Statewide
A frequent question across Texas is whether a grain sorghum producer should increase the seeding rate if moving to narrower row spacing. Most Texas grain sorghum is planted on 30-, 36-, 38-, or 40-inch rows. In general, Texas A&M AgriLife recommends that you do NOT increase the per-acre seeding rate when moving to narrower rows for several reasons:
- Many producers are actually already dropping as much if not more seed than they probably need for good production.
- If moving to a narrower spacing, let the additional space around the individual plant be the means of compensating for slightly higher yield potential. Grain sorghum does indeed compensate, and if there is more space around an individual plant, the plant will likely tiller more in response to the environment.
- Maintaining the same per-acre seeding rate is easier if you are using an air-vacuum planter that meters the seed and also has the same or similar equipment to achieve good placement of the seed.
- What about drilling grain sorghum seed?—In this case producers must be careful. We like the idea of spreading your plants out, however, most drills were not made to drop such small amounts of seed, 5 lbs. down to as little as 2 lbs., per acre. Drills measure volume of seed, not seed number. You probably can’t get most drills shut down enough, especially if they are older and worn some. If you are drilling, expect to tape or close off at least 1 of 3 drops and perhaps 1 of 2 drops. Drills do not place seed as well as planters, hence reduced seedling establishment may be expected, especially if not irrigated. Due to reduced optimum seed placement, I will allow an increase in per-acre seed drop by 10% – in other words, not much!—if you are drilling. If seedbed conditions are truly rough, then perhaps 20% increase in per acre seeding rate; however, if you get a good rain, and it all comes up, you are immediately over-populated. (If field conditions are truly rough, then use the planter anyway for managing the best seed placement you can get.)
- Moving to narrow row spacings means you forego the opportunity to conduct mechanical cultivation for weed control. Thus you have a question of narrow row spacing for weed suppression vs. retaining the ability if needed to cultivate. Since grain sorghum has few aerial over-the-top weed control options, if you anticipate weedy issues, you may prefer to not close the door on cultivation if it becomes necessary.
