土壤群落的有机质依赖于植物。
Soil communities are dependent on plants for organic matter.
加进去的和残留下来的植物物质则是土壤有机质的主要来源。
A major portion of the soil organic matter is derived from the added and residual vegetative material.
土壤有机质中含有少量的磷酸盐，且其比例始终不变。
The organic matter in soil contains a small but fairly uniform proportion of phosphate.
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