Effects of Row Spacing and Population Density on Yield of Sweet Sorghum: Applications for Harvesting as Billets

Abstract

As an emerging biofuel feedstock, sweet sorghum [Sorghum bicolor (L.) Moench] could perhaps most readily be integrated into sugarcane production systems where existing harvesters can be utilized to process the crop. This will require row spacing compatible with the harvesters, but the literature on row spacing and planting density in sweet sorghum is scarce and gives conflicting results. In North Florida in the 2012 and 2013 growing seasons, we therefore examined the effects of row spacing configurations (61 and 76 cm single rows, 71 by 107 cm double rows (DR), and 35.5 by 35.5 by 107 cm triple rows) and initial plant population densities (74,100; 98,800; 123,500; and 148,200 plant ha−1) on fresh biomass yield, Brix, estimated sugar yield, and stem diameter. We found no advantage of multiple row configurations (double and triple rows) in 2012 on biomass yield, Brix, or estimated sugar yield, and a definitive disadvantage in 2013 compared to the single row treatments. The 61‐cm single row treatment, which is amenable to harvest with a sugarcane harvester, yielded as well or better in 2013, depending on population density, than commonly used 76‐cm single rows, which cannot be harvested with a sugarcane harvester. The data also highlighted the cultural tradeoff that exists between increasing initial plant population density and decreasing stem diameter. Considering this tradeoff, an intermediate initial plant population density, such as 123,500 plants ha−1, was found to best optimize yield and stem diameter to facilitate sweet sorghum harvest as billets.