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Biomass- and Sweet Sorghum responses to Nitrogen Fertilizer


The search for alternative sources of energy to limited fossil fuels has turned attention to sorghum as a potential dedicated bioenergy crop. Sorghum hybrids can provide biomass or sugars for subsequent conversion to bioenergy but responses to agronomic management, such as nitrogen fertilization, can vary.

In the July-August issue of Agronomy Journal, researchers sought to determine the effect of five nitrogen fertilization rates two dedicated bioenergy sorghums. During the four year trial, five nitrogen application rates (0, 67, 134, 201, and 268 kg N ha-1 yr-1) were applied to biomass (Blade ES5200)-sorghum and sweet (M81-E)-sorghum. The researchers found that N fertilization increased dry matter yield in 2 out of the 4 years for biomass sorghum and there was no effect of N fertilization rate for sweet sorghum. The results indicated no further increase in dry matter yield for N rates above 67 kg N ha-1 with a maximum yield of ~18.5 Mg ha-1 for biomass sorghum and ~13.0 Mg ha-1 for sweet-sorghum.

High dry matter yields achieved in a single clipping event at the end of the growing season support sorghum as a potential dedicated bioenergy crop and highlight its potential to be productive in low input, especially N, systems. Nevertheless, the relatively lower nutrient removal rates may limit its utilization in nutrient-rich environments, such as those receiving large quantities of nutrients and water in spray fields, that require crops able to uptake large amount of nutrients to prevent accumulation in the soil.

Read the full paper in Agronomy Journal Free Preview Aug 28 - Sept 4