Santos, D. and A.J.M. Smucker
Presented at the All Scientist Meeting (1996-07-16 to 1996-07-17 )
Soil structure as affected by management influences a wide range of soil properties which in turn control crop productivity. The relationships between aggregates and soil organic matter within tilled and non-tilled agroecosystems are poorly understood. Studies on the potential of managing soil aggregation for storage and sequestration of organic carbon in soils will provide information on how changes related to cultivation affect incorporation and decomposition of organic carbon into soil aggregates.The objective of this study is to verify how different cropping and soil management systems affect recent root and soil organic matter sources of carbon sequestered at the surfaces and at layers within soil aggregates. Soils are being sampled from a tillage experiment on Kalamazoo loam (fine-loamy, mixed, mesic Typic Hapludalf). The experiment was initiated in 1988 on a soil previously under meadow (>80 years), in a randomized complete block design with six treatments and four replicates. The six treatments are: continually cropped (with the following cropping sequence: corn, bromegrass, corn, soybeans, corn and switched to alfalfa in 1995) under conventional – (CT) and no-tillage (NT) management either with (F) or without (NF) nitrogen fertilization, as well as undisturbed meadow plot (>80 yrs), (NM), and meadow plot altered by cultivation (AM) at the beginning of the experiment.Samples have been taken from replicated treatment plots at the beginning and throughout the growing season. Four soil subsamples are being collected from each plot at 0 to 5 and 5 to 15 cm depth, combined in a composite sample and stored field moist, at 4 öC, prior to analysis. All samples are sieved (20-mm opening), prior to drying, re-wetting and wet sieving, to remove stones and crop stubble and to define the maximum dimensions of the aggregates for analysis. A method for removing different concentric layers of forming aggregates has been developed and tested. It will be used in combination with 13C analysis to evaluate the distribution of recently incorporated carbon using in different size fractions along a cross section through individual aggregates. In addition, data on carbon content and distribution within aggregates and its correlation with some soil physical and chemical properties will be obtained. The objectives and hypotheses forwarded include:
Back to meeting | Show |