Drought-induced nitrogen and phosphorus carryover nutrients in corn/soybean rotations in the Upper Mississippi River Basin

Authors: MEKI, NORMAN - Texas Agrilife Research; OSORIO, JAVIER - Texas Agrilife Research; STEGLICH, EVELYN - Natural Resources Conservation Service (NRCS, USDA); Kiniry, James

Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2022
Publication Date: 11/15/2022
Citation: Meki, N.N., Osorio, J.M., Steglich, E.M., Kiniry, J.R. 2022. Drought-induced nitrogen and phosphorus carryover nutrients in corn/soybean rotations in the Upper Mississippi River Basin. Sustainability. 14(22). Article 15108. https://doi.org/10.3390/su142215108.
DOI: https://doi.org/10.3390/su142215108

Interpretive Summary: When droughts reduce crop yields, nutrient uptake from the soil is reduced. When this happens, some residual nitrogen (N) and phosphorus (P) is available to subsequent crops. We applied the computer simulation model APEX to simulate continuous corn (Zea mays L.)/soybean (Glycine max [L.] Merr.) rotations on 3,703 farm fields within the Upper Mississippi River Basin (UMRB) from 1960 to 2006. We used a standardized drought index to identify the drought years, and then evaluated potential drought induced N and P carryover credits in corn/soybean rotations relative to near normal and very to extremely wet years. Corn N carryover credits during the drought years ranged from –18 to 37 kg N ha-1, while those for soybean ranged from 10 to 43 kg N ha-1. For the near normal years corn and soybean N credits ranged from –50 to 6 kg N ha-1 and 13 to 68 kg N ha-1, while for the very to extremely wet years, corn and soybean N credits ranged from –44 to -13 kg N ha-1 and 8 to 89 kg N ha-1, respectively. The corn P credits during the drought years ranged from 5 to 19 kg P ha-1, while for the near normal and very to extremely wet years, P credits both ranged from 3 to 11 kg P ha-1 but with average P credits of 6 kg P ha-1 and 8 kg P ha-1, respectively. Soybean P credits during the drought and near normal years ranged from 1 to 6 kg P ha-1, while P credits for the severe to extreme wet years ranged from 2 to 9 kg P ha-1. The magnitude of the N and P carryover credits was impacted by site-specific factors of soil type: highly erodible land vs. non-highly erodible land, soil texture, and soil hydrologic group. This paper addresses challenges of N and P nutrient management after a drought, that affects the efficiency of N and P fertilizer use in corn/soybean rotations. Accounting for plant nutrients that are retained in the soil will help optimize crop yields and nutrient use efficiency will benefit farmers, soil sustainability and offsite water quality.

Technical Abstract: Droughts reduce crop yields, which translate to reduced nutrient uptake or removal from the soil. Under such conditions, it may be possible to credit some of the residual plant nutrients such as nitrogen (N) and phosphorus (P) to subsequent crops. We applied the Agricultural Policy Environmental eXtender (APEX) model to simulate continuous corn (Zea mays L.)/soybean (Glycine max [L.] Merr.) rotations on 3,703 farm fields within the Upper Mississippi River Basin (UMRB) over a 47-year timescale:1960 to 2006. We used the Standardized Precipitation Index (PSI) to identify the drought years between 1960 to 2006, following which we evaluated potential drought induced N and P carryover credits in corn/soybean rotations relative to near normal and very to extremely wet years. Corn N carryover credits during the drought years ranged from –18 to 37 kg N ha-1, while those for soybean ranged from 10 to 43 kg N ha-1. For the near normal years corn and soybean N credits ranged from –50 to 6 kg N ha-1 and 13 to 68 kg N ha-1, while for the very to extremely wet years, corn and soybean N credits ranged from –44 to -13 kg N ha-1 and 8 to 89 kg N ha-1, respectively. The corn P credits during the drought years ranged from 5 to 19 kg P ha-1, while for the near normal and very to extremely wet years, P credits both ranged from 3 to 11 kg P ha-1 but with average P credits of 6 kg P ha-1 and 8 kg P ha-1, respectively. Soybean P credits during the drought and near normal years ranged from 1 to 6 kg P ha-1, while P credits for the severe to extreme wet years ranged from 2 to 9 kg P ha-1. The magnitude of the N and P carryover credits was impacted by site-specific factors of soil type: HEL (highly erodible land) vs. non-HEL, soil texture, and soil hydrologic group. This paper addresses the frontier challenges of N and P nutrient management after a drought, an important topic that affects the efficiency of N and P fertilizer use in corn/soybean rotations, especially given the fact that climate change-induced droughts could become more of a reality. Accounting for plant nutrients that are retained in the soil will help optimize crop yields and nutrient use efficiency with resultant benefits to farmers, soil sustainability and offsite water quality.