几种有机物对紫色土镉的溶出效应与吸附-解吸行为影响的研究

研究了天然有机物胡敏酸和富里酸 ,螯合剂EDTA和DTPA和四种简单有机酸对紫色土镉的溶出效应和吸附解吸行为的影响。结果表明 ,供试八种有机物均能显著促进镉从紫色土中的溶出。作用大小顺序为 :EDTA≥DTPA >柠檬酸 >胡敏酸 >草酸 >富里酸 >酒石酸≥水杨酸。有机物对土壤镉溶出和迁移的影响是其对土壤镉吸附和解吸综合作用的结果。有机物显著降低了紫色土对镉的吸附 ,其作用大小顺序与其对镉的溶出能力的相对大小顺序一致 ,同时也改变了吸附镉的解吸特性。有机物影响下 ,紫色土镉的吸附动力学模型以双常数方程拟合最佳。而吸附等温曲线以Freundlich方程拟合最好 ,吸附常数n与有机物对土壤镉的溶出率之间存在良好的相关性。     

有机酸对土壤中镉的解吸及影响因素

研究了酒石酸和柠檬酸对两种不同处理土壤 (镉质土和污染土 )中Cd的解吸行为 ,探讨了介质pH值、支持电解质等对其解吸镉质土和污染土中Cd的影响。结果表明 ,随有机酸浓度升高 ,柠檬酸和酒石酸对镉质土和污染土中Cd的解吸率呈先降低后升高变化 ,出现一波谷 ,波谷位置与有机酸和土壤类型有关。当解吸液起始pH值由 2升至 8时 ,柠檬酸对镉质土和污染土中Cd的解吸率呈降低—升高—降低的变化 ,先后出现一波谷和一波峰 ,且柠檬酸浓度高时变化趋势尤为明显 ;而酒石酸对镉质土和污染土中Cd的解吸率则一直降低。解吸液中支持电解质浓度提高 ,酒石酸对镉质土和污染土中Cd的解吸率增大 ,且以KCl为支持电解质时的解吸率要高于KNO3。     

火烧对土壤性质的影响

火烧以后 ,土壤的各种性质会发生较大变化 ,原因是火向土壤中施加了热量、灰烬 ,并且改变了土壤环境和微气候 ,土壤性质也可因植被和生物活性的改变而发生相应的变化。本文对火烧后土壤生态系统中养分的浓度、有效性、迁移性 ,土壤中的生物和酶活性 ,土壤有机碳库等的变化进行了综合评述 ,以期为森林火灾、草地烧荒后的土壤管理等提供理论参考。     

植物篱枝叶有机碳分解研究

研究植物篱枝叶的分解和养分矿化过程对该模式下养分的有效利用具有重要意义。在金沙江干热河谷坡耕地上利用分解袋法对新银合欢、山蚂蝗等 6个植物篱树种枝叶的分解进行了研究 ,结果显示山蚂蝗和新银合欢分解最快 ,前 2个星期有机碳分解了48 6 %和 5 0 0 % ;山毛豆和云南合欢次之 ,前 4星期有机碳累积分解量为 5 1 5 %和 45 6 % ;圣诞树和黑荆树分解最慢 ;将枝叶埋入土壤中比覆盖地表分解快。有机碳的分解规律可以用单指数模型Ct=C0 (1 e kt)和双指数模型Ct=C0 1 (1 e k1t) C0 2 (1 e k2 t)拟合 (式中 ,Ct 为有机碳累积分解量占全碳百分数 ,C0 、C0 1 和C0 2 分别为易分解有机碳和难分解有机碳百分数 ,k和k1分别为易分解有机碳分解常数 ,k2 为难分解有机碳分解常数 ) ,双指数模型更具合理性。研究表明有机碳的累积分解量与枝叶初始C/N比呈负相关 ,枝叶分解速度可用有机碳 (或易分解有机碳 )半减期来衡量。     

土壤有机硫矿化动力学特征及影响因素

利用开放培养系统，分别在20℃和30℃，好气和淹水条件下研究了四种土壤（黑土、褐土、黄棕壤和红壤）有机硫矿化特征。结果表明，30℃条件下土壤有机硫累积矿化量显著高于20℃下的矿化量（P＜0．01）。20℃和30℃好气条件下累积矿化量分别为17．53－24．35mg kg^-1和34．20－54．33mg kg^-1，分别占有机硫总量的2．5％－6．5％和5．－14．5％，20℃和30℃淹水条件下累积矿化量分别为18．14－21．15mg kg^-1和26．86－30．63mg kg^-1，分别占有机硫总量的2．6％－5．6％和4．0％－7．7％。好气和淹水下30℃与20℃的有机硫累积矿化量之比分别为1．85－2．23和1．28－1．71。用一级动力学方程和双倒数方程计算土壤有机硫矿化势（S0）表明，20℃好气培养时S0分别为17．82－24．88mg kg^-1和17．83－27．7mg kg^-1，S0分别为17．50－21．49mg kg^-1和19．19－22．50mg kg^-1,30℃淹水条件下S0分别为28．26－35．87mg kg^-1和26．59－34．25mg kg^-1。土壤有机硫矿化速率常数（K）和矿化量达50％矿化势（S0）所需的时间（K1）受不同土壤和培养温度的影响，都可用一级动力学方程和双倒数方程来评价。碳键硫对有机硫矿化的贡献较大，尤其在淹水条件下更明显。     

Tillage and crop sequence effects on organic carbon and total nitrogen content in an irrigated Alberta soil

A better understanding of tillage effects on soil organic matter is vital for development of effective soil conservation practices. The objective of this research is to determine the effect of tillage and crop sequence on soil organic carbon (OC) and total nitrogen (TN) content in an irrigated southern Alberta soil. A field experiment was conducted using a split–split plot design from 1994 to 1998 in Alberta, Canada. There were two crop sequences (Sequence 1: spring wheat (Triticum aestivum L.)–sugar beet (Beta vulgaris L.)–spring wheat–annual legume; and Sequence 2: spring wheat–spring wheat–annual legume–sugar beet) and two tillage practices (CT: conventional tillage and MT: minimum tillage). Surface soil under MT had significantly higher OC (30.1 Mg ha⁻¹) content than under CT (28.3 Mg ha⁻¹) after 4 years of treatment. The MT treatment retains crop residue at the soil surface, reduces soil erosion and slows organic matter decomposition, which are key factors in enhancing the soil fertility status of southern Alberta irrigated soils.     

Influence of management practices on soil organic matter changes in the Northern China plain and Northeastern China

Soil organic matter (SOM) is strongly related to soil type and management practices. Changes in government policy have brought drastic changes in farm management practices in the last two decades in rural China. This study investigates changes in SOM in two different soils: Ustepts and Udolls. Ustepts, in the North China Plain where the climate is warm and sub-humid, developed from an alluvial flood plain with organic matter <10 g kg⁻¹. Udolls, in Northeastern China where the climate is cool and sub-humid, developed from loess-like materials with organic matter >20 g kg⁻¹. Two locations for Ustepts and three locations for Udolls were used to collect 567 soil samples in 1980–1982 and again in 2000 for SOM analysis. Soil organic matter increased for Ustepts and decreased for Udolls soils over the sampling period, resulting from differences in fertilizer rates and crop residue input to soil. Higher fertilizer input and crop intensity and initially very low SOM content in Ustepts all contributed to greater OM input than oxidation release. In contrast, lower fertilizer input and crop intensity, and initially high SOM content in the Udolls, led to lower OM input than oxidation release. Increasing SOM content through higher mineral fertilizer input is a valuable option for sustainable agriculture production in areas where SOM is low and there is a shortage or potential shortage of food supply.     

Chemical and biochemical properties in a silty loam soil under conventional and organic management

To improve soil fertility, efforts need to be made to increase soil organic matter content. Conventional farming practice generally leads to a reduction of soil organic matter. This study compared inorganic and organic fertilisers in a crop rotation system over two cultivation cycles: first crop broad bean (Vicia faba L.) and second crop mixed cropped melon-water melon (Cucumis melo-Citrullus vulgaris) under semi-arid conditions. Total organic carbon (TOC), Kjeldahl-N, available-P, microbial biomass C (Cmic), and N (Nmic), soil respiration and enzymatic activities (protease, urease, and alkaline phosphatase) were determined in soils between the fourth and sixth year of management comparison. The metabolic quotient (qCO₂), the Cmic/Nmic ratio, and the Cmic/TOC ratio were also calculated. Organic management resulted in significant increases in TOC and Kjeldahl-N, available-P, soil respiration, microbial biomass, and enzymatic activities compared with those found under conventional management. Crop yield was greater from organic than conventional fertilizer. The qCO₂ showed a progressive increase for both treatments during the study, although qCO₂ was greater with conventional than organic fertilizer. In both treatments, an increase in the Cmic/Nmic ratio from first to second crop cycle was observed, indicating a change in the microbial populations. Biochemical properties were positively correlated (p < 0.01) with TOC and nutrient content. These results indicated that organic management positively affected soil organic matter content, thus improving soil quality and productivity.     

山东主要土类有机质及其与供磷特性的关系

山东省3大土类中棕壤的有机质含量最高,平均为10.69g kg-1,其次为褐土和潮土;高产农田的有机质含量平均为10.9g kg-1,高于中低产田。相关分析结果表明,土壤的主要养分含量中有机质含量与土壤有效磷含量的密切正相关,进一步分析表明,土壤的有机质含量与土壤全磷、有机磷、有效磷、磷酸化酶活性和土壤微生物转化难溶性磷的强度均呈正相关,而与磷吸附最大缓冲容量MBC、固磷百分率、解吸能Qm呈负相关;逐步回归结果表明有机质对棕壤中的中度活性有机磷MLOP、潮土中的Ca2-P、褐土中的A l-P、高产农田中的A l-P,中低产田的Fe-P均显著的正相关;而且这种相关性均是高产农田大于中低产田。有机质不仅直接丰富了高产农田的磷库,而且通过提高磷酸化酶的活性,降低土壤磷的吸附、固定,促进解吸,增加了土壤磷的有效性。     

潮土区土壤有机质含量的趋势演变研究——以禹城市为例

通过分析山东省禹城市100个采样点1980年和2003年耕层土壤的有机质含量,研究了土壤有机质的时空变异特征,探讨了潮土区有机质含量的变化,形成了研究区1980年和2003年有机质含量空间分布图及1980~2003年有机质含量的空间变化图。分析了研究区有机质含量增加的原因。研究结果表明,该市目前土壤有机质含量平均为14.68g kg-1,比1980年的6.0g kg-1增加了8.68 g kg-1,年均提高0.38g kg-1。土壤表层含盐量的降低为土壤养分含量提高提供了条件。