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May 15, 2023

Why Elemental Sulfur Fertilizer Is a Valuable Tool in Irrigation Systems.

irrigation sprinklers in crop

Irrigation is an essential practice for crop production in key regions across North America. However, this practice can also negatively impact soil pH and sulfur availability.

In this article, we’ll explore the challenges that irrigation causes for soil pH and sulfur deficiency and how they can be mitigated with elemental sulfur fertilizer.

Irrigation can accelerate sulfur and micronutrient deficiency.

Irrigation practices can also cause sulfur deficiency in soils. Sulfate (the plant-available form of sulfur) is a relatively mobile nutrient. Continuous irrigation can cause sulfate to leach from the soil. This is a particular problem in sandy soils with low organic matter content.

High soil pH can also result in micronutrient deficiencies, such as iron, manganese, and zinc. These micronutrients are essential for plant growth, and deficiency can lead to poor plant growth and yield.

Irrigation can cause a pH imbalance.

Soil pH is critical for plant growth as it affects nutrient availability and microbial activity.

The ideal soil pH for most crops is between 6.0 and 7.0. However, irrigation can cause soil pH to rise due to the accumulation of salts in the soil. This can create stress in the plant.

The reason is that irrigation water often contains dissolved salts that can build up in the soil over time. The salts include sodium, calcium, and magnesium ions, which are positively charged and can displace hydrogen ions (H+) in the soil. This can result in the soil becoming less suitable for some crops.

An amendment using elemental sulfur can be an effective way to increase soil acidity to lower pH to the desired level in sodic soil.

“Something that I know for absolute fact is that most growers never analyze their water.”

Elston Solberg

Irrigation can also impact soil structure and water infiltration.

High soil pH can affect soil structure and reduce water infiltration, making it more difficult for crops to access water and nutrients. Depending on the salts, the soil can be affected in different ways.

Increased soil sodicity:

If the issue is specifically the accumulation of sodium (Na), this will elevate soil sodicity.

Large sodium ions get between clay particles and cause them to expand – which results in swelling and soil dispersion. This causes the soil to harden and lose its structure. Pores are sealed, which reduces permeability, infiltration and hydraulic conductivity and causes surface crusting. This prevents water from getting to the roots and can lead to erosion.

Using good irrigation water and proper irrigation methods can help reverse the effects. There are two options for soil amendment. If free lime is present, adding elemental sulfur can help lower pH which will rebuild soil structure and reverse dispersion. If not, a calcium product may be recommended.

Increased soil salinity:

An accumulation of salts such as chlorides, sulfates, carbonates, and bicarbonates (calcium, magnesium, sodium, and potassium) can cause fine soil particles to bind (a process called flocculation). There are no quick fixes using chemicals, but there are a number of recommended strategies.

Increased groundwater use is making the situation more pronounced.

River and lake water tend to impact soil pH to a lesser degree than groundwater, making it the preferred choice for irrigation. In many western states, farmers have been required to turn to groundwater for irrigation systems due to drought. This is a significant problem in the seven states that form the Colorado River Basin.

3 ways to reduce the impact of irrigation on soil health:

1. Test your irrigation water.

Based on his recent work modeling systems for irrigation expansion in Alberta and Saskatchewan, agricultural consultant Elston Solberg noted that one of the biggest challenges is that growers don’t know what’s in their water. As he shared in a recent podcast:
“Something that I know for absolute fact is that most growers never analyze their water,” Solberg said.

“Most experts out there assume that there’s a lot of sulfur coming out of the water, which is not necessarily true because it’s highly dependent on the water source.”

His advice is to get your irrigation water tested so you know what you’re dealing with and if there is potential for an issue due to salts.

2.  Use degradable sulfurs to reduce nutrient loss.

If sulfur deficiency is a challenge, farmers should be using sulfur fertilizers. This will help to increase soil sulfur levels and improve crop growth and yield.

Degradable elemental sulfur products made with bentonite clay are considerably less prone to leaching than sulfate fertilizers, as the elemental sulfur will slowly convert to sulfate. This makes them well-adapted to irrigation farming.

Another option is to provide sulfate fertilizer through fertigation. This can be done at key stages in the growing cycle.

3. Amend the soil.

If irrigation has led to a pH imbalance, you may be advised to amend your fields to improve soil structure and water-holding capacity. This can help to reduce and prevent the accumulation of salts in the soil and restore the pH balance. In many cases, elemental sulfur provides an economical solution that also addresses the impact of leaching.

Drainage is also important in sodic soils.

In a recent webinar on elemental sulfur usage, senior researcher and agri-coach Elston Solberg noted that you can’t simply put on a ton of elemental sulfur and hope for the best. He explained that the salts need a place to go, so consideration must be given to drainage. There is a broader management strategy involved.

That’s a lot to soak in!

Irrigation is essential to crop production in many areas across North America where rainfall is insufficient to meet crop needs. One of the trade-offs is the impact on soil pH and sulfur availability. However, by following best agronomic practices you can provide the moisture essential for healthy crops – while maintaining productive soil at the same time.

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