Dynamics of humus content and crop yields for dernopodzolic sandy loam soil with regard to application of mineral and organic fertilizers.

摘要

Positive correlations were found between yields for crops (cultivated on dernopodzolic sandy loam soil in the Vladimir oblast, Russia between 1988 and 1996) and humus content of soil for experimental plots where fertilizers were not used. Indirect correlations were found for plots where fertilizers were applied. Optimum humus contents were determined for grain crops (1.5%, 800-1000 mg C/kg soil) and root crops (2.4%, 1000-1200 mg C/kg soil), and related to fertilizer application rates and individual crops. Application of 10 t manure/ha per year combined with NPK mineral fertilizers prevented decreases in humus content (originally 0.75 or 1.50%) of soil. Doubling this application to 20 t/ha per year combined with mineral fertilizers stabilized humus content at 2.4%. It is concluded that application of manures regulated overall and mobile humus contents, whereas plant matter mainly regulated mobile humus contents.