Taylor & Francis Group
Browse
tssp_a_1716389_sm0983.pdf (164.74 kB)

Contribution of fallow weed incorporation to nitrogen supplying capacity of paddy soil under organic farming

Download (164.74 kB)
journal contribution
posted on 2020-01-28, 19:00 authored by Kazunobu Toriyama, Taku Amino, Kazuhiko Kobayashi

We studied soil nitrogen (N) management in a farmer’s organic rice farming in Japan, where the farmer applied no external N but incorporated gramineous fallow weeds and rice residues as in situ N sources. We focused on the effect of fallow weed incorporation on N-supplying capacity of the paddy soil by tracking decomposition of 15N-labeled fallow weeds after incorporation. The result fits well to the first order kinetics with the decomposition rate of 34.3% a year. A model of soil N accumulation and mineralization based on the first order kinetics showed that soil organic N originated from the incorporated weed would become saturated at the level 1.92 folds the annual input of weed N after several consecutive years of the incorporation. Mineralizable soil N (Min-N) of the weed origin would also become saturated after several years accounting for 21.2% of the total Min-N which includes the indigenous soil N from plow layer. We suspended weed incorporation (SWI) in a sub-plot of the fields for two consecutive years to compare Min-N therein with that in another subplot in the same fields subjected to continued weed incorporation (CWI). After 2 years of the suspension treatment, Min-N in SWI decreased to a similar extent as estimated with the soil-N model based on the first-order kinetics, with which we estimated that 16.9% of annual N uptake by the rice plants originated from the weed including 5.9% from the weed incorporated in the same year and 11.0% from that in the past years. N inflow to soil organic N from the weed was very close to N outflow attaining the steady state. The rice yield could thus be sustained by maintaining the soil N-supplying capacity via the internal cycling of fallow weed N.

Funding

This work was supported by the Japan Society for the Promotion of Science [Grant-in-aid for scientific research (B) 26310304].

History

Usage metrics

    Soil Science and Plant Nutrition

    Licence

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC