Effect of seedbed cultivation and soil macrostructure on the establishment of winter wheat (Triticum aestivum)

Soil physical properties affect the establishment of crops; these properties are influenced by cultivation incurred during seedbed preparation and vary greatly depending upon the intensity of applications. However, there is little quantified data concerning the influence of cultivation upon the precise soil structural arrangement and the effects of this on crop establishment. The dynamics of soil macrostructure properties on a range of seedbeds and how they relate to crop establishment are considered in this paper. Significant interactions between cultivation techniques, soil physical properties, the soil macropore structure of the seedbed and the interaction with crop establishment were identified. The relationship between soil structure and crop establishment was highly significant, with increased pore space reducing final establishment numbers. An improvement to a previously developed model (soil quality of establishment (SQE)) was developed following the addition of soil macrostructure properties, accounting for improved predictability of between ca. 6% and 19% of the variation accounted across soil types, environmental conditions.     

Effects of soil water content during primary tillage – laser measurements of soil surface changes

Soil water content during tillage can have a large impact on soil properties and tillage outcome. Measurement of soil relief in relation to fixed elevation points provides a non-destructive method of monitoring loosening/compacting processes during the year. The main objective of this study was to determine the effect of soil water content during primary tillage on soil physical properties.

The treatments included mouldboard and chisel ploughing of a clay soil on three occasions in the autumn, with gradually increasing water content (0.76, 0.91 and 1.01 × plastic limit). Soil surface height was measured by laser within a 0.64 m² area from fixed steel plates after each tillage occasion, and before and after seedbed preparation in the following spring. The measurements of surface height were compared with measurements of other soil physical properties, such as bulk density, saturated hydraulic conductivity and seedbed properties.

Tillage at the lowest water content (0.76 × plastic limit) produced the greatest proportion of small aggregates, and generally the most favourable soil conditions for crop growth. Soil loosening, as measured by increase in soil height during primary tillage, was highest for mouldboard ploughing and for tillage at the lowest water content. Differences between tillage treatments decreased with time, but were still significant after sowing in the spring. Natural consolidation during winter was smaller than the compaction during seedbed preparation in the spring. No significant differences in bulk density were found between treatments, and thus soil surface height was a more sensitive parameter than bulk density determined by core sampling to detect differences between treatments.

Late tillage under wet conditions caused a greater roughness of the soil surface and the seedbed base, which was also found in the traditional seedbed investigation. The effect of tillage time on seedbed properties also resulted in a lower number of emerged plants in later tillage treatments.

The laser measurements were effective for studying changes in soil structure over time. The results emphasize the need to determine changes in soil physical properties for different tillage systems over time in order to model soil processes.     

Intrinsic soil physical parameters influencing intensity of cultivation procedures for sugar beet seedbed preparation

Despite relatively narrow ranges in soil physical properties and in climatological conditions, the intensity of cultivation treatments necessary for sugar beet seedbed preparation in Ireland varies considerably. In an attempt to understand some of the underlying causes and reasons for this phenomenon, experimental treatments of autumn deep loosening and spring seedbed preparation for sugar beet (Beta vulgaris L.) were imposed on 12 sites in 1982, 1983 and 1984. Seedbed preparation methods studied included powered rotary, disc harrow and spring-tine cultivation on deep loosened and non-loosened soil. Seedbed aggregate size distributions were influenced by cultivation treatment and intrinsic soil physical parameters. The intrinsic parameters (clay content, fine sand/coarse sand ratio, organic-matter content, water stable aggregates, moisture content at field capacity, liquid limit, plastic limit, plasticity index and plastic limit/field capacity ratio) of the 12 sites were closely correlated with each other. They exerted a large influence on soil workability and explained why some soils required more intensive tillage operations. Prediction equations for moisture content at cultivation time, number of cultivation passes and aggregate size distribution were derived, based on the intrinsic soil physical parameters. The equations provided indicators of which soil physical properties are most important in sugar beet seedbed preparation on a range of Irish tillage soils.     

Influence of spring preparation date and soil water content on seedbed physical conditions of a clayey soil in Sweden

Secondary tillage performed under inadequate soil water contents usually leads to a poor seedbed. Under normal Swedish weather conditions, clayey soils ploughed during autumn form a very dry top layer in spring, which acts as an evaporation barrier so that deeper layers remain wet. Thus, the conventional approach considering soil workability in relation to a single value of soil water content is difficult to apply. Hence, a field experiment was carried out to study the effect of seedbed preparation date, the associated soil water contents and traffic consequences on the physical properties of a spring seedbed. The field was autumn ploughed and the experiment started as soon as the field was trafficable after winter thawing. The seedbed preparation consisted of three harrowing operations on plots 8 m×8 m (three replications) with a spring tined harrow and a tractor mounted with dual tyres and was performed on 10 occasions from the beginning of April to the middle of May. With the exception of some short periods after rain, the soil had a clear water stratification during the experiment, with a very dry superficial layer (5–20 mm thick) contrasting to water contents over 300 g kg⁻¹ from only 40 mm depth. After the harrowing operation, the seedbed aggregate fraction less than 2 mm increased from about 40% at the beginning of April to about 60% for the last four treatments in May. Contributing factors to the rise were attributed to the lower water contents of the top layer (<40 mm) and the drying–wetting and freezing–thawing cycles that occurred in the surface layer during April. There were no significant differences in bulk density after harrowing between the treatments but an increase in penetration resistance up to a depth of 180 mm in the harrowed plots was statistically significant (P<0.001). In the non-harrowed soil, penetration resistance also increased, including in those soil layers where water contents kept nearly constant.

In conclusion, the seedbed preparation dates had only a minor effect on soil compaction, as measured by bulk density and penetration resistance, due to the slow drying beneath the dry top layer. The fraction of fine aggregates in the seedbed increased with time. Thus, the optimal time for seedbed preparation depended mainly on soil friability and not on the risk of compaction.     

Effect of mouldboard and chisel ploughing and their timing on seedbed quality

The effects of tillage on weed growth are supposed to depend largely on the type of implement, the timing of the operation and the type of soil. Experiments on the effect of mouldboard and chisel ploughing with duckfeet, used for the main tillage operation and the timing of the main tillage operation on seedbed quality and weed development in sugar-beet were carried out from 1981–1983 on silty clay, silty loam and two sands. Seedbed quality was only slightly influenced by type and timing of the main tillage operation. Soil texture affected seedbed quality significantly: seedbeds on light soils compared with silty soils had a finer tilth, were deeper and were scarcely sorted (stratified according to particle size). Chisel ploughing with duckfeet to the full depth of the arable layer required much tractor power and during the late autumn on silty loam and in spring on sand, chiselling was impossible because the soil was too wet; the mouldboard plough did not cause problems of this kind. Moreover, soil inversion by the mouldboard plough was attended by a surface free of crop residues and weeds after the main tillage operation and a strong suppression of weeds during winter, sowing time and in the young crop.     

Effects of reduced tillage and liming on microbial activity and soil properties in a weakly-structured soil

The effects of reduced tillage and lime on crop yield and soil physical and microbial properties were studied in a weakly-structured silty clay loam soil. Two autumn primary tillage practices were compared, mouldboard ploughing to 20–25 cm and cultivation to 12 cm. Seedbed preparation was carried out by several harrowing operations in the mouldboard ploughed treatment, and with a PTO-driven harrow in the same operation as sowing in the shallow cultivation treatment. The tillage treatments were applied alone or were combined with liming aimed at soil structural improvement. Lime was added as 6.5 Mg CaO ha⁻¹ before the start of the experiment and mixed into the top 12 cm of soil with a disc cultivator. A 4-year crop rotation was used: spring barley, spring oilseed rape, spring/winter wheat and oats, and all crops were compared each year. Crop residues were retained in the experiment and incorporated at cultivation. Aggregate stability was improved by the shallower tillage depth, probably as an effect of an increase in soil organic matter and a more active microbial biomass. Liming had little effect on soil structure variables but increased microbial activity to some extent. This was reflected in higher crop yields, especially when the shallow tillage depth was combined with liming. Penetration resistance in the seedbed subsoil was highest when mouldboard ploughing was carried out in plots without liming. Data were examined with principal component analyses, and the structures in the data were presented as scores and loading plots, which revealed groupings between samples and relationships between variables, respectively.     

Twenty years of tillage research in subarctic Alaska: I. Impact on soil strength, aggregation, roughness, and residue cover

Soil properties and surface characteristics affecting wind erosion can be manipulated through tillage and crop residue management. Little information exists, however, that describes the impact of long term tillage and residue management on soil properties in the subarctic region of the United States. This study examines the impact of 20 years of tillage and residue management on a broad range of physical properties that govern wind erosion processes on a silt loam in interior Alaska. A strip plot experimental design was established in 1983 and included intensive tillage (autumn and spring disk), spring disk, autumn chisel plow, and no tillage with straw either retained on or removed from the soil surface. Soil and residue properties measured after sowing barley (Hordeum vulgare L.) in May 2004 included penetration resistance, soil water content, shear stress, bulk density, random roughness, aggregate size distribution, and residue cover and biomass. No tillage was characterized by larger aggregates, greater soil strength (penetration resistance and shear stress), wetter soil, and greater residue cover compared to all other tillage treatments. Despite crop failures the previous 2 years, crop residue management influenced residue biomass and cover, but not soil properties. Autumn chisel and spring disk appeared to be viable minimum tillage options to intensive tillage in controlling erosion. Autumn chisel and spring disk promoted greater roughness, aggregation, and residue cover as compared with intensive tillage. Although no tillage appeared to be the most effective management strategy for mitigating wind erosion, no tillage was not a sustainable practice due to lack of weed control. No tillage also resulted in the formation of an organic layer on the soil surface over the past 20 years, which has important ramifications for long term crop production in the subarctic where the mean annual temperature is <0 °C.     

不同轮耕方式对渭北旱塬麦玉轮作田土壤物理性状与产量的影响

为研究不同轮作模式对渭北旱作冬小麦?春玉米一年1熟轮作田土壤物理性状和产量的影响,于2007—2014年在陕西省合阳县冬小麦?春玉米轮作田连续7年实施了保护性耕作定位试验,测定和分析了免耕/深松、深松/翻耕、翻耕/免耕、连续免耕、连续深松和连续翻耕6种轮耕模式下麦田0~60 cm土层物理性状、0~200 cm土层土壤湿度和小麦产量的变化。结果表明:1)不同轮耕模式0~40 cm土层土壤容重、孔隙度和田间持水量差异显著,其中以免耕/深松效果最显著;0~60 cm土层免耕/深松轮耕处理平均田间持水量较连续翻耕处理提高12.9%;2)轮耕对土壤团聚体特性影响明显,免耕/深松0.25 mm水稳性团聚体含量(R0.25)最高,结构体破碎率和不稳定团粒指数(ELT)最低,水稳性均重直径(WMWD)最高,水稳性和力稳性团聚体分形维数(D)均最低;3)小麦生育期间免耕/深松处理0~200 cm土层土壤蓄水量和小麦产量较连续翻耕分别增加17.7 mm和9.5%。综合可知,轮耕有利于耕层土壤物理结构改善,免耕/深松更有利于耕层土壤大团聚体形成和土壤结构稳定,利于土壤蓄水保墒和作物增产,为渭北旱塬区麦玉轮作田较适宜的轮耕模式。     

Soil degradative effects of slope length and tillage methods on alfisols in western Nigeria. III.Soil physical properties

Effects of six slope lengths, 60 m to 10 m with 10-m increments, on soil physical properties were evaluated for plough-based conventional till and no-till seedbed preparation on field runoff plots for three consecutive years from 1984 to 1987. Soil physical properties measured included texture, bulk density, infiltration capacity, and soil moisture retention characteristics. Conventional till treatment caused a rapid increase in soil bulk density and penetration resistance, and decrease in available water capacity and equilibrium infiltration rate. Gravel content increased with cultivation duration. Soil bulk density of 0–5 cm depth was 1·20 Mg m⁻³ for 1984, 1·39 Mg m⁻³ for 1985 and 1·46 Mg m⁻³ for 1986 for conventional till; and 1·13 Mg m⁻³ for 1984, 1·33 Mg m⁻³ for 1985, and 1·27 Mg m⁻³ for 1986 for the no-till treatment. The penetration resistance of the no-till treatment was relatively low and increased with cultivation duration. Mean penetration resistance for 0–5 cm depth was 2·2 kg cm⁻² in 1984, 2·71 kg cm⁻² in 1985, and 3·79 kg cm⁻² in 1986. The available water capacity decreased in both tillage methods without any consistent trends with regard to slope length. The equilibrium infiltration rate declined drastically for long slopes and conventional till methods. The data support the conclusion that these soils should be managed with short slope lengths and a no-till method of seedbed preparation. © 1997 John Wiley & Sons, Ltd.     

Soil quality changes under continuous cropping for seventeen seasons of an alfisol in western Nigeria

Tillage and soil management effects on soil physical and chemical qualities were monitored for eight years from 1979 through 1987 in a long-term experiment involving 17 consecutive crops of maize. Effects of no-till and plow-till methods of seedbed preparation were compared at two levels of residue management (residue removed versus residue returned) and two levels of fertilizer application (without fertilizer versus recommended fertilizer). Soil chemical quality was better for no-till compared with plow-till methods. Mean soil chemical properties of 0–5 cm depth for no-till and plow-till treatments respectively were 18·6 g kg⁻¹ versus 12·2 g kg⁻¹ for soil organic carbon content, 1·9 g kg⁻¹ versus 1·1 g kg⁻¹ for total soil nitrogen, 0·14 units yr⁻¹ versus 0·18 units yr⁻¹ rate of decline in soil pH, 63·1 mg kg⁻¹ versus 31·8 mg kg⁻¹ for Bray-P, and 6·0 cmol kg⁻¹ versus 2·3 cmol kg⁻¹ for Ca⁺². Soil chemical quality consistently declined, although the rate of decline differed among tillage and fertilizer treatments. There were also differences in soil physical quality. Soil bulk density increased with cultivation duration in both tillage methods, and use of furadan in no-till plots drastically increased soil bulk density. Infiltration rate and soil moisture retention at all suctions was consistently more for no-till than plow-till treatments. Decline in soil quality with cultivation was reflected in decrease in crop yields. © 1998 John Wiley & Sons, Ltd.     

少免耕土壤结构与导水能力的季节变化及其水保效果

通过对黑土坡耕地免耕、少耕与传统耕作土壤物理性状全生育期观测,比较研究土壤结构和导水性状季节变化差异及其与水土流失的关系。结果表明,表层0~20 cm土壤,免耕土壤容重全生育期维持在1.20~1.30 g cm-3,变化小,大于0.25 mm的水稳性团聚体含量(WR0.25)和平均重量直径(MWD)高于传统耕作,初始和稳定入渗速率均高于少耕和传统耕作,土壤含水量分别较少耕和传统耕作高4.7和4.4个百分点,较传统耕作分别减少地表径流和土壤流失量86%和100%;少耕除夏季各项性状均介于免耕和传统耕作之间,夏季垄沟深松后,垄沟土壤容重显著降低,较免耕和传统耕作降低0.15 g cm-3以上,提高土壤初始入渗速率30%以上,较传统耕作减少水和土壤流失量20%和40%。传统耕作土壤容重,垄台由播种时的0.91 g cm-3增加至收获时的1.23 g cm-3,垄沟一直维持在1.30 g cm-3左右,WR0.25、MWD、土壤稳定入渗速率、含水量均较低,全生育期10%的雨水流失,土壤流失量615 t km-2a-1。免耕土壤结构稳定,蓄水保水最佳,为效果显著的水土保持耕作措施,少耕也有一定的保水保土作用;免耕和少耕均能够改善土壤物理性状。     

科学耕作与留茬改良小麦-玉米两熟农田土壤物理性状及增产效果

为了探讨不同覆盖耕作方式对农田土壤物理性状及作物产量的影响,该试验研究了免耕、常规2种耕作方式和4种留茬高度的玉米秸秆还田处理,对麦-玉两熟农田土壤含水率、容重、孔隙度以及作物产量的影响。结果表明:在0～40cm土层内,秸秆还田的集雨和保水效果显著,免耕留茬0.5m还田处理的含水率比免耕无覆盖处理增加了15.95%。秸秆还田量对0～40cm内土壤贮水量的影响不同。耕作措施显著影响了土壤容重,小麦播种前常规留茬1m还田、常规全量还田处理容重低至1.0g/cm3左右。秸秆还田能增加土壤总孔隙度、降低毛管与非毛管孔隙度的比值。单一免耕处理降低了作物产量,而免耕覆盖能增产,其留茬1m还田处理比无还田处理增产22.44%,比常规留茬0.5m还田处理高3.64%。因此,免耕留茬1m还田处理在改善农田土壤物理性状和增加作物产量方面显著,该研究可为农田管理过程中耕作措施和秸秆还田量的选择提供参考依据。     

秸秆还田与旋耕对川中土壤物理性状及玉米机播质量的影响

为明确川中丘陵地区紫土小麦-玉米两熟种植模式下机播玉米生产适宜的秸秆还田方式与耕作方式,改善土壤的瘠薄、黏性过大等问题,提高耕层土壤的播种条件、播种质量,达到作物高产的目的,设置秸秆还田旋耕(RTS)、秸秆还田免耕(NTS)、秸秆不还田旋耕(RT)、秸秆不还田免耕(NT)4个处理,研究麦秸还田与旋耕对川中丘区紫色黏土物理性状及机播夏玉米播种质量的影响。结果表明:与秸秆不还田相比,麦秸还田显著增加了拔节期0~10 cm土层土壤毛管孔隙度和免耕处理0~10 cm全生育时期土壤含水量,显著降低出苗率、播种均匀度和幼苗整齐度等指标。与免耕相比,旋耕处理降低了0~10 cm土壤容重、含水量,增加了毛管孔隙度,出苗率提高9.9%,幼苗株高、茎粗、叶面积和干重显著提高。麦秸还田条件下,旋耕处理较免耕处理0~10cm土壤容重降低2.0%~12.1%,出苗率、播种均匀度、每穴苗数、幼苗整齐度显著提高,其中出苗率增加17.9%。玉米出苗率与0~10 cm土壤含水量呈显著正相关,播种均匀度与幼苗整齐度均与0~10 cm土壤容重呈显著负相关。可见,麦秸还田下旋耕处理改善了土壤结构,增加了土壤含水量,更有利于川中丘陵地区小麦-夏玉米种植模式机播玉米质量和幼苗素质的提高。     

Tillage implement disturbance effects on soil properties related to soil and water conservation: a literature review

The effects of tillage implement distrubance on the physical properties of soil have been widely studied. However, because soil properties resulting from the use of a given implement vary due to implement factors (depth and speed of tillage) and soil factors (water content, texture, residue cover, etc.), soil properties for a given operation are difficult to visualize, let alone predict. This report summarizes the ranges of selected soil property responses observed in previous tillage studies and identifies factors that must be considered in developing useful models to predict the effects of tillage on soil properties that are related to soil and water conservation. Considered are soil mechanical properties (surface micro-relief, aggregate size distribution and bulk density) and hydraulic properties and processes (water retention, saturated conductivity, infiltration and evaporation). For future literature reports on tillage to be useful for developing comprehensive relationships between tillage and soil properties, the reports should include information on: soil classification, texture, water content (or time of precipitation), bulk density, mechanical impedance and organic matter concentration; tillage method, depth and speed of operation; previous crop, including availability of crop residues; and previous soil management history (compacted soil, irrigated or dryland, etc.).     

Seasonal differences in tillage draught on a sandy loam soil with long‐term additions of animal manure and mineral fertilizers

Energy requirements for soil tillage are closely linked to soil properties, such as clay, water and soil organic carbon (SOC) contents. Long‐term application of inorganic fertilizer and organic amendments affects SOC content but little is known about seasonal differences in tillage draught requirements of soils subject to contrasting nutrient management regimes. We assessed autumn and spring tillage draught following harvest of early‐sown and timely sown winter wheat grown on a sandy loam in the Askov Long‐Term Experiment on Animal Manure and Mineral Fertilizers. Draught force was related to soil texture, soil water and SOC content, shear strength and bulk density, nutrient management, and yield of the preceding winter wheat. Contents of clay and SOC ranged from 8.9 to 10.6% and from 0.98 to 1.36%, respectively. In the autumn and spring, SOC normalized by clay content explained 38 and 5% of the variation in specific draught, respectively. Specific draught did not differ significantly among individual fertilization treatments. SOC was closely correlated with clay and water contents and bulk density, and with yield of the preceding wheat. Draught force was significantly smaller in the spring than in the autumn. In the autumn when soils were drier (?700 hPa), tillage draught was correlated with several soil characteristics, whereas water content was the dominating parameter in the spring when soils were wetter (?100 hPa). The range of SOC contents observed in this study aligns with that observed in Danish sandy loams under intensive cultivation, and within this range, SOC per se had little effect on draught requirements.     

紫色土坡地土壤性质对耕作侵蚀的影响

[目的]揭示土壤性质对耕作侵蚀土壤的敏感性,为紫色土区域采取适宜的耕作措施提供依据。[方法]利用磁性示踪技术定量旋耕机上下耕作和等高耕作的土壤耕作位移和土壤位移量,选取土壤容重、土壤含水量、土壤有机质、土壤全氮、土壤有效磷、土壤抗剪强度和土壤紧实度等土壤理化性质和力学性质指标,研究土壤性质对旋耕机上下耕作和等高耕作的耕作侵蚀的影响特征。[结果]旋耕机上下耕作和等高耕作的土壤净位移和净位移量不仅受坡度影响,也受土壤性质的影响。土壤力学性质和土壤物理性质对旋耕机耕作侵蚀有显著影响,对于上下耕作的土壤抗剪强度、土壤紧实度和土壤容重与土壤净位移量呈显著正相关。对于等高耕作措施的土壤抗剪强度、土壤紧实度、土壤容重和土壤含水量与土壤净位移量呈显著正相关,其他指标关系不显著。[结论]土壤抗剪强度、土壤紧实度和土壤容重可以作为评价耕作侵蚀的土壤可蚀性指标。     

A comparison between continuous and controlled grazing on a red duplex soil. II. Subsequent effects on seedbed conditions, crop establishment and growth

The effects of past grazing management practice on subsequent seedbed condition, draft requirements, fuel consumption, crop establishment and growth, and grain yield and quality were examined using three tillage systems on two sowing dates. The crop was wheat (Triticum aestivum), sown on a fragile sandy clay loam (red duplex soil) in a dryland agricultural area (307 mm average annual rainfall) of Western Australia. The three tillage-sowing systems investigated were: (i) scarifying followed by sowing with wide (180 mm) points; (ii) direct drilling with wide (180 mm) points; (iii) direct drilling with narrow (50 mm) inverted ‘T’-shaped Super-Seeder points. The two sowing dates provided differences in seedbed water content at sowing time. The three grazing management strategies practised in the previous pasture year were: (i) traditional set-stocking (where sheep were grazed continuously for 17 weeks, beginning soon after the start of the early winter rains); (ii) controlled grazing (where sheep were temporarily removed from the enclosure when the topsoil was close to its plastic limit); (iii) no grazing (where the pasture was mown to simulate grazing without trampling).Tillage prior to sowing with wide points reduced the mechanical impedance of the soil following set-stocking and provided a good seedbed for successful crop establishment and growth. In both the controlled-grazing management treatment and the treatment where the pasture had been mown the soil was suitable for direct drilling with both wide and narrow points (i.e. no pre-sowing tillage was required). The use of narrow points had the added advantage of requiring less fuel, but the need for a suitable implement to cover seeds was more critical than for wider sowing points. There were no advantages with respect to grain yield from adopting a controlled-grazing management practice owing to the lack of finishing rainfall. However, grain protein levels were higher in both the controlled and ungrazed treatments compared with the set-stocking treatment.     

Tillage and no-tillage effects on physical and chemical properties of an Argiaquoll soil under long-term crop rotation in Buenos Aires,Argentina

No-tillage systems are able to reduce the negative effects of agricultural intensification on soil properties. However, knowledge of long-term impacts of no-tillage systems on soil properties is insufficient. It is essential to know which soil quality indicators are the most sensitive to management practices in each particular environment. Therefore, the objective of this work is to determine which soil quality properties are more sensitive to the impact of two tillage systems in a vertic Argiaquoll soil from Buenos Aires, Argentina. This work started in 2006 and included crop rotation and tillage systems, including both tillage and no-tillage. Physical and chemical properties were measured in three consecutive years (2013–2015) at two depths (0–10 cm and 10–20 cm). The tillage system modified soil physical and chemical properties, mainly in the surface layer. No-tillage showed significantly higher bulk density (2013–2015 p < 0.05), gravimetric moisture (2013; 2014 p < 0.05), organic carbon (2013–2015 p < 0.05), and aggregates stability in the face of a heavy rain (2013; 2015 p < 0.05), than soil under tillage. Soil saturation (or total porosity) was significantly greater under tillage. The tillage system did not affect hydraulic conductivity, total nitrogen and extractable phosphorus from the surface, nor physical and chemical properties from the second depth. No-tillage alleviates, but is not enough to mitigate, the loss of soil organic carbon and aggregate stability caused by continuous cropping in this vertic Argiaquall. Bulk density, organic carbon, aggregates stability and saturation are indicators for future studies performed in environments with similar soil and climate conditions.     

不同耕作深度对红壤坡耕地耕层土壤特性的影响

红壤坡耕地不同耕作深度对耕层质量和作物产量具有重要影响。以江西红壤坡耕地示范区耕层为研究对象,从土壤属性角度,对红壤坡耕地不同耕作深度处理下垂直深度土壤水分、容重、孔隙度、土壤紧实度、土壤抗剪强度、土壤有机质、有效磷和速效钾等进行分析。结果表明:(1)不同耕作深度对土壤孔隙度、饱和含水量和田间持水量的影响为免耕翻耕20 cm翻耕10 cm常规耕作翻耕30 cm,对容重的影响为翻耕30 cm常规耕作翻耕10 cm免耕翻耕20 cm;与常规耕作比较,翻耕30 cm使土壤饱和含水量、田间持水量和土壤孔隙度分别提高了18.17%,12.67%,5.94%,土壤容重降低6.90%。(2)不同耕作深度下土壤紧实度表现为翻耕30 cm翻耕10 cm翻耕20 cm免耕常规耕作,土壤抗剪强度表现为翻耕30 cm常规耕作翻耕10 cm免耕翻耕20 cm;与常规耕作对照,翻耕30 cm使土壤紧实度和抗剪强度分别降低27.07%和24.82%。(3)土壤有机质含量以翻耕20 cm处理下最高(13.48 g/kg),免耕处理含量最低(9.39 g/kg),土壤速效养分主要集中分布在0-20 cm土层,但20-40 cm土层中翻耕处理较免耕处理有不同程度的增加,以翻耕20 cm和常规耕作表现显著。(4)主成分分析结果表明,翻耕30 cm处理对红壤坡耕地土壤的综合改善效果最好。研究结果可为红壤坡耕地耕层土壤改善和合理耕层构建提供技术参考。     

Trends in tillage practices in relation to sustainable crop production with special reference to temperate climates

The concept and some definitions of sustainable agriculture are reviewed. Most of these definitions include economic, environmental and sociological aspects. The finite area of land emphasizes the need for consideration of soil conservation and of soil quality in relation to sustainability. An important element of soil quality is rooting depth. Therefore loss of soil by erosion is a dominant factor in long-term sustainability. The effects of tillage on soil parameters in minimum data sets that have been proposed to describe soil quality are reviewed. Soil organic matter may be one of the most important soil quality characteristics in relation to tillage because of its influence on other soil physical, chemical and biological properties. Conservation tillage practices can increase the organic matter content, aggregate stability and cation exchange capacity (CEC) of the topsoil. However, bulk density and penetrometer resistance are also increased, especially with zero tillage. Although such soil quality parameters may form a basis for describing some of the consequences of particular tillage practices, they do not provide a basis for predicting the outcome in terms of crop growth and yield. This is both because critical values of soil quality parameters have not been defined and because in some soils biopore formation in zero or minimally tilled land can modify the soil for water movement and for root growth and function.

The effects of tillage on crop growth and yield in long-term experiments are reviewed. The review only includes experiments in North America, Europe and New Zealand that have lasted 10 years or more to allow for seasonal variation in weather, possible progressive changes in soil conditions and the learning phase often experienced when new tillage methods are used. While there is a good deal of variation in the results of these tillage experiments some patterns have emerged. In long-term experiments, yields of maize in Europe and the US and soybeans in the US have been similar after ploughing and no-tillage, especially on well-drained soils. In Europe, yields of winter cereals have also been similar after traditional and simplified tillage but yields of spring cereals have sometimes been less after direct drilling than ploughing.

Trends in tillage practices are reviewed. Conservation tillage in the US is increasing and is used on about 30% of cropland, including no-till on about 10% of cropland. This increase in use of conservation tillage is mainly attributed to the legal requirement for farmers who are in government price support programs to adopt conservation plans which may involve conservation tillage. However, the allowable rates of erosion in these plans are likely to be in excess of rates of erosion for long-term sustainability. Survey information on tillage practices needs to be considered in relation to predictions on suitability of conservation tillage based on experimental results. In the semi-arid prairies of Canada there is a trend toward fewer cultivation operations, but in eastern Canada the mouldboard plough is still the dominant tillage method. In Europe although erosion is less obvious it is believed to be increasing, but minimum tillage is not widely used. This is because of the need to remove at least some straw for successful minimum tillage in sequential winter wheat and barley crops, but there are few economic uses for straw, and burning is illegal in many countries. In the more moist cooler conditions of Europe grass weed proliferation is another constraint, at least with present technology. So far, the overall success of conservation tillage has not been limited by the growing problem of genetic resistance of weeds to herbicides. Societal attitudes to the continued use of herbicides may pose longer-term problems for some conservation tillage practices.