managing Director Allan Piercy and Soil Scientist Dr Gordon Rajendram

Hamilton, New Zealand – July 8, 2024 – Recent trials conducted by Dr Gordon Rajendram, a distinguished soil scientist and consultant, have revealed significant improvements in pasture production on Canterbury dairy farms through the use of soil compaction treatments. Dr Rajendram, formerly of AgResearch and MAF, led these trials to assess the impact of soil compaction on pasture growth and to demonstrate the effectiveness of Agraforum’s soil treatments. Dr Rajendram stated that “The trials have shown that addressing soil compaction through targeted treatments can significantly enhance pasture production, providing a sustainable solution for farmers to boost their productivity.”

Pasture production is influenced by five primary factors (1):

1. Soil Moisture: Adequate rainfall or irrigation is crucial, with less than 25% soil moisture negatively impacting growth.

2. Soil Temperature: Grass growth ceases when the soil temperature at 10 cm depth falls to 5-6 degrees Celsius.

3. Soil pH and Nutrients: Thirteen essential elements for plant growth, along with Co, Se, and I for animal health, are vital.

4. Soil Microbiology: Beneficial microbial activity supports plant health.

5. Soil Air Space (Air-Filled Porosity or Macroporosity): Compacted soil, with less than 10% air-filled porosity (AFP), significantly reduces pasture production. Each percentage drop below this threshold results in a 10% reduction in yield (based on AgResearch trials)(2).

Since 1995, the Waikato Regional Council has been monitoring soil quality at 150 sites across the Waikato region, focusing on volcanic ash and pumice soils used for dairying, beef, cropping, and forestry. Seven soil quality tests are conducted at each site, including air-filled porosity. The 2019 data revealed that 94% of dairy farming sites had concerning soil quality, with excessively high fertility and soil compaction affecting approximately 85% of the sites. (Waikato Regional Council)(3).

Aim and Methodology

The aim of the trials was to demonstrate that Agraforum’s soil compaction treatment can improve soil aeration and pasture growth. The trials involved:

– Four irrigated Canterbury dairy farms, with two using Agraforum’s treatments for several years and two untreated.

– Monthly pasture measurements using a ride-on mower and digital scales.

– Soil temperature monitoring, starting at 14 degrees Celsius and dropping to 5 degrees Celsius by the third cut.

Each farm had ten plots (2m x 10m), and the trials commenced in the last week of February 2024, with pasture cuts taken over a 105-day autumn period.


The results were conclusive:

– The two treated farms produced approximately 1,000 kg DM/ha (33%) more dry matter than the best untreated farm.

– Compared to the second untreated and most compacted farm, the treated farms yielded over 2,000 kg DM/ha (80%) more pasture.

Graphs from the study clearly illustrate the superior performance of treated farms in terms of total pasture grown and growth rates, particularly for the first cut.

Graph 1: Shows Total pasture grown for ~ 105 days for the 2 Agraforum Treated and Untreated Farms.

Graph 2: Shows the growth rates for the first cut for the farms. The Treated farms grew twice and 3 times the more pasture than the Untreated farms for the first cut.

Raw Data

Agraforum- Treated -Farm 1Kg DM hectareDays GrowthKg DM/dayTemperature
Cut 11958277314
Cut 21226353510
Cut 33884395
Agraforum Treated -Farm 2Days GrowthKg DM/day
Cut 118272963
Cut 211804030
Cut 3307369
Non Treated Farm-3Kg DM hectareDays GrowthKg DM/day
Cut 111274028
Cut 211735322
Cut 3   
230093(105)25 (22)
Non Treated Farm – 4Kg DM hectareDays GrowthKg DM/day
Cut 14293014
Cut 2262348
Cut 3   
69164(105)11 (7)


These findings highlight the importance of addressing soil compaction to improve pasture production. Agraforum’s soil aeration treatments have proven to be highly effective, offering a practical solution for farmers seeking to enhance productivity and sustainability.

It takes ~ 10 kg of Dry matter of good quality pasture to produce 1 kg milk solid.(4)

Four other field trials alongside Agraforum will be commencing this Spring in the Otago region, so watch this space.

“By improving soil aeration and reducing compaction, we can unlock the full potential of pasture growth, ensuring healthier soils and more productive farms.” – Dr Gordon Rajendram, PhD, Soil Scientist/Consultant

About Dr Gordon Rajendram

Dr Gordon Rajendram is a renowned soil scientist and independent consultant with extensive experience in soil fertility, agronomy, and farm environmental consultancy. His expertise has been instrumental in bringing scientific solutions to the agricultural sector, improving productivity and sustainability for farmers across New Zealand.

About Allan Pirecy

Allan Piercy is a seasoned vet who worked in a rural clinic in South Taranaki for 20 years before moving to Mid Canterbury, where he headed a large veterinary practice. His primary focus was on dairy cattle, preventive medicine, and ensuring economic returns for farmers. Recognising that many animal health and production issues stemmed from poor soil nutrition and structure, Allan founded Agraforum New Zealand in 2007, aimed at addressing animal health and production issues through improved soil and crop management. Allan’s guiding principle is, “Correct the cause of a problem, don’t continue to treat the symptoms.”

Contact Agraforum New Zealand

0800 488 118

Allan: 0274 485 159



Contact Information:

Dr Gordon Rajendram 

Soil Scientist/Consultant 

9 Kakanui Avenue, Hillcrest, Hamilton 3216 

Cell: 021 466 077 



‘Bringing Science to the Farm’


Contact Media PA

027 458 7724


1. Rajendram G.S. Soil fertility, soil nutrients and their fate.

2. Betteridge K, Drewry J, Mackay A, Singleton P. (2003). Managing treading damage on dairy and beef farms in NZ. Booklet by CRI, AgResearch – Land and Environment Management Group. Research on dairy and beef cattle in Northland, Waikato, Manawatu, and Southland in the 1990s.

3. Waikato Regional Council. Soil quality monitoring data (2019).


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