AJPS  Vol.8 No.8 , July 2017
The Effects of Stabilized Urea and Split-Applied Nitrogen on Sunflower Yield and Oil Content
Abstract: Sunflower is an efficient nitrogen (N) accumulator due to its aggressive taproot and extensive root system. While N rate studies in sunflower have shown a yield response, the response is often highly variable and difficult to predict in many instances. Additionally, since most sunflower production is intended for the oil market, surplus nitrogen tends to decrease oil content. Therefore, it is critical to hone nitrogen rates to maximize both yield and oil production and to incorporate alternative approaches to fertilizer application, which includes timing and method of application. The objective of the present study was to assess the efficacy of a split-application of N at either the V4 or R1 growth stage to increase yield and/or oil content in sunflower. A second objective was to examine whether a urease inhibitor could be used to retain soil N longer and achieve a similar effect as a split-application. Studies were conducted at two locations over two growing seasons in South Dakota, USA. A target rate of 90 kg·ha-1 was applied as urea-ammonium nitrate (UAN) either as an at-planting application or split-applied. Overall, N additions did significantly increase yield over a control. On average, the urease inhibitor tended to increase grain yields over split-applying N at either growth stage, however, there was no statistical effect on either grain yield or oil content. Based on 15N analysis, approximately 27% of the N in the grain was derived from the UAN fertilizer, which indicates a relatively large reliance upon soil N for grain N content. The addition of a urease inhibitor significantly increased average fertilizer uptake by nearly 6% to 32.7%.
Cite this paper: Graham, C.J. and Varco, J.J. (2017) The Effects of Stabilized Urea and Split-Applied Nitrogen on Sunflower Yield and Oil Content. American Journal of Plant Sciences, 8, 1842-1854. doi: 10.4236/ajps.2017.88125.

[1]   R Development Core Team (2011) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria.

[2]   Dardanelli, J.L., Bachmeier, O.A., Sereno, R. and Gil, R. (1997) Rooting Depth and Soil Water Extraction Patterns of Different Crops in a Silty Loam Haplustoll. Field Crops Research, 54, 29-38.

[3]   Connor, D.J. and Sadras, V.O. (1992) Physiology of Yield Expression in Sunflower. Field Crops Research, 30, 333-389.

[4]   Kuznetsova, A., Brockhoff, P.B. and Bojesen-Christensen, R.H. (2016) lmerTest: Tests in Linear Mixed Effects Models. R Package Version 2.0-30. (accessed 11/15/2016).

[5]   Zubriski, J.C. and Zimmerman, D.C. (1974) Effects of Nitrogen, Phosphorus, and Plant Density on Sunflower. Agrononmy Journal, 66, 798-801.

[6]   Schatz, B., Miller, B., Zwinger, S. and Henson, B. (1999) Sunflower Response to Nitrogen Fertilizer. Proceedings of the 21st Sunflower Research Workshop, Fargo, ND., 193-197.

[7]   Scheiner, J.D., Gutierrez-Boem, F.H. and Lavado, R.S. (2002) Sunflower Nitrogen Requirement and 15N Fertilizer Recovery in Western Pampas, Argentina. European Journal of Agronomy, 17, 73-79.

[8]   Steer, B.T., Hocking, P.J., Kortt, A.A. and Roxburgh, C.M. (1984) Nitrogen Nutrition of Sunflower (Helianthus annuus L.): Yield Components, the Timing of Their Establishment and Seed Characteristics in Response to Nitrogen Supply. Field Crops Research, 9, 219-236.

[9]   Goswami, B.K. and Srivastava, G.C. (1988) Effect of Foliar Application of Urea on Leaf Senescence and Photosynthesis in Sunflower (Helianthus annuus L.). Photosynthetica, 22, 99-104.

[10]   Davidson, E.A., David, M.B., Galloway, J.N., Goodale, C.L., Haeuber, R., Harrison, J.A., Howarth, R.W., Jaynes, D.B., Lowrance, R.R., Nolan, B.T., Peel, J.L., Pinder, R.W., Porter, E., Snyder, C.S., Townsend, A.R. and Ward, M.H. (2012) Excess Nitrogen in the U.S. Environment: Trends, Risks and Solutions. Issues in Ecology, 15, 2-16.

[11]   Foley, J.A., DeFries, R., Asner, G.P., Bradford, C., Bonan, G., Carpenter, S.R., Chapin, F.S., Coe, M.T., Daily, G.C., Gibbs, H.K., Helkowski, J.H., Holloway, T., Howard, E.A., Kucharik, C.J., Monfreda, C., Patz, J.A., Prentice, I.C., Ramankutty, N. and Snyder, P.K. (2005) Global Consequences of Land Use. Science, 309, 570-574.

[12]   Galloway, J.N., Aber, J.D., Erisman, J.W., Seitzinger, S.P., Howarth, R.W., Cowling, E.B. and Cosby, B.J. (2003) The Nitrogen Cascade. BioScience, 53, 341-356.[0341:TNC]2.0.CO;2

[13]   Vitousek, P.M., Aber, J.D., Howarth, R.W., Likens, G.E., Matson, P.A., Schindler, D.W., Schlesinger, W.H. and Tilman, D.G. (1997) Human Alteration of the Global Nitrogen Cycle: Sources and Consequences. Ecological Applications. 7, 737-750.[0737:haotgn];2

[14]   Halvorson, A.D., Snyder, C.S., Blaylock, A.D. and Del Grosso, S.J. (2014) Enhance Defficiency Nitrogen Fertilizers: Potential Role in Nitrous Oxide Emission Mitigation. Agronomy Journal, 106, 715-722.

[15]   Van, E.H.M., Kay, B.D., Melkonian, J.J. and Sogbedji, J.M. (2007) Nitrogen Management for Maize in Humid Regions: Case for a Dynamic Approach. In: Bruulsema, T., Ed., Managing Crop Nutrition for Weather, International Plant Nutrition Institute Publisher, Philadelphia, 70-74.

[16]   Hatfield, J.L. and Venterea, R.T. (2014) Enhanced Efficiency Fertilizers: A Multi-Site Comparison of the Effects on Nitrous Oxide Emissions and Agronomic Performance. Agronomy Journal, 106, 679-680.

[17]   Motavalli, P.P., Goyne, K.W. and Udawatta, R.P. (2008) Environmental Impacts of Enhanced-Efficiency Nitrogen Fertilizers. Crop Management, 7.

[18]   Schneiter, A. and Miller, J.F. (1981) Description of Sunflower Growth Stages. Crop Science, 21, 901-903.

[19]   Follett, R.F., Porter, L.K. and Halvorson, A.D. (1991) Border Effects on Nitrogen-15 Fertilized Winter Wheat Microplots Grown in the Great Plains. Agronomy Journal, 83, 608-612.

[20]   Sanchez, C.A., Blackmer, A.M., Horton, R. and Timmons, D.R. (1987) Assessment of Errors Associated with Plot Size and Lateral Movement of Nitrogen-15 when Studying Fertilizer Recovery under Field Conditions. Soil Science, 144, 344-351.

[21]   Bates, D., Maechler, M., Bolker, B. and Walker, S. (2015) Lme4: Linear Mixed-Effects Models Using Eigen and S4. Journal of Statistical Software, 67.

[22]   Pena, E.A. and Slate, E.H. (2006) Global Validation of Linear Model Assumptions. Journal of the American Statistical Association, 10, 341-354.

[23]   Hocking, P.J. and Steer, B.T. (1983) Distribution of Nitrogen during Growth of Sunflower (Helianthus annuus L.). Annals of Botany, 51, 787-799.

[24]   Hatfield, J.L. and Parkin, T.B. (2014) Enhanced Efficiency Fertilizers: Effect on Agronomic Performance of Corn in Iowa. Agronomy Journal, 106, 771-780.

[25]   Vrebalov, T. (1974) Rate of N, P, K Assimilative Uptake of Sunflower Variety VNIIMK 8931. Proceedings of 6th International Sunflower Conference, Bucharest, 22-24 July 1974, 205-212.