Long-Term Nitrogen and Phosphorus Fertilization of Irrigated Grain Sorghum

Kansas Agricultural Experiment Station Research Reports, Aug 2016

Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated grain sorghum in western Kansas. In 2015, N applied alone increased yields 66 bu/a, whereas N and P applied together increased yields up to 92 bu/a. Averaged across the past 10 years, N and P fertilization increased sorghum yields up to 76 bu/a. Application of 40 lb/a N (with P) was sufficient to produce 88% of maximum yield in 2015 which is slightly above the 10-year average. Application of potassium (K) has had no effect on sorghum yield throughout the study period. Average grain N content reached a maximum of ~0.7 lb/bu while grain P content reached a maximum of 0.15 lb/bu (0.34 lb P2O5/bu) and grain K content reached a maximum of 0.19 lb/bu (0.23 lb K2O/bu).

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Long-Term Nitrogen and Phosphorus Fertilization of Irrigated Grain Sorghum

Kansas Agricultural Experiment Station Research Reports Long-Term Nitrogen and Phosphorus Fertilization of Irrigated A. Schlegel 0 1 2 H. D. Bond 0 1 2 Kansas State University 0 1 2 0 1 2 0 Kansas State University , USA 1 This report is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Kansas Agricultural Experiment Station Research Reports by an authorized administrator of New Prairie Press. Copyright , USA 2 Kansas State University Agricultural Experiment Station and Cooperative Extension Service , USA Follow this and additional works at: https://newprairiepress.org/kaesrr Part of the Agronomy and Crop Sciences Commons Recommended Citation Schlegel, A. and Bond, H. D. (2016) "Long-Term Nitrogen and Phosphorus Fertilization of Irrigated Grain Sorghum," Kansas Agricultural Experiment Station Research Reports: Vol. 2: Iss. 6. https://doi.org/ - Long-Term Nitrogen and Phosphorus Fertilization of Irrigated Grain Sorghum Abstract Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated grain sorghum in western Kansas. In 2015, N applied alone increased yields 66 bu/ a, whereas N and P applied together increased yields up to 92 bu/a. Averaged across the past 10 years, N and P fertilization increased sorghum yields up to 76 bu/a. Application of 40 lb/a N (with P) was sufficient to produce 88% of maximum yield in 2015 which is slightly above the 10-year average. Application of potassium (K) has had no effect on sorghum yield throughout the study period. Average grain N content reached a maximum of ~0.7 lb/bu while grain P content reached a maximum of 0.15 lb/bu (0.34 lb P2O5/bu) and grain K content reached a maximum of 0.19 lb/bu (0.23 lb K2O/bu). Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 License. This southwest research-extension center is available in Kansas Agricultural Experiment Station Research Reports: https://newprairiepress.org/kaesrr/vol2/iss6/10 Kansas Fertilizer Research 2016 Long-Term Nitrogen and Phosphorus Fertilization of Irrigated Grain Sorghum Summary Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated grain sorghum in western Kansas. In 2015, N applied alone increased yields 66 bu/a, whereas N and P applied together increased yields up to 92 bu/a. Averaged across the past 10 years, N and P fertilization increased sorghum yields up to 76 bu/a. Application of 40 lb/a N (with P) was sufficient to produce 88% of maximum yield in 2015 which is slightly above the 10-year average. Application of potassium (K) has had no effect on sorghum yield throughout the study period. Average grain N content reached a maximum of ~0.7 lb/bu while grain P content reached a maximum of 0.15 lb/bu (0.34 lb P2O5/bu) and grain K content reached a maximum of 0.19 lb/bu (0.23 lb K2O/bu). Introduction This study was initiated in 1961 to determine responses of continuous grain sorghum grown under flood irrigation to N, P, and K fertilization. The study is conducted on a Ulysses silt loam soil with an inherently high K content. The irrigation system was changed from flood to sprinkler in 2001. Procedures This field study is conducted at the Tribune Unit of the Southwest Research-Extension Center. Fertilizer treatments initiated in 1961 are N rates of 0, 40, 80, 120, 160, and 200 lb/a N without P and K; with 40 lb/a P2O5 and zero K; and with 40 lb/a P2O5 and 40 lb/a K2O. All fertilizers are broadcast by hand in the spring and incorporated before planting. The soil is a Ulysses silt loam. Sorghum (Pioneer 8500/8505 from 2006–2007, Pioneer 85G46 in 2008–2011, Pioneer 84G62 in 2012-2014, and Pioneer 86G32 in 2015) was planted in late May or early June. Irrigation is used to minimize water stress. Sprinkler irrigation has been used since 2001. The center two rows of each plot are machine harvested after physiological maturity. Grain yields are adjusted to 12.5% moisture. Grain samples were collected at harvest, dried, ground, and analyzed for N, P, and K concentrations. Grain N, P, and K content (lb/bu) and removal (lb/a) were calculated. Results Grain sorghum yields in 2015 were 22% greater than the 10-year average (Table 1). Nitrogen alone increased yields 66 bu/a while P alone increased yields 13 bu/a. However, N and P applied together increased yields up to 92 bu/a. Averaged across the past 10 years, N and P applied together increased yields up to 76 bu/a. In 2015, 40 lb/a N (with P) produced about 88% of maximum yield, which is slightly above the 10-year average of 84%; 120 lb/a N (with P) and 160 lb/a N (with P) produced 98% and 100% of maximum yield, respectively. Sorghum yields were not affected by K fertilization, which has been the case throughout the study period. The 10-year average grain N concentration (%) increased with N rates but tended to decrease when P was al (...truncated)


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A. Schlegel, H. D. Bond. Long-Term Nitrogen and Phosphorus Fertilization of Irrigated Grain Sorghum, Kansas Agricultural Experiment Station Research Reports, 2016, Volume 2, Issue 6,