河西绿洲灌区保护性耕作对土壤风蚀特征的影响

为研究河西绿洲灌区保护性耕作对土壤风蚀的影响,通过春小麦田间试验,设置免耕不覆盖、免耕秸秆覆盖、立茬和残茬压倒4种保护性耕作处理,以传统耕作为对照,分析了河西绿洲灌区不同保护性耕作措施对田间输沙量、风蚀深度、风蚀物粒径组成、风速的影响。结果表明：0~30 cm高度输沙量能敏感地反映不同耕作措施之间输沙量的差异。与传统耕作相比,免耕不覆盖、免耕秸秆覆盖、立茬和残茬压倒处理0~30 cm高度输沙量分别减少17.4%~46.7%、21.7%~45.2%、24.7%~48.2%和10.7%~42.4%。风蚀深度传统耕作为1.22~1.44 mm,4种保护性耕作处理均为0 mm。与传统耕作相比,保护性耕作处理风蚀物粒径组成无显著变化,但<0.063 mm细粒占比有减小趋势。立茬处理20 cm高度风速显著降低24.1%~39.5%,其他保护性耕作措施风速降低不显著。综上所述,河西绿洲灌区不同保护性耕作措施能不同程度地抑制土壤风蚀,立茬处理是相对较优的保护性耕作措施,适宜该地区推广应用。     

Friction velocity and aerodynamic roughness of conventional and undercutter tillage within the Columbia Plateau, USA

Friction velocity (u_*) and aerodynamic roughness (z_o) at the soil–plant–atmosphere interface affect wind erosion, but no attempts have been made to quantify these parameters as affected by tillage systems within the Columbia Plateau region of the Pacific Northwest United States. Wind velocity profiles above adjacent field plots (>2 ha), with plots subject to conventional or undercutter tillage during the summer fallow phase of a winter wheat–summer fallow rotation, were measured over 50 high wind events (wind velocities in excess of 6.4 m s⁻¹ at a height of 3 m) during 2005 and 2006 near Lind, Washington to determine u_* and z_o of tillage treatments. Wheat stubble plots were subject to either conventional (disks) or undercutter (wide V-shaped blades) tillage in spring and then periodically rodweeded prior to sowing winter wheat in late summer. Prior to sowing, u_* for conventional and undercutter tillage respectively averaged 0.36 and 0.46 m s⁻¹ in 2005 and 0.38 and 0.40 m s⁻¹ in 2006 while z_o for conventional and undercutter tillage respectively averaged 2 and 7 mm in 2005 and 2 and 4 mm in 2006. The aerodynamically rougher surface of undercutter tillage was predicted to suppress vertical dust flux; this was collaborated with observations in the field where undercutter tillage reduced dust flux as compared with conventional disk tillage. Undercutter tillage, therefore, appears to be an effective management practice to roughen the surface and thereby suppress dust emissions from agricultural land subject to summer fallow within the Columbia Plateau.     

Trends in the use of conservation tillage in US agriculture

Abstract. In 1996 conservation tillage was used on nearly 36% of the cropped area of the USA. This level has remained relatively unchanged over the past few years. The use of conservation tillage varied by crop and was dependent on site-specific factors including soil type, topsoil depth, and local climatic conditions. A number of economic, demographic, geographic, and policy factors have affected the adoption of conservation tillage. While it was not possible to quantify exactly the impact of these factors, it was clear that management complexities and profitability are key factors impeding an increase.     

保护性耕作综合效益评价体系构建及实例分析

保护性耕作是防治农田土壤风蚀起尘的重要技术方法之一,对于从源头上控制颗粒物污染有重要作用。为了综合评价保护性耕作技术的生态环境效益、社会效益和经济效益,该研究构建了一个包含3个一级评价指标、8个二级评价指标、19个三级评价指标的综合效益评价指标体系,并以天津市大港区苏家园村为例,对传统耕作、免耕覆盖、深松耕3种耕作方式下的生态、经济、社会及综合效益进行评价,以验证评价指标体系的可行性。结果表明:从生态环境效益方面来看,传统耕作免耕覆盖深松耕,其指标值分别为0.182、0.540、0.875;从综合效益来看,传统耕作深松耕免耕覆盖,其指标值分别为0.279、0.435、0.584。保护性耕作比传统耕作具有更高的生态环境和综合效益。该研究可为合理地评价保护性耕作综合效益提供参考,对发展保护性耕作起到良好的导向作用。     

The adoption of annual subsoiling as conservation tillage in dryland maize and wheat cultivation in northern China

Soil compaction caused by random traffic or repetitive tillage has been shown to reduce water use efficiency, and thus crop yield due to reduced porosity, decreased water infiltration and availability of nutrients. Conservation tillage coupled with subsoiling in northern China is widely believed to reduce soil compaction, which was created after many years of no-till. However, limited research has been conducted on the most effective time interval for subsoiling, under conservation tillage. Data from conservation tillage demonstration sites operating for 10 years in northern China were used to conduct a comparative study of subsoiling interval under conservation tillage. Three modes of traditional tillage, subsoiling with soil cover and no-till with soil cover were compared using 10 years of soil bulk density, water content, yield and water use efficiency data. Cost benefit analysis was conducted on subsoiling time interval under conservation tillage. Yield and power consumption were assessed by based on the use of a single pass combine subsoiler and planter. Annual subsoiling was effective in reducing bulk density by only 4.9% compared with no-till treatments on the silty loam soils of the Loess plateau, but provided no extra benefit in terms of soil water loss, yield increase or water utilization. With the exception of bulk density, no-till and subsoiling with cover were vastly superior in increasing water use (+10.5%) efficiency and yield (+12.9%) compared to traditional tillage methods. Four years of no-till followed by one subsoiling reduced mechanical inputs by 62%, providing an economic benefit of 49% for maize and 209% for wheat production compared to traditional tillage. Annual subsoiling reduced inputs by 25% with an increased economic benefit of 23% for maize and 135% for wheat production. Yield and power consumption was improved by 5% and 20%, respectively, by combining subsoiling with the planting operation in one pass compared with multipass operations of subsoiling and planting. A key conclusion from this is that annual subsoiling in dryland areas of northern China is uneconomical and unwarranted. Four years of no-till operations followed by 1 year subsoiling provided some relief from accumulated soil compaction. However, minimum soil disturbance and maximum soil cover are key elements of no-till for saving water and improving yields. Improved yields and reduced farm power consumption could provide a significant base on which to promote combined planter and subsoiling operations throughout northern China. Further research is required to develop a better understanding of the linkages between conservation tillage, soil quality and yield, aimed at designing most appropriate conservation tillage schemes.     

The influence of soil tillage system on Salsola kali L. emergence during the fallow period within cereal fields

With the move towards conservation agriculture, we have seen an increase in weeds such as Salsola kali L., well known as Russian thistle, which are wind spread over fallow land. The emergence of this weed species seemed erratic, perhaps connected to climate conditions and management techniques. In order to shed some light on this issue, we carried out a field experiment over 3 years to monitor Russian thistle density in fallow plots, comparing three tillage systems. This study provides an insight about the limitations of assuming no-tillage techniques within a cropping system that include fallow in the rotation sequence. Our results show that no-tillage systems are more vulnerable to S. kali. Low spring rain leads to high S. kali density, especially in no-tillage plots. High spring rainfall reduced the emergence in all tillage systems because of soil water saturation. Minimum tillage technique served to maintain control over this species even in weather conditions that favoured its emergence in other systems. In order to reduce the need for herbicide in fallow lands under conservation systems, we recommend the implementation of minimum tillage to combat Russian thistle infestation.     

华北平原缺水区保护性耕作技术

针对华北平原缺水地区农田生产效益偏低和地下水严重超采导致的生态环境问题,以建立节水、高产、固碳的华北平原缺水区保护性耕作集成技术为目标,在国家科技支撑计划长期支持下,建立了华北平原历时最长的保护性耕作长期定位试验平台(2001年—),开展了小麦/玉米两熟制保护性耕作理论和关键技术研究,集成了农机农艺结合的高产节水型保护性耕作技术体系,并在河北省进行广泛示范推广。主要结果:1)华北平原冬小麦/夏玉米一年两熟区保护性耕作具有固碳、减排、节水、提高土壤质量等生态效应。长期保护性耕作具有土壤养分分层表聚现象:0~5 cm土层的土壤C、N、P、K、有机质含量高于5~10 cm土层,旋耕(RT)和免耕(NT1:秸秆直立免耕;NT2:秸秆粉碎免耕;NT3:整秸秆覆盖免耕)处理土壤有机碳(SOC)的层化比率为1.74~2.04,显著高于翻耕处理(CK和CT)的1.37~1.45。保护性耕作的固碳效应与机制:保护性耕作实施9年后不同耕作方式年固碳量(0~30 cm)NT2处理为840 kg·hm~(-2)·a~(-1)、RT处理为780 kg·hm~(-2)·a~(-1)、CT处理为600kg·hm~(-2)·a~(-1),14年后土壤有机碳(0~30 cm)发生了变化,NT2处理为540 kg·hm~(-2)·a~(-1)、RT处理为720 kg·hm~(-2)·a~(-1)、CT处理为710 kg·hm~(-2)·a~(-1);长期免耕减少了土壤的扰动而降低了土壤碳的矿化率,土壤碳的累积主要固定在土壤大团聚体的颗粒有机碳中,固定态碳首先进入活性易分解有机碳库,然后缓慢转入稳定碳库。保护性耕作的减排效应:不同耕作系统全球增温潜力的计算结果表明,免耕是大气增温的碳汇,而其他耕作系统为碳源。NT处理每年农田生态系统净截留碳947~1 070 kg(C)·hm-2;CK、CT和RT每年向大气分别排放等当量碳3 364kg(C)·hm-2、989 kg(C)·hm-2和343 kg(C)·hm-2。保护性耕作的土壤微生物多样性机制:保护性耕作显著提高了土壤中真菌、细菌、氨氧化古菌和亚硝酸还原酶(nir K)基因的反硝化微生物的多样性,但对氨氧化细菌与含nir S基因的反硝化微生物的多样性影响不大。保护性耕作节水保墒的土壤结构与水力学机制:常规耕作对土壤有压实的作用,而保护性耕作改善了土壤结构,有效提高了储水孔隙、导水率、田间持水量和有效水含量,秸秆覆盖又能有效减少土壤蒸发,具有开源与节流双重节水机制。2)建立了趋零蒸发的麦田玉米整秸覆盖全免耕种植模式。在小麦/玉米一年两熟种植区,首次提出了玉米整秸秆覆盖小麦全免耕播种的种植模式,实现了小麦玉米全程全量秸秆机械化覆盖,形成土壤无效蒸发趋于零的保护性耕作体系与方法;研制了实现趋零蒸发的4JS-2型梳压机和2BMF-6型小麦全免耕播种机组,比目前推广的2BMFS-6/12小麦免耕播种机减少作业动力45.2%,降低作业费用33.3%。3)建立了3年一深松(翻)的少免耕-深松轮耕模式,集成了节水高产保护性耕作技术体系。制定了华北平原冬小麦/夏玉米一年两熟区保护性耕作技术体系等河北省地方标准,与农业、农机部门联合示范,推动了河北省保护性耕作技术的推广和应用。成果在河北平原冬小麦/夏玉米一年两熟区进行了示范推广,社会效益和生态效益显著,2013年获河北省科技进步一等奖。     

长期保护性耕作对黄土高原旱地土壤肥力质量的影响

长期定位试验研究了黄土高原西部旱农区传统耕作措施和5种保护性耕作措施对豌豆-小麦(P→W)和小麦-豌豆(W→P)轮作序列的耕层土壤肥力质量的影响。结果表明,与传统耕作(T)处理相比,传统耕作秸秆还田(TS)和免耕秸秆覆盖(NTS)处理有机质含量分别提高11.61%～12.21%和12.13%～16.99%,全氮提高7.29%～8.42%和11.58%～12.95%,全磷提高10.35%～14.63%和13.79%～18.29%,全钾提高7.32%～7.51%和8.78%～9.15%,速效磷提高11.10%～12.41%和16.29%～20.99%,速效钾提高25.11%～43.26%和31.62%～44.22%,pH降低0.11～0.17个单位和0.09～0.16个单位。进一步利用加乘法则和加权综合法两种模型评价不同耕作方式下的土壤肥力质量,结果表明,土壤肥力质量指数排序为NTS处理TS处理NTP处理NT处理T处理TP处理(P→W轮作序列)和NTS处理TS处理NT处理NTP处理TP处理T处理(W→P轮作序列)。在黄土高原雨养农作系统中,实施免耕结合秸秆覆盖,对促进和维持土壤养分平衡,提高土壤肥力质量具有重要意义。     

基于因子和聚类分析的保护性耕作土壤质量评价研究

基于长期定位试验,选择12项反映土壤质量特性的定量因子作为评价指标,采用因子分析对不同耕作模式的土壤质量进行综合评价,并运用欧氏距离最短法对其进行聚类分析。12项理化及生物属性指标归纳为5个公因子:保肥供肥因子、有机质因子、容重因子、磷素因子、酶活性因子。因子得分的结果表明:不同耕作模式的5个公因子优势差异明显。相比较而言传统耕作的土壤质量综合得分最低,说明在研究区保护性耕作模式条件下土壤在物理、化学、生物学性质方面都有所改善,土壤质量有所提高。土壤质量综合得分最高的前3种处理为隔年深松(NS2)、秸秆覆盖联合浅松、旋耕(SR2)、连年深松(NS3),说明深松、旋耕及秸秆还田与旋耕技术联合作业在改善土壤结构和培肥土壤方面优势更突出。聚类分析结果表明,同一耕作措施的不同模式土壤质量差异较小,说明在本研究试验条件下,耕作措施是影响土壤质量的关键因素。     

保护性耕作对土壤养分分布及冬小麦吸收与分配的影响

通过田间试验研究了华北平原山前平原区不同耕作方式下土壤氮、磷、钾等养分分布及冬小麦吸收与分配变化和对产量的影响。试验设深翻耕秸秆还田(MC)、秸秆还田旋耕(X)、秸秆粉碎免耕(NC)和整秸覆盖免耕(NW) 4 种冬小麦播前土壤耕作方式。试验结果表明, 6 年的不同耕作处理对土壤养分分布及冬小麦吸收与分配有显著影响。秸秆还田旋耕可显著提高土壤表层(0~5 cm)有机质、全氮以及碱解氮、速效磷、速效钾含量,但随土壤深度增加, 提高效果呈逐渐下降趋势; 20~30 cm 土层土壤有机质、全氮和速效氮含量显著低于秸秆粉碎免耕处理。两种免耕模式(NC、NW)植株的全氮、全磷、全钾含量在苗期明显低于翻耕(MC)和旋耕(X)模式,在返青期差异最为显著。到拔节和扬花期, 免耕(NC、NW)植株的全氮、全磷、全钾含量与翻耕(MC)和旋耕(X)之间的差异逐渐减少, 并最终影响到籽粒养分的积累。     

基于Meta分析评价东北黑土地保护性耕作与深耕的区域适宜性：以作物产量为例

为防治黑土退化、保护好利用好黑土地,本研究基于东北黑土区已发表61篇文献543组研究数据,利用Meta分析和随机森林模型等方法,分析黑土地保护性耕作与深耕对作物产量的影响及其驱动因素,耦合东北黑土地区气候、地形和土壤等信息,评价保护性耕作与深耕的适宜性。结果表明：与传统耕作相比,东北黑土地区整体而言保护性耕作增产不明显（1.21%）,而深耕增产显著（12.3%）,区域分析表明前者仅在辽河平原显著增产14.6%,而后者在三江、松嫩和辽河平原均增产10%以上。因素分析表明黑土区保护性耕作产量效应主要受多年平均气温（20%）、积温（19%）和干燥指数（16%）的影响,深耕产量效果则受坡度影响最大（14%）,平坦区域适宜深耕,陡坡耕地适宜保护性耕作。综合上述因子评价区域适宜性程度,东北地区的西南部,包括辽宁省西部、吉林省西部以及内蒙古自治区东部（赤峰市、通辽）等严重风蚀区域实行保护性耕作效果更佳;典型黑土带以及三江平原等湿润、冷凉、低洼区域深耕的效果较好。本研究成果可为保护性耕作与深耕技术在东北黑土区的推广应用提供参考。     

Assessment of tillage erosion rates on steepland Oxisols in the humid tropics using granite rocks

Soil translocation by tillage may be an important factor in land degradation in the humid tropics. The objective of this study was to evaluate tillage-induced soil translocation on an Oxisol with 25% and 36% slopes in Claveria, Philippines for three tillage systems: contour moldboard plowing (CMP), moldboard plowing up and downslope (UMP), and contour ridge tillage (CRT). Small rocks 3–4 cm in “diameter” were used as soil movement detection units (SMDU). The SMDUs were placed at 10 cm intervals in a narrow 5-cm-deep trench near the upper boundary of each plot, the position of each rock recorded, and the trench backfilled. Five tillage operations used to produce one corn crop were performed during a one month period: two moldboard plowing operations for land preparation (except for CRT), one moldboard plowing for corn planting, and two inter-culture (inter-row cultivation) operations. After these operations, over 95% of the SMDU were recovered manually and their exact locations recorded. Mean annual soil flux for the 25% slope was 365 and 306 kg m⁻¹ y⁻¹ for UMP and CMP, respectively. For the 36% slope, comparable values were 481 and 478 kg m⁻¹ y⁻¹. Estimated tillage erosion rates for the 25% slope were 456 and 382 Mg ha⁻¹ y⁻¹ for UMP and CMP, respectively, and increased to 601 and 598 Mg ha⁻¹ y⁻¹, respectively, for the 36% slope. The mean displacement distance, mean annual soil flux, and mean annual tillage-induced soil loss for both slopes were reduced by approximately 70% using CRT compared to CMP and UMP.     

Impact of conservation tillage and organic farming on the diversity of arbuscular mycorrhizal fungi

Communities of arbuscular mycorrhizal fungi (AMF) are strongly affected by land use intensity and soil type. The impact of tillage practices on AMF communities is still poorly understood, especially in organic farming systems. Our objective was to investigate the impact of soil cultivation on AMF communities in organically managed clay soils of a long-term field experiment located in the Sissle valley (Frick, Switzerland) where two different tillage (reduced and conventional mouldboard plough tillage) and two different types of fertilization (farmyard manure & slurry, or slurry only) have been applied since 2002. In addition, a permanent grassland and two conventionally managed croplands situated in the neighborhood of the experiment were analyzed as controls. Four different soil depths were studied including top-soils (0–10 and 10–20 cm) of different cultivation regimes and undisturbed sub-soils (20–30 and 30–40 cm). The fungi were directly isolated from field soil samples, and additionally spores were periodically collected from long-term trap culture (microcosm) systems. In total, >50,000 AMF spores were identified on the species level, and 53 AMF species were found, with 38 species in the permanent grassland, 33 each in the two reduced till organic farming systems, 28–33 in the regularly plowed organic farming systems, and 28–33 in the non-organic conventional farming systems. AMF spore density and species richness increased in the top-soils under reduced tillage as compared to the ploughed plots. In 10–20 cm also the Shannon–Weaver AMF diversity index was higher under reduced tillage than in the ploughed plots. Our study demonstrates that AMF communities in clay soils were affected by land use type, farming system, tillage as well as fertilization strategy and varying with soil depth. Several AMF indicator species especially for different land use types and tillage strategies were identified from the large data set.     

Soil C and N changes on conservation reserve program lands in the Central Great Plains

The Conservation Reserve Program (CRP) was initiated to reduce water and wind erosion on marginal, highly erodible croplands by removing them from production and planting permanent, soil-conserving vegetation such as grass. We conducted a field study at two sites in Wyoming, USA, in order to quantify changes in soil C and N of marginal croplands seeded to grass, and of native rangeland plowed and cropped to wheat–fallow. Field plots were established on a sandy loam site and a clay loam site on wheat–fallow cropland that had been in production for 60+ years and on adjacent native rangeland. In 1993, 6 years after the study was initiated, the surface soil was sampled in 2.5 cm depth increments, while the subsurface soil was composited as one depth increment. All soil samples were analyzed for total organic C and N, and potential net mineralized C and N. After 60+ years of cultivation, surface soils at both study sites were 18–26% lower (by mass) in total organic C and N than in the A horizons of adjacent native range. Six years after plowing and converting native rangeland to cropland (three wheat–fallow cycles), both total and potential net mineralized C and N in the surface soil had decreased and NO₃–N at all depths had increased to levels found after 60+ years of cultivation. We estimate that mixing of the surface and subsurface soil with tillage accounted for 40–60% of the decrease in surface soil C and N in long-term cultivated fields; in the short-term cultivated fields, mixing with tillage may have accounted for 60–75% of the decrease in C, and 30–60% of the decrease in N. These results emphasize the need to evaluate C and N in the entire soil solum, rather than in just the surface soil, if actual losses of C and N due to cultivation are to be distinguished from vertical redistribution. Five years after reestablishing grass on the sandy loam soil, both total and potential net mineralized C and N in the surface soil had increased to levels equal to or greater than those observed in the A horizon of the native range. On the clay loam soil, however, significant increases in total organic C were observed only in the surface 2.5 cm of N-fertilized grass plots, while total organic N had not significantly increased from levels observed in the long-term cultivated fields.     

Tillage erosion within potato production in Atlantic Canada: II: Erosivity of primary and secondary tillage operations

To date, tillage erosion experiments in Canada have only been conducted on conventionally tilled corn-based production systems in Ontario and conventionally tilled cereal-based production in Manitoba. Estimates and assumptions have been made for all other production systems. Therefore, the objective of this study was to evaluate the erosivity of primary and secondary tillage operations within conventional and conservation potato production systems used in Atlantic Canada. Regression analysis determined that a direct relationship exists between slope gradient and both the mean displacement distance of the tilled layer (T_L) and the mass of translocated soil (T_M) for the chisel plough (CP), mouldboard plough (MP) and offset disc (OD), but not for the vibrashank (VS). Overall, the potential for tillage erosion of the MP, CP, and OD was similar (1.8–1.9 kg m⁻¹ %⁻¹ pass⁻¹) and larger than that of the VS (0.3 kg m⁻¹ %⁻¹ pass⁻¹). The regression coefficients for each implement were improved after including slope curvature, and we recommend that curvature be included in any future tillage erosion modelling. Our results show that both residue management to control wind and water erosion and soil movement to control tillage erosion must be considered when choosing implements and developing best management practices with regards to reducing the negative impacts of total soil erosion on potato production systems in Atlantic Canada.     

水土保持耕作及施肥对盛花期大豆光合生理的影响

依据陕西安塞田间试验,采用LI-6400便携式光合仪,在自然条件下对黄土丘陵区旱作农田传统翻耕化肥(CF)、翻耕有机肥(CM)、翻耕无肥(CN)、免耕化肥(NF)、免耕有机肥(NM)、免耕无肥(NN)等处理下盛花期大豆叶片的净光合速率、气孔导度、水分利用效率及影响因子日变化进行了研究.结果表明:6种不同处理的大豆叶片净光合速率日变化均为双峰曲线,峰值分别在11:30、16:00出现.NM、NF处理对提高大豆净光合速率有明显的促进作用,其中以有机肥(NM)最为显著.气孔导度与蒸腾速率之间达极显著正相关(P<0.01,r=0.999 4).气孔导度日变化也为双峰,峰值分别出现在11:30、16:00.不同处理下,大豆的水分利用效率呈单峰曲线,峰值出现在10:00,低谷出现在13:00以后.其中,NF、NM处理能显著提高大豆盛花期的水分利用效率.相关分析表明:气孔导度、蒸腾速率、叶温、光合有效辐射及基于叶温的蒸汽压亏缺是大豆光合作用的促进因子,而胞间CO2浓度、空气CO2浓度、空气相对湿度则为主要的限制因子.CF、NF处理在8:30～10:20和13:00,CM、NN处理在8:30、11:30～13:00、17:30,CN、NM处理则在8:30、13:30各影响因子与净光合速率相关程度较高,相关系数一般在±0.9以上.在黄土丘陵区旱作农田大豆最适宜的管理方式为NM、NF.     

Effect of tillage management on energy-use efficiency and economics of soybean (Glycine max) based cropping systems under the rainfed conditions in North-West Himalayan Region

The study on energy-use efficiency and economics of soybean based cropping system, viz., soybean–wheat (Glycine max 9 L., Triticum aestivum L. emend. Fiori & Paol.), soybean–lentil (Lens culinaris Medicus) and soybean–field pea (Pisum sativum L., sensu lato), was carried out at the Hawalbagh experimental farm of Vivekananda Institute of Hill Agriculture, Almora, Uttarakhand, India during 2001–2003 (29°36′ N, 79°40′ E). These cropping systems, under rainfed conditions, were evaluated with different tillage management practices, viz., zero tillage (ZT), minimum tillage (MT) and conventional tillage (CT). Each tillage management practice, under each cropping system was evaluated for total energy output, energy input–output ratio, gross income, net income and marginal income, to variable cost of cultivation. Results revealed that the maximum energy was consumed in terms of chemical fertilizers, followed by seed and plant protection chemicals, in all cropping systems. Equivalent energy was used from literature for conversion purpose. The maximum output energy was observed in CT (44,253 MJ/ha), followed by MT for soybean–lentil cropping system (43,450 MJ/ha). The output–input energy ratio was maximum in ZT for soybean–lentil (4.9) followed by MT for soybean–pea cropping system (4.6). The economic analysis also revealed that the maximum benefits could be obtained from these sequences. Conventional tillage for all cropping sequences was found to be a better option as compared to minimum tillage and zero tillage. Benefit–cost ratios were higher in conventional tillage in all the three cropping systems. However, from the point of energy saving or cost reduction, zero tillage and minimum tillage may be considered depending on resources.     

长期保护性耕作对黄绵土总有机碳和易氧化有机碳动态的影响

长期定位试验研究了黄土高原西部旱农区不同耕作措施(传统耕作T、免耕+秸秆覆盖NTS、免耕NT、传统耕作+秸秆翻埋TS、传统耕作+地膜覆盖TP和免耕+地膜覆盖NTP)对黄绵土土壤总有机碳和易氧化有机碳的影响。结果表明, 土壤有机碳含量随土壤深度的增加而降低, 10~30 cm土层土壤有机碳含量的下降较为明显, 并且在0~5 cm、5~10 cm和10~30 cm土层中, 均表现为由研究初期各处理相对差异较小到试验中后期各处理出现显著差异的变化。不同耕作措施下0~30 cm土壤总有机碳和易氧化有机碳在2002-2012年的平均含量均为NTS>TS>NTP>NT>T>TP。与传统耕作相比, 免耕各处理和传统耕作秸秆翻埋处理可增加1.2%~7.2%的土壤总有机碳, 5.3%~16.6%的土壤易氧化有机碳含量, 而传统耕作覆膜处理分别降低4.3%和2.7%。免耕和秸秆覆盖处理均有利于黄绵土土壤有机碳和易氧化有机碳的积累, 免耕结合秸秆覆盖效果最佳, 而多年传统耕作覆盖地膜后有机碳明显降低。免耕秸秆覆盖处理土壤总有机碳和易氧化有机碳含量平均值在2004年、2006年、2008年、2010年及2012年分别较2002年提高9.5%和42.9%、13.2%和67.6%、21.5%和71.5%、1.1%和15.9%、2.7%和12.6%。因此, 在西部黄土高原黄绵土区, 采用免耕结合秸秆覆盖的保护性耕作措施有利于土壤总有机碳和易氧化有机碳含量的提高, 从而有利于土壤质量的持续改善。易氧化有机碳对不同耕作措施的响应比总有机碳更灵敏, 可以将其作为指示黄绵土有机碳变化的早期指标。     

紫色土丘陵区保护性耕作下旱地土壤呼吸及影响因素

为了探讨保护性耕作对旱作农田土壤呼吸的影响,采用LI6400XT便携式光合作用测量系统自带的土壤呼吸室(6400-09)在重庆北碚西南大学试验农场对传统耕作(T,traditional farming)、垄作(R,ridge planting)、传统耕作+秸秆覆盖(TS,traditional farming+straw mulching)、垄作+秸秆覆盖(RS,ridge planting+straw mulching)、传统耕作+秸秆覆盖+秸秆速腐剂(TSD,traditional farming+straw mulching+decomposing agent)、垄作+秸秆覆盖+秸秆速腐剂(RSD,ridge planting+straw mulching+decomposing agent)6种处理下的西南紫色土丘陵区小麦/玉米/大豆套作体系中作物生长季节的土壤呼吸及其水热因子进行了测定和分析。结果表明,6种处理中土壤呼吸速率的季节变化明显,各处理日均土壤呼吸速率差异显著。其中在小麦-大豆条带,小麦土壤呼吸速率均值为1.53μmol m-2s-1,大豆土壤呼吸速率日均值为4.10μmol m-2s-1,各处理日平均土壤呼吸速率大小排序为TRTSTSDRSRSD。在空地-玉米-空地条带,玉米土壤呼吸日均值为2.56μmol m-2s-1,介于小麦和大豆土壤呼吸速率之间,各处理日平均土壤呼吸大小排序为RTRSTSRSDTSD。整个套作体系土壤呼吸总量C为1 543~2 134 g m-2,表现为TRRSTSTSDRSD。研究结果还显示土壤温度和土壤水分是影响旱地农田土壤呼吸的主要因素,二者分别解释了土壤呼吸季节变化的28.9%~53.7%和13.7%~42.0%。水热因子与土壤呼吸速率的回归分析表明,指数方程较好地模拟了土壤呼吸与10 cm土温的关系,土壤呼吸的温度敏感性指标Q10值在2.25~2.69之间;而土壤呼吸与5 cm土壤水分的关系以抛物线型函数模拟最优。土壤呼吸对土壤水分的响应阈值为14.94%。该研究为明确农田生态系统土壤呼吸变化规律及影响因素的控制机理提高参考,对估算全球碳平衡、评估区域碳源汇具有重要意义。     

保护性耕作对太行山前平原土壤质量的影响

保护性耕作被认为是华北平原农业可持续发展的重要措施, 但目前缺乏这些措施对土壤质量影响的系统报道。本研究以长期定位试验为基础, 探讨了太行山前平原两熟制高产农田不同耕作措施对麦田土壤质量的影响。试验始于2001 年, 设置翻耕玉米秸秆不还田(非保护性耕作对照, CK)、翻耕玉米秸秆粉碎还田(CT)、旋耕玉米秸秆粉碎还田(RT)和免耕玉米秸秆直立还田(NT)4 个处理。2007 年冬小麦收获后分层测定土壤有机碳(soil organic carbon, SOC)含量、容重(ρ_b)、水稳性团聚体、水分特征曲线、饱和导水率(K_s)和微生物量碳氮。2008 年测定了剖面SOC 含量、ρ_b 和蚯蚓数量。结果表明, 连续多年保护性耕作后土壤剖面的SOC 储量无显著变化, 但保护性耕作(RT 和NT)下SOC 的层化比率(1.74~2.04)显著高于翻耕处理(CK 和CT, 1.37~1.45); 保护性耕作显著提高了表层微生物量碳、氮含量以及单位面积土壤中的蚯蚓数量。NT 处理导致耕层(0~20 cm)土壤ρ_b 增加, 但提高了土壤团聚体的稳定性。CK 和CT 处理显著增加了0~5 cm 土层裂隙(>500 μm)和传输孔隙(500~50 μm)的比例, 而NT 处理则增加储水孔隙(50~0.5 μm)的含量。另外, 保护性耕作提高了土壤的K_s、田间持水量和有效水含量。对土壤质量指标S 的分析结果表明, 实施保护性耕作后, 太行山前平原地区土壤质量总体上得到改善。