Last week’s column discussed the broad differences between grass crops such as corn and wheat compared to broadleaf crops such as soybeans and alfalfa. Today, let’s get more specific about differences between the two and why these differences matter.
• Germination – Grass seeds consist of the embryo, the plant, and a food source to establish the plant, the endosperm. The seed stays where it is and sends up the cotyledon to the surface protected by a sheath, the coleoptile. So only a long narrow point has to emerge from the soil. The rest of the seed stays in the soil and in most cases can be found months after emergence. In a crop like soybeans the two cotyledons, the seed leaves are the food source and the entire seed, except for sometimes the seed coat emerges above the soil. This takes more “oomph” and energy as you have to pull the cotyledons up through the soil in an arch and break through the surface.
• Growing points – The growing point in grasses stays below the soil surface for an extended period of time and is protected. For broadleaves, the growing point is above the soil surface at emergence. This matters for several reasons. First for weeds, a contact herbicide like Paraquat will kill young broadleaf weeds as they kill the growing point. But for seedling grass weeds, the growing point is protected and you need a systemic herbicide. Second, this affects planting date and the danger of frost. A frost on a seedling soybean plant can kill the growing point while the grass would only lose the above ground growth. This dictates when you can safely plant. Third, since the growth is above the growing point in grasses, it is much easier to graze grasses compared to alfalfa. In alfalfa, when it is grazed or hayed, you are removing all the growing points and dormant growing points are activated. In grasses, you keep the growing point and growth immediately resumes. Think of your grass lawn and how rapidly is grows after mowing.
• Root system – For a broadleaf crop like soybeans, the seed root (radicle) becomes the main root system as a tap root below the seed. For a grass crop like corn the radicle sticks around for a while and roots termed seminal roots develop and support the developing plant early on. However, the root system that develops into the main root system forms above, not below, the spot where the seed was planted from what are termed adventitious roots. This isn’t a taproot system but a fibrous root system and is much closer to the soil surface than the taproot system. This is important for two reasons. First, even with good soil moisture a producer has to be careful not to plant the seed to near the surface or the root system will be vulnerable to desiccation or if there are surface residues, it may even form on the soil surface. For the broadleaf plant, the shallow planting has less impact as the root system forms below the seed. Second, here on the Great Plains, grasses can better survive our rainfall patterns since most precipitation events are 0.20 inches or less and don’t penetrate deeply into the soil. Grasses are better positioned to take advantage of this pattern.
Next week will wrap up this topic. For now, enjoy the Memorial Day Weekend and reflect on those who gave their life for our liberty and safety.

Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.