森林土壤肥力以维持和恢复自然肥力为主，人工施肥为输。
Forest soil fertility mainly relies on maintaining and resuming natural fertility and combines with artificially applying fertilizer.
家属区人工菜园土壤有机质含量较高，与居民人工施肥有关。
The organic content of soil is higher in the garden in front of inhabitant building because it may be fertilized by the inhabitants.
氮素是植物必要的营养元素之一，其主要来源有：生物固氮作用、降雨和灌溉水以及人工施肥。
Nitrogen for plant nutrition is mainly obtained from three sources: nitrogen-fixing plant, rain water and manure.
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