A spatially explicit representation of conservation agriculture for application in global change studies

Conservation agriculture (CA) is widely promoted as a sustainable agricultural management strategy with the potential to alleviate some of the adverse effects of modern, industrial agriculture such as large‐scale soil erosion, nutrient leaching and overexploitation of water resources. Moreover, agricultural land managed under CA is proposed to contribute to climate change mitigation and adaptation through reduced emission of greenhouse gases, increased solar radiation reflection, and the sustainable use of soil and water resources. Due to the lack of official reporting schemes, the amount of agricultural land managed under CA systems is uncertain and spatially explicit information about the distribution of CA required for various modeling studies is missing. Here, we present an approach to downscale present‐day national‐level estimates of CA to a 5 arcminute regular grid, based on multicriteria analysis. We provide a best estimate of CA distribution and an uncertainty range in the form of a low and high estimate of CA distribution, reflecting the inconsistency in CA definitions. We also design two scenarios of the potential future development of CA combining present‐day data and an assessment of the potential for implementation using biophysical and socioeconomic factors. By our estimates, 122–215 Mha or 9%–15% of global arable land is currently managed under CA systems. The lower end of the range represents CA as an integrated system of permanent no‐tillage, crop residue management and crop rotations, while the high estimate includes a wider range of areas primarily devoted to temporary no‐tillage or reduced tillage operations. Our scenario analysis suggests a future potential of CA in the range of 533–1130 Mha (38%–81% of global arable land). Our estimates can be used in various ecosystem modeling applications and are expected to help identifying more realistic climate mitigation and adaptation potentials of agricultural practices.     

长期不同耕作措施对土壤团聚体特征及微生物多样性的影响

以豫西丘陵地区15年的保护性耕作试验为平台,研究了不同耕作措施对土壤水稳性团聚体分布及稳定性和土壤细菌、古菌及真菌多样性的影响.结果表明: 与传统耕作相比,免耕、深松覆盖和小麦-花生两茬耕作处理增加了>2000 μm粒级团聚体的相对含量,减少了<53 μm粒级团聚体的相对含量;显著提高了土壤团聚体平均质量直径(MWD),提高幅度分别为18.0%、12.2%和50.4%.免耕、深松覆盖和两茬耕作处理均可提高细菌、古菌和真菌的Shannon指数(H),细菌分别提高0.3%、0.3%和0.6%,古菌分别提高20.2%、40.5%和49.1%,真菌分别提高23.7%、19.5%和25.8%.土壤细菌和古菌的H指数与大团聚体含量(R_0.25)和MWD显著相关,而真菌的H指数与R_0.25和MWD相关性不显著.综上,采用免耕、深松结合小麦秸秆覆盖以及小麦-花生轮作等措施均可改善土壤团聚体状况,提高土壤微生物多样性指数.
     

保护性耕作对陇中旱作农田水分特征的影响

陇中旱农区生产力水平低而不稳,而保护性耕作措施是农业可持续发展的重要途径.本研究依托2001年建立在陇中旱农区的长期不同耕作措施的定位试验,研究了不同耕作措施对土壤水分入渗、蒸发、作物产量和水分利用效率的影响.该试验共设6个处理,分别为传统耕作(T)、免耕秸秆覆盖(NTS)、免耕(NT)、传统耕作+秸秆翻入(TS)、传统耕作+覆膜(TP)、免耕覆膜(NTP),春小麦和豌豆年间轮作.结果表明:与T处理相比, NTS处理的小麦地和豌豆地的土壤容重显著降低,总孔隙度显著增加.保护性耕作措施降低了豌豆地0～5 cm土壤渗吸率,NTS处理渗吸率比T处理降低56.2%.保护性耕作提高了土壤饱和导水率,无论小麦地和豌豆地,NTS均比T处理显著提高了饱和导水率,增幅为52.8%～107.1%.保护性耕作显著降低了作物生育期棵间蒸发量,NTP、TP、NTS比T处理降低了14.4%～50.8%,并减弱了雨后土壤蒸发.保护性耕作提高了作物产量和水分利用效率,NTS、TP、NTP的产量比传统耕作提高了9.5%～62.8%,水分利用效率比传统耕作提高了0.4%～50.9%.因此,在陇中旱农区,保护性耕作措施可以提高水分利用效率,增加作物产量.     

渭北旱作麦田长期保护性耕作土壤肥力特征综合评价

以渭北旱作麦田10年长期定位试验4种土壤物理指标和7种化学指标组成的土壤肥力性质为评价指标,研究长期实施6种保护性耕作处理后11种土壤指标的累积效应,并运用主成分分析对不同耕作处理下土壤肥力的累积效果进行综合评分,以期为渭北旱塬土壤可持续利用和管理提供科学依据.结果表明: 与传统连续翻耕(CT/CT)比较,免耕与深松轮耕(NT/ST)、深松与翻耕轮耕(ST/CT)、翻耕与免耕轮耕(CT/NT)处理土壤容重分别降低了6.6%、5.9%、6.6%,连续免耕(NT/NT)与连续翻耕差异不明显.>0.25 mm力稳性团聚体含量以NT/NT最高,水稳性团聚体含量以NT/ST最高.与传统翻耕相比,5种耕作处理力稳性团聚体增加了1.7%～10.1%,土壤有机质增加了0.6%～11.2%,氮、磷、钾含量也均有提高.通过主成分分析将11种土壤指标分为两个主成分综合表征土壤质量,第1主成分的贡献率为75.5%,在其上有较高载荷的指标为土壤有机质、水稳性团聚体、全氮、全磷、全钾、碱解氮、速效磷、速效钾含量,容重、孔隙度,第2主成分的贡献率为13.2%,力稳性团聚体在其上有较高载荷,两者共解释了88.6%的原变量.长期不同耕作效果逐渐累加形成的土壤肥力水平依次表现为:NT/ST>ST/CT>CT/NT>NT/NT>ST/ST>CT/CT,NT/ST处理形成了一个相对平衡和较高肥力质量的土壤状况,为渭北旱作麦田最适宜的轮耕模式.     

不同耕作方式对内蒙古旱作农田土壤侵蚀的影响

研究黄河流域内蒙古黄土高原丘陵区农田土壤侵蚀状况,对本区域生态农业建设具有重要的意义。试验于2006年在内蒙古呼和浩特市清水河县进行,设免耕(NT)、免耕覆盖(NS)和传统耕作(CT)3种耕作处理方式,种植作物为胡麻和燕麦,观测了全年降雨量和地表水径流量及土壤流失量。结果表明:免耕覆盖及免耕能显著减少降雨对土壤的侵蚀,与传统耕作相比,免耕覆盖处理的燕麦地地表水径流量和土壤的流失量分别减少21.9%和88.3%;3种耕作方式的土壤侵蚀量均受到坡度的影响,并随着坡度的增大而增大,相同环境条件下,不同作物存在一定差异;通过对3种耕作方式下,胡麻和燕麦田土壤侵蚀量与降雨量的关系符合幂函数,且拟合优度良好,均>0.9。     

稻田实行保护性耕作对水稻产量、土壤理化及生物学性状的影响

在江西双季稻田进行长期田间定位试验,分析了多年保护性耕作对水稻产量、土壤理化性状及生物学性状的影响。连续8a稻田保护性耕作处理的平均产量高于传统耕作4.46%—8.79%,各处理的有效穗数、每穗粒数和结实率均高于对照,而各处理间穗长和千粒重差异不显著。实行稻田保护性耕作处理的土壤容重低于传统耕作3.6%—5.6%,而总孔隙度和毛管孔隙度分别高出传统耕作1.6%—17.4%、2.4%—16.7%。与传统耕作相比,连续8a保护性耕作显著提高了土壤有机质(2.9%—10.0%)、有效磷(4.8%—31.6%)、速效钾(9.7%—25.7%)。在2005年免耕+插秧的土壤真菌数量最多,显著高于对照处理51.6%,免耕+抛秧在2008年达到最大,显著高于对照处理54.1%。2012年免耕+抛秧、免耕+插秧显著高于对照126.1%、121.1%;另外,各处理间过氧化氢酶、脲酶活性均差异不显著。8a间土壤转化酶活性变化范围在0.292—0.451 mg/g之间,其中2005—2007、2012年均是免耕+抛秧达到最大,与对照相比,增加范围为72.7%—137.7%,且差异显著(P0.05)。因此,实行稻田保护性耕作是适合江南丘陵区双季稻区农业可持续发展的有效模式之一,其中免耕+抛秧和免耕+插秧两种方式效果最为显著。     

旱地农田不同耕作系统的能量/碳平衡

摘要：加强农田土壤保持耕作管理,科学认识和调控农田耕作系统能流碳流,提高农业生态系统固碳减排能力,对于减缓农业对全球温室效应的贡献具有重要意义。本研究以北方半湿润偏旱区山西寿阳旱作春玉米土壤保持耕作试验研究为基础,利用田间定位观测数据、辅助能投入参数,土壤呼吸田间原位测定,以及农业生态系统能量/碳平衡分析及碳循环过程模拟方法,综合分析和比较不同耕作（CT传统、RT少耕和NT免耕）系统能量/碳平衡及能-碳关联影响。与CT比较,采用RT和NT措施下工业能耗CO2-C损失降低约4%—12%（相当11—35 kg CO2-C?hm-2?a-1）。在RT和NT系统下耗能系数可降低约6%—10%,能量生产效率可提高约7%—12%。2006—2007年由田间原位测定土壤呼吸CO2-C释放通量估算,在玉米休闲期（尤其是秋耕处理后）,NT条件下土壤呼吸速率一般为最低（NT NT（2005380）>CT（1987375）。不同耕作下的玉米籽粒产量与生育期土壤呼吸通量趋势基本吻合,如2006-2007年玉米产量（kg?hm-2?a-1）平均为,RT（5614268）>NT（5533564）>CT（5487278）。玉米籽粒产量与生育期土壤呼吸通量之间呈密切相关（R2=0.88）。本研究结果得出,RT和NT对农田耕作系统的影响呈碳汇效应,且一般为NT >RT;而CT处理表现为碳源。RT和NT通过增加土壤碳投入是维持和提高土壤有机碳的有效途径。     

Climate drives global soil carbon sequestration and crop yield changes under conservation agriculture

Conservation agriculture has been shown to have multiple benefits for soils, crop yield and the environment, and consequently, no‐till, the central practice of conservation agriculture, has rapidly expanded. However, studies show that the potential for carbon (C) sequestration in no‐till farming sometimes is not realized, let alone the ability to maintain or improve crop yield. Here we present a global analysis of no‐till‐induced changes of soil C and crop yield based on 260 and 1,970 paired studies; respectively. We show that, relative to local conventional tillage, arid regions can benefit the most from conservation agriculture by achieving a win‐win outcome of enhanced C sequestration and increased crop yield. However, more humid regions are more likely to increase SOC only, while some colder regions have yield losses and soil C loss as likely as soil C gains. In addition to site‐specific characteristics and management, a careful assessment of the regional climate is needed to determine the potential benefits of adopting conservation agriculture.     

Assessment of carbon sustainability under different tillage systems in a double rice cropping system in Southern China

Purpose

Adoption of the carbon (C)-friendly and cleaner technology is an effective solution to offset some of the anthropogenic emissions. Conservation tillage is widely considered as an important sustainable technology and for the development of conservation agriculture (CA). Thus, the objective of this study was to assess the C sustainability of different tillage systems in a double rice (Oryza sativa L.) cropping system in southern China.

Methods

The experiment was established with no-till (NT), rotary tillage (RT), and conventional tillage (CT) treatments since 2005. Emission of greenhouse gasses (GHG), C footprint (CF), and ecosystem service through C sequestration in different tillage systems were compared.

Result and discussion

Emission of GHG from agricultural inputs (Mg CO₂-eq ha^?1 year^?1) ranged from 1.81 to 1.97 for the early rice, 1.82 to 1.98 for the late rice, and 3.63 to 3.95 for the whole growing season, respectively. The CF (kg CO₂-eq kg^?1 of rice year^?1) in the whole growing seasons were 1.27, 1.85, and 1.40 [excluding soil organic carbon (SOC) storage] and 0.54, 1.20, and 0.72 (including SOC storage) for NT, RT, and CT, respectively. The value of ecosystem services on C sequestration for the whole growing seasons ranged from ¥3,353 to 4,948 ha^?1 year^?1 and followed the order of NT > CT > RT. The C sustainability under NT was better than that under RT for the late, but reversed for the early rice. However, NT system had better C sustainability for the whole cropping system compared with CT.

Conclusions

Therefore, NT is a preferred technology to reduce GHG emissions, increase ecosystem service functions of C sequestration, and improve C sustainability in a double rice cropping region of Southern China.     

不同耕作措施对土壤真菌群落结构与生态特征的影响

以传统耕作（T）为对照，研究了免耕秸秆覆盖（NTS）、免耕（NT）、秸秆还田（TS）3种保护性耕作措施对黄土高原西部雨养农业区耕层土壤真菌数量、垂直分布及群落结构的影响。结果表明：不同耕作措施对土壤真菌数量有一定影响，耕层土壤真菌总数．TS〉T，NTS〉NT，T〉NT；耕作措施对真菌群落结构的影响比较明显，3种保护性耕作处理其土壤均以绿僵菌属（Metarrhizium）、腐霉属（Phythium）、曲霉属（Aspergillus）占绝对优势，B-P优势度指数三者之和都在0．6左右；而T处理占绝对优势的菌属是绿僵菌属（Metarrhizium）和镰刀菌属（Fusarium），B—P优势度指数二者之和在0．7左右；土壤真菌群落的多样性指数和均匀性指数均呈现NTS〉TS〉T〉NT。因此，在黄土高原西部雨养农业区实施NTS和TS耕作措施，既有利于土壤有益真菌数量的增加，提高养分转化率，又有利于促进该区农业的可持续发展。     

不同耕作措施对黄土高原旱地土壤呼吸的影响

在甘肃省定西市李家堡镇设置不同耕作措施试验,对春小麦、豌豆双序列轮作下的土壤呼吸及其对应时间的冠层温度、土壤水分进行了测定.结果表明：春小麦和豌豆在整个生育期内的土壤呼吸都表现出不同的变化趋势,春小麦地土壤呼吸在拔节前期、灌浆期和收后分别达到高峰期;豌豆地土壤呼吸在五叶期、吐丝期、开花结荚期和收后分别达到高峰期.免耕秸秆覆盖处理和传统耕作处理下春小麦地土壤呼吸日变化明显,免耕秸秆覆盖处理明显低于传统耕作处理;而豌豆地土壤呼吸日变化不明显.春小麦和豌豆冠层温度均与土壤呼吸呈显著线性相关,春小麦孕穗期相关性最高,灌浆期次之;豌豆开花结荚期相关性最高,分枝期次之.土壤含水量与土壤呼吸间存在极显著的凸型抛物线型相关,保护性耕作下的相关性都高于传统耕作,其中免耕秸秆覆盖处理的春小麦地和豌豆地土壤含水量与土壤呼吸的相关性在各层次土壤中均为最高,10～30 cm土壤含水量对春小麦地土壤呼吸的影响最大,5～10 cm土壤含水量对豌豆地土壤呼吸的影响最大.与传统耕作相比,免耕秸秆覆盖、免耕、传统耕作秸秆还田、传统耕作结合地膜覆盖、免耕结合地膜覆盖5种保护性耕作措施都能不同程度地降低土壤呼吸,其中免耕秸秆覆盖优势最明显.     

Population Dynamics of Heterodera glycines in Conventional Tillage and No-Tillage Soybean/Corn Cropping Systems

The effects of no-tillage (NT), conventional tillage (CT), and crop rotation on soybean yield and population dynamics of Heterodera glycines were compared during a 7-year study in a silty clay loam soil with 6% organic matter. Either H. glycines-resistant ''Linford'' soybean or susceptible ''Williams 82'' soybean was rotated with corn and grown on 76-cm-wide rows in both tillage systems. Soybean was planted in 1994, 1996, 1998, 1999, and 2000. Yield of Linford was significantly greater than Williams 82 in all years. Soybean yield was affected by tillage in 1999 and 2000. No-tillage production tended to support more reproduction (R = number of eggs at harvest/number of eggs at planting) on both cultivars. The largest R for Williams 82 were in 1998: 58.35 for NT plots and 11.78 for CT plots. For Linford, the largest R were 12.09 for NT plots in 1996, and 3.71 for CT in 1999. When corn was planted, R decreased more in NT. When soybean was planted in years subsequent to 1994, numbers of eggs at harvest (Pf) were greater for Williams 82 NT than for Williams 82 CT or Linford in both tillage systems; however, crop rotation with corn negated these population increases. The soil became suppressive to H. glycines in 1999 and was suppressive in 2000. After the 3 years of continuous soybean, Pf per 250 cm[sup3] soil were 2,870 for Williams 82 NT, 791 for Williams 82 CT, 544 for Linford NT, and 990 for Linford CT in 2000, compared with Pf of 13,100 for Williams 82 NT, 15,000 for Williams CT, 2,360 for Linford NT, and 2,050 for Linford CT in 1994. Describing population dynamics solely on the basis of R was not adequate, but also required independent examination of initial populations following overwintering and Pf after the growing season. Planting soybean either NT or CT in rotation with corn did not result in long-term increases in numbers of H. glycines eggs.     

渭北旱塬农田不同耕作模式对土壤性状、玉米产量和水分利用效率的影响

通过渭北旱塬黑垆土8年定位试验,研究了秸秆还田下6种耕作方式,即连年翻耕(CT/CT)、免耕(NT/NT)、深松(ST/ST)和免耕/深松(NT/ST)、翻耕/免耕(CT/NT)、翻耕/深松(CT/ST)对土壤团聚体、有机碳、作物产量和水分利用效率(WUE)的影响.结果表明:与CT/CT相比,NT/NT、ST/ST及3种轮耕措施减小了土壤力稳性团聚体的平均质量直径;NT/NT、ST/ST和NT/ST措施增加了20～50 cm土层>0.25 mm水稳性团聚体的含量(WR_0.25)和平均质量直径,降低了土壤团聚体结构破坏率(PAD).在0～10 cm土层,NT/ST、CT/NT、NT/NT和ST/ST处理土壤有机碳含量显著高于CT/CT处理.随着土层加深,各耕作处理土壤有机碳含量下降,但3种单一耕作处理(ST/ST、NT/NT和CT/CT)下降幅度大于3种轮耕处理(CT/NT、ST/CT和NT/ST).与CT/CT相比,其他5种耕作方式均增加了农田0～200 cm土层的土壤蓄水量、作物产量和水分利用效率,其中,NT/ST处理作物产量和WUE分别显著提高了15.1%和27.5%.相关分析表明,玉米产量、WUE与0～200 cm土层生育期和休闲期的蓄水量呈显著正相关,且生育期蓄水量与0～50 cm土层的WR_0.25呈显著正相关,与PAD呈显著负相关;其中,20～50 cm土层的WR_0.25、PAD与玉米产量、生育期蓄水量以及WUE关系最密切;生育期蓄水量和WUE还与0～10 cm土层的有机碳含量呈显著正相关.综合考虑不同耕作措施对土壤结构、作物产量和水分利用效率的影响,免耕/深松是最适宜于渭北旱塬区黑垆土春玉米种植的耕作方式.     

不同耕作方式下长期秸秆还田对旱作春玉米田土壤碳、氮、水含量及产量的影响

为了探索渭北旱塬春玉米田保护性轮耕模式的土壤培肥效果和增产增收效应,于2007—2014年在陕西合阳实施了秸秆覆盖或还田条件下免耕/深松(NT/ST)、深松/翻耕(ST/CT)、翻耕/免耕(CT/NT)、连续免耕(NT)、连续深松(ST)和连续翻耕(CT)等6种耕作处理田间定位试验,测定并分析了2010—2014年玉米收获期各耕作处理下0～60 cm土壤有机碳、氮储量,0～200 cm土层土壤含水量变化及春玉米产量差异.结果表明: 6种耕作处理中以NT/ST处理增加土壤有机碳和全氮储量最为明显.与2007年试验前相比,6种耕作处理均增加了0～60 cm土层土壤有机碳储量,5年平均值增幅为12.3%～28.3%,5种保护性耕作处理土壤有机碳储量5年平均值较CT对照处理显著增加7.1%～13.2%.NT/ST、ST/CT、CT/NT等3种轮耕处理和NT处理0～60 cm土层土壤氮储量5年平均值较试验前增加2.5%～7.3%.NT/ST、ST/CT、CT/NT、NT和ST处理土壤氮储量5年平均值比连续翻耕增加3.6%～11.1%.5种保护性耕作处理土壤含水量较CT处理依次增加5.7%、2.3%、2.0%、5.5%和4.4%,以NT/ST处理土壤含水量最高.6种耕作处理春玉米平均产量表现为NT/ST>ST/CT>ST >NT>CT/NT>CT,以NT/ST处理最高,分别较其他5种处理显著增产4.2%、13.0%、11.3%、4.7%和13.8%;经济效益平均表现为NT/ST>ST/CT>ST>NT>CT/NT>CT.在6种耕作处理中,免耕/深松轮耕处理在改善土壤环境质量、提升土壤肥力和增产增收方面都表现出优越性,为旱作春玉米田较适宜的土壤轮耕模式.     

耕作和覆盖对黄土高原果园土壤水分和温度的影响

研究了几种不同耕作方式（免耕、旋耕和翻耕）和覆盖措施（覆草、生草和覆膜）对黄土高原果园土壤水分和温度的影响.结果表明：5月不同耕作方式下0～1 m土层土壤水分差异极显著,表现为免耕（14.28%）>旋耕（14.13%）>翻耕（13.57%）,9月差异不明显;不同覆盖措施中,覆草处理的土壤水分最高,且与生草、覆膜、裸地处理间差异极显著;不同耕作方式和覆盖组合处理中以免耕覆草保水效果最好.不同覆盖处理白天土壤平均温度表现为覆膜>裸地>生草>覆草,土壤温度变幅表现为裸地>覆膜>生草>覆草.各覆盖处理的蓄水量与其土壤温度并不都呈负相关,而是由不同覆盖物的保水效果和保温性质共同决定.综上所述,黄土高原果园的保护性耕作体系应以免耕覆草为主.     

四川盆地稻田多熟高效保护性耕作模式的生态系统服务价值评估

运用生态系统服务功能价值评估方法,对四川盆地稻田保护性耕作条件下多熟高效保护性种植模式进行生态经济评价。结果表明,油-稻-芋模式比油-稻传统耕作种植模式的农产品服务价值高32．42％,固定CO2和释放O2的价值高17．03％;麦-稻保护性耕作模式比麦-稻传统种植模式农产品服务价值高55．21％。固定CO2和释放O2的价值高9．40％。油-稻秸秆还田双免耕模式比油-稻传统耕作种植模式土壤积累有机质的价值高0．23％,农田生态系统维持营养物质循环的价值高12．35％;麦-稻保护性耕作种植模式比麦-稻传统耕作种植模式土壤积累有机质的价值高0．39％,农田生态系统维持营养物质循环的价值高12.81％;稻草覆盖还田后油菜田的农田涵养水分价值增加11．66％,小麦田农田涵养水分价值增加32．63％。     

保护性耕作对农田碳、氮效应的影响研究进展

作物产量的高低主要取决于土壤肥力,如何保持并提高土壤肥力是确保我国粮食安全和农业可持续发展的重要任务,也是众多学者关注的焦点。土壤有机碳和氮素是评价土壤质量的重要指标,其动态平衡直接影响土壤肥力和作物产量。随着全球气候变化及环境污染问题的愈加突出,农田土壤固碳及提高氮效率成为各界科学家研究的热点。目前,保护性耕作已成为发展可持续农业的重要技术之一,对土壤固碳及氮素的利用具有很大的影响。深入了解保护性耕作对土壤有机碳固持与氮素利用效率提高的影响机制,对于正确评价土壤肥力有着重要意义。但由于气候、土壤及种植制度等条件不一致,关于保护性耕作对农田碳、氮效应结论不一。阐述了国际上保护性耕作对农田系统土壤有机碳含量变化及其分解排放(如CO₂和CH₄)、氮素变化及其矿化损失(如NH₃挥发、N₂O排放与氮淋失)和碳氮素相互关系(如C/N层化率)影响的研究进展,并分析了其影响因素和相关机理。尽管国内保护性耕作的研究已进行30 多年,但在土壤有机碳与氮素方面与国外相比依然有较大的差距。保护性耕作对土壤固碳与氮素利用的影响机制,碳素和氮素在土壤-植株-大气系统中的转移变化,及结合农事管理等综合评价其生态效应的研究很少。在此基础上,提出未来我国保护性耕作在土壤有机碳固定和氮素利用方面的重点研究方向:(1)在定位试验基础上进一步探讨保护性耕作对土壤有机碳及氮素利用的影响机制;(2)深入研究土壤有机碳和氮素的相互关系及其对土壤肥力的影响;(3)结合环境保护与土壤可持续管理对保护性耕作农田土壤固碳及氮素高效利用的系统评价研究;(4)加强保护性耕作对农田碳、氮效应的宏观研究,合理评价保护性耕措施下对农田碳、氮综合效应。     

东北黑土区耕作措施对地表节肢动物多样性的影响

【目的】调查不同耕作措施下东北黑土地表节肢动物群落类群多样性以及营养功能群结构, 有利于揭示地表节肢动物多样性对土地管理措施的响应。【方法】本研究于2012年7－9月在黑龙江海伦中国科学院海伦农田生态系统国家野外科学观测研究站采用陷阱法对东北典型黑土区免耕、 少耕、 平翻、 旋耕和组合5种耕作措施长期定位试验区的地表节肢动物群落组成、 类群多样性以及功能群结构进行调查, 计算各处理地表节肢动物类群相对多度、 类群丰富度、 Shannon Wiener多样性指数、 Pielou均匀度指数、 Simpson优势度指数、 Cody指数和Srensen指数。【结果】本次调查共收集黑土农田地表节肢动物个体数为2 942, 隶属7目18科。免耕样地收集节肢动物15科, 占所有类群83.34%; 少耕和组合样地均为11科, 占61.12%。所有耕作措施下鞘翅目和蜘蛛目类群相对多度最高, 步甲科为黑土农田优势地表节肢动物类群。免耕样地节肢动物类群丰富度和多样性指数最高, 少耕样地最低。除旋耕样地外, 其他耕作样地地表节肢动物功能群均以捕食性为主。群落相似性指数分析表明, 不同耕作措施间群落相似性不同, 免耕与组合之间相似性较高, 而平翻与组合之间较低。【结论】步甲科是黑土农田地表节肢动物群落中的优势类群。不同耕作措施影响近地表土壤以及植被微生境, 进而影响地表节肢动物群落组成、 数量和营养功能群。免耕样地具有较高节肢动物类群丰富度和捕食性动物类群, 有利于维持黑土农田地表节肢动物多样性。     

Biological nitrogen fixation in resource-poor agriculture in South Africa

Farm lands of resource-poor communities in South Africa are depleted of nutrients due to continuous mono-cropping, limited use of fertilisers, and sometimes leaching caused by high rainfall. Despite the well-known advantages of biological nitrogen fixation (BNF) in cropping systems, less than 10% of the grain crops planted annually in these areas are legumes. Using a participatory research and development approach, resource-poor farmers were introduced to conservation agriculture (CA) practices, including BNF, that promoted zero (or reduced) tillage, increased retention of soil cover, as well as crop diversification. Because crop rotation and intercropping of legumes with cereals are known to contribute to soil fertility while enhancing food security, resource-poor farmers from various Provinces in South Africa were trained on the benefits of legume culture for eight years. As a result, these resource-poor farmers did not only get training in inoculation techniques, but were also supplied with inoculants for use on their farms. Data collected from Farmers Demonstration Trials at Belvedere, Dumbarton and Lusikisiki, showed that the grain and fodder yield of maize planted after legumes, and maize intercropped with legumes, were comparable to those of maize receiving high N fertilizer dose (i.e. 54 kg N at planting and 54 kg N as top-dressing). The same data further showed thatRhizobium inoculation, when combined with application of low levels of P and K, significantly increased crop yields within farmers’ trial plots. BNF therefore offers a great opportunity for resource-poor farmers in South Africa to increase their crop yields and thus improve the quality of their livelihoods through the adoption of affordable and sustainable biological technologies that enhance soil fertility.     

不同保护性耕作措施对旱作农田土壤水分的影响

研究了黄土高原西部旱农区传统耕作措施和五种保护性耕作措施对土壤水分垂直分布、动态变化、作物耗水量、水分利用效率及作物产量的影响。结果表明,不同保护性耕作措施对表层0~10cm土壤水分含量影响较大,免耕秸秆覆盖(NTS)在作物播种期可以显著增加播种期表层土壤含水量。0~200cm土壤剖面贮水量年变化分春夏作物旺盛生长失墒期(5月中旬~7月中旬)、夏秋雨季增墒期(7月中旬~10月下旬)和冬春稳墒期(11月~翌年5月上旬)3个阶段。尽管不同保护性耕作措施对0~200cm剖面贮水量影响不大,但作物耗水量却存在显著差异。免耕秸秆覆盖在增加作物耗水量的同时也提高了作物产量以及水分利用效率。地膜覆盖在有些年份也有利于降水的高效利用和作物产量的提高,但与秸秆覆盖相比不利于土壤肥力的持续提高。而且,如果种植小麦,出苗前若一次性降水较多时地膜覆盖将造成严重板结,影响出苗,进而降低产量和水分利用效率。因此,在黄土高原西部旱农区实施免耕 秸秆覆盖的保护性耕作措施,既有利于作物对有限降水的高效利用,提高作物产量,也可以促进农业可持续发展。