The summer months of 2013 were definitely more conducive to growing a reasonable corn plant under less stress than 2012, the year with what seemed we lived too close to the furnace. This year at the Orthman Research & Demonstration Farm we planted large 32 row plots x 30 inch row spacing corn by 1500 feet long of Conventionally tilled compared to Strip-Till and No-Till, plots were adjacent to one another. We planted a 111 day maturity group of corn on the 10^th of May. All plots were fertilized the with N-P-K-S-Zn and micro nutrients and irrigated the same.  Planting population was 32K seeds per acre.  Final stand was 29.5K-30.25K.

As you observe the diagrams below of our numerous root digs which depict what was happening below ground the last week of July, you will see what much cooler soils, some soil compaction and lack of precision fertilizer placement to the root development.

2013 Summer Program

The two views you see of the rooting from this year’s corn growth offers me as a soil scientist a perspective that tillage and fertility placement can enhance the rooting potential. With the strip-till, we placed N-P-K-S-Zn prior to planting which enhanced the growth and expansion of the rootzone. We saw the strip-tilled zone warm early for the rooting environment to encourage the seedling root and first two sets of nodal roots to grow as profuse as possible which is from the shallow (4-5 inch) placement of fertility. Then since we apply the 9-10 inch depth portion of the pre-plant fertility program, the nodal roots number 3, 4, & 5 will expand outwards and deep as possible. Thusly giving you the grower the best rootzone to absorb nutrients and water for a top notch yield unless some storm event wreaks havoc.

As irrigators in South Central Nebraska under pivot irrigation, we do apply a portion of the Nitrogen required for the corn crop through an injection system at the pivot center point.  Both tillage trials received the same total amount of N.  Under the No-Till or Direct Seeding system we applied with drop nozzles right on the soil surface where the seed would be placed via the RTK guided tractor 92lbs of N 14 days ahead of the planter.  The strip-till was within a day of that timeframe but applied with the 1tRIPr below the soil surface at 4 and 10 inches deep at a 30% shallow and 70% deep approach.  For us and many other strip-tillers this is a common approach/methodology to supply pre-plant fertilizers with the 1tRIPr.

Discussion Of Our Observations

We see the rooting profile in the Direct Seeding method more shallow roots in the upper 14-18 inches of the soil profile, as depicted from actual root digs at Lexington, Nebraska shown on the left just below.  On the right is the corn plants no more than 5 feet away of the No-Till plot is our strip-till which is depicted on the right.  You see the Strip-Till system, same corn variety, on the right immediately below. (Diagrams are from actual root dig, late June 2013)

No-Till Corn 2013 – 111 day variety corn

Strip-Tilled Corn 2013 – 111 day variety

From 2 feet on down, the strip-tilled crop (on the right) has a higher quantity of roots to absorb water when the temperatures remain high after tassel and pollination. Something of a generalization (rule of thumb) for every 1000 cubic inches of soil explored by roots, the plant is able in medium textured or heavy textured soils to absorb another gallon of water, similar to another 1 to 2 inches of rain. That is significant with today’s hybrids.

As a deep rooted corn variety can explore and obtain more moisture below 18 inches the crop potential is more assured. We know with corn the root system is opportunistic, some say lazy, when it can exist in a cooler environment early to mid season, the rooting profile remains shallow. Often in a Direct Seeding environment the soils remain less than 60-63°F up to late June (Northern Hemisphere) in the first 24-30 inch depth.  As I have written before and spoke to the issue of the University of Georgia study 1999-2001 where scientists studied the prime root growing environment for numerous crops including corn – 60-63°F is below the optimal soil temperature for lateral root development. So as the soil warmed slowly, the left over residue kept the soils much cooler the dominance of lateral and vertical roots remained in the upper 18 inch depth.

With sprinkler irrigation as is our system on the Orthman Farm, adding cold aquifer water of 48-50°F, the soils remain cooler keeping root development shallow. This scenario is something of a two edged sword for gaining a full capacity rooting profiles.  How do I mean?

In weather patterns that turn off hot (93-105°F) quickly and rain events dry up – shallow roots will take the entire moisture available, struggle to get root growth again for the deeper segment of the soil profile and be negatively affected in growth and yield. Yes, cooling down the soil profile is helpful to the overall respiration of the corn plant with the addition of 50°F water. Consider the natural rainfed corn farmer, his/her corn when roots when they are shallow and little to no deep penetration of nodal roots being the norm – corn again will suffer.

Under a strip-till system, a grower has a much better opportunity to allow the soil profile to warm early (April into June for the Northern Hemisphere - September into early November for the Southern Hemisphere) and as the summer continues the soils warm deeper and roots will follow the warming front downward.  This has been something we have observed quite consistently at the Orthman Research Farm as well as many studies I have conducted across the Great Plains of the U.S.

In Conclusion

As we have observed this year (2013) and years past, gaining deeper root systems as the corn hybrid allows – we have realized with Strip-Till bigger/taller plants, stronger, healthier corn plants which will yield more kernels per cob.

We have done numerous kernel count per ear by our agronomy team, Product Specialists, agronomists from partners involved with our research and seed dealers.  Their initial counts are finding 10 to 60 kernels less per ear in the Direct Seeding plots compared to the Strip-Till plots.  When we nose the combine into the field we will know the truth of the matter.