北方半干旱地区梯田土壤有机碳密度影响因素研究

针对北方半干旱地区小流域内旱地梯田的地形因子以及农作物类型对土壤有机碳密度的影响进行了研究,为合理地保障农作物生产和维持小流域的生态安全提供理论依据。试验地点在敖汉旗大五家流域,在流域内选取样地25块,共计125个土壤剖面,主要针对地形因子和农作物类型来分析其对土壤有机碳密度的影响,并得出以下结论:(1)玉米、高粱、谷子和绿豆4种作物的土壤有机碳密度随土壤深度的增加呈先下降再上升的趋势,在50~100 cm深度时土壤有机碳密度最大;(2)玉米、高粱、谷子和绿豆4种作物的土壤有机碳密度在不同的海拔高度表现不同,海拔为400~500 m时土壤碳密度最大,其次为海拔≥600 m的区域,海拔为500~600 m的区域最小;(3)玉米、高粱、谷子和绿豆4种作物的土壤有机碳密度随坡度的增大均呈现先下降后升高的趋势,坡度≤2°时土壤有机碳密度最小,在坡度为2~6°时最大;(4)在p0.05水平下,玉米、高粱、谷子和绿豆4种作物的土壤有机碳密度在不同坡向表现不同,谷子和玉米为南坡北坡西坡东坡,而高粱和绿豆则为北坡南坡西坡东坡;(5)玉米、高粱、谷子和绿豆4种作物中,绿豆的有机碳密度高于其他3种作物,平均土壤有机碳密度为0.81 g·cm-2。     

陇东黄土丘陵区坡改梯田土壤有机碳累积动态

采用时空互代法,以不同年限坡改梯田为研究对象,分析了陇东黄土丘陵区梯田土壤有机碳（SOC）的时空分布特征。结果表明,1）陇东黄土丘陵区黄绵土在坡改梯后近50 a内,农田060 cm土层土壤有机碳处于持续累积状态,2040 cm与4060 cm土层SOC较坡耕地的增幅分别为54.6%和52.4%,大于表层增幅 （33.7%）（P0.05）;各土层SOC随梯田年限的变化趋势基本一致,在修建初期（0~8 a）累积较快并超过坡耕地SOC水平（P0.01）,24 a 后有了显著提高（P0.05）,后期SOC累积变化不显著。2）不同土壤类型及地形下SOC含量及累积速率有所差异,020 cm 土层的SOC在黄绵土中累积最为明显,2040 cm与4060 cm 两个土层SOC在红粘土中的累积量最为显著（P0.05）;阴坡表层SOC大于阳坡,梯田修建25 a 后阴坡平均SOC较阳坡高22.1%。3）梯田土壤有机碳的时空变异受土壤类型的影响最大,其贡献率达62.0%,海拔和坡向影响次之,两者可解释20.4%的有机碳的变异;梯田年限和施用有机肥可分别解释11.7%和5.8%的变异。陇东黄土丘陵区坡改梯田土壤在当前经营状况下表现出较弱的碳汇效应。     

小流域土壤有机碳含量的空间变异特征研究——以内蒙古赤峰市黄花甸子流域为例

选择内蒙古赤峰市敖汉旗黄花甸子流域为研究对象,运用地统计学和ArcGIS空间分析工具相结合的方法研究流域内土壤有机碳含量的空间变异特征以及地形因子对其的影响,旨在为半干旱区土壤碳库的研究提供参考。结果表明:研究区表层（0—20 cm）与全剖面（0—100 cm）土壤有机碳平均含量分别为7.54 g/kg和6.19 g/kg,二者块金基台比均较小,为22.77%～28.36%,说明流域土壤有机碳的空间变异主要是由结构性因素引起的,随机因素对其变异影响较小。地形因子对土壤有机碳的影响表现为:土壤有机碳含量随坡度的增加而降低;不同坡向土壤有机碳含量由高到低呈现出阴坡 > 半阴坡 > 半阳坡 > 阳坡的明显分布规律;土壤有机碳含量随海拔增加呈现先增加后降低的抛物线走势。     

名山河流域不同土壤类型和土地利用方式下有机碳的分布特征

以名山河流域不同类型土壤为研究对象,研究了不同土地利用方式下土壤有机碳和团聚体中有机碳含量的分布特征。结果表明:(1)名山河流域3种类型的土壤有机碳含量在17.50~34.70g/kg之间,含量高低表现为水稻土黄壤紫色土,水稻土含量分别是黄壤和紫色土的1.32,1.39倍;从不同的土地利用方式看,水田土壤有机碳及活性有机碳含量显著高于旱地、茶园和果园,土壤活性有机碳与土壤有机碳呈极显著正相关(R2=0.884 6);(2)土壤有机碳含量在土壤剖面中表现出随着土层深度的增加而降低的趋势,表层土壤(0—20cm)有机碳含量由高到低依次为水稻土黄壤紫色土,下层土壤(20—40cm)有机碳含量为水稻土紫色土黄壤,土壤活性有机碳含量的分布具有相似规律;(3)在不同土地利用方式下,表层土壤(0—20cm)有机碳含量大小关系表现为水田旱地果园茶园,下层土壤(20—40cm)有机碳含量表现为水田果园茶园旱地,水田表层、下层土壤活性有机碳含量均极显著地高于旱地、果园、茶园,再次证明活性有机碳是表征有机碳特性的重要指标;(4)3种类型土壤的团聚体在不同的利用方式下的有机碳含量表现出随着土壤剖面加深而降低的趋势,土壤团聚体的单位有机碳含量随着粒径的减小呈现波浪形的变化趋势,各粒径团聚体中的有机碳含量与土壤有机碳含量呈正相关关系。综上可知,土壤类型的差异和土地利用方式的不同会对土壤有机碳及各粒径团聚体中有机碳的含量及分布特征产生一定的影响。     

三江平原土壤有机碳含量及其密度的空间变异特征分析

  目的  三江平原是我国重要的粮食产地,探究三江平原土壤有机碳(SOC)含量及其密度的空间分布特征及影响因素,为该区域土壤有机碳库的维持和提升提供重要依据。  方法  在三江平原地区8 km × 8 km网格法布设采样点,共采集表层（0 ~ 20 cm）土壤样品324份,开展土壤有机碳含量及其密度空间分布特征和影响因素分析。  结果  表层土壤有机碳含量平均值为30.90 ± 25.42 g kg?1、表层有机碳密度平均值为69.05 ± 48.62 t hm?2,其空间上呈“东南低－西北高”分布特征。黑土与水稻土之间土壤有机碳含量存在极显著差异（P < 0.01),与暗棕壤之间土壤有机碳含量存在显著性差异(P < 0.05);耕地－水田土壤有机碳含量最低,为27.21 g kg?1,林草地有机碳含量最高,为44.83 g kg?1,耕地与林草地之间土壤有机碳含量存在极显著差异（P < 0.01);种植水稻的土壤有机碳含量最低,为27.31 g kg?1,种植混合林的土壤有机碳含量最高为44.83 g kg?1,种植混合林与种植玉米、水稻、豆类之间的土壤有机碳含量存在极显著差异（P < 0.01)。  结论  总体看来,土地利用类型、土壤类型和作物类型三种因素对三江平原地区土壤有机碳含量及其密度均有影响,并达到显著水平。     

植被恢复对侵蚀坡地表层土壤性质的影响

为了评价表层土壤有机碳和养分对放牧和不同植被类型互作的反应,选择四川省西昌市西溪乡牛郎村马家松坡放牧丘陵坡地,分别在坡顶、上、中、下部各层采集有乔木(桉树)、灌木(米油枝)、草本3种类型植被覆盖以及无植被覆盖的0—5 cm表层土壤,测定分析了土壤容重、土壤有机碳、速效氮含量。结果表明,植被对改善表层土壤有机碳和速效氮含量的作用大小顺序为:米油枝>草本植物>桉树。米油枝、草本植物能显著提高土壤有机碳和速效氮含量,桉树改善表层土壤有机碳和速效氮含量的作用则比较小。不同坡位对土壤有机碳、速效氮含量无显著影响。不同植被类型下表层土壤容重变化为:米油枝下土壤<桉树下土壤<草地<裸地。米油枝能显著降低表层土壤容重,而在不同坡位间无显著差异。不同植被类型下表层土壤对放牧的反应不同。放牧显著降低了桉树林下表层土壤有机碳和速效氮的含量,对米油枝和草本植物覆被下表层土壤性质的影响不显著。     

秸秆和地膜覆盖条件下玉米农田土壤有机碳组分生长季动态

基于黄土高原8 a的春玉米覆盖定位试验,研究了秸秆和地膜覆盖下土壤有机碳、微生物量碳、潜在可矿化碳及颗粒有机碳在作物不同生育期的季节变化特征,探讨旱作农田不同碳组分对地表覆盖的响应规律。结果表明:1)秸秆和地膜覆盖下土壤有机碳及其各组分含量在玉米生长期间总体呈苗期下降、拔节期上升、大喇叭口—抽雄期下降、灌浆和收获期回升的变化趋势。2)与不覆盖对照相比,秸秆覆盖在大部分作物生育期均显著提高了土壤有机碳各组分含量,有助于培肥地力和土壤固碳;而地膜覆盖在作物生育后期导致土壤有机碳及各组分含量显著下降。3)秸秆覆盖下表层土壤颗粒有机碳对总有机碳变化具有重要贡献,地膜覆盖后土壤有机碳变化可能主要来自于潜在可矿化碳和颗粒有机碳,而土壤微生物量碳相对含量在不同处理间差异不大。4)对照和地膜覆盖处理土壤潜在可矿化碳和颗粒有机碳的相对含量在大喇叭口—抽雄期均有显著下降,而秸秆覆盖下两种组分的相对含量则保持平稳,表明秸秆覆盖对生育后期土壤潜在可矿化碳和颗粒有机碳有重要的补给作用。总之,黄土高原的春玉米田秸秆覆盖具有明显的提升土壤有机碳及组分含量的作用,地膜覆盖则无明显效果,且在春玉米生育后期降低了土壤总有机碳及各组分的含量。     

黔中石漠化地区水土保持措施对土壤有机碳的影响

土地石漠化是中国西南喀斯特地区的重大生态问题,石漠化治理引发土壤碳转变并对陆地碳循环产生影响。然而,石漠化地区水土保持措施对土壤有机碳的影响机制还不明确。选取典型石漠化区梯田嵌套鱼鳞坑(NL)、鱼鳞坑(FSP)、梯田(TR) 3种水土保持措施作为研究对象,以无任何水土保持措施的退耕还林地(CK)作为对照,研究不同水土保持措施土壤有机碳含量分布规律。结果表明：鱼鳞坑土壤有机碳含量分别是梯田嵌套鱼鳞坑和梯田的1.4,6.2倍,有机碳储量分别比梯田嵌套鱼鳞坑和梯田提高30.78%和444.44%,活性有机碳含量也显著大于其他2种水土保持措施,因此固碳效果最好。土壤有机碳储量与活性有机碳组分易氧化碳、可溶性碳、微生物量碳呈极显著相关(p<0.01),易氧化碳与可溶性碳、微生物量碳呈极显著相关(p<0.01),可溶性碳与微生物量碳呈显著相关(p<0.05),因此土壤活性有机碳组分能在一定程度上反映土壤质量变化情况。鱼鳞坑和梯田措施土壤全氮含量和碳氮比的增加会促进土壤有机碳固存。鱼鳞坑可作为石漠化地区生态恢复中优先考虑的治理措施。     

耕作方式对麦–玉轮作农田固碳、保水性能及产量的影响

【目的】 农田固碳保水性能是影响作物产量的关键因素,研究耕作方式对耕层 (0—20 cm) 土壤碳、水含量和产量的影响,为选择适宜该地区的最佳耕作措施提供参考。 【方法】 保护性耕作长期定位试验始于2002年,种植制度为冬小麦–夏玉米一年两熟,两季秸秆全量粉碎 (3～5 cm) 还田,试验设传统翻耕、深松、旋耕和免耕4种耕作方式。对2015—2016年作物生长各时期土壤有机碳含量、土壤含水量、碳水储量、产量和等价产量等进行了测定。 【结果】 不同处理麦–玉轮作农田0—20 cm土层有机碳含量有所不同。耕作措施对土壤有机碳含量有显著 (P < 0.05) 影响,表现为深松和免耕能显著增加0—10 cm土层有机碳含量,且以深松效果最为显著 ( P < 0.05)。与传统翻耕相比,免耕和旋耕降低了10—20 cm土层土壤有机碳含量;深松比传统翻耕显著 ( P < 0.05) 增加了小麦季土壤有机碳含量,玉米季没有显著性差异 ( P < 0.05)。0—10 cm土层,玉米季旋耕和免耕处理的土壤含水量高于深松和传统翻耕;在10—20 cm土层小麦季免耕处理土壤含水量高于其他三种耕作方式。产量结果表明,深松能有效增加作物的有效穗数、穗粒数和千粒重,进而增加籽粒产量和周年等价产量;免耕显著 ( P < 0.05) 降低了亚表层 (10—20 cm) 有机碳含量,降低穗粒数和千粒重,不利于作物增产。两年小麦玉米单作产量和周年等价产量均表现为深松 > 传统翻耕 > 旋耕 > 免耕。 【结论】 深松能有效促进耕层土壤有机碳积累和保水性能提高,增加作物的有效穗数、穗粒数和千粒重,从而增加产量;免耕显著 (P < 0.05) 提高了表土层 (0—10 cm) 碳储量,有助于增强耕层土壤的保水性能。      

东北红松阔叶林土壤有机碳空间分布异质性研究

红松阔叶林是北方森林系统的一种典型类型,在北方森林结构与功能中占有重要的地位。为了解红松阔叶林土壤有机碳空间分布规律,试验采用样线法调查了红松阔叶林土壤有机碳在剖面层次、坡向以及海拔高度方面的异质性。结果表明,红松阔叶林土壤有机碳存在明显的剖面、坡位垂直分异性和坡向水平分布异质性。随剖面深度加深有机碳含量逐渐减少,腐殖质层土壤有机碳对剖面土壤有机碳贡献率达44.2%~68.4%;土壤有机碳含量受山体坡位和坡向综合影响,阳坡腐殖质层和淀积层有机碳含量分布按坡位由高到低为:坡中部坡上部坡下部,而阴坡腐殖质层有机碳含量则在坡下部最高,坡中部最小;阳坡有机碳密度表现为坡中部坡下部坡上部,而阴坡有机碳密度随海拔升高呈显著下降趋势。     

几种绿肥的根系分泌物对土壤锌的活化效应

由于北方石灰性土壤锌有效性低,作物锌含量无法满足人体营养需求.前期研究发现种植绿肥可提高后茬小麦锌含量且后者与自身吸锌量正相关,但机制尚不明确.通过田间试验测定绿肥(黑麦豆、绿豆、高丹草)地上部锌含量,水培试验收集分析绿肥根系分泌物组成,土壤浸提试验测定根系分泌有机酸对土壤pH值及土壤锌的影响,从而揭示绿肥吸锌能力及其...     

有机物料对不同作物根系土壤腐殖质组成和结构的影响

为探讨施用有机物料后不同作物根系土壤腐殖质各组分含量和胡敏酸元素组成的变化情况,以吉林农业大学试验田培肥2a的黑土为研究对象,试验选取3种作物(玉米、大豆、白菜),每种作物设4种施肥处理,包括化肥(CK)、玉米秸秆配施化肥、树叶配施化肥和鸡粪配施化肥。采用腐殖质修改法提取水溶性物质(WSS)、胡敏酸(HA)、富里酸(FA)、胡敏素(HM),利用重铬酸钾外加热法测定腐殖质各组分有机碳含量,采用分光光度计法测定HA和FA的光学性质,通过光密度E_4/E_6值和元素组成分析HA的结构变化。结果表明:土壤总有机碳(TOC)和腐殖质各组分有机碳含量均表现为白菜玉米大豆。相比CK,配施有机物料后作物根系土壤TOC、WSS、HA含量分别显著增加5%~8%,34%~55%,8%~20%,FA含量变化不明显。相比树叶和鸡粪,秸秆可显著提高TOC含量;WSS在各物料之间差异不明显;HM含量表现为秸秆树叶鸡粪CK。有机物料对PQ值的影响因作物而异,秸秆和鸡粪对玉米、大豆根系土壤PQ值(HA占腐殖酸的比率)的影响相似,而鸡粪对白菜根系土壤PQ值的影响显著高于玉米秸秆。施用有机物料后HA的E_4/E_6未发生明显改变,FA的E_4/E_6显著提高。有机物料使根系土壤HA缩合度升高,分子结构更加复杂,且有利于HA含氮基团的形成,以秸秆处理作用最好。由此可见,有机物料具有良好的培肥效果,其中鸡粪对白菜根系土壤培肥效果最显著,秸秆与鸡粪对玉米、大豆根系土壤培肥效果相似,均显著高于化肥。     

Response of Different Crops to Arbuscular Mycorrhiza Fungal Inoculation in Phosphorus-Deficient Soil

Arbuscular mycorrhizal fungi (AMF) have the capability to improve crop yields by increasing plant nutrient supply. A pot experiment was conducted under natural conditions to determine the response of AMF inoculation on the growth of maize (Zea mays L.), sorghum (Sorghum bicolor L.), millet (Pennisetum glaucum L.), mash bean (Vigna mungo L.), and mung bean (Vigna radiata. L.) crops during 2008. The experiment was conducted as a completely randomized design in three replications using phosphorus (P)–deficient soil. Three plants were grown in 10 kg soil up to the stage of maximum growth for 70 days. Spores of AMF were isolated from rhizosphere of freshly growing wheat and berseem crops and mixed with sterilized soil with fine particles. Crops were inoculated in the presence of indigenous mycorrhiza with the inoculum containing 20 g sterilized soil mixed with 40–50 AMF spores. Inoculation with AMF improved yield and nutrient uptake by different crops significantly over uninoculated crops. Inoculated millet crop showed 20% increase in shoot dry matter and 21% in root dry matter when compared with other inoculated crops. Increases of 67% in plant nitrogen (N) and iron (Fe) were observed in millet, 166% in plant P uptake was observed in mash beans, 186% in zinc (Zn) was measured in maize, and 208% in copper (Cu) and 48% in manganese (Mn) were noted in sorghum crops. Maximum root infection intensity of 35% by AMF and their soil spore density were observed in millet crop followed by 32% in mash beans. Results suggest that inoculation of AMF may play a role in improving crop production and the varied response of different crops to fungi signifies the importance of evaluating the compatibility of the fungi and plant host species.     

黄土区梯化坡地不同土地利用方式对土壤理化性质的影响

[目的]研究覆膜作物、牧草地和撂荒地模式下梯化坡地不同土地利用方式对土壤理化性质的影响,为黄土区梯化坡地优化农业生产管理提供科学依据。[方法]以黄土区甘肃省陇西县梯化坡地为研究对象,选择5种土地利用方式(玉米地、苜蓿地、撂荒地2 a,撂荒地4 a和荒草地)按不同坡位(挖方段、中间段、填方段)进行土壤取样,对0—40 cm土层土壤理化性质进行研究。[结果]在5种土地利用方式下,土壤含水量、容重均随土层深度增加而增大,其中玉米地土壤含水量最高,容重最小;土壤机械组成均表现为:细砂粒黏粒粉粒粗砂粒;土壤含水量、容重、黏粒和粉粒均表现为:挖方段中间段填方段,而粗砂粒、细砂粒、有机碳、速效钾和水解性氮则呈现相反的趋势。土壤pH值均值变化为苜蓿地最大,撂荒地最小,且方差分析差异不显著(p0.05)。土壤有机碳、速效钾和有效磷均值均表现为玉米地最大,水解性氮均值表现为:苜蓿地玉米地撂荒地2 a荒草地撂荒地4 a。[结论]覆膜玉米地表现出对土壤含水量、容重及养分的促进作用均优于其他土地利用方式,且填方段的土壤更加肥沃,耕作中应注重加强对挖方段的施肥。     

Effects of organic manure and chemical fertilizer on soil fertility and productivity of plant and ratoon crops of sugarcane

A long-term field experiment was initiated in November, 1967 at Research Area of Department of Soil Science to study the response of nitrogen to pearl millet-wheat cropping system at various doses and modes of farmyard manure application. The soil organic carbon increased with farmyard manure application and ranged from 0.68% in control to 1.82% in the plot receiving the highest annual dose (90 Mg ha^?1) of farmyard manure. To study the contribution of farmyard manure on the productivity of pearl millet and wheat crops, the constants (intercept and slope) were determined between the grain yield of pearl millet and wheat crops with increasing dose of fertilizer nitrogen. Another linear regression was fitted between the intercept of the linear model and the soil organic carbon content. It has been observed that with each unit increase in the soil organic carbon, the productivity of pearl millet increased by 273 kg ha^?1 and that of wheat by 1591 kg ha^?1. The regression between the slope and soil organic carbon was linear in case of pearl millet (R² 0.49) but in case of wheat there was no relationship.     

Inclusion of upland crops in rice‐based rotations affects chemical properties of clay soil

In the Mekong Delta, alluvial clay soils have been used intensively over many generations for rice monoculture. Currently, farmers are confronted by problems of declining land productivity. Rotations comprising rice and upland crops can increase soil quality, but appropriate cropping systems for paddy soils have received relatively little attention. We therefore established a multiyear field experiment to evaluate the long‐term effects of cropping systems with different rotations on soil chemical quality. Systems laid out in a randomized complete block design with four replications were as follows: (i) traditional rice monoculture with three rice crops per year (R‐R‐R), (ii) rotation with two rice crops and maize (R‐M‐R), (iii) rotation with two rice crops and mung bean (R‐Mb‐R) and (iv) rotation with one rice crop and two upland crops – mung bean and maize (R‐Mb‐M). We hypothesized that systems with rotations of upland crops and their temporary beds improve chemical quality of paddy rice soil. Soil chemical parameters were determined to better understand and evaluate the sustainability of the cropping systems. Results showed an improvement in soil chemical quality for cropping systems with rotations of rice and mung bean or maize grown on temporary beds (R‐M‐R, R‐Mb‐R and R‐Mb‐M), particularly the content of soil organic carbon and a presumed hydrolysable labile carbon fraction compared with rice monoculture. Less pronounced improvements in EC, CEC and total acidity were also found with inclusion of upland crops. Cropping systems of rice with upland crops improved rice grain and straw yield in subsequent season in contrast with rice monoculture.     

Effect of Cropping System on Physical Properties of Clay Soil Under Intensive Rice Cultivation

Cropping systems are thought to alter soil quality in paddy rice fields. This study was conducted to quantify the long‐term effects of continuous crop production under different cropping systems with different crop rotations on physical properties of alluvial clay soil in the Mekong Delta, Vietnam. Soil samples were collected from four treatments: (i) traditional intensive rice monoculture with three rice crops per year (R–R–R); (ii) rotation with two rice crops and maize (R–M–R); (iii) rotation with two rice crops and mung bean (R–Mb–R); and (iv) rotation with one rice and two upland crops, mung bean and maize (R–Mb–M). We hypothesized that cropping systems with rotations of upland crops and their temporary beds improve the physical quality of paddy rice soil; hence, they are better options towards sustainable agriculture. Results show an improvement of soil physical quality for systems with two rice crops and one upland crop (R–M–R and R–Mb–R) and those with one rice crop with two upland crops (R–Mb–M) compared with intensive rice monoculture (R–R–R). This was translated in decreased bulk density and soil strength, increased soil organic carbon and total porosity, and higher aggregate stability index, plant‐available water capacity, and Dexter's S index, especially at depths of 10–20 and 20–30 cm. The systems with different upland crops (maize or mung bean) showed similar high physical quality improvement. To maintain soil quality in future seasons, introducing a cropping system with at least one upland crop in rotation with rice is recommended. Copyright © 2014 John Wiley & Sons, Ltd.     

Soil carbon as affected by cover crops under no‐till under tropical climate

In tropical, low‐fertility soils, crop yields are dependent on soil carbon, and cropping systems under no‐till can increase soil C stocks. Plant residues supplied by cover crops in no‐till systems may improve aggregate stability and soil carbon, which may be further increased with the introduction of a legume in the cropping system. This research studied the effects of cover crops in rotation with soybean under no‐till on soil carbon and nitrogen, in Botucatu, Brazil, for 3 yr. The cover crops were millet (Penninsetum americanum Leek), cober crop (Sorghum bicolor × Sorghum sudanense) and sunn hemp (Crotalaria juncea L.), grown in the spring. Fallow without cover crops was used as a control. Grain sorghum (Sorghum bicolor L. Moench) and soybean (Glycine max (L.) Merril) were grown in fall–winter and summer, respectively. Generally, cover crops increased soil carbon contents, but soil N was only increased by sunn hemp in the particulate organic C fraction. An increase in the labile carbon fraction in the topsoil layers was closely related to cover crop root development. Fallow in spring should not be recommended in degraded soils with lowcarbon stock. Labile‐fractioned soil organic carbon and total carbon levels are more efficiently increased by grasses than by legumes in the short term, and grasses cropped in spring increase soil C/N ratio. Conversely, the introduction of a legume (sunn hemp) maintained a more stable C/N ratio, that is around 10, which would be more effective in increasing soil C in the long term.     

植被覆盖条件下纳米碳对黄土坡面养分流失调控的试验研究

将纳米材料应用于坡面养分流失调控对减少黄土坡面养分流失等有着重要意义。基于神木六道沟流域上的坡面人工模拟降雨试验,分析了不同纳米碳含量(质量百分比分别为0%,0.1%,0.5%,0.7%,1.0%)对黄土坡面养分迁移过程的影响。结果表明:(1)同一作物的小区添加不同纳米碳含量对养分流失影响不明显;5种下垫面条件下,养分流失量均呈随纳米碳含量增加而降低的趋势,其中纳米碳含量为0.5%及0.7%对降低径流养分流失量的效果最好。不同纳米碳含量条件下,径流中的养分流失量从小到大为:空地玉米柠条绿豆苜蓿。(2)人工模拟降雨条件下,土壤表层养分在0—5cm内均有明显减少。而大于5cm深度的土壤中的养分值在降雨后有所增加,但随着深度增大养分增加量减少,而且添加不同浓度纳米碳导致养分值减少的速率不同。(3)不同纳米碳含量下与不同植被覆盖下径流中各离子的养分流失调控效果评价是径流中不同离子的平均浓度与平均流失率均随纳米碳含量的增加而减小,规律性较为明显。     

不同饲料作物对苏打盐碱土改良效应研究

为探明不同饲料作物种植对苏打盐碱土改良的影响，以内蒙古科尔沁旗苏打盐碱地为研究对象，设置3个土壤等级(中、良、优)和5个饲料作物种类(高丹草、稗草、青贮玉米、湖南稷子、甜高粱)，共计15个处理，研究不同土壤等级下，饲料作物对土壤盐化碱化、养分含量变化的影响，并根据模糊物元-熵权模型进行土壤改良效应评价。结果表明：饲料作物收获后土壤平均p H较播种前降低1.64%，种植前后土壤p H差异不显著；土壤EC、总可溶性盐、碱化度显著降低(P<0.05)。不同饲料作物种植降低土壤Ca²⁺、Mg²⁺、HCO₃^–+CO₃^2–含量，提高土壤K⁺+Na⁺、Cl^–含量，对土壤SO₄^2–含量影响存在差异，收获后土壤碱解氮和速效钾含量比播种前分别降低15.15%、24.06%。基于模糊物元-熵权模型得出，青贮玉米对土壤盐渍化程度较高的土壤改良效果更佳，而甜高粱与高丹...