ABSTRACT
Soil organic matter (SOM) has been reduced by cultivation in many agroecosystems, irrespective of climatic and edaphic characteristics. Losses of soil carbon (C) have contributed significantly to global carbon dioxide (CO2) levels. Quantifying SOM dynamics as related to agroecosystem management is fundamental to identifying pathways for soil C sequestration. This chapter examines the effect of crop sequence on soil organic C concentration, source, and C dynamics. A field study with 14 crop sequence treatments was initiated in 1981 at the University of Minnesota Southwest Experiment Station near Lamberton, MN. The treatments consisted of various lengths of corn and soybean crop sequences including continuous corn and continuous soybean. The chapter analyses only eight of these treatments. Soil samples from continuous corn and continuous soybean crop sequence treatments were physically separated into primary size fractions. Sub-samples were gently crushed by hand and passed through a 2 mm sieve.
