19 Apr Sorghum Seeding Rates
Sorghum Seeding Rates
Seeding rates get a lot of attention in most crops and the reality is that unless you are making drastic changes, what happens in the field is much different than you think. For crops that have a tremendous ability to compensate, slight changes in seeding rates often have no impact on yields. Sorghum, wheat, soybean, and cotton fit this group. These crops have very wide seeding rate optimum ranges.
Grain sorghum seeding rates should be yield goal driven. Having higher seeding rates in high yielding fields increases your chances of maximizing yields. Lower seeding rates in lower yielding environments reduces seed costs and might reduce stress should drought stress occur. Despite what many believe, to actually reduce the impact of water stress, more drastic measures need to be taken like skip rows or bunch planting. Drastic reductions in seeding rates are needed to reduce canopy development enough to reduce water use and mitigate drought stress. These lower sorghum seeding rates might reduce yield potential should the field experience good growing conditions.
Sorghum seeding rates are often based on rainfall which implies a yield potential. The following table can be found in Grain Sorghum 101 on our Sorghum Partners web site and a similar table can be found in Kansas State Universities Sorghum Management publication (MF3046). If you are planting in narrow rows using an air seeder or drill, we recommend that you use the upper end in each group.
As sorghum planting is delayed, tiller production goes down. The pros and cons of tillers are subject to debate, but tillers are one way that sorghum compensates for environmental changes during the growing season. If tiller production is reduced by late planting, sorghum becomes more like corn with head size being the most important component of yield. Increasing seeding rates to adjust for lower tiller survival in late plantings or double crop plantings are necessary. (Figure 1). Increasing seeding rates by 20% is a good recommendation in these scenarios.
Figure 1. Tiller contribution to sorghum yields by plant density and planting date (Jaiyesimi, 1979)
Links and Citations
Jaiyesimi, S.T. 1979. Yield and tillering response of grain sorghum to planting date and density. Ph.D. Dissertation. Kansas State University. 50 p.