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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. 2018. Soil-test biological activity with the flush of CO2: III. Corn yield responses to applied nitrogen. Soil Science Society of America Journal. 82:708-721. Interpretive Summary: Soil testing for nitrogen availability in cropping systems requires a rapid and reliable indicator to assess nitrogen availability. A scientist from USDA-ARS in Raleigh NC evaluated corn grain and silage response to sidedress nitrogen application in a series of 47 field trials throughout North Carolina and Virginia. Relative yield with no sidedress nitrogen application was positively associated with plant available nitrogen (residual inorganic and mineralizable fractions) and with the simple indictor of the flush of CO2 following rewetting of dried soil. Yield production with initial dose of nitrogen fertilizer and economically optimum nitrogen fertilizer requirement were negatively associated with nitrogen availability indices. The strong negative association of the flush of CO2 with yield response to initial dose of nitrogen fertilizer corroborated use of the flush of CO2 as a rapid and reliable indicator of soil N availability. These results will be valuable for farmers wanting to make efficient applications of nitrogen to enhance profit and steward natural resources. Technical Abstract: Corn (Zea mays L.) is an important cereal grain in many states and typically receives large N fertilizer inputs, irrespective of historical management. Tailoring N inputs to soil-specific conditions would help to increase efficiency of N use and avoid environmental contamination. A total of 47 trials were conducted on research stations and private farms in four different regions of North Carolina and Virginia from 2014-2016 to associate soil N availability with yield response to sidedress N application. Corn grain yield was 10.6 +/- 3.4 Mg/ha on 36 sites and silage yield was 44.6 +/- 8.2 Mg/ha on 11 sites. Relative yield without sidedress N application compared with no N limitation was associated with both plant available N (residual inorganic N + net N mineralization during 24 d) and the flush of CO2 following rewetting of dried soil during 3 days. Economically optimum N fertilizer requirement (EONR) at sidedress declined with increasing level of plant available N and soil-test biological activity (i.e. the flush of CO2). The scalable N factor for production at EONR declined from 20 kg N/Mg grain (1.1 lb N/bu grain) with no soil biological activity to no N required with soil-test biological activity of 600 mg CO2-C/kg soil/3 d (0-10-cm depth). The flush of CO2 when determined in spring at or prior to planting corn was considered an ideal soil-test indicator of soil biological activity due to its simple, rapid, and reliable characteristics related to potential soil N mineralization and corn yield responses to applied N fertilizer. |
