Abstract: The mechanical stable aggregates，water-stable aggregates，aggregate stability and the organic carbon content of aggregates in Nanfeng tangerine orchards intercroppig Trifolium repens and Lolium multtiflorum were investigated. The results showed that the mechanical stable aggregates（> 5 mm）occupied 28.52%–35.14% in sod culture Nanfeng tangerine orchards，while the aggregates（< 0.25 mm）were 35.51%–36.86% in clear tillage tangerine orchards. The water-stable aggregates（< 0.25 mm）were the dominant and accounted for 55.71%–80.47% in all treatments. The overall change trend of aggregate R0.25 was Lolium multtiflorum treatment > Trifolium repens treatment > control. At the 0–10 cm and 10–20 cm soil layers in tangerine-white clover intercropping system，the mean weight diameter（MWD）of mechanical stable aggregates and water-stable aggregates increased by 126.03%，106.8% and 57.69%，31.25% and the polyagglomerate destruction rate（PAD）reduced by 13.29% and 12.41% compared with the control respectively. Simultaneously，MWD of mechanical stable aggregates and water-stable aggregates increased by 140.41%，125.17% and 82.69%，64.58% and PAD decreased by 12.85% and 16.61% in tangerine-Lolium multtiflorum intercropping system compared with the control，respectively. It showed that sod culture contributed to the formation of large aggregates and improved the soil structure stability and quality. And the improvement effect on the soil by intercropping Lolium multtiflorum was better than that by intercropping Trifolium repens. The sod culture greatly increased the total organic carbon content of water-stable aggregates and organic carbon content in different aggregate size classes at the 0–10 cm top soil，and the influence of Trifolium repens cultivation was superior than that of Lolium multtiflorum cultivation. Correlation analysis showed that the MWD and GMD was positively related to the organic carbon content of particle size aggregate（1–5 mm）and PAD was on the contrary. Naturally grown grass could increase the soluble sugar，soluble solids and vitamin C content，reduce the titratable acid content and improve the fresh food quality of Nanfeng mandarin fruit. And Trifolium repens had better improvement effect on fruit quality than Lolium multtiflorum.

Key words: citrus, orchard, sod culture, soil, aggregates, organic carbon, fruit quality