Objective]The objective of this study is to obtain fertilizing effects of interplanting forage legumes and corresponding handling modes,which would be lay a basis for fertilizing measures of young orchard in hilly red soil region of south Hunan,China.[Method]In order to explore effects of interplanting forage legumes and corresponding handling modes on soil fertility in young citrus orchards, a field experiment was carried out interplanting six species of forage legumes,includingTrrifoliumrepens, Chamaecradtanictitans,Chamaecristarotundifolia,ChamaecristarotundifoliaCPI 86134, Macroptiliumlathyroides,andLotononisbainesiiwere,separately and designed to have the crops, harvested,laid over or plowed down,in a young citrus plantation in a hilly red soil region of South Hunan. Soil physicochemical properties of all the plots were measured after the experiment for analysis of the effects.[Result]Compared with CK(no crop interplanted),all the plots,on the whole,increased in contents of organic matter,total nitrogen,alkali-hydrolyzable nitrogen,and available phosphorus, and the increasing effects were the highest in the plots with the crops plowed down or incorporated,but decreased in content of readily available potassium and pH,and the decreasing trends were the lowest in the plots with the crops plowed down. Among all the plots,the plot withChamaecradtanictitansplowed down raised the contents of organic matter,total nitrogen,alkali-hydrolyzable nitrogen,and available phosphorus contents the highest in margin and lowered the content of readily available potassium the least, and the plot withChamaecristarotundifoliaincorporated came the next in the effects. Besides,the plot with Chamaecradtanictitansincorporated lowered soil pH the least. Compared with CK,all the plots increased fruit yield,single fruit weight,and tree height,canopy diameter,and number and length of spring/autumn branches of the orange trees. The effect of the plot withChamaecradtanictitansincorporated was the most significant and the plot withChamaecristarotundifoliaincorporated came the next. Besides,the plot with Chamaecradtanictitansincorporated was the highest in biomass of the forage legume yielded,and in amount of nitrogen and phosphorus returned into the soil,and in soil microbial biomass carbon,soil microbial biomass nitrogen,and urease activity,too.[Conclusion]Therefore,it can be concluded that the practice of interplantingChamaecradtanictitansand then incorporating the crop is the most suitable soil building mode for young citrus orchards,but it needs supplementation of some potassium and phosphorus fertilizers. Besides,it is also necessary to apply some alkaline material,like lime,to offset the effect of interplanting forage legumes lowering soil pH.%在幼龄桔园套种了白三叶（Trrifolium repens）、圆叶决明（Chamaecrista rotundifolia）、羽叶决明（Chamaecradta nictitans）、决明86134（Chamaecrista rotundifoliaCPI 86134）、大翼豆（Macroptilium lathyroides）和罗顿豆（Lotononis bainesii）6个豆科牧草品种，研究了牧草种植后土壤理化特征的变化，为果园选择适宜的套种牧草种类和处理方式。结果表明，与开展不同耕作处理前的基础样相比，牧草在刈割、保留和翻压处理下土壤有机质、全氮、碱解氮、有效磷含量总体得到提升，翻压处理升幅最大，土壤速效钾和pH总体呈下降趋势，翻压处理降幅最小；羽叶决明翻压处理的土壤有机质、全氮、碱解氮、有效磷含量的升幅最大，土壤速效钾含量降幅最小，其次是圆叶决明翻压处理，羽叶决明翻压处理下土壤pH降幅最小。与裸地处理相比，牧草处理提高了桔子产量和单果重，增加了桔树树高、冠径及春秋梢的个数和长度，其中，羽叶决明翻压处理的均最高，其次是圆叶决明翻压处理。羽叶决明翻压处理的牧草生物量最大，归还到土壤中的氮磷也最多，其土壤微生物生物量碳氮和脲酶活性也显著高于其他处理。羽叶决明翻压是一种较好的幼龄果园培肥模式，但在栽培过程中需补充磷肥和钾肥，同时，有必要増施石灰等碱性物质，以防治种植豆科牧草培肥时土壤 pH下降。
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