Straw management and tillage effects on soil water storage under field conditions

Abstract. A two year field study was conducted to evaluate the effects of straw management and tillage on the soil profile (1.5m) water storage, nature of the moisture profile, infiltration and sorptivity as influenced by rainfall, evaporativity (E₀) and soil texture. The straw mulch treatment stored more moisture under low E₀ rainy conditions in three coarse to medium textured soils. Straw incorporation treatment was better under low E₀ rain free conditions, as well as under high E₀ rainy conditions in the two coarser textured soils. In the coarsest textured soil, tillage and straw mulching were not effective in maintaining greater soil water storage under high E₀ because of the very open nature of the soil. The soil moisture profiles showed a sharper increase in water content below the tilled layer in the tillage and straw- incorporation treatments than the untreated and straw mulch treatments. Tillage and straw incorporation treatments increased the sorptivity of the soil compared with untreated and straw mulch treatments respectively. The results of this study suggest that when selecting a suitable soil water conservation practice to increase water storage in the soil profile, information on soil texture and weather (rain and evaporativity) must be considered.     

Rotation and tillage effects on available soil water for winter wheat in a semi-arid environment

The recent adoption of conservation farming systems in the semi-arid Canadian prairies opens up the possibility of replacing the traditional fallow period with non-cereal crops (oilseeds, legumes). However, information on changes to soil water regimes by inclusion of these crops, especially in combination with zero tillage, is sparse. A study was initiated in 1984 on a sandy clay loam soil at Lethbridge, Alberta, to investigate the performance of winter wheat (Triticum aestivum L.) under conventional, minimum and zero tillage in monoculture and in 2-year rotations with fallow, canola (Brassica campestris L.) or lentils (Lens culinaris Medic.)/flax (Linum usitatissimum L.). Conventional tillage in the Lethbridge region is shallow cultivation (10 cm) with a wide-blade (sweep) cultivator. Continuous cropping greatly depleted soil water reserves, resulting in some crop failures. Averaged over 10 years, available water for establishment of winter wheat in fall was least after canola (45 mm), followed by continuous winter wheat (59 mm), lentils/flax (74 mm) and fallow (137 mm). In this semi-arid region, the effect of rotation on soil water was much greater than that of tillage. Zero tillage had relatively little impact on available water to 1.5 m depth. However, once the experiment had been established for 6–7 years, available water in the 0–15 cm depth under winter wheat in spring was greatest under zero tillage. Precipitation storage efficiency during the fallow year was generally unaffected by tillage system.     

Soil biopore estimation: effects of tillage, nitrogen, and photographic resolution

Networks of biopores created by plant and animal activity might accumulate in untilled cropping systems. These would be relatively well connected to the soil surface. The objective of this study was to count biopores after long-term no-till in comparison to recently tilled soil. Biopores were counted and measured to 80 cm depth at 10 cm increments in plots either under no-till wheat production for 1 year or for 17 years, and receiving zero or 130 kg ha⁻¹ N. The measurements were repeated using different photographic methods with increased resolution. The only significant difference between the long and short term no-till was in biopore sizes over 1 mm diameter, where long-term no-till produced from 30 to 100% more biopores, probably caused by increased earthworm activity. Over 99% of biopores measured were less than 1 mm diameter. There was no difference between tillage or N treatments in the number of these smaller biopores at any depth. This means small biopores did not accumulate either above or below the plow layer in an untilled cropping system. Improved resolution in the second set of measurements produced a 100-fold increase in detection of biopores in the 0.3–0.5 mm range. This provides evidence that a substantial portion of biopores are very small and were missed in the first year of this study and perhaps in other studies of this type. It is hypothesized that biopores of 0.05–0.5 mm diameter make up over half of total biopore volume and might have a significant role in movement of water and gases.     

玉米-大豆轮作中耕作方式和磷肥施用对土壤磷组分冬季变化特征的影响

Determining how agricultural management practices affect soil phosphorus(P) over the winter may further our understanding of the soil P cycle under specific environmental conditions in eastern Canada. This study assessed changes over winter for soil P fractions and other selected chemical properties as affected by tillage and P fertilization. In 1992, a long-term corn(Zea mays L.) and soybean(Glycine max L.) rotational experiment was established in the province of Quebec, Canada. Soil samples(0–15 cm) were collected in fall 2001 and 2007 after a soybean harvest, and in the following spring 2002 and 2008 before corn seeding, in main plots under moldboard plow and no-till managements and selected subplots fertilized with 0, 17.5, or 35 kg P ha-1and 160 kg N ha-1. Soil samples were analyzed for P fractions and other chemical properties to assess changes over winter for 2001–2002 and 2007–2008. Changes over winter of all soil P fractions were significant for the two periods, indicating the occurrence of soil P transformation and movement over winter. The Mehlich-3-extractable Fe, Al, Ca, and Mg decreased during the two studied periods. Tillage had no significant effect on all soil P fractions. The resin-extractable P in 2001–2002 and Na HCO3-extractable inorganic P and Na OH-extractable organic P during the two winters were significantly increased under P fertilization. This study demonstrated that P in cultivated soils changed during winter as a result of changes in labile P fractions possibly due to the solubilization of residual fertilizer P combined with environmental factors.     

The influence of tillage on NO and N2O fluxes under spring and winter barley

Abstract. There is a lack of information about the influence of tillage and time of sowing on N₂O and NO emission in cereal production. Both factors influence crop growth and soil conditions and thereby can affect trace gas emissions from soils. We measured fluxes of NO and N₂O in a tillage experiment where grassland on clay loam soil was converted to arable by either direct drilling or ploughing to 30 cm depth. We made measurements in spring for 20 days after fertilizer application to spring-sown and to winter-sown barley. Both were the second barley crop after grass. Direct drilling enhanced N₂O emission primarily as a result of restricted gas diffusivity causing poor aeration after rainfall. Deep ploughing enhanced NO emission, because of the large air-filled porosity in the topsoil. NO and N₂O emissions were smaller from winter sown crops than from spring sown crops.   The three rates of N fertilizer application (40, 80 or 120 kg N ha^–1) did not produce the expected linear response in either soil available N concentrations or in NO and N₂O fluxes. We attributed this to the lack of rainfall in the ten-day period after fertilizer application and therefore very slow incorporation and movement of fertilizer into and through the soil.     

Straw incorporation and immobilization of spring-applied nitrogen

Abstract. The effect of rate and timing of autumn/winter straw incorporation on the immobilization of spring-applied N-fertilizer are studied. The immobilization of ¹⁵N-labelled fertilizer by straw was determined in pot trials with a sandy loam soil (Wick series) collected from two field experiments. In experiment 1, straw was incorporated at four different rates in the autumn; experiment 2 had a fixed rate of straw (7.5 t/ha) incorporated at monthly intervals from September to March. Immobilization in spring was not enhanced when only stubble was incorporated in autumn. However, autumn incorporation of 7.5 t/ha straw resulted in a significant increase in the immobilization of spring-applied N, equivalent to 10 kg/ha; when 15 t/ha straw was incorporated, immobilization increased to 18 kg/ha. The enhancement of immobilization, immediately following fertilizer application, was dependent on the extent of straw decomposition prior to N application. Thus immobilization was related to cumulative thermal time (day °C above 0°C; Tsum between the date of straw incorporation and fertilizer application). Straw which had been incorporated for Tsum > 1200 no longer caused appreciable immobilization of spring fertilizer.     

Effects of ploughless tillage and straw incorporation on evaporation

The effects of ploughness tillage (stubble cultivation with a disc tiller or a spring tine cultivator, or with both in combination, replacing mouldboard ploughing) on evaporation were investigated using undisturbed soil lysimeters (height = 350 mm, diameter = 300 mm) excavated after spring cultivation in May from field experiments in eastern Sweden. The evaporation process was measured on ploughed and unploughed soil lysimeters, both with or without precipitation and with or without a seedbed. The effects on evaporation of incorporating crop residues with or without precipitation into a ploughed seedbed were also measured. The results from a heavy clay and from a silty clay loam showed that both ploughless tillage and incorporated straw reduced cumulative evaporation. The water-conserving effect was greater in irrigated treatments. The positive effect on water conservation was also greater on the silty clay loam than on the heavy clay. The soil structural changes brought about by ploughless tillage in layers under the seedbed acted to reduce the rate of evaporation from soil.     

坡耕地保护性耕作措施的水土保持效应

为探索不同保护性耕作技术在黑龙江省西部半干旱区坡耕地的水土保持效应,于2007、2008年在甘南县东兴村坡耕地径流小区进行不同耕作措施的降雨径流、土壤储水量和土壤流失量试验研究。结果表明：土壤储水量的动态变化趋势与天然降雨趋势一致;与常规耕作措施相比,所研究的3种耕作措施均可不同程度地增加土壤储水量、减少地表径流和土壤流失量,其中,垄向区田措施减少径流效果最好,覆膜＋垄向区田技术集成措施增加土壤储水和减少土壤流失效果最好,免耕秸秆覆盖措施在以上3方面的效果均为最差;垄向区田和覆膜＋垄向区田措施具有增加土壤储水深度的作用。研究结果可为黑龙江省西部半干旱区坡耕地水土保持措施的合理选择提供参考。     

Weed seed bank affected by tillage intensity for barley in Alaska

The weed seed bank of a long-term tillage study in subarctic Alaska was studied at the end of 10 years of continuous spring barley (Hordeum vulgare L.). Tillage treatments were: no-till, disked once (spring), disked twice (spring and fall), and chisel plow (fall). Soil cores were obtained from each tillage treatment and seeds were manually separated from soil after washing through sieves. Tillage treatment had a significant effect on seed density of shepherds purse (Capsella bursa-pastoris (L.) Medic.), cinquefoil (Potentilla norvegica L.), foxtail barley (Hordeum jubatum L.), and on total seed density. Seed density was higher for these species and total seed density was greater under no-till than under other tillage treatments. Seed density was higher near the soil surface under no-till and chisel plow treatments than under disked treatments, which helps explain the greater difficulty of controlling weeds under reduced tillage.     

华北典型区域土壤耕作方式对土壤特性和作物产量的影响

华北平原是我国重要的小麦玉米种植区,长期土壤旋耕免耕和秸秆全量还田带来耕层变浅、犁底层变厚和上移、土壤养分表聚等现象,通过耕作方式改变,解决上述问题对维持区域粮食生产有重要意义。试验以冬小麦-夏玉米轮作系统为研究对象,分别在代表华北平原高产区的栾城试验区和代表中低产区的南皮试验区进行,设置冬小麦播种前进行土壤深耕、深松、窄深松3种处理,以生产上常用的旋耕为对照。所有处理夏玉米季均采用土壤免耕播种,测定项目包括土壤容重、作物根系、作物产量和水分利用效率。结果表明,不同耕作方式对土壤特性和作物产量的影响具有区域差异。南皮试验区土壤深耕(松)显著地(P0.05)提高了作物产量,深耕、深松和窄深松处理的冬小麦产量比旋耕分别增加16.5%、19.3%和13.1%,夏玉米产量分别增加17.3%、16.2%和21.9%,周年产量分别增加16.9%、17.6%和17.8%;深耕、深松和窄深松处理间作物产量差异不显著。栾城试验区冬小麦、夏玉米产量和周年产量各处理之间差异不显著。土壤深耕、深松、窄深松和旋耕均能降低0～20 cm土层土壤紧实度和土壤容重。冬小麦播种后,与土壤耕作前比较,土壤深耕、深松和旋耕处理土壤紧实度南皮试验区分别平均降低71.6%和68.2%,栾城试验区分别降低88.8%和?7.7%,常用的旋耕模式在栾城试区没有降低土壤紧实度。小麦收获时不同耕作方式0～40cm土层的土壤容重均低于土壤耕作前的土壤容重,至夏玉米收获时不同耕作处理的土壤容重与耕作前基本一致,不同耕作处理对土壤容重的影响差异不显著。在南皮试验区, 3种耕作方式与旋耕相比,均显著提高了冬小麦和夏玉米水分利用效率;在栾城试验区,各处理冬小麦和夏玉米水分利用效率差异不显著。本研究结果显示在华北平原高产区连续实施土壤旋耕模式没有影响作物产量,而在中低产区实施土壤深耕或者深松模式更利于作物产量提高。     

Nitrous oxide emissions after incorporation of winter oilseed rape (Brassica napus L.) residues under two different tillage treatments

The aim of this study was to investigate the effect of crop residues from winter oilseed rape on N₂O emissions from a loamy soil and to determine the effect of different tillage practices on N₂O fluxes. We therefore conducted a field experiment in which crop residues of winter oilseed rape (Brassica napus L., OSR) were replaced with ¹⁵N labelled OSR residues. Nitrous oxide (N₂O) emissions and ¹⁵N abundance in the N₂O were determined for a period of 11 months after harvest of OSR and in the succeeding crop winter wheat (Triticum aestivum L.) cultivated on a Haplic Luvisol in South Germany. Measurements were carried out with the closed chamber method in a treatment with conventional tillage (CT) and in a treatment with reduced soil tillage (RT). In both tillage treatments we also determined N₂O fluxes in control plots where we completely removed the crop residues. High N₂O fluxes occurred in a short period just after OSR residue replacement in fall and after N‐fertilization to winter wheat in the following spring. Although N₂O emissions differed for distinct treatments and sub‐periods, cumulative N₂O emissions over the whole investigation period (299 days) ranged between 1.7 kg and 2.4 kg N₂O‐N ha^?1 with no significant treatment effects. More than half of the cumulative emissions occurred during the first eight weeks after OSR replacement, highlighting the importance of this post‐harvest period for annual N₂O budgets of OSR. The contribution of residue N to the N₂O emission was low and explained by the high C/N‐ratio fostering immobilization of mineral N. In total only 0.03% of the N₂O‐N emitted in the conventional tillage treatment and 0.06% in the reduced tillage treatment stemmed directly from the crop residues. The ¹⁵N recovery in the treatments with crop residues was 62.8% (CT) and 75.1% (RT) with more than 97% of the recovered ¹⁵N in the top soil. Despite our measurements did not cover an entire year, the low contribution of the OSR residues to the direct N₂O emissions shows, that the current IPCC tier 1 approach, which assumes an EF of 1%, strongly overestimated direct emissions from OSR crop residues. Furthermore, we could not observe any relationship between tillage and crop residues on N₂O emission, only during the winter period were N₂O emissions from reduced tillage significantly higher compared to conventional tillage. Annual N₂O emission from RT and CT did not differ.     

An economic comparison of barley production under zero and conventional tillage

Zero tillage consistently resulted in reduced costs associated with equipment operations, in reduced barley yields, and in higher herbicide costs at all 4 locations. Summation of these major effects indicated that zero tillage on the average was $48.77 ha⁻¹ (range of $18.43–68.79) less economical than conventional tillage. Long-term effects, such as erosion control, changes in soil structure and nutrients, or the indirect consequences of increased herbicide use were not considered in the economic analysis.     

正反转旋耕作业的秸秆混埋效果比较

秸秆混埋是增强土壤碳汇的重要技术途经。为分析和比较正、反转旋耕作业的秸秆混埋效果,进行了正、反转旋耕秸秆混埋对比试验。测取旋耕处理后的地貌形态及秸秆在土壤空间中的分布状况,并使用Pro-E造型展示秸秆的空间分布状况。结果表明三维数字化仪配合虚拟造型技术能够直观反映混埋后秸秆在土壤空间的分布状态。2种旋耕处理方式的地表形态及土壤空间内秸秆分布对比分析表明,正转旋耕的秸秆埋覆率及纵向空间分布总体均匀率优于反转旋耕,而反转旋耕的秸秆在沿土壤深度方向的空间分布均匀率、秸秆-土壤混合效果、耕幅内地表平整度等优于正转旋耕。综合分析表明正转旋耕的秸秆混埋质量略有优势,但具体选择混埋模式时还应考虑田间秸秆残留情况。秸秆量较少时反转旋耕较适宜,反之正转旋耕更好。     

Soil displacement and tillage erosion during secondary tillage operations: the case of rotary harrow and seeding equipment

This study reports the results of a series of experiments that were set up on agricultural land in central Belgium to investigate soil translocation and erosivity resulting from a secondary tillage operation using an implement sequence of a rotary harrow and seeder. Aluminium cubes were used as tracers of soil movement. Results show that soil displacement resulting from tillage with such an implement sequence is far from insignificant. This is mainly related to the relatively shallow tillage depth as well as to the loose initial soil condition of such secondary tillage operations. The calculated value for the tillage transport coefficient k (123 kg m⁻¹ per tillage operation) is comparable with k-values from implements that are considered to be more erosive, like mouldboard and chisel implements. In conclusion, this study shows that tillage erosion not only results from relatively aggressive tillage operations such as mouldboard and chisel passes, but that secondary operations contribute significantly to soil displacement and tillage erosion.     

Soil respiration from winter wheat-based cropping systems in the US Southern Great Plains as influenced by tillage managements

This study compared soil respiration (SR) fluxes from winter wheat-based cropping systems in the US Southern Great Plains (SGP) under reduced and conventional tillage. The study consisted of four sets of paired paddocks assigned to conventional or reduced tillage with a four-year crop rotation applied over time. During the 2016–2017 study year, four sets of paired paddocks were planted to: winter wheat managed for grazing, dual-purpose (grazing and grain production), and grain-only systems of production, and winter canola. Heterotrophic SR fluxes were measured using a plant and root exclusion method on eight permanently deployed PVC cores per paddock. Fluxes from the cores were measured manually using a closed chamber connected to an infrared gas analyser on 12–13 dates during the winter wheat growing season (October through May). There were strong seasonal patterns of SR flux, with lower rates during dry and cold periods, and higher rates during warm and wet periods. Large rainfall induced pulses of SR flux were observed for both tillage systems. There was no consistent large-scale difference in SR flux between tillage treatments applied to paired paddocks. Results from this study indicate SR fluxes from winter wheat-based cropping systems are controlled more by soil environmental conditions than form of tillage.     

Soil microbial community response to controlled-release urea fertilizer under zero tillage and conventional tillage

Soil microorganisms mediate many important biological processes for sustainable agriculture. The effect of a polymer-coated controlled-release urea (CRU, ESN^®) on soil microbial communities was studied at six sites across western Canada from 2004 to 2006. Fertilizer treatments were CRU, urea and an unfertilized control. Timing of fertilizer application (fall vs. spring) was studied in 9 of the 18 site-years (combinations of sites and years). Wheat (Triticum aestivum L.), canola (Brassica napus L.) and barley (Hordeum vulgare L.) were grown in rotation at five sites, and silage corn (Zea mays L.) was grown in all 3 years at one site, under conventional tillage (CT) or zero tillage (ZT). The fertilizers were side-banded at 50–60 kg N ha⁻¹ for wheat, barley and canola, and broadcast at 150 kg N ha⁻¹ for corn. Microbial biomass C (MBC) and bacterial functional diversity and community-level physiological profiles (CLPPs) were determined at about the flowering stage of each crop. In situ CO₂ evolution (soil respiration) was measured, and microbial metabolic quotient (qCO₂) determined, at one site in 2 years. In the rhizosphere, fertilizer effects on MBC and functional diversity were observed in 1 and 5 of 18 site-years, respectively; and in bulk soil in 4 site-years each. These effects were usually positive relative to the control. CRU increased MBC or functional diversity more than urea in 3 site-years, but the opposite was observed in 1 site-year. Time of fertilizer application affected MBC in 1, and functional diversity in 2, of 9 site-years in the rhizosphere, and no effects were observed in bulk soil. Fall-applied fertilizer increased MBC more than spring-applied fertilizer, but the opposite was observed for functional diversity. Tillage affected MBC and functional diversity in 4 and 5 of 18 site-years, respectively, in the rhizosphere, and in 3 and 4 site-years in bulk soil. Tillage effects were usually in favour of ZT. There were no treatment effects on CO₂ evolution, but an interactive effect of fertilizer and tillage on qCO₂ was observed in 1 year when qCO₂ in the control treatment was greater than that in either fertilizer treatment under CT, but urea increased qCO₂ relative to the control under ZT. Shifts in CLPPs were sometimes observed where the treatment effects described above were not significant. Notwithstanding the limitations of culture-dependent CLPPs, most fertilizer effects on soil microbiological properties were not statistically significant. Therefore, these fertilizers probably did not adversely affect most soil biological processes.     

Soil foodwebs in agroecosystems: impacts of herbivory and tillage management

Soil rhizospheres are one of the principal ‘hotspots’ of terrestrial ecosystems. Using isotopic ¹⁴carbon (¹⁴C) tracer techniques, we measured impacts of aboveground herbivory on rhizosphere microbial growth and subsequent repercussions in an agroecosystem detrital foodweb. Soil microarthropods in conventionally tilled (CT) agroecosystems accumulated more radiocarbon tracer than in no-tillage ones (NT), reaching concentrations as high as those in the roots. Nematodes, in contrast, accumulated more tracer in the NT systems, possibly reflecting the greater proportion of label going initially to bacterial communities in the rhizospheres. With a simulation model of the decomposition of ¹⁴C-labeled litter, we evaluated the relative contributions of bottom-up and top-down forces in the detrital foodweb. Microbial biomass was more resource-regulated, and microbivorous fauna (nematodes, protozoa, microarthropods) was more sensitive to second- and third-order predators in the system.     

Of macropores and tillage: influence of biomass incorporation on cover crop decomposition and soil respiration

Carbon sequestration in agricultural soils may help to reduce global greenhouse gas concentrations, but building up soil carbon levels requires accumulating organic matter faster than it is lost via heterotrophic respiration. Using field and laboratory studies, this study sought to elucidate how tillage, the below‐ground incorporation of cover crop residue, and soil macroporosity affect soil respiration and residue decomposition rates. In the field, residue from a cover crop mixture of barley (Hordeum vulgare ) and crimson clover (Trifolium incarnatum ) was placed into litter bags that were left on the surface versus incorporated into the soil at three depths (4, 8 or 12 cm), while the laboratory study compared surface‐placed versus incorporated litter (8 cm depth). To assess tillage effects on cover crop decomposition, the field study simulated no‐till and conventional tillage treatments, while the laboratory and field studies both included treatments in which artificial soil macropores were created. The field study showed that conventional tillage and the presence of macropores enhanced soil respiration, while in the laboratory study, incorporating cover crop residue resulted in higher soil respiration and faster litter decomposition rates. Additionally, the laboratory measurements showed that macropores increased soil respiration in wet conditions, likely by enhancing oxygen diffusion. Thus, organic matter incorporation and macropores may represent important factors that affect soil respiration and carbon dynamics.     

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.