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Title: CARBON SEQUESTRATION AND AGGREGATE SIZE DISTRIBUTION AS AFFECTED BY CROPPING INTENSITY

Author
item Mikha, Maysoon
item Vigil, Merle
item Benjamin, Joseph
item Nielsen, David
item Henry, William
item Calderon, Francisco

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2005
Publication Date: 11/9/2005
Citation: Mikha, M.M., Vigil, M.F., Benjamin, J.G., Nielsen, D.C., Henry, W.B., Calderon, F.J. 2005. Carbon sequestration and aggregate size distribution as affected by cropping intensity. Agronomy Abstract. Presented at the 2005 ASA, CSSA-SSSA International Annual Meeting. Nov. 6-10, 2005. Salt Lake City, UT.

Interpretive Summary:

Technical Abstract: The predominant cropping system in the Central Great Plains winter wheat summer fallow (W-F) is not sustainable. Intensive cropping systems with reduced tillage and fallow frequency are management practices that provide more residues and may increase soil C and N content. This study investigated the effect of five different crop rotations on soil total C (TC), total N (TN), yield, and aggregate-size distribution. The experiment was established in 1990 on a Weld loam (fine, smectitic, mesic aridic Paleustolls). Various cropping intensities comprised of winter wheat (Triticum aestivum L.), corn (Zea mays L.), proso millet (Panicum miliaceum L.), seed pea (Profi Pea), and fallow were evaluated. In 2004, soil samples were collected from 0- to 5 and 0- to 15-cm depths. Sample from 0- to 5-cm depth were separated into four aggregate size fractions, macroaggregates (>1000 and 250-1000 micron) and microaggregates (53-250 and 20-53 micron) by wet sieving. Fourteen years of continuous cropping improved soil TC compared to NT and CT W-F rotation at 0- to 15-cm depth. Continuous cropping such as W-C-M, significantly (p < 0.1) increased soil TC (0- to 5-cm) compared with NT W-F and W-C-F cropping systems. Soil TC and TN significantly (p < 0.05) increased with NT W-F compared to CT W-F especially at 0- to 5 cm depth. More than 40% of TC and TN was associated with 0- to 5 cm depth except for CT W-F were TC and TN represent 35 and 33% of 0- 15 cm, respectively. Eight year average Wheat yields were significantly affected by cropping intensity. Aggregate-size distribution was affected by tillage but not by cropping intensity. Across cropping intensity, more than 45% of the sand-free water-stable aggregates were associated with microaggregates rather than macroaggregates. Generally, NT and continuous cropping with reduced fallow frequency improved soil TC and yield.