28 Aug Sorghum Silage Harvest Timing
As the summer winds down, sorghum silage harvest is the first of the many fall harvests that will soon be here. Sorghum silage harvest timing is one of the most important decision to be made. All other management decisions may have been made perfectly but delaying sorghum silage harvest can erase some of the gains made earlier in the year.
The ideal stage for sorghum silage to be harvested is the soft dough stage. Harvesting earlier than soft dough has fewer down sides than waiting until later in grainfill. Even though starch contents increase, and yields increase as harvested is delayed (Fig 1) the available starch to the animals fed the silage decline as the sorghum kernel becomes more mature (Fig 2.). A more mature kernel is harder and unless it is cracked by the harvesting process, may not be digested by the animal. Sorghum’s small kernel size results in pretty poor performance by kernel processors that are found on most silage harvesters.
How do know what stage you are at? There are several ways to determine if your sorghum silage crop has progressed from the milk stage to soft dough. Remove a kernel from the top of the head and if you can split it easily with your thumbnail and there is little or no milk present, the crop is at soft dough and at ideal harvest stage. Another way is to look at the grain color. As the head begins to change from green and show some “color” you are at or near soft dough (Fig 3). Sorghum typically has higher harvest moisture content than corn, so if you are monitoring silage moisture content, target dry matter levels between 30 and 35%.
Figure 1. Sorghum yield, starch content, and crude protein levels from boot to soft dough. Source: Cornell Agronomy Fact Sheet 92: Guidance for growing BMR Brachtyic Dwarf Forage Sorghum.
Figure 2. Extent of ruminal starch digestibility at soft and hard dough in silage sorghum. Source: Optimizing starch availability in Forage Sorghum. 2018 Report to Texas Grain Sorghum Board, Jourdan Bell, Texas Agrilife Bushland.
Cornell Agronomy Fact Sheet 92: Guidance for growing BMR Brachtyic Dwarf Forage Sorghum.