Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/1997
Publication Date: N/A
Interpretive Summary: Cultivation of soils in the warm and semiarid climate of the Southern Plains contribute to the decline in organic matter (OM) and weak structure of soils. Various tillage equipment are used to mix and aerate the soil, and to incorporate soil amendments, cover crops, and crop residues into the tillage zone. Tillage also exposes organic matter in soil particles and aggregates to rapid decomposition. The loss causes a continual decline in organic matter and lowers the productivity of the soil. Carbon dioxide gas loss was measured in soils that either have been plowed or no-till. The goal was to relate changes in soil gases to differences in OM storage that can be attributed to the use of a particular tillage and crop residue management method. Large pulses of carbon dioxide loss were generated from plowed soils immediately after tillage or rain and lasted about three days. Each soil-engaging activity or operation contributed from 0.4 to 0.6% of the soil OM content in a 60-day period at an average of 54 lbs. of OM per acre per day. In no-till soils, carbon gas loss was constant and at half or two-third lower in size. It was concluded that tillage could be reduced to decrease C loss and the resultant degradation in soil quality. Adoption of conservation tillage could result in net increases in organic matter storage in agricultural lands.
Technical Abstract: Short-term CO2 fluxes following wheat (Triticum aestivum L.) harvest were determined in year 11 of a tillage study established on a Paleustoll. Soil respiration was measured from 1 Aug. to 30 Sept. using closed chambers. Treatments were tillage methods (moldboard plowing [MT] and no-till [NT]) and crop residue rates (0 and 4 Mg ha**-1 standing or buried at 0.20 m). Peak flux densities ranged from 2.9 to 4.1 g m**-2 d**-1 in MT soils without and with buried residues, and lasted for 77 hr. Flux densities in NT soils ranged from 1.3 to 1.4 g m**-2 d**-1 that decreased to a steady- state of 0.4 g m**-2 d**-1 after 53 hr. CO2-C pulses coincided with ATP accumulations and water additions to MT soils. Such events did not cause a corresponding increased release of CO2-C in NT soils. Organic C levels differed between tillage plots in 0 to 0.2-m depth but no difference in short-term effects of residue removal on OC was detected. Respired C in the 60-d period accounted for 0.19 to 0.22% and 0.42 to 0.58% of whole soi OC in NT and MT soils, respectively. Residues and tillage method affected C mineralization and atmospheric fluxes, suggesting that tillage intensity could be decreased to reduce C loss and resultant degradation in soil quality.