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Title: Soil-test biological activity in corn production systems: I. Soil C and N characteristics and associations

Author
item Franzluebbers, Alan
item PERSHING, MARY - North Carolina State University
item CROZIER, CARL - North Carolina State University
item OSMOND, DEANNA - North Carolina State University
item SCHROEDER-MORENO, MICHELLE - North Carolina State University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2018
Publication Date: 5/10/2018
Citation: Franzluebbers, A.J., Pershing, M.R., Crozier, C., Osmond, D., Schroeder-Moreno, M. 2018. Soil-test biological activity in corn production systems: I. Soil C and N characteristics and associations. Soil Science Society of America Journal. 82:685-695.

Interpretive Summary: Soil testing for nitrogen availability in cropping systems is currently not practiced due to lack of appropriate methodology that is rapid and reliable. Scientists from USDA-ARS in Raleigh NC and North Carolina State University evaluated a suite of soil carbon and nitrogen tests to associate with net nitrogen mineralization potential of soils collected from North Carolina and Virginia. A simple, rapid, and reliable indicator was highly related to nitrogen mineralization potential across the 47 fields evaluated. Soil textural class had little influence on the overall calibration, although sand concentration was a statistically significant variable that altered the calibration by less than 1%. This evaluation corroborated the use of a simple, rapid, and reliable indicator (the flush of CO2 during 3 days) for soil-test biological activity that could be used to predict nitrogen availability. These results will be valuable for farmers wanting to make efficient applications of nitrogen to enhance profit and steward natural resources.

Technical Abstract: Nitrogen limits crop production when insufficient and harms the environment when excessive. Tailoring N inputs to cropping systems remains a high priority to achieve production and environmental goals. We collected soils from 47 corn production fields in North Carolina and Virginia at depths of 0-10, 10-20, and 20-30 cm and evaluated soil C and N characteristics in association with soil N mineralization. Soil organic C at a depth of 0-10 cm varied among sites from 10 to 80 g/kg, and generally declined with depth due to many sites with no-tillage management. Net N mineralization during 24 d of aerobic incubation (25 deg C, 50% water-filled pore space) was 54-114 mg N/kg/24 d at 0-10 cm, 22-41 mg N/kg/24 d at 10-20 cm, and 12-22 mg N/kg/24 d at 20-30 cm (middle 50% of observations at each depth). Total soil N was highly associated with net N mineralization (r2 = 0.58), but the flush of CO2 during 3 d was even more closely associated with net N mineralization (r2 = 0.77). Association between the flush of CO2 and net N mineralization did not change significantly when data were sorted by different regions or soil textural classes. This evaluation corroborated the use of the flush of CO2 as an appropriate indicator for soil-test biological activity with requirements for being rapid, reliable, and robust. The strong association of the flush of CO2 with net N mineralization also corroborated use of the flush of CO2 as a rapid and reliable indicator of soil N availability.