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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #301747

Research Project: Soil Processes in Production Systems that Incorporate Biofuel Feedstocks into Southeastern Agriculture

Location: Southeast Watershed Research

Title: Effect of conservation practices on soil carbon and nitrogen accretion and crop yield in a corn production system in the southeastern coastal plain, USA

Author
item Strickland, Timothy - Tim
item Scully, Brian
item Hubbard, Robert - Retired ARS Employee
item Sullivan, Dana - Turf Scout,llc
item Savabi, Reza - Retired ARS Employee
item Lee, Dewey - University Of Georgia
item Olson, Dawn
item Hawkins, Gary - University Of Georgia

Submitted to: Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: 7/27/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary: Although conservation tillage is widely believed to be an agricultural management practice effective for increasing soil carbon accretion and associated soil quality, there is limited research suitable to determine whether conservation tillage increases net carbon accretion versus simply altering the distribution of carbon content by soil depth. We implemented conservation farming practices (winter cover cropping plus strip tillage) for a non-irrigated corn production system in the southern coastal plain of Georgia, USA that had been previously been managed under a plow and harrow tillage regime. Conservation farming practices increased soil carbon 20 Mg ha-1 with 3-6 Mg C ha-1 of the increase at a soil depth of 35-65cm. Carbon stored in the soil was 36% of the total crop biomass produced. Corn yield increased 2200 kg ha-1 during the same time and data suggest that the yield increase was from a soil carbon mediated an increase in plant-available soil water. Calculations of increased soil water holding capacity suggest that carbon accretion in the top 35cm may have increased water storage enough to supply up to four days worth of additional crop water demand. These results indicated that conservation farming practices can increase soil carbon accretion in degraded sandy soils of the humid southeastern US coastal plain, and that increased soil carbon may mitigate the deleterious effects of short term rainfall deficits in non-irrigated production systems.

Technical Abstract: We implemented conservation farming practices (winter cover cropping plus strip tillage) for a non-irrigated corn production system in the southern coastal plain of Georgia, USA that had been previously been managed under a plow and harrow tillage regime. Total soil carbon and nitrogen were measured on samples (0-65cm) collected from 57 sites at the beginning of the experiment and after five years under conservation farming practices. Crop yield, winter and summer above ground crop biomass production, and biomass carbon and nitrogen content were also measured annually at each site. Soil carbon increased an average of 20 Mg ha-1 (6-62 Mg C ha-1, depending upon slope position). Although 72-80% of the carbon accretion was in the top 35cm, 3-6 Mg C ha-1 was accreted from 35-65cm. The soil carbon accreted during the study amounted to 36% of the net biomass carbon produced. Corn yield increased 2200 kg ha-1 (1200-2500 kg ha-1, depending upon slope position) during the same time. Step-wise multiple linear regression indicated that soil carbon content from 15-35cm and sand content from 35-45cm were the only significant predictors of corn yield. Growing season rainfall through silking for both corn production years was the lowest in the past 45 years (20-25cm below the net crop demand) suggesting that soil carbon-mediated increase in plant-available soil water was the mechanism improving corn yield. Calculations of increased soil water holding capacity suggest that carbon accretion in the top 35cm of soil potentially increased water storage enough to supply up to four days worth of additional crop water demand. These results indicated that conservation farming practices can increase soil carbon accretion in degraded sandy soils of the humid southeastern US coastal plain, and that increased soil carbon may potentially mitigate the deleterious effects of short term rainfall deficits in non-irrigated production systems.