Journal Title
Title of Journal: Biogeochemistry
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Abbravation: Biogeochemistry
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Publisher
Kluwer Academic Publishers
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Authors: Yu Jia FengMin Li XiaoLing Wang JinZhang Xu
Publish Date: 2006/06/03
Volume: 80, Issue: 3, Pages: 233-243
Abstract
We explore the dynamics of soil organic carbon of various forms and its relation with soil fertility in seeded alfalfa grassland established using a field microcatchment technique to harvest water on the semiarid Loess Plateau in China Five regimes were set up 1 conventional flat cultivation without mulch CK 2 ridges and furrows were set up alternately on flat land with 15 cm between each so that the distance between successive ridges or successive furrows was 30 cm and the ridges were mulched with plastic film M30 3 similar to M30 but with twice the distance between furrows and ridges M60 4 similar to M30 but the ridges were not mulched B30 5 similar to M60 but the ridges were not mulched B60 The increase in alfalfa forage yield in the mulch regimes promotes soil organic carbon SOC content the light fraction of organic carbon LFOC the heavy fraction of organic carbon HFOC and microbial biomass carbon MBC MBC was significantly higher in M30 and M60 than in the other regimes Significant positive correlation is found between MBC and LFOC R=089 P00001 and MBC and HFOC R=082 P=000016 At the end of our threeyear experiment the C/N ratio of 1009 in M60 was significantly P0005 higher than the other regimes Since a lower C/N ratio accelerates SOC decomposition in this region the higher C/N ratio in M60 could limit mineralization of soil nitrogen conserving soil nitrogen and SOC The lower ratio of nitrate and nitrite nitrogen to total nitrogen of 1074 in M60 at the end of this experiment than in the other regimes and before sowing supports this point The correlations of SOC with available P and with the ratio of available P to total P are positive in the dry year of 2001 but negative in the wet year of 2002 This can be explained on the basis that a high forage yield of alfalfa requires more soil available P in the wet years than in the dry years
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