Statewide
This continues a series to examine production of grain sorghum vs. corn in relation to dryland and limited water conditions as well as water-use efficiency of grain sorghum vs. corn.
As noted in my previous Sorghum Tip, from an agronomic perspective, we want to know the following:
- What is the incremental change (increase) in yield per unit of available water?
- How much available water does it take to produce the first bushel of grain?
Research from several workers in Texas is summarized in the graph below for corn vs. grain sorghum. This graph is simplistic, but it is useful for explaining water use efficiency relationships for corn and grain sorghum. First note the yield relationship for both corn and grain sorghum here is portrayed as linear, and that is not the case as we move to higher water use, but rather it usually tails off some (less yield per 1” of water at the higher total water amounts). Second note that the graphs for each crop requires a minimal amount of water before the first bushel of grain is produced.
This data is mostly derived from irrigated research in the High Plains, but the principles are applicable across Texas. In this depiction, which originally reported corn and grain sorghum data prior to 2005, corn and grain sorghum yields are equal at about 20” of total seasonal water use. More recent data in the High Plains suggests the corn line (red) likely has a steeper slope meaning that the corn yield per unit of incremental water (after initial yield is obtained) has increased slightly and the “Equal Point” is at about 18”, likely the result of newer corn hybrids with new technologies in the seed (water use efficient, sometimes called ‘drought tolerant’ corn, of which there are several commercial names). This is all the result of hundreds of millions of dollars invested in corn seed and hybrid research (unlike grain sorghum) where corn has an advantage of a several dozen fold higher expenditures in developing new corn hybrids compared to grain sorghum.
In this depiction, corn is yielding 476 lbs. of grain per inch of water after initial grain yield is achieved, and grain sorghum yields 355 lbs. per inch. Other data suggests similar results between corn and grain sorghum so that in summary corn tends to yield up to 1/3 more grain per inch of available water—but only once initial grain yield is achieved. In Texas, with lower agronomic plant populations for corn it still takes 9 to 10 inches of water to get the first bushel of grain yield whereas for grain sorghum this number is much lower, as low as 5 inches of water to get the first bushel of grain yield (again, low plant population crop).
This matter of minimum water to achieve is initial grain production is a key consideration. This is why grain sorghum is a better fit for much of Texas than corn as potential grain yields are more for grain sorghum in limited water situations than for corn.
The above graph is one means to compare grain sorghum vs. corn. Two additional considerations will be noted in the next Sorghum Tip so stay tuned:
- What effect does grain price have on the corn vs. grain sorghum relationship per unit of water?
- What effect do production costs for corn and grain sorghum have in terms of profitability in response to water use?
