Title: The effect of nitrogen fertilization and cover cropping systems on sorghum grain characteristics Authors
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 2013
Publication Date: May 27, 2013
Citation: Kaufman, R.C., Wilson, J.D., Bean, S.R., Presley, D.R., Blanco-Canqui, H. and Mikha, M.M. 2013. The effect of nitrogen fertilization and cover cropping systems on sorghum grain characteristics. Journal of Agricultural and Food Chemistry. 61:5715-5719. Interpretive Summary: Sorghum is the 5th leading cereal grain produced worldwide. Due to sorghum’s tolerance to heat and drought conditions it is commonly grown under non-irrigated conditions in semi-arid parts of the United States, such as Kansas, Oklahoma, and Texas. The practice of no-till farming has become an increasingly popular cropping system, due to increased water and soil conservation. Recently, cover cropping has been added to the system to aid in weed prevention and also increase soil fertility. This study investigated different levels of nitrogen on a no-tilled soil with differing preceding cover crops (Sunn hemp and soybean) grown on specific plots. The nitrogen fertilization and cover cropping systems appeared to enhance the soil by increasing both total soil nitrogen and soil organic carbon. Results also indicate cover crop systems provided an increase in the agronomic effect as well as overall sustainability of the production system without causing negative effects on end product quality. The treatments also increased the amount of protein in the grain without reducing digestibility, thus allowing for greater digestible protein yield. Since, cover cropping appears to provide both agronomic and end product quality benefits, increased utilization of this cropping system could be useful as another tool for the producer interested in sustainable agriculture.
Technical Abstract: The practice of no-till farming has become an increasingly popular cropping system, due to increased water and soil conservation. Recently, cover cropping has been added to the system to aid in weed prevention and also increase soil fertility. The objective of this study was to determine the effect of cropping system and nitrogen (N) fertilization on sorghum grain properties. The experimental design was a 3x4 factorial with three cover crop treatments (none, soybean, and Sunn hemp) crossed with four N rates (0, 33, 66, and 100 kg ha-1) in plots following the harvest of winter wheat. A sorghum hybrid was then planted the following spring in each plot. The hardness and size of kernels was measured by the single kernel characterization system (SKCS). The average kernel hardness across all N rates was 74.7, 74.6, and 69.7 for soybean, Sunn hemp, and none, respectively. The kernel weight and diameter was also significantly larger for the cover crop treatments compared to no cover crop. The soybean cover crop had the highest protein content at 9.2% followed by Sunn hemp at 8.8% and no cover crop at 8.2%. The 0 and 33 kg ha-1 N rates had significantly lower hardness values (68.7 and 70.0) than the 66 and 100 kg ha-1 (76.2 and 77.3) treatments. The protein content of the grains ranged from 8.1% in the 0 kg ha-1 rate to 9.5% in the 100 kg ha-1 rate. The protein digestibility values and starch granule size distributions were not affected by N rate or the cover cropping treatments. The utilization of cover crops appears to increase the protein content without causing a deleterious effect on protein digestibility. The end-product quality is not hampered by the use of beneficial cropping systems necessary for sustainable agriculture.