2.结构良好,土层深厚耕翻后的表土,常常可以看到许多小米粒到高梁粒大小的土团,叫做团粒结构。它是由腐殖质和土壤中的粘粒把粉砂,细砂胶结成小于0.5毫米的微团粒,再由微团粒进一步胶结而成的。团粒结构多的土壤是结构良好的土壤。因为在团粒内部有很多微团粒(见图1),而微团粒内部和微团粒之间,存在着许多小孔隙,称为毛细管孔隙。这些小孔隙能长期吸持水分,不断地供给作物吸收利用。因此,一个团粒 2. Well-structured, deep soil plowed over the topsoil, you can often see many millet grains to sorghum size soil group, called the crumb structure. It is made of humus and soil clay to silt, fine sand cementing less than 0.5 mm of the micro-particles, and then by the further aggregation of micro-particles formed. Soil with more aggregate structure is a well-structured soil. Because there are many micro-aggregates inside the pellet (see Figure 1), and there are many small pores inside the micro-pellet and between the micro-aggregates, called capillary pores. These small pores can hold water for a long time, and continuously supply and absorb crops. So a pellet