Great Bend Tribune
Published September 30, 2018
First, moisture conditions for planting compared to the last several years are much better. There is moisture, although a light rain or two wouldn’t be a bad thing. Harvest shouldn’t be delayed like last year so producers planting wheat after a summer crop shouldn’t be planting in November unless we receive heavy rains at the wrong time. The biggest problems in spots is controlling weeds and the volunteer wheat resulting from recent moisture as the area is now in the recommended start of planting based on the fly free date. Today, let’s discuss something we often don’t pay attention to since we can’t easily see them – roots.
Agronomists become excited at planting time about planting depth. For some crops they are worried about placing seed too deep while for other crops not deep enough. Naturally, producers want the seed in adequate moisture to become established and not too deep so the seedling can emerge. However, there is another reason – where the root system forms.
All crop seeds initially have a seed root termed the radical. This is the first structure to emerge from the germinating seed. In broadleaf crops such as soybeans, canola, and alfalfa, this radicle develops into the main root system – a tap root. This root system forms below the seed. From the taproot, lateral (horizontal) roots form with smaller roots and root hairs branching off from the tap root. For grass crops such as corn, wheat, grain sorghum, oats, etc., in addition to the radicle, seminal roots emerge from the seed tip. The radicle and seminal roots supply the developing seedling with water and nutrients, however, unlike in broadleaf crops, these roots don’t develop into the main root system. Instead after the seed leaf, cotyledon, emerges, the root system develops above the seed between the seed and seed leaf. This is termed an adventitious since it doesn’t arise from root tissue. Instead of a taproot with lateral branches, this root system is fibrous with many smaller roots. The broadleaf root system tends to have more roots deeper in the soil while the grasses have a shallower fibrous root system nearer the surface. As a side note, this is why our native grasses our better adapted to our climate where the average rain is 0.20” or less. Grasses are better able to take advantage of the moisture. So where does planting depth come into this?
Broadleaf crops can be planted shallower if there is adequate moisture. This matters due to the way they emerge where the whole seed is pulled out of the soil which is more challenging than with grasses. So here you are concerned about planting too deep. However, since the grass root system forms above the seed and the seed stays in the soil, you are concerned about not planting deep enough, a minimum planting depth. You don’t want the root system too shallow for obvious reasons here in Kansas. And with heavy residue on the surface, the root system can actually form above the soil and below the residue. If/when conditions turn dry, it can kill the root system. Or in the case of winter wheat, freezing temperature can damage/kill the root system. That is the root of the matter.