Effects of different organic fertilizer treatments on distribution and stability of soil aggregates in the semiarid area of South Ningxia

A study was conducted on the size distribution and stability of soil aggregates in the semiarid area of South Ningxia after 3-year fertilization.The experiment has three levels of fertilizer treatments,and every level repeated three times.The test crop was wheat Xifeng 26.The distribution of soil aggregates was measured by dry sieving and wet sieving.The results showed that the proportion of the bigger soil aggregates was increased significantly by organic fertilizer treatments and there was a positive correlation between organic fertilizer amount and the proportion.The stability of soil aggregates was also improved by organic fertilizer treatments.Compared with that of natural soil,the content of 0.25 mm water-stable aggregates in 0～10 cm and 30～40 cm layers of soil with fertilizer treatments increased by 35% and 75%,respectively;and the content of ≥0.5 mm water-stable aggregates also had a increasing trend,with the greatest increment of that of 5 mm and 2～5 mm water-stable aggregates.On the contrary,the change of the content of 0.25～0.5mm water-stable aggregates was not significant.The significant difference between these treatments was mainly reflected in 5 mm and 0.25 mm aggregates.After dry sieving,5 mm aggregates were the main part.Compared with the control,the content of 0.25 mm aggregates increased in varying degrees in organic fertilizer treatments.There was significant difference between these organic fertilizer treatments in 0～20 cm soil layer.Through aggregate stable percentage comparing,organic fertilizer treatments had the most influential effect on 30～40 cm soil layer,and the soil stable percentage of 30～40 cm soil layer was increased by 87% compared to that of 0～20 cm soil layer.The mean weight diameter(MWD) of soil with fertilizer treatment was greater than that of natural soils,and it was significantly correlated with the content of 0.25 mm water-stable aggregates.So the organic fertilizer treatments can not only enhance the proportion of bigger aggregates,but also improve the structure of soil,and the suitable amount of organic fertilizer application is about 60 000 kg/hm2.