The ultimate guide to field drainage systems

With ever-growing global food demands, the agricultural industry is constantly searching for ways to maximize the quantity and quality of crop yields. Soil health and composition take center stage in these efforts as decades of intensive farming begin to take their toll on soil fertility.

When it comes to soil composition, farmers aim for a golden ratio of 50% soil, 25% air, and 25% water. These are the conditions in which most agricultural crops will thrive and achieving it can be the difference between a profitable harvest or one that simply drains resources.

This is where field drainage is having a significant impact, especially in parts of northern Europe where rain is frequent and increasingly heavy.

_{Why do farmers need field drainage?}

The golden ratio comes under threat when there is too much rainfall in a short period of time. As rain is absorbed, the groundwater table rises, and air is pushed out — jeopardizing the 50:25:25 balance.  

The consequences of too much water in the soil include poor root development, limited yields, crop disease, soil erosion, and flooding — just to name a few. Field drainage offers a relatively simple solution to keep these issues at bay and ensure farmers have more control over the quality and quantity of their harvests. 

_{What are field drainage systems and how do they work?}

Field drainage systems vary in complexity, but in simple terms, they consist of subsurface pipe networks. The pipes are perforated at the top so water can drain into the line and be carried away. 

The process works like this:
 

• Rain enters the soil

• Gravity pulls it down through the soil structure until it reaches the groundwater table

• As rainfall increases, the water table rises

• As the water table rises above the buried pipeline, it is drained through holes in the top side of the pipe

• The pipe network carries the excess water away, usually to a nearby waterbody or non-arable land

• The water table lowers, and the soil composition is restored

_{Evaluating the impact of field drainage} 

While the basic functionality of field drainage systems might be clear, it is still necessary to determine exactly how worthwhile the investment is and what any potential shortcomings may be.

We’ll address these concerns in the following breakdown to give an in-depth understanding of why and how these systems could make the difference to a successful harvest. 

_{The business view}

_Cost 

Field drainage systems are expensive. They are extensive, custom jobs that require specialized machinery, expertise and soil analysis. The investment required may be beyond reach for many farmers, but subsidies for this kind of land improvement infrastructure are increasingly offered by the European Union.  

While cost can be a major obstacle, the impact field drainage can have on yields generally leads to the systems paying for themselves within a few years.

_{Increased yields and productivity gains} 

Drainage systems help achieve the ideal proportions of water, air and soil in a field. This is critical for excellent root development and disease prevention, which in turn ensure crops grow plentiful, strong and resilient against changing weather patterns.

There are also significant operational benefits to having a well-drained field. Seeding can begin earlier in the season and field work can resume faster after heavy rains thanks to faster soil drying times.  

_{Agronomic performance}

_{Nutrient absorption}

As the water table rises and air is pushed out, the soil becomes a low-oxygen environment. Plant roots depend on oxygen to generate the energy required to take on nutrients and water in the soil. Even if there is plenty of water around, oxygen starved roots will struggle to absorb it. 
 

_{Root resilience} 

A lower water table encourages healthy downward root growth as plants go in search of water. When the water table is high, roots tend to grow horizontally rather than vertically, which reduces the plant’s structural integrity and leaves it vulnerable to high winds.

The vertical root development stimulated by drainage is also great preparation for the dry season. During periods of drought, the water table drops even lower. But given the roots have already grown to a healthy depth, they are more likely to be successful in finding the lower water table. Roots that have remained near the surface in their early development will have no chance when the water table drops significantly in dry summer months. 

_{Organisms and denitrification}

The beneficial bacteria, insects and fungi that create healthy soil need air. Oxygen-loving microbes break down organic matter in the soil, making the nutrients available for plants to absorb.

Conversely, low-oxygen soils allow disease-causing organisms to thrive and even create certain types of bacteria that steal oxygen from the nitrates in fertilizers, rendering them useless.

Field drainage systems help maintain air content in the soil, so it remains a fertile environment for the organisms that keep crops healthy.  

_{Nutrient loss} 

A concern some farmers have about field drainage is nutrient leaching. As water is removed from the soil, it takes fertilizer and minerals with it — wasting resources and minimizing growth opportunities.

However, a good field drainage expert will conduct a thorough soil analysis before installation. When the soil profile is understood, they can design the system to be laid at a depth where the vast majority of nutrients remain in the soil. Soil is a natural filter and water that enters the pipe should be of near drinking water quality. 

That said, farms that use a lot of fertilizer may not be able to fully rely on the natural filtering properties of soil. In these cases, carbon-rich biochar distributed under the soil has been proven to absorb nitrogen and phosphorus, ensuring these nutrients remain in the soil mass as the water drains.
 

_Salinization

Farms in coastal areas can have higher saltwater content in their soil. Since saltwater naturally sits lower in the ground than freshwater, it is mainly freshwater that gets evacuated through field drainage — leaving behind a higher saltwater concentration in the soil.

In the absence of a strong protective layer of freshwater, the saltwater can move upwards through capillary action into the root zone, which can be detrimental to crop growth. 

However, this is not necessarily an issue with field drainage; it’s a recognition of how important it is to find the right system for each specific field. In farms that are vulnerable to salinization, a closed drainage system can make all the difference.

Instead of freshwater being drained away from the field entirely, it is harvested and reused to irrigate the field when fresh groundwater levels get too low to protect the root zone against encroaching saltwater.

_{Environmental risks and mitigation} 

_{Flood damage and water pollution}

Without drainage, heavy rain on waterlogged fields can lead to soil erosion and runoff. Here, the chance of nutrient leaching is much higher as water hasn’t filtered through the soil and instead runs off the surface — taking dissolved fertilizer and soil with it.

This runoff can cause the eutrophication of local waterbodies and harm the wildlife that live there. In extreme cases, soil erosion can even toxify drinking water sources.

Flooding can also have huge consequences for roads, railways and buildings as runoff is uncontrolled and indiscriminate. When field drainage is seen as preventative measure against the cost of flood damage, many find the upfront costs more palatable. 

Well drained soil has the structure needed for heavy rain to deeply penetrate and reach the water table, or filter through and drain into the pipe network to be conveyed to a safe place.

_{Plastic in the ground}

An environmental argument against field drainage systems is that they use plastic piping. While the material properties of PVC, PP and PE make them well suited to underground drainage, burying plastic in the ground can of course have long-term consequences if it is not responsibly disposed of.

However, modern field drainage systems come in a wide variety of setups that include compostable and recyclable components, and are designed to last at least 50 years.

_{Types of field drainage systems}

Depending on the topography, soil profile and location, different fields can have vastly different drainage requirements with varying levels of complexity.

_Traditional

Traditional field drainage systems focus purely on removing excess water from the soil to prevent waterlogging and improve soil conditions.

These are the most common systems and work on the basic principle discussed earlier: Water in the soil is drained away once the water table rises above the pipeline.

_{Level-controlled}

Level-controlled drainage systems are a step more advanced: They gives farmers manual control over groundwater levels by choosing when to allow the pipe contents to drain.

Retaining rainwater in the soil like this can reduce irrigation needs and minimize nutrient runoff. It’s ideal for regions with fluctuating rainfall or irrigation challenges, helping to maintain consistent moisture levels in the soil.

Closed harvesting systems also come under this category, but vary in that instead of retaining the rainwater in the soil, they harvest the drained water and use it for reirrigation when necessary.

_{Climate-adaptive} 

Climate-adaptive drainage systems use real-time data to anticipate weather changes and automatically adjust the soil moisture in preparation for extreme conditions — lowering groundwater levels if heavy rain is expected, for example.

These are all-encompassing solutions that require minimal active input from the farmer and are best suited in areas with unpredictable and intense weather changes.

_{Cultivating a reliable future}

At its core, field drainage helps reclaim control over the growing environment. By maintaining the perfect balance of air, water and soil, farmers can ensure their crops have the best possible chance to grow strong and healthy.

While the high upfront installation costs remain a hurdle for many, the long-term gains in yield, operational flexibility and flood prevention make a strong case for the return on investment.

Couple this with arguments for making the most of fertilizers and the environmental benefits to local water bodies, and it becomes clear that field drainage has an important role in farms that hope to run a sustainable operation.

While specific land and operational requirements will determine the most suitable system, there is no doubt field drainage can provide farmers with much needed reliability in a climate of increasingly extreme weather, over-farmed land and wavering markets.