Lime, in the form of limestone, has been an important resource in Australian agriculture for many decades. Limestone is a natural source of calcium carbonate and is commonly used for soil amendment purposes across broadacre cropping systems and pastures. Australia has significant limestone deposits across many regions, particularly in southern areas where soil acidification is an ongoing challenge for farmers.

History of Agricultural Lime Usage
The use of lime as a soil amendment in agriculture can be traced back to ancient Greece and Rome. However, it was not until the 19th century that lime began to be widely adopted by Australian farmers to address acid soils. Early experimentation showed that applying limestone could raise soil pH and make previously unproductive soils viable for crops and pastures. Through the 20th century, as agricultural production intensified, liming became a routine practice on many Australian farms and continues to play a vital role in supporting crop yield and quality.

Lime Sources and Forms
Raw limestone in its natural state can be sourced from geological deposits located near agricultural areas. Common limestone types suitable for agricultural use include calcitic limestone, dolomitic limestone, and shell or coral limestone. Additional processes may be involved to grind the raw limestone into smaller particles to increase its reactive surface area and speed of neutralizing acidity. Finely ground limestone is typically sold as agricultural lime, which farmers then apply to their paddocks.

Effects of Lime on Soil Properties
The primary benefit of applying agricultural Australia Lime is to raise soil pH level in acid soils. Through a chemical reaction, the calcium carbonate content of lime neutralizes free hydrogen ions in the soil, thereby increasing pH. Maintaining optimal soil pH, typically in the range of 5.5-7.0, has flow on benefits including improved plant nutrient availability and microbial activity. Lime also supplies calcium, an essential plant nutrient, and can add magnesium to the soil profile if dolomitic limestone is used. Over the long-term, regular liming helps to buffer soils against pH decline caused by fertilizer and organic matter reactions.

Recommendations and Best Practices
The amount of lime required for a paddock is determined through routine soil testing. Tests measure existing pH and provide lime requirements to reach the target zone. Factors like soil type, rainfall, and crop influence lime needs. For example, acidic sandy soils will generally demand higher application rates than heavier clay soils. Experts recommend re-testing soil pH every 3-5 years and reapplying lime as needed to maintain levels. It takes 6-12 months for applied lime to fully interact with the soil.

Liming Programs across Different Cropping Systems
Broadacre cropping: Many Australian grain growers run long-term liming programs, routinely applying 2-5 tonnes of agricultural lime per hectare every 2-5 years to common soils like red-brown earths. Winter crops such as wheat, barley and canola show strong yield responses to maintaining pH above 5.5.

Pastures: Perennial pastures for livestock grazing rely on a fertile soil pH environment. Most grazing land soils need 1-3 tonnes of lime per hectare applied every 5 years or so to optimize ryegrass and clover growth. Maintaining soil pH aids pasture persistence and productivity.

Horticultural crops: High-value vegetables, fruit and nut crops demand even closer pH control. Orchards may have lime applied and incorporated every 1-3 years at rates of 5-10 tonnes per hectare to maintain pH between 6-7 depending on soil type. Timely liming secures crop quality and shelf-life.

Factors Affecting Lime Application Rates
Several interrelated factors influence how much lime is actually needed when it comes to on-farm application rates:

– Soil texture: Heavier clay soils versus lighter sandy soils require different quantities of lime to raise pH due to their variable cation exchange capacities and buffering abilities.

– Soil organic matter: High organic matter soils have greater buffering than low organic matter soils, requiring higher lime rates for effective pH change.

– Initial soil pH: More lime is needed to raise strongly acidic soils versus moderately acidic soils to reach the optimal range.

– Form of lime used: Finely ground lime reacts faster than larger applications of coarse lime particles, but both achieve pH change over time.

– Incorporation method: Lime works faster if incorporated into the root zone rather than surface applied alone as it mixes better with the soil profile.

The Benefits of Lime Outweigh the Costs
While purchasing and applying agricultural lime requires an upfront investment for farmers, the economic and production benefits realized through improved soil health and higher crop yields readily offset these costs. Maintaining soil pH over the long-term is one of the most affordable and effective fertility management practices for Australian farms across many climate zones and agricultural systems. As a locally sourced input, lime also represents a sustainable solution for supporting robust and resilient agricultural production into the future.

Lime has played an indispensable role in Australian agriculture by helping overcome the inherent acidity found in much of the country’s soil resource. Decades of research and on-farm experience have shown the vital importance of maintaining adequate pH levels through liming programs tailored to different soil types and farming systems. With modern agricultural practices intensifying acidification risks, lime continues to be a cornerstone practice sustaining highly productive Australian agriculture.

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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it