ARS | Publication request: Nitrogen rates for biomass sorghum production across tillage systems

Submitted to: Southern Conservation Agricultural Systems Conference
Publication Type: Abstract Only
Publication Acceptance Date: December 20, 2012
Publication Date: N/A

Technical Abstract: Biomass yields and nutrient removal across different tillage systems and nitrogen rates are not well established for forage sorghum (Sorghum bicolor L. Moench) grown as an energy source in the Southeast. An experiment was initiated in long-term conventional and conservation tillage systems on a Compass loamy sand to determine total dry matter (TDM) production and selected nutrient uptake across six different N rates (0, 34, 67, 101, 134, 168 kg ha-1) and two sorghum cultivars, a photoperiod sensitive (ES 5200) and a non-photoperiod sensitive sweet sorghum (Sugar T) with four replications. Total dry matter yields averaged 16.3 Mg ha-1 (2010), 15.4 Mg ha-1 (2011) and 16.5 Mg ha-1 (2012) across N rates, tillage systems, and cultivars. Preliminary optimum N fertilizer rates were between 101 and 134 kg N ha-1. Nitrogen uptake was highest in 2010 (148.8 kg ha-1) compared to 2011 (99.3 kg ha-1) and 2012 (110.4 kg ha-1), but was not consistent across tillage systems. Phosphorus uptake for the top three N rates increased 21% compared to no N, but this was only observed for ES 5200. Potassium uptake was 22% greater in 2010 (162.2kg K ha-1) compared to 2011 (132.8 kg K ha-1), but was inconsistent across tillage systems and sorghum cultivars. However, preliminary results indicate that root knot nematode (Meloidogyne incognita) numbers were increased under the ES 5200 cultivar. As a result, TDM yields for this cultivar were consistent, but much lower than expected. This study is an on-going study with one more year of data collection planned. Results to date have shown some inconsistencies that may be attributed to the nematode pressure observed with the ES 5200 cultivar, but results for the sweet sorghum cultivar appear to be unaffected by nematodes.