Western Kansas Research-Extension Centers

Fertility

Long-Term Nitrogen, Phosphorus and Potassium Fertilization of Irrigated Grain Sorghum

A. Schlegel and H. D. Bond
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 2020, N applied alone increased yields 60 bu/a, whereas N and P applied together increased yields up to 83 bu/a. Averaged across the past 10 years, N and P fertilization increased sorghum yields up to 82 bu/a. The application of 160 lb/a N (with P) produced the maximum yield in 2020, which is slightly less than the 10-year average (2011–2020). The application of potassium (K) has had no effect on sorghum yield throughout the study period. The 10-year 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). At the highest N, P, and K rate, apparent fertilizer recovery in the grain was 33% for N, 69% for P, and 40% for K. Nitrogen fertilization increased soil organic matter and decreased soil pH. Phosphorus fertilization tended to maintain or increase soil test P levels.

Long-Term Nitrogen and Phosphorus Fertilization of Irrigated Corn

A. Schlegel and H. D. Bond
Abstract: Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated corn in western Kansas. In 2020, N applied alone increased yields by 85 bu/a, whereas P applied alone increased yields 10 bu/a. Nitrogen and P applied together increased yields up to 136 bu/a which is 11 bu/a less than the 10-year average of 147 bu/a. The application of 120 lb N/a (with highest P rate) produced 98% of maximum yield in 2020, which is greater than the 10-year average (2011–2020). The application of 80 instead of 40 lb P2O5/a increased average yields 1 bu/a. The 10-year average grain N content reached a maximum of 0.6 lb/bu while grain P content reached a maximum of 0.15 lb/bu (0.34 lb P2O5/bu). At the highest N and P rate, apparent fertilizer nitrogen recovery in the grain (AFNRg) was 43% and apparent fertilizer phosphorus recovery in the grain (AFPRg) was 63%. Nitrogen fertilization increased soil organic matter and decreased soil pH. Phosphorus fertilization at 40 lb/a P2O5 was not sufficient to maintain soil test levels.

Related Publications

  • Schlegel, A.J. and J. L. Havlin. 2020. Irrigated grain sorghum response to 55 years of nitrogen, phosphorus, and potassium fertilization. Agron. J. n/a:n/a. DOI:10.1002/agj2.20453

  • Obour, A.K., A.J. Schlegel, R. Perumal, J.D. Holman, D. Ruiz Diaz. 2019. Evaluating grain sorghum hybrids for tolerance to iron chlorosis. J. Plant Nutrition. DOI:10.1080/01904167.2018.1549677

  • Schlegel, A.J., Y. Assefa, H.D. Bond, L.A. Haag, and L.R. Stone. 2017. Changes in soil nutrients after 10 years of cattle manure and swine effluent application. Soil Tillage Res. 172:48-58. DOI: 10.1016/j.still.2017.05.004

  • Schlegel, A.J. and J.L. Havlin. 2017. Corn yield and grain nutrient uptake from 50 years of nitrogen and phosphorus fertilization. Agron. J. 109:335-342. DOI: 10.2134/agronj2016.05.0294

  • Schlegel, A.J., Y. Assefa, H.D. Bond, S.M. Wetter, and L.R. Stone. 2015. Corn response to long-term applications of cattle manure, swine effluent, and inorganic N fertilizer. Agron. J. 1701-1710. DOI: 10.2134/agronj14.0632

  • Schlegel, A.J., Y. Assefa, H.D. Bond, S.M. Wetter, and L.R. Stone. 2015. Soil physicochemical properties after 10 years of animal waste application. Soil Sci. Soc. Am. J. 79:711-719. DOI: 10.2136/sssaj2014.11.0461

  • Sohm, G., C.R, Thompson, Y. Assefa, A.J. Schlegel, and J. Holman. 2014. Yield and quality of bermudagrass as a function of nitrogen rate. Agron. J. 106:1489-1496