More roots = happier plants!

A New Look at How Strip-Tillage Gives an Advantage Due to Larger Root Length to Soil Volume – This Affects Plants to Tolerate Stress Better

by Michael Petersen, Lead Agronomist

For 8 years now we at Orthman have been honing our skills to better understand what happens with strip-tillage and corn rooting. How is this all happening so corn plants can tolerate heat and drought stress better?

Figure 1: A top-notch seedbed to plant into – Courtesy Greenfield Ag, Ohio

It is our agronomic opinion that we are first accomplishing with the Strip-till implement a “better seedbed” to establish an environment where the germinating plant can extend a longer and more profuse seedling root. We have seen this in corn, cotton, grain sorghum and soybeans with strip-till compared to conventional tillage and direct seeding. Our observations have been at 15 days after emergence (DAE) and 25 DAE with the monocots (corn and grain sorghum), and 25DAE with the dicots (soybeans and cotton).

What are those factors? First, we are seeing warmer soils in the upper 4 inches (10cm) of the soil profile in the strip-till zone– from 1 to 7 degrees Fahrenheit warmer. With cotton, grain sorghum and soybeans (which all germinate closer to 58 – 60° F), those few degrees of temperature are vital to good germination and stand establishment. I’m not saying it is not important for corn, but corn does tolerate a few degrees cooler. A critical point – the soil density for the seedling root in the zone that is strip-tilled is very conducive to root elongation and early lateral root development off the seedling root with Strip-Till. All of this early root development feeds the plant, gets the plant off on the right foot so to speak when the inevitable chill of May comes and then heat of the summer. We all know the wind will blow hard at some point in the first 25-30 days of growth after emergence. Having a well established root system will not only anchor the plant but help it sustain life.

Secondly, as farmers are placing nutrients with more precision these days (which we highly recommend with the Orthman 1tRIPr) the roots are in direct contact with the nutrient source and will continue to thrive going into the critical stages of the life cycle. It is well known that crop roots are the dominant site (>98%) where nutrients are absorbed and taken into the plant for photosynthesis and carbohydrate storage – yield. This second pillar, “Precision placement of fertility” is talked about often here at Orthman as being vital to higher sustained yields. For instance in corn; near the time of 45 DAE the corn genetic road map has determined the number of kernel rows around the cob. Having a rich environment of nutrients (whether organic or inorganic) around the roots can influence the switches to be turned on across the gene map to expand from 12 to 14 to 16 to 18 or even 20 rows. More availability to the nutrients and roots accessing those products invigorates the plant to establish a larger ear, offering that multiplier effect. Having a larger root length density (RLD) which we will expand upon here shortly in this article is critical for the grower to reach higher yield potentials.

The 3rd pillar of the Precision Tillage concept is having an optimal root zone to facilitate an environment for more water and nutrient uptake for the planted crop. This underground environment is unseen by most and really needs to be considered, whether you are a grower, fertilizer dealer, or even agronomist in the field. I have spent 40+ years digging to understand the “ways” of the soil system as a soil scientist and it is important that all understand this message. The physical distribution of roots in the soil profile is dominated and affected by several factors:

  1. Gravity
  2. Soil temperature
  3. Soil moisture
  4. Chemistry of the soil solution
  5. Soil density
  6. Crop root architecture [crop genetics]

Of those six, gravity, soil chemistry and the wet/dryness are not changeable without irrigation.

Soil temperature in the spring can be altered slightly as mentioned earlier.

Maintaining residues on the soil surface can help hold moisture, add to soil foodstuffs for microbes and critters in the soil as well as mycorrhizal fungi helping nearly all crops.

Soil density is something tillage can alter (either for good or it can be detrimental).

Crop rooting architecture is a given but can be facilitated to reach all of its potential with Strip-Tillage.

Let us consider the root-zone from a Strip-Tillage perspective: first, early soil warm-up. Getting that germination started with good seed-to-soil contact, warmer for the early root system, right in the presence of readily available nutrients – like feeding a toddler on into the teen years when food is inhaled and kids shoot up. Feed them properly and they perform whether kids or corn and soybeans. For instance, proper nutrition and a soil environment is conducive to root expansion without limitations. By the time it is 75 days old, a corn plant can have a root system over 750 feet in total length and longer – precise placement of nutrients with Strip-Till is a big part of that success. We have actually measured over 1,326 feet of total root length under one corn variety that was strip-tilled in Eastern Colorado studies. Growers across the United States can tell you that amount of roots will be way bigger than they can imagine in a strip-till system, especially when we consider that rootworm pressure, nematodes, root rots, compaction, early water logging, and cold soils all take away from a crops root proliferation.

Figure 2: Robust corn root system at 25DAE with strip till

That brings us to how much of a root system is important to making the plant a “big crop”, especially in a year when rainfall is considerably limited? So think on this; Root Length Density (RLD) is defined as root length per unit volume of soil [cm root/cm3 soil]. If RLD averages above 0.35cm/cm3 below the 80cm (36 inches) depth, the corn plant will be able to pump water from depth to the upper portion of the root system and sustain life much longer than plants with lower RLD. When we can help promote an even larger RLD for the entire rooting profile with Strip-Tillage (such as measured in Nebraska and Colorado in 2013 over 3.95 cm/cm3 at two different study sites!), the concept is onto something! Those same studies show a full-width tillage rooting system of just 2.35 cm/cm3. It is our goal with Precision Tillage and placement of fertilizer products to encourage plants of corn to grow deeper, expand into more segments of the soil profile so to absorb more water and nutrients which in turn leads to better yields and dry matter.

Other researchers have measured in natural rainfed agriculture root systems that had RLD’s of 0.7 to 1.25 cm/cm3.

Here in at Orthman we have seen the value of establishing a strong and dynamic root system making yield differences every year at the Orthman Research Center near Lexington, Nebraska. Getting you an ideal seedbed, placing fertility in the root pathway and making sure you have an optimal root zone is what strip-till growers benefit from. M

Do not hesitate to call or e-mail amy of us on the agronomy team . We want to be a resource for you, as strip-till is the fastest growing smart and sensible tillage method on the planet.

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