Soil carbon fractions and relationship to soil quality under different tillage and stubble management

Effect of 19 years of different tillage (direct drilled vs. conventional tillage) and stubble management (stubble retained vs. burnt) on soil carbon fractions were studied in a red earth, an Oxic Paleustalf at Wagga Wagga, NSW. The changes in carbon fractions were related to observed changes in soil structural stability and nitrogen availability. Significant differences in total organic carbon (TOC) were detected to 0.20 m depth, but the largest differences existed in the top 0.05 m where a difference of 8.0 g/kg (equivalent to 5.2 t ha⁻¹) was found between the extreme treatments (direct drilled/stubble retained (DD/SR) vs. conventional cultivation/stubble burnt (CC/SB)). Tillage had a much greater effect in reducing total carbon than stubble burning accounting for 80% of the total difference between the extreme treatments in 0–0.05 m layer. Tillage and stubble burning resulted in lower levels of different organic carbon fractions with tillage preferentially reducing the particulate organic carbon (POC) (>53 μm) (both free and associated POCs), whereas stubble burning reduced the incorporated organic carbon (<53 μm). We also found that tillage and stubble burning both significantly lowered the water stability of aggregate >2 mm, whereas stubble burning was related to the reduction of water stability of aggregates <50 μm. Furthermore, tillage was related to the decline in mineralisable nitrogen (MN) due to the loss of POC, especially the free POC fraction. POC was a more sensitive indicator of soil quality changes under different tillage and stubble management than TOC.     

Effects of rotation, stubble retention and cultivation on take-all and eyespot of wheat in northeastern Victoria, Australia

The effects of different rotations and methods of seed-bed preparation on take-all (Gaeumannomyces graminis var. tritici) (Ggt) and eyespot (Tapesia yallundae; anomorph Pseudocercosporella herpotrichoides) of wheat (Triticum aestivum) were investigated in 1984–1986 in a long-term field experiment (established in 1981), on a fine sandy-clay loam in northeastern Victoria. One treatment, representing the conventional practice, involved burning stubble from the preceding crop followed by four passes with a scarifier in the autumn before sowing wheat each year. Other treatments were direct drilled each year (sown without prior cultivation) and included two stubble treatments (retained or burnt) in either continuously cropped wheat or in lupin (Lupinus angustifolius)-wheat rotations.

High levels of take-all and eyespot developed in the continuously cropped wheat (up to 79% and 66% plants affected, respectively). On the other hand, the incidence of plants with either disease was very low or negligible in wheat that was preceded by lupins. In continuous wheat the incidence of plants with Ggt lesions were up to two times higher in the conventionally cultivated treatment (14% 74% and 79% plants affected in 1984, 1985 and 1986, respectively) than in direct drilled treatment (5%, 36% and 39% plants affected, respectively). Generally, the incidence of plants with Ggt lesions and the severity of root symptoms in direct drilled wheat did not differ significantly between the two stubble treatments.

The incidence of eyespot in direct drilled wheat was exacerbated by the retention of wheat stubble on the uncultivated plots (3%, 46% and 66% plants affected in 1984, 1985, and 1986, respectively) but was reduced by burning the stubble (4%, 19% and 33% plants affected in 1984, 1985, 1986, respectively). However, cultivating soil after burning stubble resulted in more plants with eyespot (14%, 39% and 46% plants affected in 1984, 1985 and 1986, respectively) than did burning stubble alone, and in one year the incidence of affected plants in the cultivated treatment was as high as in wheat direct drilled into stubble. The incidence of eyespot was positively correlated (r=0.85, 0.84 and 0.61 in 1984, 1985 and 1986, respectively) with the incidence of lodged tillers. The incidence of lodging was, generally, highest each year in wheat sown directly into wheat stubble and was reduced by burning wheat stubble or by cropping wheat after lupins.

Wojnowicia graminis was frequently isolated, as was Tapesia yallundae, from eyespot lesions suggesting that perhaps not all symptoms of lodging in Victoria can be attributed to Tapesia yallundae.     

Relationship between soil structure and runoff/soil loss after 24 years of conservation tillage

A better understanding of tillage and stubble management effects on surface soil structure is vital for the development of effective soil conservation practices for the long-term. Relationships between aspects of soil structure and runoff/soil loss were investigated in 24 year old field experiment on an Oxic Paleustalf, in NSW, Australia. Two tillage/stubble management systems were compared, namely direct drilled/stubble retained (DD/SR) versus conventional tillage/stubble burnt (CC/SB). Tillage and stubble burning significantly increased bulk density and decreased the macro-aggregate stability, mean weight diameter (MWD), geometric mean diameter (GMD) and total porosity, particularly macroporosity (>60 μm). For the 0–5 cm layer, DD/SR had significantly higher water stability of macro-aggregates >2 mm than CC/SB (165 g/kg versus 78 g/kg), and the volume of pore space of diameter >60 μm at 0–5 cm depth was significantly greater (more than 11%) for DD/SR than for CC/SB. Under simulated rainfall (100 mm/h) and the removal of surface stubble, both runoff and soil loss were significantly higher under CC/SB compared to DD/SR. The infiltration rate at the end of the experiment under DD/SR was 3.7 times that of CC/SB (85 mm/h versus 23 mm/h). There were significant correlations between the proportion of soil particles >0.25 mm measured after wetting by rain and both final infiltration rate (P < 0.001) and soil loss (P < 0.001). It was concluded that 24 years of direct drilling and stubble retained practices significantly reduced runoff and soil erosion hazards, due to a fundamental change in soil structure, viz. higher soil aggregate stability and higher macroporosity of the surface soil.     

Impact of tillage, stubble management and crop rotation on nematode populations in a long-term field experiment

The population abundance of free-living and plant-parasitic nematodes was investigated in a long-term rotation/tillage/stubble management experiment at Wagga Wagga Agricultural Institute, New South Wales (NSW), Australia. The treatments were a combination of two crop rotations: wheat (Triticum aestivum)–wheat and wheat–lupin (Lupinus angustifolius); two tillage systems: conventional cultivation (CC) and direct drill (DD); and two stubble management practices: stubble retention (SR) and stubble burnt (SB). Plots of one of the wheat–wheat treatments received urea at 100 kg N ha⁻¹ during the cropping season. Soil samples from 0–5 and 5–10 cm depths were collected in September (maximum tillering), October (flowering) and December (after harvest), 2001, to analyse nematode abundance. Soil collected in September was also analysed for concentrations of total and labile C, and pH levels.Three nematode trophic groups, namely bacteria-feeders (primarily Rhabditidae), omnivores (primarily Dorylaimidae excluding plant-parasites and predators) and plant-parasites (Pratylenchus spp. and Paratylenchus spp.) were recorded in each soil sample. Of them, bacteria-feeders (53–99%, population range 933–2750 kg⁻¹ soil) dominated in all soil samples. There was no difference in nematode abundance and community composition between the 0–5 cm and 5–10 cm layers of soil. The mean population of free-living and plant-parasitic nematodes varied significantly between the treatments in all sampling months. In most cases, total free-living nematode densities (Rhabditidae and Dorylaimidae) were significantly (P < 0.001) greater in wheat–lupin rotation than the wheat–wheat rotation irrespective of tillage and stubble management practices. In contrast, a greater population of plant-parasitic nematodes was recorded from plots with wheat–wheat than the wheat–lupin rotation. For treatments with wheat–wheat, total plant-parasitic nematode (Pratylenchus spp. and Paratylenchus spp.) densities were greater in plots without N-fertiliser (295–741 kg⁻¹ soil) than the plots with N-fertiliser (14–158 kg⁻¹ soil).Tillage practices had significant (P < 0.05) effects mostly on the population densities of plant-parasitic nematodes while stubble management had significant effects (P < 0.05) on free-living nematodes. However, interaction effects of tillage and stubble were significant (P < 0.01) for the population densities of free-living nematodes only. Population of Rhabditidae was significantly higher in conventional cultivated plots (7244 kg⁻¹ soil) than the direct drilled (3981 kg⁻¹ soil) plots under stubble retention. In contrast, plots with direct drill and stubble burnt had significantly higher populations of Dorylaimidae than the conventional cultivation with similar stubble management practice. No correlations between abundance of free-living nematodes, and concentration of total C and labile C in soil were observed in this study. These results showed that stubble retention contributed for enormous population density of free-living (beneficial) nematodes while conventional cultivation, irrespective of stubble management, contributed for suppressing plant-parasitic nematodes.     

Crown rot and common root rot in wheat grown under different tillage and stubble treatments in southern Queensland, Australia

In southern Queensland, crown rot caused by Fusarium graminearum Group 1 and common root rot caused by Bipolaris sorokiniana are common soilborne diseases of wheat and barley. The incidence of these diseases was measured in the susceptible wheat (Triticum aestivum L.) cultivar, Hartog which was grown under no tillage, reduced tillage (two tillage operations plus herbicides) and where stubble was retained or removed by burning (1984–1986) or physically removed (1987–1993). Primary tillage was with blade, disc or chisel implements. The level of crown rot and common root rot was higher where stubble was retained than where it was removed. There was a significant interaction in incidence of crown rot between stubble management and some types of tillage. Where there was no tillage, incidence of crown rot was significantly higher where stubble was retained (32.2%) than where it was removed (4.7%) whereas under disc tillage, there was no significant difference in disease level between stubble treatments (12–17%). Incidence of crown rot was not affected by the type of tillage employed. The incidence of deadheads (heads without grain) caused by crown rot was lowest in the no tillage plots (4.3%) and highest in the reduced (19.3%) and conventional (12.2%) disc tillage stubble retained treatments. Available soil water (depth of 1.2 m) at sowing and anthesis was lowest in the conventional disc stubble retained plots and highest in the no tillage stubble retained plots. It is hypothesised that the high levels of deadheads were due to moderate to high levels of disease and low available soil water at planting and anthesis. Although incidence of crown rot was high under no tillage, incidence of deadheads was lower than in other treatments due to the higher availability of soil water. Severity of common root rot was lower in stubble removed, than in stubble retained, treatments and also lower in no tillage than in any of the other tillage treatments.     

Effect of different tillage systems on soil properties and wheat yield in Middle Anatolia

Field experiments were conducted on a clay soil in entisol to determine the effect of different tillage tools on soil properties, emergence rate index and yield of wheat in Middle Anatolia. There were four different tillage treatments: mouldboard ploughing followed by disc harrowing twice; rotary tillage twice; stubble cultivator followed by a disc harrowing; heavy globe disc twice. The smallest aggregate mean weight diameters and surface roughness were produced by rotary tillage. Decreasing mean weight diameter decreased the surface roughness. There was a significant (P < 0.01) effect of the four different tillage systems on moisture content, bulk density, penetration resistance, aggregate mean weight diameter and surface roughness. Tillage systems had a significant effect on emergence rate and yield of wheat. Emergence rate index and yield of wheat varied from 15.24 to 18.88 and from 3065 kg ha⁻¹ to 4265 kg ha⁻¹, respectively. The greatest emergence rate index and yield were obtained with stubble cultivator followed by disc harrowing treatment.     

Tillage impacts on aggregate stability and crop productivity in a clay-loam soil in central Iran

To take advantage of conservation tillage systems (including direct drilling and non-inversion) in central Iran, it is important to study the effects of different cultivation practices on soil structural stability as a physical indicator. A four-year study was conducted to investigate the effects of seven tillage systems on aggregate properties of a clay-loam soil (Calcic Cambisol) with continuous wheat (Triticum aestivum L.) production. Crop productivity was also evaluated. Tillage treatments were moldboard plowing+disking (MD) as conventional tillage; chisel plowing +disking (CD); chisel plowing+rotary tilling (CR); chisel plowing (twice)+disking (2CD); plowing with Khishchi (a regional rigid cultivator)+disking (KD) as non-inversion methods; and till-planting with cultivator combined drill (TP); and no-till (NT) as direct drilling methods. A randomized complete block design consisting of four replications was used. Samples were taken from three different soil depths. A wet sieving method was used to determine aggregate size distribution (ASD), and mean weight diameter (MWD) as indices of soil aggregate stability. Soil organic carbon was also determined. For the first three years of the experiment, ASD and MWD at 0–15 cm were similar in different tillage treatments, except for direct drilling which had a significantly higher amount of aggregate greater than 2 mm and 2–1 mm diameter compared to the conventional method. At the second and third sampling depths all treatments had similar influence on ASD and MWD. Tillage treatments showed a significant effect on ASD and MWD in the fourth year of the experiment in all three depths. Almost 70% of the aggregates in the MD system were less than 0.25 mm, while only 55% of the aggregates in the direct drilling methods were less than 0.25 mm diameter. The four-year yield average for conventional and non-inversion tillage systems was 7264 and 6815 kg ha⁻¹, respectively. Although, direct drilling improved soil structural stability, its lower yield (5608 and 4731 kg ha⁻¹ for TP and NT, respectively) potential would indicate that reduced tillage systems (i.e. CD) appear to be the accepted alternative management compared to conventional practice (MD).     

Soil biotic and biochemical factors in a long-term tillage and stubble management experiment on a vertisol. 2. Nitrogen deficiency with zero tillage and stubble retention

The aim of this investigation was to find the cause of poor growth of barley that occurred with zero tillage and stubble retention in a long-term fallow management experiment on a vertisol in southern Queensland. The experiment compares 12 treatments comprising three factors of tillage (zero, mechanical), stubble (burnt, retained) and nitrogen fertilizer (0, 23 and 46 kg ha⁻¹ year⁻¹) in four randomised blocks. Dry matter yield of barley at anthesis showed a highly significant Mitscherlich relationship with tissue nitrogen (N) concentration. Cate-Nelson analysis indicated a critical N concentration of 1.58%N. The barley responded to fertilizer N although 9 of 12 zero-till, stubble-retained plots and 5 of 12 mechanical-till, stubble-retained plots still lay below the critical N concentration. Zero-till, stubble-retained treatment had least nitrate-N in the soil profile to 120 cm indicating a problem in N supply rather than in N recovery by the roots.

The effects of the long-term treatments on properties related to the N supplying capacity of the soil were investigated by determinations on topsoil samples from which undecomposed stubble was removed. Soil from zero-till, stubble-retained treatment had more organic carbon (C) and Kjeldahl N than mechanical-till, stubble-retained treatment which had more than stubble-burnt treatments. The C:N ratio of the soil was lower in stubble retained treatments. Kjeldahl N was higher with annual N fertilization only where stubble was retained. Organic C increased and Kjeldahl N decreased over a 3 year period in all treatments. Respiration of CO₂, mineralizable N, and microbial biomass C and N in the soil were all greater with long-term stubble retention than with stubble burning irrespective of tillage treatment.

Numbers of root-lesion nematodes (Pratylenchus thornei Sher and Allen) and stunt nematode (Merlinius brevidens (Allen) Siddiqi) following a wheat crop were substantially greater with zero-till than with mechanical-till. Root-lesion nematode were increased by N fertilization of previous crops while stunt nematodes were increased by stubble-retention. Earthworm numbers were increased by stubble retention particularly when combined with zero tillage.

Factors responsible for observed differences in soil nitrate and crop response to N in this field experiment appear to be: (a) N immobilization by recently retained stubble, (b) lower rates of mineralization of soil N under surface-retained stubble, and (c) higher rates of leaching in zero-till treatment.     

Tillage and straw management for modifying physical properties of a subarctic soil

Conservation tillage practices are intended to minimize soil erosion. Yet little is known concerning changes in physical properties of subarctic soils subject to tillage practices. This study ascertained whether physical properties of a newly cleared subarctic soil are altered after 7 years of continuous barley (Hordeum vulgare L.) using different tillage and straw management strategies. Tillage and straw treatments were established in 1983 near Delta Junction, Alaska, and consisted of conventional fall and spring disk, fall chisel plow, spring disk, and no-tillage. Tillage plots were split by straw management practices, which included straw and stubble, stubble only, and no straw or stubble. Soil samples were collected from the upper 0.15 m of the profile in the spring of 1990 to assess water content, bulk density, saturated hydraulic conductivity, dry aggregate and mechanical stability, penetration resistance, water retention, and particle size distribution. Percent non-erodible aggregates, mechanical stability, and penetration resistance were greater for no-tillage compared to conventional tillage, chisel plow, and spring disk. No-tillage soils were also typically wetter, denser, and had a greater hydraulic conductivity. The spring disk treatment was least susceptible to erosion and also conserved soil water compared with chisel plow. Straw maintained on the surface conserved water and promoted soil stability.     

Yield and N uptake as affected by soil tillage and catch crop

Two field trials with spring barley (Hordeum vulgare L.) were conducted at two locations in Denmark in order to evaluate the effects of tillage and growth of a catch crop on yield parameters under temperate coastal climate conditions. Ploughing in autumn or spring in combination with perennial ryegrass (Lolium perenne L.) as a catch crop was evaluated on a coarse sand (Orthic Haplohumod) from 1987 to 1992 at three rates of N fertiliser application (60, 90 and 120 kg N ha⁻¹ year⁻¹). Rotovating and direct drilling were also included as additional tillage practices. The experiment was conducted on a 19-year-old field trial with continuous production of spring barley. Ploughing in autumn or spring in combination with stubble cultivation and a catch crop, in addition to minimum tillage, was evaluated in a newly established field trial on a sandy loam (Typic Agrudalf) from 1988 to 1992. Yield parameters and N concentrations in grain and straw were determined. On the coarse sand, N uptake in the grain in ploughed plots without a catch crop was significantly greater when spring ploughed as opposed to autumn ploughed, but grain and straw yields did not differ significantly. Grain yield, straw yield and total N uptake did not differ significantly between direct drilled and autumn ploughed plots, but the trend was for grain yield to be lower with direct drilling. After 19 years of catch crop use, yield parameters in ploughed plots were greater than in plots without catch crops. This was most pronounced in the autumn ploughed plots. Rotovating the catch crop in the spring decreased grain yield compared with underploughing the catch crop in autumn or spring. No significant interactions were found between tillage and N rates. On the sandy loam, grain as well as straw yield and total N uptake were not significantly affected by catch crop or time of ploughing. Grain yield was significantly lower with reduced tillage (stubble cultivation in autumn) than in all other treatments.     

不同复垦模式对土壤团聚体及水溶性阳离子的影响

以新疆玛河流域冲积扇缘盐碱地为研究区,分析了盐碱弃耕地不同复垦模式对土壤团聚体组成及水溶性Na⁺,K⁺,Ca²⁺,Mg²⁺分布的影响。结果表明:与弃耕地相比,采用单作、间作及轮作种植模式均可显著降低土壤pH值和电导率（p < 0.05）,土壤pH值分别较弃耕地降低了10.7%,9.7%,10.6%,EC相应降低了19.2%,71.0%,84.1%;不同复垦模式 > 0.25 mm粒径团聚体含量显著增加（p < 0.05）,单作、间作、轮作分别较弃耕地增加了15.8%,13.2%和15.6%,且显著高于其他粒径（p < 0.05）,土壤团聚体结构显著改善;不同复垦模式中水溶性阳离子含量主要分布于 < 0.25 mm粒径的微团聚体中,在团聚体中表现为Ca²⁺ > Mg²⁺ > Na⁺ > K⁺,间作和轮作均显著减少水溶性阳离子含量（p < 0.05）。建议在盐碱弃耕地复垦过程中采用轮作或间作种植模式更有利于弃耕地植被恢复。     

旋耕转深松和秸秆还田增加农田土壤团聚体碳库

土壤耕作和秸秆还田能够显著影响土壤结构和养分周转,也是土壤团聚体分布及更新周转的主要驱动因素。该研究基于连续9 a的旋耕-深松定位试验,对比了长期旋耕农田转变为深松以及秸秆还田对农田土壤0~50 cm土壤团聚体分布、稳定性及团聚体碳含量的影响,分析了团聚体碳对土壤有机碳的贡献率及相互关系。研究结果表明,将长期旋耕农田转变为旋耕-深松农田显著影响了0~50 cm土层的团聚体分布及其碳含量。旋耕-深松配合秸秆还田(RTS-STS)模式能够显著提高表层土壤较大粒级团聚体的比例,且显著提高了土壤团聚体稳定性,分别比旋耕-深松无秸秆还田(RTA-STA)、旋耕秸秆还田(RTS)和旋耕无秸秆还田(RTA)处理高6.1%、65.4%和87.8%;同时,RTS-STS处理显著提高了0~20 cm土层团聚体碳含量和对有机碳的贡献率,虽然在20~30和30~50 cm土层之间,2个处理的团聚体碳含量差异并不明显,但RTS-STS处理的团聚体碳含量对有机碳的贡献率较0~20 cm土层和RTS处理显著降低。通过耕作方式转变、秸秆还田和两者的交互作用对土壤团聚体分布及其碳含量影响的作用力分析可看出,耕作、秸秆及其交互作用是影响不同土层中各处理在不同粒级团聚体分布比例及碳含量差异的主要因素。通过相关分析表明,土壤有机碳含量与团聚体稳定性及其自身碳含量之间存在显著或极显著的正相关关系。旋耕-深松配合秸秆还田(RTS-STS)模式促进了0~20 cm土壤团聚体的形成和稳定,提高了土壤团聚体碳库和对有机碳的贡献,对提升土壤有机碳水平具有积极意义。     

Barley yield and evapotranspiration governed by tillage practices in interior Alaska

Tillage and residue management practices are sought in the subarctic where small grain production is often curtailed by the lack of soil water. Barley (Hordeum vulgare L.) grain yield and evapotranspiration were compared among four tillage and three residue management practices near Delta Junction, Alaska, USA from 1988 through 1991. Barley was hand-harvested in the fall whereas soil water content was determined biweekly during the growing season by neutron attenuation. Grain yield was similar for spring disk, fall chisel, and conventional (fall and spring disk) tillage across years. No tillage, however, resulted in a 260 kg ha⁻¹ greater yield as compared with fall chisel and conventional tillage in 1990 when evaporative demand exceeded that in other years by nearly 10%. In 1990 and 1991, grain yield from plots devoid of stubble and loose straw was at least 200 kg ha⁻¹ greater than from plots with stubble or stubble and loose straw. Barley consumed at least 15 mm more water to achieve the greater yield on no tillage or no stubble and loose straw plots. Water-use efficiency did not vary among tillage treatments, but was greatest in 1990 for plots devoid of stubble and loose straw. This study suggests that, in dry years with high evaporative demand, no tillage or removal of stubble and loose straw from the soil surface will enhance grain production and water-use efficiency of barley in the subarctic.     

Effect of tillage and field condition on soil physical properties, cane and sugar yields in Vertisols of Kenana Sugar Estate, Sudan

An experiment was conducted to study the effect of heavy disc harrowing in combination with chisel ploughing to depths of 10, 20, and 30 cm, on soil physical properties, cane yield, and sugar yield. The experiment was executed in two non-fallow, two semi-fallow and one fallow field conditions, in Kenana Sugar Estate, Sudan.

Results showed that the final surfaces for all tillage treatments were clean and smooth. Percent residue cover ranged from 4.2 to 5.4. After seedbed preparation percent clods greater than 1 cm in diameter ranged from 31.1 to 35.8, while gravimetric moisture content in the tillage zone ranged from 29.9 to 30.5. No significant differences were observed between treatments in residue cover, clod size and moisture content.

Soil penetration resistance in the five sites measured after the last irrigation showed no significant differences. Cone index ranged from 802 to 934 kPa. Bulk density measurements also showed no significant differences between tillage treatments.

Yield data showed that chisel ploughing to depths of 20 and 30 cm before disc harrowing, significantly increased cane and sugar yields than conventional tillage at Kenana. The highest field productivity (105.27 Mg ha⁻¹) was obtained with the combined disc harrowing and 20 cm chisel ploughing. Yield of cane per hectare under this method was 8.38 Mg ha⁻¹ higher than that under the conventional method. Sugar yield per hectare increased by 1 metric ton, which was 8.6% higher than that of the conventional method.

The relation between tillage depth (x) and cane yield (Y), in tons of cane per hectare, for average Kenana field condition could be expressed by the third-order polynomial:

Y=158.141−7.725x+0.293x²−0.003x³

The fallow, semi-fallow and non-fallow sites were not significantly different in cane yield.

All tillage methods studied were more intensive than adequate levels for soil conservation practices found in the reviewed literature; it is suggested to omit the re-harrowing operation of Kenana conventional tillage.     

留茬对小麦/玉米间作氮素吸收和硝态氮分布、淋失的影响

为减少高产农田硝态氮累积对地下水的潜在污染,在甘肃石羊河流域绿洲灌区设置裂区试验,研究不同留茬方式对单作小麦、单作玉米、小麦/玉米间作氮素吸收、土壤硝态氮分布、淋失的影响。结果表明:不同留茬方式对作物籽粒、秸秆含氮量影响较小。间作比单作显著提高了作物的籽粒吸氮量和氮收获指数;2种作物无论间作或单作,立茬土壤0-20cm硝态氮累积显著高于焚烧和翻还,20-60cm则相反,60cm以下受留茬方式影响差异不显著;土壤硝态氮残留单作小麦翻还比焚烧和立茬处理分别高11.41%和8.13%,单作玉米焚烧比立茬和翻还分别高26.97%和17.02%;植株总吸氮量小麦/玉米间作立茬和翻还分别比焚烧高9.58%和6.10%;硝态氮淋失量小麦/玉米间作平均比单作处理低30.75%,小麦/玉米间作立茬和翻还分别比焚烧处理低28.04%和10.23%。综上所述,小麦/玉米间作立茬硝态氮淋失最少,更有利于环境保护。     

Effects of Tillage Methods on Soil Carbon and Wind Erosion

Current interest in soil‐conserving tillage in China has developed from the concern that Chinese agricultural land loses 73·8 Mg C annually. Previous research has shown that changing from conventional tillage to conservation tillage field management increases soil C sequestration. The aim of this study is to determine if no tillage with stubble retention can reduce soil carbon loss and erosion compared with conventional tillage for a cornfield in northern China. We found that soil organic C storage (kg m⁻²) under conservation tillage in the form of no post‐harvest tillage with stubble retention increased from 28% to 62% in the soil depths of 0–30 cm (p < 0·01) compared with the conventional tillage. Retaining post‐harvest stubble with a height of 30 cm and incorporating the stubble into the soil before seeding the next spring increased soil organic carbon the most. Carbon storage (kg ha⁻¹) in aboveground and belowground biomass of the corn plants in seedling and harvest stages was significantly greater (p < 0·01) with stubble retention treatments than with conventional tillage. Carbon content in root biomass in all treatments with stubble retention was significantly greater than that with conventional tillage. Soil erosion estimates in the study area under conservation tillage with stubble retention was significantly lower than that under conventional tillage during the monitoring period. Given the complexities of agricultural systems, it is unlikely that one ideal farming practice is suitable to all soils or different climate conditions, but stubble retention during harvesting and incorporation of the stubble into soil in the next spring appears to be the best choice in the dry northern China where farmlands suffer serious wind erosion. Copyright © 2015 John Wiley & Sons, Ltd.     

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。     

Tillage effects on soil aggregation and soil organic carbon profile distribution under Mediterranean semi‐arid conditions

In rainfed semi‐arid agroecosystems, soil organic carbon (SOC) may increase with the adoption of alternative tillage systems (e.g. no‐tillage, NT). This study evaluated the effect of two tillage systems (conventional tillage, CT vs. NT) on total SOC content, SOC concentration, water stable aggregate‐size distribution and aggregate carbon concentration from 0 to 40 cm soil depth. Three tillage experiments were chosen, all located in northeast Spain and using contrasting tillage types but with different lengths of time since their establishment (20, 17, and 1‐yr). In the two fields with mouldboard ploughing as CT, NT sequestered more SOC in the 0–5 cm layer compared with CT. However, despite there being no significant differences, SOC tended to accumulate under CT compared with NT in the 20–30 and 30–40 cm depths in the AG‐17 field with 25–50% higher SOC content in CT compared with NT. Greater amounts of large and small macroaggregates under NT compared with CT were measured at 0–5 cm depth in AG‐17 and at 5–10 cm in both AG‐1 and AG‐17. Differences in macroaggregate C concentration between tillage treatments were only found in the AG‐17 field at the soil surface with 19.5 and 11.6 g C/kg macroaggregates in NT and CT, respectively. After 17 yr of experiment, CT with mouldboard ploughing resulted in a greater total SOC concentration and macroaggregate C concentration below 20 cm depth, but similar macroaggregate content compared with NT. This study emphasizes the need for adopting whole‐soil profile approaches when studying the suitability of NT versus CT for SOC sequestration and CO₂ offsetting.     

Effects of mouldboard ploughing and direct planting on yield and nutrient uptake of potatoes in Norway

The use of conservation tillage systems is now widespread for cereals in erosion-prone areas of Norway. However, few growers are willing to adopt such practices for other crops. An experiment was conducted in southern Norway (60°46′N, 10°49′E) from 1987 to 1993 to compare the effects of two different tillage treatments on potato (Solanum tuberosum L.) yield and quality. The conventional labour-intensive treatment, with autumn mouldboard ploughing, levelling and two passes with a spring-tine harrow in spring was compared with planting directly into untilled barley (Hordeum vulgare L.) stubble, with straw removed. The soil type in the experiment was a morainic, stony loam (Typic Cryoboroll, Orthic Melanic Brunisol). Prior to the start of the experiment direct-planted plots had not been ploughed for 9 years. During the trial years (1987–1993) a pattern of two different yield curves emerged as functions of the date of harvesting. The yield curve for direct planting was steeper, crossing that of conventional tillage on approximately 10 September, thus predicting higher tuber yield for direct planting when harvesting occurred after this date, but lower tuber yield than with conventional tillage in the case of early harvesting. The reason for this is thought to be cooler soil and delayed growth and maturation with direct planting. Furthermore, direct planted potatoes gave higher haulm yield, and also had higher contents of N, P and K in both haulm and tubers. No significant differences in tuber quality were found between the two treatments. A strong negative correlation was found between the yield increase caused by direct planting and mean air temperature in August. The trial indicated that direct planting of potatoes in cereal stubble is a viable alternative to conventional plough tillage on loam soil in Norway, provided that the growing season is adequately long.     

吉林省西部不同耕作模式下秸秆还田土壤团聚体特征

  【目的】  通过研究不同耕作模式下土壤团聚体特征,探明耕作模式对土壤团聚体质量指标的影响,为解决区域长期传统耕作模式所引起的土壤结构质量下降问题及构建土壤合理耕作层提供科学依据。  【方法】  从2016年10月开始,在吉林省西部松原市宁江区开展田间试验,采用随机区组设计,将耕作结合秸秆还田设置了4个处理,分别为常规耕作 (秸秆清除后进行旋耕,LR)、连续旋耕 (秸秆粉碎还田后进行旋耕,SR)、翻耕–旋耕 (秸秆粉碎还田后,轮流进行翻耕和旋耕,STR)、翻耕–免耕 (秸秆粉碎还田后,轮流进行翻耕和免耕,STN)处理。于2018年10月采集0—20和20—40 cm土层土壤样品,分析了土壤团聚体组成分布、团聚体稳定性及团聚体各粒级有机碳含量。  【结果】  与LR处理相比,秸秆还田可明显改善土壤团聚体结构及稳定性 (P < 0.05)。秸秆还田条件下,STR和STN土壤中大于0.25 mm的机械稳定性团聚体含量比连续旋耕 (SR) 处理显著增加10.6% (P < 0.05)。与LR处理相比,STR和STN处理耕层土壤机械稳定性团聚体几何平均直径 (GMD) 明显提高,而STR和STN处理土壤团聚体分形维数（D）平均降低3.9%,耕层不稳定团粒指数 (E_lt) 也显著降低。STN处理 在0—20 cm土层具有较高的土壤团聚体有机碳含量。  【结论】  秸秆还田下,两种轮耕模式具有更高的团聚体稳定性,且有较小的分形维数,进而具有较好的抗蚀能力,其中翻耕–免耕轮耕模式团聚体稳定性更好,耕层土壤中团聚体有机碳含量更高。因此,翻耕–免耕轮耕模式是吉林省西部地区土壤肥力保育的有效措施和耕作模式。