Study On The Ecological Impacts And Allelopathy Of Interplanting Grass In Hilly Orchards

The research was carried out on the hilly orchard with grass cover in red soil region. To clarify the impact of sod cultivation on fruit trees, the root activity of Citrus grandies L. and the changes of soil physical and chemical characteristics were analysed. In view of allelopathy, the organic compounds extracted from pot root exudations and field soil extraction were separated and identified by gas chromatography-mass sepectrometry(GC-MS). The results showed that:1．In the hilly orchard with interplanting grass measure systems, the soil moisture content increased evidently compared with clean cultivation plot. Thereinto, The Pspalum Wettsteinii plot had the most significant increase and the Pspalum Wettsteinii plot was in the next place, with 27．49% and 24．59% higher than clean cultivation plot, respectively. And the distinction to each other was significant.2．Hilly orchard with interplanting grass measure would obviously improve the soil organic matter (SOC) and available nutrient .Compared with check (CK), the effect of increasing the SOC between Chamaecrista Rotundifolia plot and Pspalum Wettsteinii plot was nearly , about 47．98% and 46．04% higher than control. However, the distinctions between these two treatments to others were significant. As for the available nutrient, the soil available P had the biggest active rate under sod treatments. In the Paspalum notatum Flugge plot , available P was 75．00% higher than that in control. The content of available N in the Pspalum Wettsteinii plot was higher than any other plots, and it had evident difference between other pasture treatments. While, Paspalum notatum Flugge contained the most available K, and the differences with other sod cultivations were obvious.3．Hilly orchard with sod cultivation would obviously decrease the root activity of Citrus grandies L. Especially in the Pspalum Wettsteinii plot, the root activity was the lowest with the value of 317．11μg·g^-1·h^-1 ,which was 42．12% lower than CK. And the root activity of Chamaecrista Rotundifolia plot was the highest, with the value of 493．73μg·g^-1·h^-1 . Except Chamaecrista Rotundifolia and Arachis pintoi, there were obvious distinctions of root activity between all sod treatments.4．Organic compounds extracted from pot root exudations and soil extraction wereindentified by gas chromatography-mass sepectrometry(GC-MS),the result showed that, the content sequence of organic compounds in pot root exudation was: PspalumWettsteinii>Arachis pintoi>Paspalum notatum Flugge>ChamaecristaRotundifolia>CK. And the content sequence in field soil extraction was: PspalumWettsteinii> Arachis pintoi> Chamaecrista Rotundifolia> Paspalum notatumFlugge> CK. As known once the organic compounds came into soil, they occurred aseries of transfer and transform, as a result, the oganic compounds content in pot rootexudations was higher than that in field soil extraction. In the root exudations,alcohols was the main allelochemicals, while in the soil extraction, hydrocarbonworked mainly.In short, hilly orchard with interplanting grass measures would obviouslyincrease the soil water and nutrient content, but the root activity of Citrus grandies L.decreased as a result of the impacts of allelochemicals which excreted by postures.