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Solutions to simultaneously meet crop phosphorus (P) demand and reduce P loss from agricultural systems are required to improve the sustainability of our production. Our objective was to determine the effect of cover crop addition (with cover crop [CC], and without cover crop [NC]) and P fertilizer management (zero P control [CN], fall broadcast [FB], and spring injected [SI]) on P cycling, agronomic P use efficiency (PUE), and environmental P use efficiency (EPUE), measured as the percent of P lost in runoff water, in a no‐till corn (Zea mays)–soybean [Glycine max (L.) Merr.] rotation. The experiment was a 2 × 3 factorial. Both FB and SI increased P cycling through the main crop and cover crop tissue, compared to the CN. Cover crop did not affect main crop P uptake, removal in grain, or return to soil in crop residue, but CC treatment increased total P uptake and return in the system. Cover crop effects on P uptake, removal, and return were the same regardless of P fertilization treatments. Phosphorus fertilizer and CC treatments did not affect PUE. Both FB and SI P fertilizer management decreased EPUE, although SI tended to decrease EPUE less than FB. Cover crop significantly improved EPUE only in 2019, when CC reduced erosion losses. Therefore, cover crops were not consistently beneficial for reducing the environmental effects of P fertilization, and their use cannot replace the importance of sound P fertilizer stewardship, including sub‐surface P placement. However, cover crops play an important role in improving EPUE in years with high erosion loss potential. Core Ideas: Cover crops increased total P return to the soil surface by 30%.Agronomic phosphorus use efficiency was not affected by cover crops or phosphorus fertilizer management.Cover crops had variable effects on environmental phosphorus use efficiency.Reducing P loss is the most important factor for improving environmental P use efficiency. [ABSTRACT FROM AUTHOR]

Cover crops (CCs) have been promoted as a key strategy to reduce nitrous oxide (N2O) emissions by scavenging excess mineral nitrogen (N) after cash crop harvest. Optimum N fertilizer application rates are also critical to minimize N2O emissions. Integrating these strategies requires research to understand how they interact to drive N2O emissions. The objective was to evaluate N2O emissions from winter wheat (Triticum aestivum L.) harvest through the subsequent fallow period and grain sorghum [Sorghum bicolor (L.) Moench] production phase of a long‐term, no‐till winter wheat–grain sorghum–soybean [Glycine max (L.) Merr] cropping system. Fallow management treatments included chemical fallow (CF), double‐crop soybean (DSB), and two CCs: sorghum‐sudangrass (Sorghum bicolor × sorghum bicolor var. sudanese) and daikon radish (Raphanus sativus L.). Nitrogen fertilizer rates (0, 90, and 180 kg ha−1) were applied within 1 wk after sorghum planting. Soil nitrate‐N was consistently greater in CF than in the other treatments during the fallow period. Although, on average, CCs and DSB decreased cumulative N2O emissions (cN2O) by 1.75‐fold, during the fallow period compared to CF, they significantly increased cN2O in the following sorghum crop. Emissions increased with greater applications of N regardless of how the fallow was managed, indicating that N fertilizer application in the following sorghum tended to offset any potential mitigating effects of CCs and DSB. These results highlight the importance of evaluating N2O emissions for the system (fallow + following cash crop) to account for potential tradeoffs that could offset cN2O mitigation when N fertilizer is applied. [ABSTRACT FROM AUTHOR]