Nutrient movement and root uptake

The nutrient needs of corn continue to evolve, especially as modern corn hybrids and agronomic practices advance. There are a lot of factors that play a role in the nutrient needs of plants, nutrient availability and plant uptake, and nutrient utilization throughout the season. In this blog post, we’ll explore those factors, the variables at play and new approaches that can help us better provide nutrients to corn throughout the season.

Nutrient movement in the soil
Nutrients get to the corn plant in two ways – either the roots grow to the nutrient or the nutrient gets to the roots via soil water. The movement of nutrients throughout the soil profile is dependent on several factors.

  • Soil Structure: Soil structure plays a large role in how nutrients get to plants. Soil compaction can limit the ability of roots to move toward nutrients and the ability of water to move throughout the profile to get nutrients to the root system. Changes in soil density can also restrict root growth and nutrient movement.
  • Nutrient Concentration: The overall concentration of nutrients in the soil impacts movement of nutrients to the root system. Inevitably, the higher the concentration of nutrients throughout the soil profile increases the opportunity for nutrient movement to the plant. That’s why monitoring nutrient levels and ensuring available nutrients throughout the season is important.
  • Nutrient Absorption: How strongly connected are the nutrients to the soil? If strongly, it will be harder for them nutrients to freely move to the roots. Is it easier to take candy away from a toddler or a grown man?Nutrient Mobility
  • Nutrient Mobility: The speed at which nutrients can move throughout the soil profile impacts nutrient uptake, as well. Mobility varies from nutrient to nutrient. This chart shows the nutrient mobility – very mobile nutrients like nitrates (N) and sulfur (S) can move quickly through the profile and reach plant roots more easily than immobile nutrients like phosphorus (P) and potassium (K).

Nutrient uptake by the root system.
Nutrients reach the root system for plant uptake in a number of ways. Each different course is beneficial for certain nutrients depending on how those nutrients move throughout the soil profile.

  • Root Interception: Root interception is the process in which roots grow through the soil profile to come in contact with nutrients. This process is dependent on the roots to do the work and grow throughout the soil to seek out nutrients. As the root grows through the soil it generally only comes in contact with about 1% of soil volume. Good soil structure is especially important in the process of root interception. Compaction can greatly limit root growth and interception with nutrients throughout the profile.
  • Mass Flow: Nutrient movement to the roots via water is called mass flow. As the corn plant transpires water, it draws water from throughout the soil profile up through the root system. Mass flow accounts for nutrient uptake of mobile nutrients, such as nitrogen and sulfur. Nutrient concentration plays a huge role in the amount of nutrients taken up through mass flow – more nutrients available throughout the soil profile, the more nutrients that are moved by water to the root system.
  • Diffusion: During diffusion, roots grow throughout the profile and use up nutrients directly around the root system and the root hairs. As the concentration of nutrients around the root system drops, nutrients from higher concentrated areas move – or diffuse – toward low concentration areas and toward the roots. They only move a small distance, though. Potassium (K) and phosphorus (P) mostly move through diffusion. And, since P and K aren’t extremely mobile, it is important to have a high concentration of those nutrients throughout the soil, and to apply those nutrients as close to the root zone as possible.

As you can see, there are a lot of variables that impact the nutrient uptake of corn. Nutrient concentration and placement are vital to ensuring optimum uptake and utilization of nutrients throughout the season. Hear more about plant health and nutrient uptake from my presentation at 2015 Yield Summit.