粒级分布 meaning in English

distribution of grain size
size-grade distribution

After wet sieving , water stable aggregate showed the highest fraction at the size of < 0 . 25mm , while micro - aggregate was distributed from 0 . 25mm to 0 . 01mm size . aggregate stability of soils increased with an increased clay content
土壤水稳性团聚体的粒级分布( psd )均以0 . 25mm居多，土壤微团聚体的粒级分布则以0 . 25 - 0 . 01mm粒级为主。