In the world of agriculture, farming systems vary greatly in their approach to crop production. While monoculture farming has traditionally been the norm, many farmers and researchers are now looking to polyculture systems as a more sustainable and productive alternative. One of the key tools used to measure the productivity of these two farming systems is the Land Equivalent Ratio, or LER.

But what exactly is the LER, and why is it so important in evaluating the efficiency of polycultures versus monocultures? Let’s break it down.

What is the Land Equivalent Ratio (LER)?

The Land Equivalent Ratio (LER) is a simple but powerful metric used to compare the productivity of mixed cropping systems (polycultures) to that of a sole cropping system (monoculture). It tells us how much land in a monoculture system is needed to achieve the same yield that can be produced in a polyculture system on a given area of land.

In other words, LER shows us how much more (or less) efficient a polyculture system is compared to a monoculture system when it comes to land usage.

Simple Explanation of LER:

LER compares how much land is needed to produce the same amount of yield.

In a polyculture system, different crops are grown together.

In a monoculture system, only one type of crop is grown.

How Does the Land Equivalent Ratio Work?

To understand how LER works, let’s first define the two systems it compares:

• Monoculture Farming: In a monoculture system, a single crop species is grown on a large area of land. The crop may be a staple such as wheat, corn, or soybeans, and the focus is on maximizing the yield of that one crop. While monoculture farming allows for specialized equipment and efficient practices, it often relies heavily on chemical fertilizers, pesticides, and irrigation, which can lead to soil degradation and reduced biodiversity.

• Polyculture Farming: In a polyculture system, multiple crop species are grown together in the same space. These crops may be complementary, benefiting each other through natural processes such as nitrogen fixation, pest control, and soil improvement. Polycultures aim to create more resilient farming systems by promoting biodiversity, improving soil health, and reducing reliance on synthetic inputs.

Diagram to help you understand how the land equivant ratio is calculated.

Formula for LER:

LER=   Total yield of monoculture crop /  Total yield of polyculture crop​

LER Example:

Let's say we have two crops, Corn and Beans, and we want to compare their yields in a mixed system versus if they were grown separately.

• Corn yield in mixed polyculture system: 3000 kg per hectare
• Beans yield in mixed polyculture system: 750 kg per hectare
• Corn yield in monoculture crop: 4000 kg per hectare
• Beans yield in monoculture crop: 1000 kg per hectare

LER Calculations:

Monoculture kg per hectare divided by polyculture kg per hectare

1. Total yield of Corn 

   • Total yield of crop = 4000 / 3000  = 0.75

2. Total yield of Beans

   • Total yield of bean crops =  1000 /750 = 0.75

Land Equivalent Ratio (LER):

Using those two figures

0.75 + 0.75 = 1.50

The LER helps us compare these fields.

An LER of 1.50 means that the mixed crop system is 50% more productive as the same area of land planted with a monoculture crop.

Higher LER values indicate more efficient use of land, as it means the mixed system is producing relatively more compared to the same area used for a sole crop.

LER of 1.50 means the polyculture field  is doing 50% better than the monoculture.

LER also tells us that you need 1.50% more land to grow the same amount of crops as in a polyculture crop.

Why Is the Land Equivalent Ratio Important?

The importance of LER lies in its ability to highlight the benefits of polyculture systems. By comparing the yields of mixed cropping systems to monoculture, LER provides insight into how different crops can complement each other in a way that maximizes overall productivity. Let’s explore why polycultures tend to outperform monocultures in terms of LER:

How Polycultures are More Efficient than Monocultures

Increased Biodiversity and Resilience

One of the key advantages of polycultures is their ability to support a diverse range of plant species. This increased biodiversity leads to stronger, more resilient systems. In contrast to monoculture systems, which are vulnerable to pests and diseases that target a single crop species, polycultures have natural pest control mechanisms. For example, some plants may repel pests, while others may attract beneficial insects. This reduces the need for chemical pesticides, improving both crop yields and environmental sustainability.

Nutrient Cycling and Soil Health

In polyculture systems, different crops can have complementary root structures, nutrient requirements, and growth patterns. For example, legumes like peas or beans can fix nitrogen in the soil, enriching it for other crops like corn or wheat that require higher amounts of nitrogen. This reduces the need for synthetic fertilizers, which are often used in monocultures to replenish soil nutrients. By improving soil health through diverse root systems, crop rotation, and organic matter buildup, polycultures can sustain high productivity without depleting the land.

Improved Water Efficiency

Polyculture farming systems are often more water-efficient than monocultures. Different crops have varying water needs and growth habits. For instance, shallow-rooted crops may benefit from the moisture retained by deep-rooted crops. This diversity in root structures can improve the overall water retention of the soil, reducing the need for irrigation. Monoculture systems, on the other hand, often require more water for uniform crop growth, especially in dry periods.

Reduced Risk and Enhanced Productivity

Growing multiple crops in the same space reduces the risk of total crop failure due to environmental factors such as drought, floods, or pests. Even if one crop fails, others may still thrive. This reduces the economic risk for farmers and can lead to more stable and consistent yields over time. In contrast, monoculture systems are more vulnerable to such risks since the entire harvest is dependent on the success of a single crop.

Maximising Land Use

LER demonstrates that polycultures can produce more food per unit of land than monocultures. This is because different crops in a polyculture system use the available resources (such as sunlight, water, and soil nutrients) more efficiently. By growing crops that complement each other, farmers can maximize the productivity of each square foot of land. As the LER rises above 1, it shows that the polyculture system is yielding more than what a monoculture could achieve on the same amount of land.

LER Polyculture Systems

The Land Equivalent Ratio (LER) is a powerful tool for evaluating the efficiency of polyculture systems compared to monoculture farming. As demonstrated, polycultures can provide numerous environmental and economic benefits, including increased biodiversity, improved soil health, better water efficiency, and reduced risk of crop failure. By calculating LER, farmers can make informed decisions about the best farming practices for their land, helping to create more sustainable and resilient food systems.

In the future, as the global demand for sustainable agriculture grows, polycultures will likely play an essential role in shaping the future of farming. By using tools like LER, we can better understand and embrace the potential of polyculture systems to help feed the world while preserving the health of our planet.