Document: ANN-3-59-76

The effect of compost and crop diversity on nutrient availability and potential carbon sequestration.

FORTUNA, A.*, E.PAUL and R.HARWOOD

Michigan State University, East Lansing, MI 48824 USA 1

Abstract:
It has been estimated that compost and residue management can offset up to 50% of the radiative forces attributed to agriculture. The sequestration of C affects the mean residence time (MRT) of C and N in soil organic matter (SOM) pools and increases the size of SOM pools fostering ecosystem sustainability. The Living Field Lab at the Kellogg Biological Station, begun in 1993, measures the interaction of crop rotation and cover crop use with compost or fertilizer applications on soil quality and productivity. Cropping treatments are continuous corn (CC) and a 4 y rotation, corn-corn-soybean-wheat (CCSW). Cover crops are crimson clover, red clover, and annual ryegrass. The fine- loamy, mixed, mesic typic haplaudalfs were sampled at a 0- 25 cm depth in 1993 and 1998 prior to tillage. Laboratory incubations indicated that the pool of potentially mineralizable organic N (N0) on compost treatments was 47 g N kg-1 soil N in 1994 and was elevated to 70 in 1998. The MRT of N more than doubled during 4 y of compost applications (246 to 768 d). Cumulative CO2-C respired to 150 d from the CC treatment with cover crop and compost, increased from 503 g C g-1 soil in 1994 to 580 in 1998. The CC treatment with cover crop and N fertilizer respired 656 g C g-1 soil in 1994 but only 579 in 1998. There were few differences between crops within the rotation. Incubation data are fit by non-linear regression to obtain slow and active pool size estimates and MRTs. The MRT of the slow pool is approximately 9 y. The slow pool constitutes 40% of the total soil C on average and is the pool that must be managed for C sequestration and sustainable agriculture. Many of the compost constituents have a field turn-over rate of several years and directly increase C sequestration.

Keywords: carbon sequestration, C & N kinetics, compost, rotations, cover crops

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