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Abstract Efforts to address economic and environmental concerns surrounding nitrogen (N) have motivated attempts to improve estimates of plant‐available N in soil. Several soil health indicators, including CO 2 burst, permanganate oxidizable carbon (C) (POXC), and autoclaved‐citrate extractable (ACE) soil protein, assess labile C and N, and therefore may help to estimate soil N mineralization in long‐term cover cropping systems (>3 years). This study evaluated the relationship of CO 2 burst, POXC, ACE‐soil protein, and pre‐sidedress nitrate test (PSNT) with agronomic optimum N rate (AONR) in corn ( Zea mays L.). The study also looked at relationship between other soil test and corn yield parameters, relative yield (RY) and yield without N sidedress at 25 long‐term cover crop sites across Virginia. Results showed relatively weak correlations between AONR and CO 2 burst, POXC, ACE‐soil protein, and NO 3 ‐N ( r = 0.00 to −0.48), which indicates that these soil health tests may not reliably predict soil N availability and corn yield. Corn yield with zero‐sidedress N rate had a negative relationship with cover crop C:N ratio ( r = −0.66) and a positive relationship with cover crop N content ( r = 0.59), and NO 3 ‐N at pre‐planting ( r = 0.54) and sidedress (PSNT) ( r = 0.63). The PSNT showed a better relationship ( r = 0.65) compared to 72‐h CO 2 burst ( r = 0.48) with RY. Soil health indicators (CO 2 burst, POXC and ACE‐soil protein) resulted in a poor or no relationship with AONR. Our results indicate that the PSNT was a more reliable indicator of the sidedress N rate in corn.
Pokhrel et al. (2024) studied this question.