Subsoil tillage enhances wheat productivity,soil organic carbon and available nutrient status in dryland fields

Tillage practices during the fallow period benefit water storage and yield in dryland wheat crops.However,there is currently no clarity on the responses of soil organic carbon(SOC),total nitrogen(TN),and available nutrients to tillage practices within the growing season.This study evaluated the effects of three tillage practices(NT,no tillage;SS,subsoil tillage;DT,deep tillage)over five years on soil physicochemical properties.Soil samples at harvest stage from the fifth year were analyzed to determine the soil aggregate and aggregate-associated C and N fractions.The results indicated that SS and DT improved grain yield,straw biomass and straw carbon return of wheat compared with NT.In contrast to DT and NT,SS favored SOC and TN concentrations and stocks by increasing the soil organic carbon sequestration rate(SOCSR)and soil nitrogen sequestration rate(TNSR)in the 0-40 cm layer.Higher SOC levels under SS and NT were associated with greater aggregate-associated C fractions,while TN was positively associated with soluble organic nitrogen(SON).Compared with DT,the NT and SS treatments improved soil available nutrients in the 0-20 cm layer.These findings suggest that SS is an excellent practice for increasing soil carbon,nitrogen and nutrient availability in dryland wheat fields in North China.

Effect of No Tillage and Conventional Tillage on Wheat Grain Yield Variability: A Review

Conservation Agriculture(CA)covers more than 205 million hectares in the world.This made it possible to face and mitigate the challenges of climate change,reducing soil erosion and providing multiple ecosystem services.The first elementary factor influenced is the yield evaluation.It has a direct effect on farmers’choices for sustainable production.The present article records a review focused on wheat yield average positive change compared between conventional tillage(CT)and no tillage(NT)systems.The international database collected showed that NT is adaptable everywhere.The results of wheat yield differentiation showed the influence of crop rotation depending on stations located in different climatic zones.In more than 40 years of research,specialists have succeeded in demonstrating the importance of crop productivity like wheat.The whole integrates also experimentations where the initiation starts more than ten years.

Optimized tillage methods increase mechanically transplanted rice yield and reduce the greenhouse gas emissions

Biaxia lrotary tillage in dryland(DBRT)can complete biaxial rotary tillage with straw incorporation,secondary suppression,and ditching,and it has been previously studied in direct-seeded rice and wheat.However,the effects of DBRT on the mechanically transplanted rice yield and greenhouse gas emissions remain unclear.To evaluate the effects of DBRT on improving the food security of mechanically transplanted rice and reducing the greenhouse gas emissions,we conducted an experiment for two years with wheat straw incorporation.Three tillage methods were set up:DBRT,uniaxial rotary tillage in dryland and paddy(DPURT),and uniaxial rotary tillage in paddy(PURT).The results showed that compared with DPURT and PURT,DBRT increased the yield of machine-transplanted rice by 7.5-11.0%and 13.3-26.7%,respectively,while the seasonal cumulative CH_(4) emissions were reduced by 13.9-21.2%and 30.2-37.0%,respectively,and the seasonal cumulative N_(2)O emissions were increased by 13.5-28.6%and 50.0-73.1%,respectively.Consequently,DBRT reduced the global warming potential by 10.7-15.5%and 23.7-28.6%,respectively,andtheyield-scaledglobalwarmingpotentialby18.2-21.8%and36.4-39.3%,respectively,compared to DPURT and PURT.These results were mainly related to the fact that DBRT significantly reduced soil bulk density and increased soil redox potential(Eh).Therefore,implementing DBRT in machine-transplanted rice fields is feasible,which cannot only increase the rice yield,but also reduce the greenhouse gas emissions.

Historical tillage promotes grass-legume mixtures establishment and accelerates soil microbial activity and organic carbon decomposition

Perennial grass-legume mixtures have been extensively used to restore degraded grasslands,increasing grassland productivity and forage quality.Tillage is crucial for seedbed preparation and sustainable weed management for the establishment of grass-legume mixtures.However,a common concern is that intensive tillage may alter soil characteristics,leading to losses in soil organic carbon(SOC).We investigated the plant community composition,SOC,soil microbial biomass carbon(MBC),soil enzyme activities,and soil properties in long-term perennial grass-legume mixtures under two different tillage intensities(once and twice)as well as in a fenced grassland(FG).The establishment of grass-legume mixtures increased plant species diversity and plant community coverage,compared with FG.Compared with once tilled grassland(OTG),twice tilled grassland(TTG)enhanced the coverage of high-quality leguminous forage species by 380.3%.Grass-legume mixtures with historical tillage decreased SOC and dissolved organic carbon(DOC)concentrations,whereas soil MBC concentrations in OTG and TTG increased by 16.0%and 16.4%,respectively,compared with FG.TTG significantly decreased the activity of N-acetyl-β-D-glucosaminidase(NAG)by 72.3%,whereas soil enzymeβ-glucosidase(βG)in OTG and TTG increased by 55.9%and 27.3%,respectively,compared with FG.Correlation analysis indicated a close association of the increase in MBC andβG activities with the rapid decline in SOC.This result suggested that MBC was a key driving factor in soil carbon storage dynamics,potentially accelerating soil carbon cycling and facilitating biogeochemical cycling.The establishment of grass-legume mixtures effectively improves forage quality and boosts plant diversity,thereby facilitating the restoration of degraded grasslands.Although tillage assists in establishing legume-grass mixtures by controlling weeds,it accelerates microbial activity and organic carbon decomposition.Our findings provide a foundation for understanding the process and effectiveness of restoration management in degraded grasslands.

Urban Soil Compaction Remediation by Shallow Tillage and Compost in Hydroseeded Lawn

Construction activities often involve removal of topsoil and compaction of the exposed soil by heavy equipments. Such compacted soils with low organic matter can lead to low infiltration and poor vegetation establishment. The objective of this study was to investigate the efficacy of tillage (shallow till) and compost on soil physical and biological properties in a hydroseeded lawn as a post-construction best management practice for soil compaction remediation. The experimental site received a total of four land treatments in five replicated trials and it was hydroseeded with common Bermuda grass: 1) No Tillage + Compost (NT-C), 2) No Tillage + No Compost (NT-NC;control), 3) Tillage + Compost (T-C), and 4) Tillage + No Compost (T-NC). Bulk density (BD), infiltration rate (IR), and wet aggregate stability (WAS) in each plot were measured to assess soil physical properties while soil organic matter (SOM) and enzyme activity (β-glucosidase, acid-phosphatase, and alkaline-phosphatase) were measured for soil biological properties. Over a 15-months of monitoring period, the shallow tillage loosened the soil initially, but its effect on BD without compost was diminished to control plot level (NT-NC) within 4 months after hydroseeding. Both tillage and compost led to an increase in IR, and it remained higher than control by 2 - 3 times throughout the observation period. The WAS and β-glucosidase activity decreased in tilled plot unless there was compost application. Turfgrass showed greener leaves and aggregated roots in the compost-amended plots (NT-C and T-C). Our results suggest that compost application plays a key role in improving soil physical and biological properties in hydroseeded lawns from construction sites.

Changes in soil susceptibility to erosion under tillage and soil fertility management practices

The degree to which soil is susceptible to erosion is measured as soil erodibility which can be influenced by different land management options.This study evaluated the dynamics of soil erodibility to tillage and soil amendments in a maize field under five consecutive cropping cycles.Tillage treatments were no-till,minimum,conventional,and grassland fallow(control).The soil amendment treatments used were no amendment(control),NPK,poultry manure(PM),and1/2NPK+1/2PM and these treatments were applied to all the tillage treatments including no-till.The study showed that tillage and soil amendment interactions had significant effects on soil erodibility(p<0.05).The mean erodibility values ranged from 13×10^(−3) to 24×10^(−3) Mg·h·MJ^(−1)·mm^(−1) in the following order:control<conventional tillage<minimum tillage<no-till.For the soil amendments,erodibility varied from NPK>poultry manure=1/2NPK+1/2PM>control(undisturbed grassland).Regardless of the type of soil amendment,the soil erodibility under conventional tillage was significantly lower than that under no-till and minimum tillage systems.The relationship between erodibility and easily measured soil parameters,such as%sand greater than 100μm,%silt plus very fine sand,clay,and saturated hydraulic conductivity,were significant at p<0.05.The higher contribution(86%)of sand and silt to the variation in erodibility indicates that any other indices of erodibility based on particle size distribution,apart from the nomograph,could satisfactorily predict erodibility values.

免耕播种机勒洛三角形镇压轮设计与试验

针对免耕播种机镇压轮在地表有残茬时,作业阻力大、作业后种沟土壤平整度差的问题,设计了一种勒洛三角形刚性镇压轮。以镇压轮的定宽高度和宽度为试验因素,以工作阻力、土壤平整度、土壤下陷量为指标,采用中心复合表面试验设计(Central Composite Face-centered design, CCF)进行离散元仿真优化试验。对试验数据进行分析并得出回归模型,获得镇压轮最优结构参数。仿真结果表明:镇压轮定宽高度为274.75 mm、宽度为78.49 mm时,作业性能最优;此时,工作阻力为32.73 N、种沟土壤平整度为2.64 mm、土壤下陷量为14.25 mm。与传统镇压轮进行田间对比试验,结果表明:勒洛三角形镇压轮作业后,土壤密度为1.16 g/cm^(3),满足农作物生长所需条件;勒洛三角形镇压轮作业阻力比传统镇压轮减少9.1%、地表平整度提高15.3%。该研究为免耕播种机镇压轮的设计提供新的思路和借鉴。

双高背景下的人才培养模式创新--德技并修“雨耕”特色职业素质教育体系构建

通过对国内外职业教育理论及人才培养实践经验的学习研究,明确“德技并修”技能人才内涵与构成要素。搭建德技并修育人平台,健全德技并修育人体系;建设机电工匠培养体系,打造技术技能人才培养高地;建设机电工匠培养特区,培养卓越技术技能人才;构建全方位育人的同心圆,推进全过程育人的大格局。创新双高背景下人才培养模式,构建德技并修“雨耕”特色职业素质教育体系,借助学校教学平台结合企业的实践平台,将职业道德和工匠精神融入学生的整个培育过程中,坚持技能和德育并重,教会学生如何做人、如何做事,树立正确的人生观、价值观,培养高素质高技能人才。

Effects of Different Tillage Techniques on Yield and Water Use Efficiency in Broomcorn Millet

[Objective] The effects of different tillage techniques on dry matter accu- mulation, soil water content, water use efficiency and yield of broomcom millet were studied. [Method] With Jinsu 9 as an experiment material, the effects of deep tillage, traditional tillage and no tillage and rotary tillage on dry matter accumulation, soil water content, water use efficiency and yield of broomcom millet were investi- gated. [Result] Dry matter accumulation rate and accumulated amount were signifi- cantly higher in the deep tillage, no tillage and rotary tillage treatments than in the conventional tillage treatment, and the highest in the deep tillage treatment. The soil water content of the deep tillage treatment at 0-100 cm was higher than those of other tillage techniques, deep tillage also exhibited the highest soil water storage, and water use efficiency values were in order of deep tillage〉rotary tillage〉no tillage〉conventional tillage. The deep tillage treatment also showed the highest grain weight per spike, 1 000-grain weight and yield, while conventional tillage exhibited the lowest values, indicating that deep tillage is most beneficial to improvement of yield and water use efficiency of broomcom millet. [Conclusion] This study provides a scientific basis for water use efficiency of broomcorh millet in its main producing areas.

On the Growth and Physiological Characteristics of Rice under Smashing Ridge Tillage

Two-line super hybrid rice （Oryza sativa L.） Guiliangyou 2 was taken as the experimental variety, the growth and physiological characteristics of rice under conventional tillage and smashing ridge tillage were compared based on field re- search. The results showed that smashing ridge tillage was beneficial to the tillering growth of rice plants in the the middle and later periods of tillering; under the tillage mode, the white root was more, the vigour was strong during the whole growing period, the SPAD was extremely significantly higher than that of conventional tillage, the net photosynthetic rate of the leaves was high and held green long, which were beneficial to the production and accumulation of photoassimilates; during mature pe- riod, the dry matter accumulation of the overground part under smashing ridge tillage was significantly higher than that of conventional tillage, and the number of productive ears under smashing ridge tillage was more than that of conventional tillage by 27.6×10^4/hm2, thus, the yield-increasing effect was significant and in- creased by 20.36%.

Effects of Nitrogen Application Rate, Density and Seedling Age on Dry Matter Accumulation of No-tillage Rape in Seedling Stage

[Objective] The aim of the research was to find the optimal nitrogen application rate, density and seedling age for no-tillage rape in seedling stage. [Method] With the D-optimal quadratic regression design for three factors, the 310 scheme was designed to study the effects of nitrogen application rate, density and seedling age on dry matter accumulation of no-tillage rape in seedling stage. [Result] With the increase of nitrogen application rate, density and seedling age, the dry matter content appeared like a parabola, increasing firstly and then declining. The change of nitrogen application rate caused greater influence than that of density and seedling age; the interaction effects between nitrogen application rate and density were greater than that between nitrogen application rate and seedling age as well as between density and seedling age. [Conclusion] Considered comprehensively, the dry matter content of no-tillage rape in seedling stage reached the highest level (4 768.2 kg/hm2) when the nitrogen application rate, the density and the seedling age were 195 kg/hm2, 93 000 plants/hm2 and 33 d, respectively.

Effects of Different Tillage and Mulching Modes on Tobacco Output Value and Soil Quality

Based on three years of long-term fixed-site field trial, the effects of differ- ent tillage and mulching modes on the yield and output value of tobacco and soil quality were investigated. The results showed that the yield and output value of to- bacco in tillage treatment were improved by 22.72 % and 37.23 % compared with non-tillage treatment, respectively; the yield and output value of tobacco in rotation treatment were improved by 1.83% and 19.41% compared with continuous cropping treatment, respectively; the yield and output value of tobacco in straw mulching treatment were improved by 3.55% and 2.4% compared with non-straw mulching treatment, respectively, which indicated that tillage, rotation and straw mulching could improve the yield and output value of tobacco to a certain extent; especially, the yield and output value of tobacco increased significantly after plowing under rotation conditions. The contents of available phosphorus （AP）, alkali-hydrolyzable nitrogen （AN）, organic matter （OM）, total nitrogen （TN） and total phosphorus （TP） in non- tillage treatment were 35.14%, 9.92%, 9.57%, 4.40% and 34.16% higher compared with tillage treatment; especially, under non-tillage conditions, soil pH and contents of available potassium （AK）, AP, AN,OM,TN,TP and total potassium （TK） in continu- ous cropping field were 2.01%, 48.68%, 73.09%, 11.45%, 7.71%, 7.31%, 47.68% and 11.78% higher compared with rotation field, indicating that non-tillage treatment and continuous cropping could improve the total content and available content of organic matter, nitrogen and phosphorus. Therefore, from the perspective of soil fer- tility improvement and sustainable tobacco production, continuous cropping under non-tillage conditions might be the most appropriate cropping pattern for local soil fertility improvement; aiming at improving the yield and output value of tobacco, green manure-tobacco→, green manure/wheat/maize→green manure-tobacco ro- tation might be the most appropriate cropping pattern.

不同耕作方式配施有机肥对盐碱地玉米根际土壤微生物群落的影响

本研究旨在探究不同耕作方式配施有机肥对盐碱地玉米根际土壤化学性质及微生物群落结构的影响,从而为改良盐碱地和了解盐碱地玉米根际土壤的微生物群落特征提供重要依据。本研究采用裂区试验设计,主区设置两种耕作措施:CT(传统翻耕)和DV(垂直深旋耕),副区设置4个有机肥施用水平:O1(0 kg·hm^(-2))、O2(7500 kg·hm^(-2))、O3(15000 kg·hm^(-2))、O4(22500 kg·hm^(-2))。研究结果表明,在DVO3和DVO4处理下,玉米根际土壤的pH和全盐含量较其他处理显著降低3.94%~9.20%和6.31%~25.96%,有机质、碱解氮、速效磷和速效钾含量较其他处理显著增加5.29%~45.24%、4.71%~24.34%、13.63%~32.67%和10.77%~34.25%,玉米产量较其他处理显著增加2.51%~22.23%,且DVO3和DVO4处理之间的差异不显著。与其他处理相比,DVO3和DVO4处理下玉米根际土壤微生物群落的丰富度和多样性明显提升,且DVO3和DVO4处理之间差异不显著。此外,DVO3和DVO4处理显著提高了细菌优势菌门中的变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes),以及真菌优势菌门中的子囊菌门(Ascomycota)和担子菌门(Basidiomycota)的相对丰度,同时显著提高了细菌优势菌属中的Ohtaekwangia、Gp6和Gp7,以及真菌优势菌属中粪盘菌属(Ascobolus)、线黑粉酵母属(Filobasidium)和毛葡孢属(Botryotrichum)的相对丰度,且DVO3和DVO4处理之间的差异不显著。上述菌门和菌属的相对丰度与玉米根际土壤有机质和速-2效养分含量呈正相关。综上所述,垂直深旋耕配施15000~22500 kg·hm有机肥能够显著降低盐碱土壤pH和全盐含量,增加速效养分和有机质含量,提高微生物丰富度和多样性,有利于盐碱地土壤改良和养分循环。

Study on Relative Soil and Water Conservation Benefits of Ridge Tillage in Different Terrain Conditions in the Black Soil Area of Northeast China

Ridge tillage, which is a very common and important tillage measure in the black soil area of northeast China, has some soil and water conservation bene- fits, but has little attention. It is very important to explore the spatial distribution of the ridge direction of the arable land and its soil and water conservation benefits in different terrain conditions in the black soil area. So Binxian County of Heilongjiang Province was selected as the study area, and 168 field investigation units were ex- tracted by stratified sampling method and investigated. According to equations of slope gradient factor and slope gradient in ridge direction, and based on the soft- ware of Arcmap, SPSS and Excel, the investigation data of soil and water loss in Binxian County were analyzed and counted, The results show that in plain, hilly and mountainous areas, the average ground slope gradients are 1.92°, 6.20° and 8.27° respectively, and the average slope gradients along ridge direction are 1.33°, 4.52°and 6.45° respectively, which account for about 70%, 73% and 78% of the average ground slope gradients in the same terrain condition; the relative quantities of soil erosion in the present ridge tillage condition account for about 55%, 69% and 67% respectively of that in down-slope ridge tillage conditions, so the present ridge tillage has obviously relative soil and water conservation benefits. Based on these results, the reasons of the present ridge tillage status were analyzed, and some reform measures were proposed. The results could not only help to comprehend the spatial distribution and soil and water conservation benefits of ridge tillage in the black soil area of Northeast China, but also provide scientific references for the layout of local soil and water conservation measures.

东北地区免耕播种机发展现状及使用指导

自保护性耕作技术推广以来,已经得到了一定的发展,而免耕播种机是保护性耕作的最重要机具之一。该文首先介绍了免耕播种的意义,论述了免耕播种机应用的必要性,其次从不同种类免耕播种机应用现状和发展难点两方面阐述了免耕播种机的发展现状,并介绍了免耕播种机及主要部件的功能和使用注意事项,以加大对免耕播种机的了解。

耕作措施对红壤坡耕地土壤CO_(2)排放的影响

[目的]探析红壤坡耕地不同耕作措施对土壤二氧化碳(CO_(2))排放的影响,为红壤坡耕地绿色低碳耕作模式构建与耕作措施优化提供理论依据。[方法]通过设置横坡垄作(RT)、顺坡垄作(DT)、覆膜耕作(PM)和传统耕作(CT)4种典型耕作措施试验小区,采用结构方程模型探究了土壤理化性状与土壤CO_(2)排放间的响应关系,并采用综合评价模型定量分析了不同耕作措施的降碳增产综合效益。[结果]RT的土壤有机碳和全氮含量总体较高,可显著增加土壤总孔隙度,降低土壤容重(p<0.05),DT则相反;PM的土壤温度及含水率显著高于其余耕作措施,RT和DT为代表的垄作措施显著高于CT。在作物生育期内,不同耕作措施的土壤CO_(2)排放通量在60.53~818.90 mg/(m^(2)·h),呈先升高后降低的波动趋势,耕作措施间土壤CO_(2)累计排放量大小关系为PM>DT>CT>RT,RT可显著减少3.4%~22.4%(p<0.05),而作物生育期间为花粒期>穗期>苗期。降雨侵蚀对红壤坡耕地土壤CO_(2)排放具有明显“Birch效应”,降雨侵蚀后耕作措施间土壤CO_(2)排放通量大小关系为DT>PM>CT>RT。红壤坡耕地主要通过调节土壤温度、土壤含水率、全氮和容重来影响土壤CO_(2)排放通量。[结论]RT对降低土壤CO_(2)排放及增加作物产量具有积极作用,可优先在南方红壤坡耕地进行推广。

Effect of subsoil tillage depth on nutrient accumulation, root distribution, and grain yield in spring maize

A four-year field experiment was conducted to investigate the effect of subsoiling depth on root morphology, nitrogen(N), phosphorus(P), and potassium(K) uptake, and grain yield of spring maize. The results indicated that subsoil tillage promoted root development,increased nutrient accumulation, and increased yield. Compared with conventional soil management(CK), root length, root surface area, and root dry weight at 0–80 cm soil depth under subsoil tillage to 30 cm(T1) and subsoil tillage to 50 cm(T2) were significantly increased, especially the proportions of roots in deeper soil. Root length, surface area, and dry weight differed significantly among three treatments in the order of T2 > T1 > CK at the12-leaf and early filling stages. The range of variation of root diameter in different soil layers in T2 treatment was the smallest, suggesting that roots were more likely to grow downwards with deeper subsoil tillage in soil. The accumulation of N, P, and K in subsoil tillage treatment was significantly increased, but the proportions of kernel and straw were different. In a comparison of T1 with T2, the grain accumulated more N and P, while K accumulation in kernel and straw varied in different years. Grain yield and biomass were increased by 12.8% and 14.6% on average in subsoil tillage treatments compared to conventional soil treatment. Although no significant differences between different subsoil tillage depths were observed for nutrient accumulation and grain yield, lodging resistance of plants was significantly improved in subsoil tillage to 50 cm, a characteristic that favors a high and stable yield under extreme environments.

Straw return and appropriate tillage method improve grain yield and nitrogen efficiency of winter wheat

Straw return is an important management tool for tackling and promoting soil nutrient conservation and improving crop yield in Huang-Huai-Hai Plain, China. Although the incorporation of maize straw with deep plowing and rotary tillage practices are widespread in the region, only few studies have focused on rotation tillage. To determine the effects of maize straw return on the nitrogen （N） efficiency and grain yield of winter wheat （Triticum aestivum L.）, we conducted experiments in this region for 3 years. Five treatments were tested： （i） rotary tillage without straw return （RT）; （ii） deep plowing tillage without straw return （DT）; （iii） rotary tillage with total straw return （RS）; （iv） deep plowing tillage with total straw return （DS）; （v） rotary tillage of 2 years and deep plowing tillage in the 3rd year with total straw return （TS）. Treatments with straw return increased kernels no. ear-1, thousand-kernel weight （TKW）, grain yields, ratio of dry matter accumulation post-anthesis, and nitrogen （N） efficiency whereas reduced the ears no. ha-1 in the 2011-2012 and 2012-2013 growing seasons. Compared with the rotary tillage, deep plowing tillage significantly increased the grain yield, yield components, total dry matter accumulation, and N efficiency in 2013-2014. RS had significantly higher straw N distribution, soil inorganic nitrogen content, and soil enzymes activities in the 0-10 cm soil layer compared with the DS and TS. However, significantly lower values were ob- served in the 10-20 and 20-30 cm soil layers. TS obtained approximately equal grain yield as DS, and it also reduced the resource costs. Therefore, we conclude that TS is the most economical method for increasing grain yield and N efficiency of winter wheat in Huang-Huai-Hai Plain.

Soil physical properties and maize root growth under different tillage systems in the North China Plain

The standard cultivation system in the North China Plain is double cropping of winter wheat and summer maize. The main effects of this cultivation system on root development and yield are decreases in soil nutrient content and depth of the plow layer under either long-term no-tillage or rotary tillage before winter wheat sowing and no tillage before summer maize sowing. In this study, we investigated the combined effects of tillage practices before winter wheat and summer maize sowing on soil properties and root growth and distribution in summer maize. Zhengdan 958(ZD958) was used as experimental material, with three tillage treatments: rotary tillage before winter wheat sowing and no tillage before summer maize sowing(RTW + NTM), moldboard plowing before winter wheat sowing and no tillage before summer maize sowing(MPW + NTM), and moldboard plowing before winter wheat sowing and rotary tillage before summer maize sowing(MPW + RTM).Tillage practice showed a significant(P < 0.05) effect on grain yield of summer maize. Grain yields under MPW + RTM and MPW + NTM were 30.6% and 24.0% higher, respectively, than that under RTW + NTM. Soil bulk density and soil penetration resistance decreased among tillage systems in the order RTW + NTM > MPW + NTM > MPW + RTM. Soil bulk densities were 3.3% and 515% lower in MPW + NTM and MPW + RTM, respectively, than that in RTW + NTM, and soil penetration resistances were respectively 17.8% and 20.4% lower,across growth stages and soil depths. Root dry matter and root length density were highest under MPW + RTM, with the resulting increased root activity leading to a yield increase of summer maize. Thus the marked effects of moldboard plowing before winter-wheat sowing on root length density, soil penetration resistance, and soil bulk density may contribute to higher yield.

Influence of Conservation Tillage on Soil Aggregates Features in North China Plain

Tillage greatly influences the aggregation and stability of soil aggregates. This study investigated the effects of conservation tillage on soil aggregate characteristics. During a four-year study period （2001-2005）, soils were sampled from no-tillage （NT）, rotary tillage （RT）, and conventional tillage （moldboard tillage, CT） plots at the Luancheng Agriculture and Ecology Experimental Station in Hebei Province, China, and the amount, size distribution, and fractal dimension of the aggregates were examined by dry and wet sieving methods. The results indicated that NT significantly increased the topsoil （0-5 cm） bulk density （BD）, while RT maintained a lower BD as CT. Dry sieving results showed that NT had higher macro-aggregate content （R0.25）, and a larger mean weight diameter （MWD） and geometric mean diameter （GMD） than other treatments in the 0-10 cm layer, while RT showed no difference from CT. In wet sieving, results showed that most of the aggregates were unstable, and the MWD and GMD of water-table aggregates showed the trend of NT 〉 RT 〉 CT. At 0-5 cm layer, the fractal dimension （D） of water-stable aggregates under NT was lower than it was under RT and CT. At 5-10 cm, RT yielded the highest D, and showed stability. After four years, NT increased the aggregation and the stability of soil aggregates; while due to intense disturbance, the aggregation and stability of the upper layer （0-10 cm） under RT and CT decreased.