Aggregate-associated soil organic carbon and total nitrogen following amendment of puddled and sawah-managed rice soils in southeastern Nigeria |
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Authors: | Charles A Igwe John C Nwite Kingsley U Agharanya Yoshinori Watanabe Sunday E Obalum Chinyere B Okebalama |
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Institution: | 1. Department of Soil Science , University of Nigeria , Nsukka , Nigeria;2. Faculty of Agriculture , Kinki University , Nara , Japan charigwe1@hotmail;4. Department of Crop Production , Federal College of Agriculture , Ishiagu , Nigeria;5. Department of Soil Science , University of Nigeria , Nsukka , Nigeria;6. Faculty of Agriculture , Kinki University , Nara , Japan;7. Faculty of Agriculture , Kinki University , Nara , Japan |
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Abstract: | Puddling during sawah rice cultivation destabilizes the soil structure. The re-formation of soil water-stable aggregates (WSA) following puddling and amendments, and their associated organic carbon (SOC) and total N were studied at Akaeze and Ikwo in south-eastern Nigeria. The amendments, which were randomized in triplicate, include control, NPK fertilizer, poultry dropping, rice husk powder and rice husk ashes (RHA). Soil samples from 0 to 15 cm depth were taken from the field after 2 years of cultivation. Most of the SOC were found in the very fine aggregates. There was no consistent trend in the treatment effects. However, the NPK-amended soils showed the lowest values of WSA > 2 mm in both locations, whereas the poultry dropping-amended soils showed the least and the highest mean-weight diameter (MWD) values at Akaeze and Ikwo, respectively. The SOC of the whole soil in Akaeze correlated positively with MWD (r = 0.92*). Irrespective of location, SOC in soils and WSA > 2.00 mm correlated positively with MWD (r = 0.56*; 0.65*, respectively) while SOC in WSA 0.50–0.25 mm accounted for low MWD values. More carbon was sequestered at Akaeze than at Ikwo, with the RHA-amended soils being the highest at both locations. |
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Keywords: | aggregate-associated carbon mean-weight diameter soil aggregates soil organic carbon thixotropic age hardening |
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