黄土区几种土壤培养过程中可溶性有机碳、氮含量及特性的变化

对不同地域农田和林地土壤进行35 d好气培养研究,结果表明:不同土壤培养过程中可溶性有机碳(SOC)含量呈明显下降,而可溶性有机氮(SON)含量却呈明显增加趋势。不同农田土壤相比,在培养起始时和培养过程中红油土SOC和SON的平均含量均高于黑垆土和淋溶褐土;同为黑垆土,林地土壤SOC和SON含量均明显高于相应农田土壤。与起始值相比,土壤培养后提取的可溶性有机物的UV280和HIXem(Hu-mification index)值均明显增加,其中HIXem值在培养的第8天和第35天时呈显著增加趋势。随着培养过程的持续,SOC/SON比值逐渐下降。相关分析发现,培养第35天时SOC的减少幅度与UV 280增加比例呈显著正相关;培养第8天时SOC的减少比例与起始HIXem值呈显著负相关。说明UV280和HIXem值可以在一定程度上反映可溶性有机物种类和结构特性的变化。     

有机肥料和土壤中的有机磷对水稻的营养效果

本文对三种有机肥料和二种土壤的肌醇六磷酸磷含量和有机磷进行了测定和分组,通过无菌溶液培养,比较了肌醇六磷酸磷与无机磷在等磷量的条件下对水稻的营养效果.结果表明:猪、鸡粪中有机磷的形态主要是以肌醇六磷酸钙镁盐为主,而土壤和牛粪是以肌醇六磷酸铁的形式为主.肌醇六磷酸磷对水稻的营养效果明显优于无机磷.磷的分组结果表明:猪、鸡粪中有机磷以活性和中等活性有机磷为主,而土壤则以稳定性有机磷为主,牛粪介于二者之间.因此,猪、鸡粪中有机磷的有效性高于牛粪,而以土壤中的有机磷为最低.     

坡耕地黑土有机碳和全氮的迁移与累积平衡

本文利用137CS示踪技术计算东北黑土坡耕地土壤再分布速率,结合表层土壤有机碳(SOC)和全氮(TN)含量动态,探索典型漫岗坡地SOC和TN流失量的空间分布特征,据此计算研究区近50年来SOC和TN迁移、累积平衡。研究结果表明:研究区土壤再分布速率介于-24.61~33.56 T/HM2/A,绝大部分地区处于中度和轻度侵蚀状态,约占研究区总面积的83.66%,沉积面积占总面积的15.62%。SOC和TN的流失量与土壤再分布速率相一致,坡肩部位SOC和TN流失量最大,侵蚀损失率分别为407.57 KG/HM2/A和39.94 KG/HM2/A;其次为坡背和坡顶,平均流失量分别为244.2 KG/HM2/A和17.93 KG/HM2/A;坡脚和坡趾表现为累积,平均累积量分别为-207.2 KG/HM2/A和-20.56 KG/HM2/A。整个研究区SOC和TN的相对流失量>50%的面积分别占10.45%和11.21%。整个研究区48年来土壤净迁移泥沙量为45.54 T/A,其中,SOC流失量为612.62 KG/A,TN流失量为47.20 KG/A。考虑迁移泥沙对土壤有机质的富集作用,迁移损失的SOC和TN量比原计算值高52%。     

Comparison of glycine uptake by pak choi in organic and conventional soil under different glycine concentrations: A pot study

Many studies have shown that plants can utilize organic N in the form of amino acids. However, it is unclear whether the glycine‐uptake capability responds differently to various farm management systems, and whether the interaction of farm management type with soil glycine concentrations affects the glycine uptake by plants. A pot experiment was conducted in which pak choi (Brassica campestris ssp. chinensis Makino var. communis Tsen et Lee) was grown in soil from organic and conventional agricultural systems for 15 d prior to labeling with 2‐¹³C, ¹⁵N‐glycine in a range of Gly concentrations (0, 0.005, 0.05, 0.5, 5, and 15 μg N g^?1 dry soil). The glycine uptake rate increased with increasing applied N concentrations, whereas the glycine recovery increased initially and then decreased. Regardless of glycine concentration, the glycine uptake rates of whole plants were moderate, but not significantly higher in organic than in conventional soil. The plant glycine recovery in organic soil was significantly higher than in conventional soil. Therefore, we suggest that pak choi glycine uptake differs under organic and conventional management systems. More research efforts should focus on the nutritional function of organic N in organic systems.     

氮锌复合作用对单播和混播牧草氮素来源的影响

在亚热带中山草地黄棕壤上研究了氮锌复合作用对单播和混播牧草氮素来源的影响 ,结果表明 :施氮降低了白三叶前期固氮百分数 ,但低水平施氮显著提高了白三叶后期固氮百分数。在各种施氮水平下 ,施锌 6mg kg之处理 %Ndfa最高。施氮显著降低了氮转移的数量 ,低量施锌促进了氮转移 ;施氮促进了牧草对肥料氮的吸收 ,所有施氮水平下 ,单播黑麦草 %Ndff以施锌 6～ 2 0mg kg较高。在施氮 3 0～ 90mg kg,混播黑麦草和混播白三叶 %Ndff以施锌 6～ 2 0mg kg较低 ;单播和混播黑麦草 %Ndfs随施氮水平增加显著下降 ,施锌对单播黑麦草的 %Ndfs影响不明显。在所有施氮水平下 ,施锌 6～ 2 0mg kg减少了混播白三叶和混播黑麦草对土壤氮的吸收     

人为活动对云南纳帕海湿地土壤碳氮变化的影响

以纳帕海湿地原生沼泽作为参照 ,选择人为干扰下的沼泽化草甸 ,草甸和排干湿地开垦的耕地作为研究对象 ,研究人为干扰对纳帕海湿地土壤碳氮变化的影响。两年的定位研究结果表明 :沼泽土壤C/N值较高 ;人为干扰下纳帕海湿地土壤空间结构上土壤有机质 0～ 2 0cm表层与 2 0～ 4 0cm下层相差 4倍 ,水平分布上则随人为干扰加强、沼泽化过程减弱而降低 ,下降幅度高达 2 2 .92 %～ 6 9.6 4 %;土壤全氮及其空间分布呈现与有机质相同趋势 ,两者相关系数r=0 .98;NH 4 N、NO-3 N与全氮和水解氮相关系数分别为r=- 0 .74、r=- 0 .6 5 ,r=- 0 .81、r=- 0 .76。表明了纳帕海湿地沼泽土壤较低的矿化量和对碳的固定及较大的氮累积量 ,以及人为活动干扰后湿地土壤碳氮养分的释放变化。     

ASSESSMENT OF LAND COVER CHANGES AND THEIR EFFECT ON SOIL ORGANIC CARBON AND SOIL TOTAL NITROGEN IN DAQING PREFECTURE,CHINA

The aim of this study was to examine the influence of land cover changes on soil organic carbon (SOC) and soil total nitrogen (STN) in the Daqing Prefecture of China, where heavy industrialisation in the form of dense oil wells has impacted the environment. Time‐series presentations for the period 1978 to 2008 of remotely sensed data and soil survey data were used to assess the extent of the changes. The study revealed soil degradation under all land cover types and in all soil types, grassland retreat (−15 per cent), swampland retreat (−45 per cent) and increases in the area of farmland (+19 per cent), sand land (+1450 per cent) and alkaline land (+52 per cent). Depletion of the SOC pool occurred in swampland (−64 per cent) both because of the decrease in the area of swampland and because of a decrease in SOC density (−34 per cent). An increase in the SOC pool occurred in alkaline land because of the increase in the area and also because of an increase in SOC density (+297 per cent), but there was little change in the SOC pool in farmland because the increase in area was largely offset by a decrease in SOC density (−14 per cent). The decrease in the STN pool was substantial (−44 per cent), with the largest contributor being the decrease in swamplands (−74 per cent), partly because of the decrease in the area of swampland and partly because of a decrease in STN density (−52 per cent). Large decreases in the STN pool also occurred in farmland (−22 per cent) and grassland (−41 per cent). The direct impacts of construction associated with the expansion of the oil industry were overshadowed by indirect impacts such as interference with water flows and water levels resulting in salinisation of soil. The study also revealed that land cover changes are much more dynamic than a simple analysis would reveal, and because of lag times in the loss of SOC, soil degradation will continue even if land cover changes cease. Copyright © 2012 John Wiley & Sons, Ltd.     

江苏下蜀林区土壤溶解有机碳与土壤因子的关系

采用TOC-5000A总有机碳仪测定了江苏下蜀森林土壤溶解有机碳(DOC)的含量,分析了土壤DOC与土壤因子的关系。结果表明:酸性森林土壤中,DOC与有机C、全N、碱解N、有效P等养分因子之间呈极显著或显著的正相关关系,土壤DOC与土壤肥力状况关系密切,因而可以作为评价土壤肥力性状的生物学指标。土壤DOC与土壤中有机络合态Fe、有机络合态Al和活性羟基Al之间呈极显著或显著的正相关。土壤中有机C的运输是调整土壤中Al和Fe的溶出及迁移的一个重要因子。土壤DOC与交换性Al、pH值、全P、速效K之间无相关关系。     

模拟酸雨对红壤中铝和水溶性有机质溶出及重金属活动性的影响

在模拟酸雨作用下 ,研究了重金属污染和未污染的酸性红壤和黄红壤中铝和水溶性有机质的溶出以及对重金属活动性的影响。结果表明 ,随模拟酸雨pH值下降 ,土壤pH值和盐基饱和度明显降低 ,而交换性酸度明显增加 ,污染土壤中交换性氢含量比未污染土壤高 ,而交换性铝含量比未污染土壤低。铝溶出量与模拟酸雨pH值密切相关 ,当模拟酸雨pH值在 5 .60～ 3.5 0时 ,供试红壤浸出液中铝浓度几乎在同一水平 ;当pH≥ 4 .5 0时 ,供试黄红壤中溶出铝亦未明显变化 ;当模拟酸雨pH =3.5 0时 ,未污染黄红壤中铝溶出明显增多 ;当pH =3.0 0时 ,供试土壤中铝溶出量急剧增加。随模拟酸雨pH值下降 ,污染土壤中铝溶出比未污染土壤低 ,而有效态重金属活动性明显增加 ;污染土壤中水溶性有机质比未污染土壤溶出明显增加 ,水溶性有机质 -重金属络合体促进了重金属的溶解迁移行为。     

SEASONAL CHANGES IN LEAF NITROGEN OF OLIVE TREES GROWN UNDER DIFFERENT IRRIGATION REGIMES AND CROP LEVEL

An experiment was conducted over 12 months using field-grown olive trees (Olea europaea) to assess the combined effect of soil water availability and fruit number on seasonal changes in leaf nitrogen (N) concentration. Three irrigation regimes were established and three trees per irrigation treatment were thinned to reduce their yield to about half that of unthinned trees. The N concentration of fully-expanded leaves from either the current-year growth or one-year old part of fruiting shoots was determined every two months. Nitrogen concentration was higher in current-year leaves than in one-year old ones at most sampling dates. Maximum values of leaf N were measured in spring, minimum values in August. Leaf N concentrations were positively correlated with leaf water potential during fruit development. This relationship was weak at the onset of rapid oil accumulation in August and became more evident at harvest. There was no correlation between leaf N and crop level.     

RATIO OF CALCIUM TO MAGNESIUM INFLUENCES BIOMASS,ELEMENTAL ACCUMULATIONS,AND PIGMENT CONCENTRATIONS IN KALE

Producers use elemental ratios, such as calcium (Ca): magnesium (Mg), in fertility programs to ensure sufficient nutrient uptake. Kale (Brassica oleracea L. var. acephala D.C.) accumulates high levels of carotenoids which can be beneficial for human health. Objectives were to determine the influence of Ca:Mg fertilization on 1) biomass, 2) essential nutrients, and 3) carotenoids in kale leaf tissues. ‘Redbor’ kale was greenhouse-grown in solution culture. Ca:Mg ratio treatments were 9:1, 6:1, 3:1, 1:3, 1:6, and 1:9. Ca:Mg ratio significantly affected biomass, nutrient accumulation, and carotenoids. Plant biomass decreased linearly (P ≤ 0.001) and β-carotene, lutein, neoxanthin, and antheraxanthin all increased, then decreased quadratically (P ≤ 0.001) as the ratio of Ca:Mg changed from 9:1 to 1:9. Ca:Mg ratio also affected leaf tissue Ca, Mg, potassium (K), sulfur (S), boron (B), manganese (Mn), molybdenum (Mo) and zinc (Zn). Results indicate that producers wishing to maximize elemental uptake and carotenoid content of kale need to consider the ratio of Ca:Mg in their fertility programs.