土壤空气的组成特点 Two important gases in soil air are carbon dioxide and oxygen. Carbon dioxide is produced as a by-product of plant root respiration and biological activity. Oxygen is consumed in the soil by the same processes, and plant roots require oxygen to function normally. For most plant species transaction of oxygen from the leaves to the roots is not adequate to supply oxygen at the required rate. Hence, plant roots must supplement oxygen supply from soil air. As a result oxygen is depleted from soil air. Oxygen content in soil air is replenished by oxygen from the atmosphere above the soil surface This transport occurs primarily by gaseous diffusion In a surface layer of a well-aerated soil the oxygen content is between 18 and 21 percent, while at a greater soil depth and specially in soils that are wet for a long period it may be very much lower The carbon dioxide content of soil air is usually between 0. 1 and 5 per cent and can reach nearly 20 per cent. Under reducing conditions soil air may contain methane hydrogen sulphide and ammonia 问題:土壤空气质量如何满足作物生长需求的? 有资料表明:如果土壤不具备通气性,那么,土壤空气中○2仅能够作物根糸呼 吸消耗12~40个小肘,可见,土壤气体更新是多么重要。土壤是如何通气的呢?一.土壤空气的组成特点 Two important gases in soil air are carbon dioxide and oxygen. Carbon dioxide is produced as a by-product of plant root respiration and biological activity. Oxygen is consumed in the soil by the same processes, and plant roots require oxygen to function normally. For most plant species, transaction of oxygen from the leaves to the roots is not adequate to supply oxygen at the required rate. Hence, plant roots must supplement oxygen supply from soil air. As a result oxygen is depleted from soil air. Oxygen content in soil air is replenished by oxygen from the atmosphere above the soil surface. This transport occurs primarily by gaseous diffusion. In a surface layer of a well-aerated soil, the oxygen content is between 18 and 21 percent, while at a greater soil depth and specially in soils that are wet for a long period it may be very much lower. The carbon dioxide content of soil air is usually between 0.1 and 5 per cent and can reach nearly 20 per cent. Under reducing conditions soil air may contain methane, hydrogen sulphide, and ammonia. 问题：土壤空气质量如何满足作物生长需求的？ 有资料表明：如果土壤不具备通气性，那么，土壤空气中O2仅能够作物根系呼 吸消耗12~40个小时，可见，土壤气体更新是多么重要。土壤是如何通气的呢？