Effects Of Long-term Orchard Management On Soil Fertility Properties In Three Gorges Area, China

Soil erosion and the resulting non-point source pollution and ecological degradation endanger regional agricultural ecosystem and the reservoir fresh water in Three Gorges Area (TGA) of China. In the last decades, some works were conducted on reducing soil and water losses from citrus slope land, but the management practices on soil fertility properties was rarely concerned. Relying on the long-term experiment of citrus management practices, this study aimed to evaluate the effects of long-term protective measures on soil fertility properties. The rainfall runoff-plot experiment has been lasted for 8 years at Zigui country, TGA, China. The treatments include: Citrus intercropping with white clover (Trifolium repens Linn) (CM); Citrus land with straw mulching (SM); Citrus intercropping with Hemerocallis (Hemerocallis flava) contour hedgerow (CH); Citrus land with impermeable membrane (MM); conventional navel citrus management (CK) and Citrus intercropping with wheat (Triticum aestivum)-peanut (Arachris hypogaea) (PC). The main results are summarized as following:(1) Compared with conventional navel citrus management, citrus land with straw and citrus intercropping with white clover significantly decreased soil BD, increased > 2 mm and > 0.25 mm water stable aggregate, soil organic carbon, total nitrogen contents, but citrus intercropping with white clover did not increase soil total phosphorus and total potassium contents.(2) Citrus intercropping with contour hedgerow and citrus land with straw impermeable membrane treatments increased > 0.25 mm water stable aggregate contents, and have the trend of increased soil organic carbon, total nitrogen, total potassium and available potassium, though most of them were lower than that of citrus intercropping with white clover and land with straw treatments.(3) Citrus intercropping crops treatment decreased soil pH and organic carbon contents, but have the trend of increased soil available nitrogen and available potassium contents.(4) Citrus land with straw and citrus intercropping with white clover caused soil organic carbon, total nitrogen, available nitrogen and available potassium enrichment at depth of 0-5 cm at lower position, while other treatments didn't have significant effect on soil nutrients enrichment.