TITLE:
Application of High Carbon:Nitrogen Material Enhanced the Formation of the Soil A Horizon and Nitrogen Fixation in a Tropical Agricultural Field
AUTHORS:
Masato Oda, Kenji Tamura, Hiroko Nakatsuka, Miki Nakata, Yukimi Hayashi
KEYWORDS:
Carbon, Food Security, Microorganisms, Nitrogen, Soil Degradation
JOURNAL NAME:
Agricultural Sciences,
Vol.5 No.12,
October
29,
2014
ABSTRACT: It is known that cropping causes soil carbon loss, which is a critical
issue, especially in tropical agriculture. Nitrogen input generally increases
net primary production but does not increase soil carbon content because
nitrogen input enhances soil organic carbon mineralization by microorganisms. A farmer conducted a trial in which he
applied material with a high carbon:nitrogen (C:N) ratio without
additional nitrogen fertilizer, and achieved a higher productivity than that of
conventional farms. Based on his results, we conducted a survey to evaluate the
effects of high C:N ratio organic material on the productivity, soil profile,
microbial activity, and carbon and nitrogen balance of soil. Results
demonstrate that high C:N ratio organic material enhanced the formation of the
soil A horizon and increased soil carbon and nitrogen content. Approximately,
15 - 20 t·ha-1·crop-1 of fresh waste mushroom bed was
applied to 15 crops over 4.5 years, and the total input of carbon and nitrogen
were 5014 and 129 g·m-2, respectively. The soil nitrate nitrogen
concentration was the same as that of the neighboring forest soil, which was
lower than the standard limit for conventional agriculture; however, the
average productivity of crops was approximately four times that of the national
average. The soil Ap horizon increased in thickness by 7 cm, and aggregates
reached a thickness of 29 cm in 4.5 years. The output/input ratios of total
soil nitrogen and carbon were approximately 2.68 - 6.00 and 1.30 - 2.35,
respectively, indicating that this method will maintain the carbon and nitrogen
balance of the system. The observed soil microbial activity was one order of
magnitude higher than that of a fallow field. The results indicate that this
agricultural method remediates soil degradation, and improves food production.