The soils of four citrus orchards in western Zhejiang were studied in this research. In order to explore the effects of lime on soil chemical properties and bacterial communities, the incubation experiment was conducted with six different dosages of lime addition, 0, 0.6, 1.2, 2.4, 4.8, 7.2 g/kg, respectively. The results showed that soil pH increased significantly (p < 0.05) and the contents of exchangeable acid decreased significantly (p < 0.05) at the early stage of lime application. As time went by, the reacidification existed in the soil of each treatment, mainly reflected in a significant (p < 0.05) decrease in soil pH. Liming increased the nitrate nitrogen content and decreased the ammonium nitrogen content in the four soils. However, the responses of other nutrient indexes to lime varied in different soils, which might be due to the different degrees of soil acidification. In general, the addition of lime increased the soil integrated fertility index (IFI) and improved the soil nutrient status. The application of lime under 2.4 g/kg significantly improved the structure of bacterial community and increased the relative abundance of soil bacterial community species, while the application of lime above 4.8 g/kg might inhibit the growth and activity of microorganisms, resulting in the reduction of soil microbial biomass and diversity. Redundancy analysis (RDA) showed that lime affected the bacterial community mainly by reducing the content of soil active acid and exchangeable acid. At the same time, network analysis showed that the bacterial community had a stronger buffer capacity against external disturbances after lime application. In conclusion, the addition of lime with appropriate amount (2.4~4.8 g/kg, corresponding to a field application rate of 5.8~11.5 t/ha) in acid orchard soil could improve soil properties, soil integrated fertility, and the diversity and stability of the bacterial community.

对浙江省典型茭白种植区表层(0～20 cm)土壤中的磷素丰缺状况和磷库特征进行调查,分析茭白种植年限与土壤磷积累的关系.结果表明:样本茭白田土壤的全磷和有效磷(Olsen-P)含量平均值分别为876.73、63.30 mg·kg-1,土壤磷积累明显,有效磷水平达丰富级别的占比高达 81.05%.样本土壤的磷素以无机磷为主,平均占比达到79.91%,水提取态无机磷(H2O-Pi)、NaHCO3 提取态无机磷(NaHCO3-Pi)、NaOH提取态无机磷(NaOH-Pi)、HCl提取态无机磷(HCl-Pi)、NaHCO3 提取态有机磷(NaHCO3-Po)、NaOH提取态有机磷(NaOH-Po)和残余态磷的平均含量分别为 16.16、122.06、213.03、103.22、22.18、158.52、241.86 mg·kg-1.除残余态磷和HCl-Pi外,其他形态磷的含量均随茭白种植年限的增加而增加.土壤磷吸持饱和度随茭白种植年限延长逐渐增加,土壤磷素随种植年限延长呈向下迁移的特点.当样本土壤的有效磷含量大于60 mg·kg-1时,土壤磷素淋失风险增加,约48.37%的样本土壤处于磷高淋失风险状态.

【Objective】 Nutrient loss from agricultural soils is a great environmental concern in many countries, and rotating crops and intercropping are believed to be one solution to slowing down this loss. The aim of this paper is to investigate the efficacy of different intercropping systems in reducing the loss of suspended solids and major dissolved nutrients from farmland. 【Method】 The experiment was conducted from 2014 to 2017 in Zhejiang province, southeast China. We compared five intercropping systems: vegetable - Zizania latifolia, vegetable - paddy rice, orchard - Zizania latifolia, mulberry - paddy rice and orchard - lotus pond, with traditional cultivation used by local farmers taken as the control. In each system, we measured the reduction in sediment loss, change in total and soluble phosphorus (P), total and soluble nitrogen (N). 【Result】 Compared with the control, all five intercropping systems reduced the loss of suspended solid and P and N by more than 70% on average. In particular, they reduced the total P loss by 90.63%, soluble P loss by 89.14%, suspended solid loss by 88.72%, soluble N loss by 86.75%, and total N loss by 86.64%. In terms of efficacy, the five systems were ranked in the order of orchard - lotus pond > vegetable - Zizania latifolia > orchard - Zizania latifolia > mulberry - paddy rice > vegetable - paddy rice. 【Conclusion】 The mechanisms underlying the intercropping systems for reducing loss of suspended solids and nutrients from soils was the reduced drainage and the increased ability of soil to absorb nutrients. Intercropping is a low-cost but efficient technology to ameliorate nutrient loss from farmland systems. For the five intercropping systems we compare, lotus pond-Zizania latifolia was most effective.

[目的]了解水耕时间对亚热带低丘水田土壤性态的影响,对水耕土壤进行正确分类.[方法]在浙江省金衢盆地内选择坡麓和岗地二种地貌单元,观测不同水耕时间的第四纪红土发育水田土壤的剖面形态特征,分层采集土样分析土壤理化性状.[结果]随着水耕时间的增加,土壤颜色由红转黄,色调由2.5YR向7.5YR或10YR演变;表层土壤黏粒含量逐渐下降,有机质与全磷及有效磷积累,pH、阳离子交换量和活性铁逐渐增加,土壤游离氧化铁逐渐下移淀积;水耕时间对土壤性状的影响由表层向心土层发展.调查表明,由于水分条件的差异,水耕时间对坡麓地带水田土壤性状的影响大于岗地水田.[结论]由第四纪红土旱地改为水田,形成典型水耕人为土约15 a,形成铁聚水耕人为土约150 a以上,水耕时间低于150 a主要形成简育水耕人为土;随着水稻种植时间的增加,活性有机质占有机质的比例随有机质积累同步增加,水稻土心土层具有较强的固碳潜力.

[目的]为了解地形对亚热带丘陵地区稻田土壤发生与演变的影响.[方法]在浙江省衢州市和杭州市分别选择了由第四纪红土和凝灰岩风化物等2类母质发育的地形系列梯田,比较分析了岗背、高坡、缓坡和坡麓等不同地形部位梯田土壤剖面发生学性状及土壤类型的差异.[结果]结果表明,由岗背经高坡、缓坡至坡麓,土壤受耕作熟化影响(包括颜色变化、酸度下降)的程度逐渐加深,土体厚度、氧化还原层厚度和铁锰新生体数量、剖面中黏粒和氧化铁含量的垂直分异呈增加的趋势,同时表土有机碳、全氮、全磷、有效磷的积累也呈现增加趋势.调查表明,2类母质发育的土壤中位于坡麓地带的梯田土壤剖面氧化铁垂直迁移显著,土壤类型属铁聚水耕人为土;岗背和高坡部分的梯田土壤剖面发育相对较弱,形成的为简育水耕人为土;缓坡地梯田中可发生铁的渗移,形成的土壤或为铁渗水耕人为土或为简育水耕人为土.[结论]研究认为,地形部分可通过改变土壤剖面中水分状况和运移影响亚热带低丘陵地区水耕人为土的发育.

山地红黄壤是亚热带地区耕地的重要来源,目前,这一地区土地开垦主要采用机械平整和人工平整方式.为了解整地方式对新造梯田耕地质量的影响,在浙江省选择酸性火山岩和泥页岩2类母质发育的红黄壤,采用多地采样分析的方法,比较机械平整和人工平整对新造梯田耕地土壤性状的影响.结果表明,与开垦前的土壤比较,无论是机械平整还是人工平整,都明显增加了表层土壤(0～20 cm)中砾石和砂粒含量,降低了土壤有机质、 有效养分的含量.人工平整的新造梯田耕地质量好于机械平整,前者土壤黏粒、 有机质、 碱解氮、 有效磷、速效钾含量分别是后者的1.25～1.27、1.42～1.57、1.35～1.39、1.26～1.37和1.13～1.14倍,土壤中>0.25 mm水稳定性团聚体含量前者是后者的1.44～1.59倍.人工平整的新造梯田耕地土壤保蓄性和保水性高于机械平整.

为了解利用方式改变引起的土壤酸度变化及其机理,从浙江省选择淡涂泥田、黄斑田和黄泥田等3类代表性水稻土,基于不同利用方式下农田水分条件及酸与盐年输入量的差异,模拟研究了多年种植水稻、露地旱作和大棚种植等环境下的土壤酸化过程.结果表明,随着模拟周期的增加,3种利用方式下土壤均呈现酸化,露地种植旱作和大棚种植环境下土壤pH的下降明显大于水稻种植环境;大棚种植环境下土壤酸化速率明显高于露天旱地.随着土壤pH的下降,土壤中交换性酸也随试验周期的延长而逐渐增加,同时交换性铝占总酸的比例却逐渐上升.不同土壤对酸的缓冲能力:黄斑田