Statewide
This begins a four-part series to examine production of grain sorghum vs. corn in relation to dryland and limited water conditions and water-use efficiency of grain sorghum vs. corn. Subsequent tips will discuss the amount of water needed for initial grain production as well as the results for grain production per one inch of water.
Here are some basics of grain sorghum vs. corn when available moisture is limited†:
- Heat unit accumulation: Corn HU are capped at 86°F whereas grain sorghum’s cap is 100°F. The corn HU cap should be re-examined in light of more recent corn developments, but it remains that grain sorghum is a more “heat efficient” crop than corn.
- Grain sorghum is self-pollinated (unless you grow a hybrid seedblock). Grain sorghum produces heads over a broader time period as tillers can be initiated and developed over several weeks. Thus short periods of drought are unlikely to seriously damage pollination and fertilization in grain sorghum. During prolonged drought, sorghum produces fewer, smaller heads but seed set is usually not impaired—you get grain. Corn is cross-pollinated and is especially vulnerable to heat and drought/ conditions at critical 2 to 3 days of silking which could lead to poor seed set. In contrast, grain sorghum flowering normally occurs over a 7 to 10 day period, so the crop is not nearly as vulnerable to a short hot spell.
- For good corn production the relationship between plants per acre and moisture supply availability is often critical but much less so with sorghum. With abundant soil moisture sorghum heads grow large and tillers that may produce heads are more likely developed. In drought conditions sorghum heads are small with a significant reduction in tillering or tiller head development as the plant adapts itself to the environment. Consequently, sorghum growers within limits can plant higher populations for potentially high yields (high plant populations for grain sorghum particularly in dry regions of Texas are too risky due to drought stress). Corn growers may choose between high populations for maximum yields or lower populations with less chance of serious loss from drought.
- Sorghum foliage resists drying. At equal moisture stress, corn leaves lose a greater percentage of water content than sorghum. Sorghum’s waxy coating on leaves and stems may be an important cause, the coating giving leaf sheaths a sticky, frosty appearance.
†Partially adapted from ‘Grain Sorghum,’ Alternative Crops Field Manual, Purdue Univ.
