Redistribution and loss of soil organic carbon by overland flow under various soil management practices on the Chinese Loess Plateau

Field rainfall simulations with intensities of 85 and 170 mm/h were conducted in 2002 and 2005 on a 15-m long slope on a loess soil in Luoyang, Henan Province, P. R. China to study the effects of different soil management practices on the redistribution and loss of soil organic carbon (SOC) by runoff and soil erosion. Field plots under winter wheat ( Triticum aestivum L.) were set up in 2001 and included the following soil management practices: subsoiling with mulch (SSM), no-till with mulch (NTM), reduced tillage (RT) and conventional tillage control (CT). The results showed that SOC for topsoil (0–20 cm) increased in the NTM and SSM plots when compared with results from 2002 and 2005. For all treatments, SOC in the lower part of the plots was higher in 2005 than in 2002. The values from the upper parts of the plots were only lower in 2005 compared with the overall values for 2002 for RT and CT. The enrichment ratio of organic carbon (ER_oc) in runoff sediment varied from 1.01 to 2.24 with a mean of 1.25. During the simulated rainfall events, ER_oc was initially high and then reduced after a short period to reach a steady value at the end of the event, always remaining ≥1. The change in SOC loss rate was more dependent on the sediment loss rate than on the changes in SOC concentration in the sediment. The best results in terms of a reduction in soil and SOC loss were obtained with NTM: no runoff and hence no soil and SOC loss were observed. SOC losses observed for SSM were on average only 4% of those observed for CT. RT resulted in 71% SOC loss compared with CT although the runoff reduction was not pronounced. For farmers, SSM and NTM are the best alternatives in terms of SOC conservation. NTM has the additional advantage that it requires less labour and is more beneficial from economic and environmental perspectives.     

Soil management effects on runoff and soil loss from field rainfall simulation

Soil erosion from agricultural lands is a serious problem on the Chinese Loess Plateau. In total, 28 field rainfall simulations were carried on loamy soils under different management practices, namely conventional tillage (CT), no till with mulch (NTM), reduced tillage (RT), subsoiling with mulch (SSM), subsoiling without mulch (SS), and two crops per year (TC), to investigate (i) the effects of different soil management practices on runoff sediment and (ii) the temporal change of runoff discharge rate and sediment concentration under different initial soil moisture conditions (i.e. initially dry soil surface, and wet surface) and rainfall intensity (85 and 170 mm h^− 1) in the Chinese Loess Plateau. NTM was the best alternative in terms of soil erosion control. SSM reduced soil loss by more than 85% in 2002 compared to CT, and its effects on runoff reduction became more pronounced after 4 years consecutive implementation. SS also reduced considerably the runoff and soil loss, but not as pronounced as SSM. TC resulted in a significant runoff reduction (more than 92%) compared to CT in the initial ‘dry’ soil, but this effect was strongly reduced in the initial ‘wet’ soil. Temporal change of runoff discharge rate and sediment concentration showed a large variation between the different treatments. In conclusion, NTM is the most favorable tillage practices in terms of soil and water conservation in the Chinese Loess Plateau. SSM can be regarded as a promising measure to improve soil and water conservation considering its beneficial effect on winter wheat yield.     

Tillage and crop management impacts on soil loss and crop yields in northwestern Ethiopia

Lack of appropriate agronomic practices is one of the major causes for soil erosion and low yields in teff (Eragrostis tef [Zucc.]) production in Ethiopia. A 3-yr study was conducted at the Aba Gerima watershed in northwestern Ethiopia, to investigate the effects of two tillage practices (reduced tillage [RT] and conventional tillage [CT]), two planting methods (row planting [RP] and broadcast planting [BP]), and two compaction options (with [+T] and without [–T] trampling) on soil loss and teff yields in a split-split plot arrangement. Sediment concentration ranged from 0.01 to 5.37 g L^?1 (mean, 0.25 g L^?1) in our study. Accordingly, the estimated total (August–October) soil loss ranged from 0.2 to 0.5 t ha^–1 (mean, 0.3 t ha^–1). The sediment concentration and total soil loss were significantly influenced (P < 0.05) by tillage, planting methods, and trampling only in the third monitoring year. RT reduced soil loss by 19% relative to that of CT, whereas RP resulted in a 13% reduction in soil loss over BP. The ?T plots showed a 15% reduction in soil loss as compared to + T plots. Results revealed significant increase in soil total carbon and nitrogen in RT and –T. Less soil loss and greater teff grain yield were obtained in plots with improved agronomic practices (RT and RP) compared to conventional ones (CT and BP). Based on our findings we conclude that the use of RT, RP, and –T practices can effectively minimize soil loss without any crop yield penalty.     

耕作措施及雨强对南方红壤坡耕地侵蚀的影响

选择典型南方红壤区平均坡度为10°的坡耕地小区进行天然降雨观测,对横坡耕作、顺坡耕作、顺坡耕作+植物篱、稻草覆盖4种耕作措施在侵蚀过程中的径流泥沙和养分流失特征进行研究。结果表明,监测期间,径流深和泥沙流失量基本随雨强的增大而增加。随着耕作措施由顺坡耕作向顺坡耕作+植物篱、横坡耕作、稻草覆盖的转换,减流效益、减氮效益和减磷效益依次增大。稻草覆盖措施减流效益最佳,为91.77%;横坡耕作措施减沙效益最佳,为98.91%;稻草覆盖、横坡耕作和植物篱3种措施在防治高强度降雨引发的土壤侵蚀和养分流失具有较高的效益。耕作措施对泥沙粒径分布有影响。与顺坡耕作、横坡耕作相比,植物篱和稻草覆盖措施能够更有效地拦截径流中的粗颗粒。该研究可为南方红壤丘陵区坡耕地选择合适的耕作措施和防治农业非点源污染提供依据。     

Saltation transport on a silt loam soil in northeast Spain

The Ebro River valley in Northeast Spain experiences regularly strong west-northwest winds that are locally known as cierzo . When the cierzo blows, wind erosion may potentially occur on unprotected agricultural lands. In this paper the first results of field measurements of soil characteristics and saltation transport in the Ebro River valley near Zaragoza are presented. An experiment was conducted on a silt loam soil in the summers of 1996 and 1997. Two plots of 135×180 m were both equipped with a meteorology tower, three saltiphones (acoustic sediment sensors) and ten sediment catchers. The plots were different with respect to tillage practices. One plot received mouldboard ploughing followed by a pass of a compacting roller (conventional tillage—CT), whereas the other plot only received chisel ploughing (reduced tillage—RT). Soil characterizations indicated that soil erodibility was significantly higher in the CT plots than in the RT plots. Consequently, no significant saltation transport was observed in the RT plots during both seasons. In the CT plot, four saltation events were recorded during the 1996 season and nine events during the 1997 season. Most events were preceded by rainfall during the previous one or two days, which reduced saltation transport significantly. It is concluded that the occurrence of wind erosion in the Ebro River valley depends on the timing and type of tillage, distribution of rainfall and soil-surface crusting. Copyright © 1999 John Wiley & Sons, Ltd.     

坡度对农业耕作措施水土保持作用的影响

农业耕作措施是水土保持三大措施之一,在坡耕地水土保持中起关键作用。利用人工模拟降雨试验方法,对不同坡度条件下农业耕作措施水土保持作用进行了研究。农业耕作措施包括等高耕作、人工掏挖和人工锄耕,以平整坡面为对照措施;降雨试验在长4m,宽1m的径流小区完成;坡度为5°,10°,15°,20°,25°;降雨强度为1,1.5,2mm/min。结果表明:与平整坡面相比,等高耕作、人工掏挖和人工锄耕分别减小产流量38.19%,32.25%和15.84%;减小产沙量均在50%以上,说明农业耕作措施具有明显的水土保持作用。通过对坡度与产流量、产沙量关系分析表明,在耕作坡面,坡度会影响产流量,但是大坡度与小坡度之间差异不显著。相反,坡度对产沙量具有显著影响,在小坡度条件下,产沙量受坡度的影响较小。当坡度大于15°后,坡度每增加1°,等高耕作、人工掏挖和人工锄耕耕作措施保土作用平均降低3.08%,4.74%和7.61%。回归分析表明产沙量与坡度之间存在指数函数关系。可见,坡度对农业耕作措施保水作用和保土作用的影响不同。     

翻耕除草对不同坡长下紫色土氮磷流失的影响

为揭示自然降雨下翻耕除草和坡长对紫色土氮、磷流失的影响,通过野外设置径流小区(2个坡面:翻耕除草与自然恢复;3种坡长:20,40,60 m,共9个小区),定位监测研究不同处理下产流产沙及氮、磷流失特征。结果表明,同一坡面不同坡长间产流产沙差异不显著(P0.05);同一坡长不同坡面处理小区的径流量、产沙量差异极显著(P0.01)。与翻耕除草相比,自然恢复坡面20,40,60 m坡长小区径流量分别减少77.55%,62.62%,79.56%,产沙量分别减少85.21%,94.97%,96.25%。仅在40 m坡长下,不同坡面处理径流中DN、DP流失量差异不显著(P0.05),其他坡长DN、DP流失量差异显著(P0.05);各坡长不同坡面处理下泥沙中TN、TP流失量差异极显著(P0.01)。与翻耕除草相比,自然恢复坡面处理径流中DN、DP流失量分别减少75.13%,80.22%,泥沙中TN、TP流失量分别减少96.07%,96.38%。在翻耕除草坡面处理下,降雨强度与径流量、产沙量及泥沙中的TN和TP流失量呈极显著幂函数关系;在自然恢复坡面处理下,上述关系均不显著。研究结果可为紫色土氮、磷流失及面源污染防治等提供理论参考依据。     

The effect of tillage systems on some microbial characteristics

Soils were sampled from plots with four variants of tillage methods: (1) conventional tillage (CT); (2) no tillage (NT); (3) minimum tillage (MTS); and (4) no tillage + mulch (NTM). Our aim was to study the influence of tillage on selected soil microbial properties. Determination of urease, dehydrogenase, invertase, arylsulphatase, potential nitrogenase activity, CFU of Azotobacter spp., and carbon microbial biomass has been conducted for time period 2002–2007. Soil samples from 0–0.1 m, 0.1–0.3 m, and 0.3–0.5 m were collected in the spring and autumn. Enzymatic activities (dehydrogenase, urease, arylsulphatase, and invertase) were significantly affected by soil depth and the tillage system employed. The statistically significant higher activity of urease was measured using the minimum tillage system (MTS), compared to the conventional tillage (CT) at soil depths of 0–0.1 m. The highest dehydrogenase activity was measured during the protective tillage treatment (NTM – no tillage with mulch). As far as other enzymatic activities (invertase and arylsulphatase) are concerned, the highest values were recorded in the protective tillage treatments. The highest counts of Azotobacter spp., as well as the highest nitrogenase activity (both statistically significant) were found in the no tillage + mulch (NTM) variant, at depths of 0.1–0.3 m. Microbial biomass (C-biomass) was the highest with the minimum tillage (MTS). The results show a positive influence of protection soil tillage on the reviving of upper layer of topsoil, especially in the variants where soil was supplied with organic matter.     

Effects of grass vegetation strips on soil conservation and crop yield under rainfed conditions in the Indian sub‐Himalayas

Vegetation strips (VS) along with conservation tillage, application of organic amendments and weed mulching improve crop yields by reducing run‐off and topsoil erosion. To investigate these issues, an experiment was conducted under rainfed conditions using grass VS for four and a half years (June 2007 to October 2011) at Dehradun, Uttarakhand, in the Indian Himalayan region. VS were incorporated in the experimental plots (Entisols) in a randomized complete block design in permanent 100 × 20 m (2000 m²) plots with a 2% slope to evaluate the effects of vegetation strips on run‐off, soil loss and crop yield. Three treatments were evaluated: (i) without VS with recommended NPK under conventional tillage, (ii) panicum as VS with recommended NPK under conventional tillage and (iii) palmarosa+ that consists of palmarosa as VS along with organic amendments (farmyard manure, vermicompost and poultry manure) and weed mulch under minimum tillage. The results show that soil loss and run‐off were significantly lower (P < 0.05) in plots under palmarosa+ than without VS treatment. Mean soil loss of 3.4, 5.2 and 7.1 t/ha was recorded from palmarosa+, panicum and without VS treated plots, respectively. Mean run‐off was 234, 356 and 428 mm from plots under palmarosa+, panicum and without VS, respectively. Maize yield was lower on the plots under palmarosa+ compared with panicum, but significantly higher (P < 0.05) than without a strip. The succeeding rainfed wheat yield was significantly greater in plots under palmarosa+ than in the initial years. The wheat yield equivalent was significantly higher in plots under palmarosa+ followed by panicum and without VS. Thus, vegetation strips are recommended for wider adoption to reduce run‐off and soil loss and to increase crop yield. The long‐term goal is to achieve a palmarosa+ system (palmarosa as a vegetation strip along with organic amendments, farmyard manure, vermicompost and poultry manure) and weed mulch under minimum tillage.     

不同耕作措施对黑土坡耕地土壤侵蚀的影响

针对黑龙江省西部半干旱区土壤流失情况,在坡耕地径流小区通过野外人工模拟降雨试验,研究不同降雨强度、不同耕作措施下降雨产沙产流特征和过程。试验结果表明:降雨强度越大,对地表径流量和侵蚀量的影响越大,即雨强与径流量和泥沙量呈正相关,各种耕作措施的土壤流失顺序是顺坡垄裸地>横坡垄裸地>等高种植地>深松地>秸杆覆盖地>垄向区田地,植被覆盖地能有效控制水土流失,垄向区田地是这几种耕作措施中减少坡耕地水土流失的有效措施。     

Quantifying soil respiration in response to short-term tillage practices: a case study in southern Turkey

Abstract

The study aimed at quantifying the rates of soil CO₂ efflux under the influence of common tillage systems of moldboard plow (PT), chisel plow (CT), rotary tiller (RT), heavy disc harrow (DT), and no-tillage (NT) for 46 days in October and November in a field left fallow after wheat harvest located in southern Turkey. The NT and DT plots produced the lowest soil CO₂ effluxes of 0.3 and 0.7 g m^?2 h^?1, respectively, relative to the other plots (P < 0.001). Following the highest rainfall amount of 87 mm on the tenth day after the tillage, soil CO₂ efflux rates of all the plots peaked on the 12th day, with less influence on soil CO₂ efflux in the NT plot than in the conventional tillage plots. Soil evaporation in NT (64 mmol m^?2 s^?1) was significantly lower than in the PT (85 mmol m^?2 s^?1) and RT (89 mmol m^?2 s^?1) tillage treatments (P < 0.01). The best multiple-regression model selected explained 46% of variation in soil respiration rates as a function of the tillage treatments, soil temperature, and soil evaporation (P < 0.001). The tillage systems of RT, PT, and CT led, on average, to 0.23, 0.22, and 0.18 g m^?2 h^?1 more soil CO₂ efflux than the baseline of NT, respectively (P≤0.001).     

自然降雨条件下秸秆还田对巢湖流域旱地氮磷流失的影响

本文通过野外径流小区观测试验,开展了自然降雨条件下秸秆覆盖对巢湖流域旱地地表径流、泥沙和氮磷流失影响的研究。试验结果表明,秸秆覆盖能有效减少地表径流量、侵蚀产沙量以及因地表径流引起的土壤氮磷流失。在整个玉米生长期间,秸秆覆盖小区的总产流量与产沙量比传统耕作小区分别减少30.47%和22.88%,表现出显著的水土保持作用。与传统耕作小区相比,秸秆覆盖小区随地表径流迁移的氮、磷流失总量分别降低27.42%和32.29%,但秸秆覆盖对径流中氮磷浓度的影响却不明显。溶解态氮是氮素流失的主要形态,颗粒态磷是磷素流失的主要形态。秸秆覆盖可以作为源头控制农业面源污染的较好措施之一加以推广。     

土壤翻耕对坡地水分转化与产流产沙特征的影响

坡耕地严重的水土流失是导致黄土高原土壤质量退化与生态环境恶化的重要原因。采用模拟降雨的方法研究了翻耕与压实对休闲黄绵土坡耕地水分转化与产流产沙特征的影响。结果表明，(1)与压实相比，土壤翻耕导致入渗率下降40%～60%，产流强度增加1至3倍，降雨向土壤水分的转化率降低50％以上。(2)翻耕条件下流失径流的平均含沙量增加近70％，坡地产沙量增加3倍，径流流失量增加1倍，因此对坡地实行免耕休闲可以有效减轻水土流失、遏制坡地土壤质量退化的态势。(3)降雨过程中，随着产流时间的延长，坡地产沙量呈加速增加的趋势，而且增加速度显著快于坡面径流，因此采取适当措施延长初始产流时间、减少产流量以及提高降雨向土壤水分的转化率均可有效减少坡地土壤流失量。     

Spatial analysis of long‐term effects of different tillage practices based on penetration resistance

Measuring penetration resistance (PR) is a common technique for evaluating the effects of field management on soils. This study focuses on the effects of long‐term tillage on the spatial distribution of PR, comparing reduced and conventional tillage (CT) practices. The study site, located in Lower Saxony (Germany), has been subdivided into three plots, with one plot having been managed conventionally, whereas reduced tillage (RT) practices have been applied to the other two. In total, PR was measured at 63 randomly selected points. The PR data were stepwise interpolated using kriging with external drift. Core samples have been taken at 20 additional sites. The results show significant differences in PR between the different tillage practices. Within the conventionally managed plot, PR ranges to 2.3 MPa less in the topsoil than under RT. However, measured saturated hydraulic conductivity and amount of biopores at the depth of 30–35 cm are significantly greater under RT, indicating improved soil properties under RT. Comparisons between the headlands (HL) and the inner field point out the effects of intense field traffic in the HL, where maximum PR values of about 6 MPa have been measured. The spatial prediction of PR values show that long‐term effects of different tillage practices result in clearly structured patterns between CT and RT and the HL. Combining extensive PR measurements and point measurements of additional soil properties supports an adequate interpretation of PR data and can lead to fieldwide derivation of soil functions influenced by field management.     

Interrelationship among slope steepness,tillage practice and rainfall properties with surface runoff and soil loss on Mollisols in Northeast China

ABSTRACT

Soil erosion and rainfall-induced runoff are well studied yet remain somewhat unpredictable from one natural rainfall to the next, due to interactions between erosion parameters. This study quantified the relationship between annual (2011–2016) and individual (2016) rain events with overland flow (runoff) and soil loss in China’s northern ‘corn-belt’. Two tillage practices and slopes were evaluated (no-till and conventional till, 5° and 7° slopes). Results showed 54 rainfall events for a total of 394 mm precipitation ranging between May and October 2016. Runoff occurred 13 times in the conventional till with 7° slope, accounting for 25.9% of the precipitation volume and caused 15.6 t ha^?1 erosion. It occurred twice in the no-till with 5° slope plot and caused 0.2 t ha^?1 erosion., Thus the no-till with 5° slope treatment is the best tillage system to protect soil in Mollisols in Northeast China. Broad analysis coupled with a detail review of three rainfall events demonstrates that water either runs off plots quickly or rapidly infiltrates while sediment moves in a pulsing manner.     

降雨条件下耕作方式对地表糙度的溅蚀效应

地表糙度是影响坡耕地土壤侵蚀的主要因素之一,为了进一步明确耕作方式对地表糙度的侵蚀效应,该文通过室内人工模拟降雨的方法,就单雨强与组合雨强条件下耕作方式对溅蚀的作用以及地表糙度的变化进行了研究。结果表明,从对照坡面,经耙耱地、人工锄耕、人工掏挖到等高耕作方式的坡面,在雨强0.62 mm/min条件下,不同耕作方式坡面向上坡溅蚀量呈先增加再减小的变化,向下坡和总溅蚀量均呈先增加再减小最后增加的变化;除耙耱地外,其他耕作方式坡面的地表糙度呈减小的变化。在雨强1.53 mm/min条件下,不同耕作方式坡面向上坡、向下坡和总溅蚀量均呈先增加再减小最后增加的变化;地表糙度与对照坡面相反,均呈增加的变化。组合雨强条件下,随降雨强度的增加,耙耱地总溅蚀量与地表糙度呈一直增加的变化趋势;其他耕作方式下,随降雨强度的增加,坡面总溅蚀量呈先增加后减小的变化趋势,地表糙度却呈先减小后增大的变化。这为揭示地表糙度的侵蚀特征提供了一定的理论依据,同时也可服务于黄土高原坡耕地的水土流失治理。     

垄作方式对薄层黑土区坡面土壤侵蚀的影响

定量评价垄作方式对坡面土壤侵蚀的影响,可为坡面土壤侵蚀防治提供理论参考。基于2012—2015年哈尔滨市野外径流小区监测资料,探讨了顺坡垄、横坡垄、无垄作(裸地休闲对照)垄作方式对坡面土壤侵蚀的影响,分析了不同垄作方式下坡面水沙关系。结果表明:不同垄作方式下径流量和侵蚀量均具有显著差异,坡面径流量和侵蚀量均表现为无垄顺坡垄横坡垄;与无垄作试验处理相比,横坡垄作使坡面径流量和侵蚀量平均减少了92.4%和98.3%,顺坡垄作使坡面径流量和侵蚀量平均减少66.4%和72.2%。当坡度由3°增加到5°时,无垄作、顺坡垄作、横坡垄作坡面侵蚀量分别增加了0.8,8.2,5.5倍。3种垄作方式下坡面水沙关系均呈现出良好的相关关系,顺坡垄作和无垄作坡面侵蚀量随径流量的增加幅度远大于横坡垄作坡面,当坡面径流量10.0mm时,二者坡面侵蚀量急剧增加。     

Influence of Residue Management and Tillage Systems on Carbon Sequestration and Nitrogen,Phosphorus, and Potassium Dynamics of Soil and Plant and Wheat Production in Semi-arid Region

Reducing the tillage and application of mulch are important strategies for soil and water conservation and sustainability of agricultural systems. Soil can be a source or sink for carbon (C) depending on management strategies and plays a major role in the global C cycle. These interacting practices can alter nutrient movement and availability to the crops, reduce water loss, slow down organic-matter (OM) decomposition, and thus enhance C sequestration. A 2-year field study was conducted to quantify the tillage and mulching effect on soil organic C (SOC), OM, nitrogen (N), phosphorus (P), and potassium (K) at two depths (i.e., 0–15 and 15–30 cm deep) in the soil profile and N, P, and K concentrations (g kg^?1) in plant shoots at harvest on a Typic Calciargids in wheat–maize rotation. The four tillage systems used were zero tillage (ZT), minimum tillage (MT), conventional tillage (CT), and deep tillage (DT), and four mulch rates [control, 2 (M₂), 4 (M₄), and 6 (M₆) Mg ha^?1 year^?1 wheat (Triticum aestivum L.) straw] were applied in combination with each tillage system, keeping recommended rates of fertilizers. There was a linear positive response of mulch application on SOC for both years, but it was more pronounced during the second year. Greater values were found in ZT and the lowest in CT at all depths, although greater SOC content was found in upper layers than in deeper ones. Greater shoot N, P, and K concentrations were found in MT, CT, and DT, whereas the lowest concentration was found in ZT. Mulch application has no effect on N, P, and K concentrations in shoots. The soil N concentration was not affected by tillage and mulch, yet greater soil N content was found at 0–15 cm than 15–30 cm deep. There was significant effect of tillage on soil P and K during one year as greater P and K concentrations were found under MT, CT, and DT compared to ZT. More N, P, K, and OM concentrations were found at 0–15 cm deep than at 15–30 cm deep during the whole study period. Mulch effect was significant on K, and significantly greater amounts were found at greater levels of mulch application. The increases in the soil OM were 34.5, 35.75, and 24% at 0–8, 8–16, and 16–24 cm deep respectively from the first year to the second year. Tillage effect on soil organic-matter content was not significant. Tillage increased grain production for both years. For the first year, 22.9 and 27% greater yields were found in CT and DT, whereas in the second year yields were 10.6, 17.9, and 57% greater, respectively, in MT, CT, and DT as compared to ZT. Grain production was increased at a result of mulch application by 12.9, 20.3, and 10.6% during the first year and 11.45, 23.74, and 10.9% during the second year as compared to control (i.e., without mulch). Results show the importance of mulch application and crop residue retention. Both can increase the SOC content and water-holding capacity, which will result in improved production and soil physical health over long and continuous use of mulch.     

覆盖免耕土壤棵间蒸发的研究

本文以翻耕、铁茬等常规耕作为对照,采用Micro-1ysimeter对覆盖免耕夏玉米田的土壤棵间蒸发进行了较为系统地研究。同翻耕、铁茬等相比,免耕有效地减少土壤棵间蒸发,免耕土壤日蒸发量最低,铁茬其次,翻耕最高;从阶段土壤棵间蒸发量变化看,翻耕的蒸发量较高,前期与免耕和铁茬差异较大,后期差异减小,免耕最低;从蒸发占蒸散的比例看,翻耕蒸发比例高,免耕比例最低。免耕可以有效地减少土壤蒸发量,增加作物蒸腾耗水。     

耕作方式对长期免耕农田土壤微生物生物量碳的影响

以华北冬小麦-夏玉米两熟区长期免耕土壤为研究对象, 研究不同耕作方式(免耕、翻耕和旋耕)对长期免耕土壤微生物生物量碳(SMBC)的影响, 为制定合理的轮耕制度提供依据。试验结果表明: 长期免耕土壤进行耕作处理后SMBC 的时空分布和稳定性产生显著变化。不同耕作处理SMBC 含量在0~5 cm 和5~10 cm 土层变化明显, 小麦起身期含量最低, 收获期最高; 深层SMBC变化不明显。免耕处理SMBC 随土壤层次明显降低, 且各土壤层次SMBC 差异达显著(P<0.05)水平; 翻耕、旋耕处理0~5 cm 和5~10 cm 土层间SMBC 无明显差异, 其他层次间差异显著(P<0.05)。从生育期平均值看, 0~5 cm 土层免耕处理SMBC 含量较高, 翻耕和旋耕处理则分别比免耕降低6.7%、6.1%; 与免耕相比, 5~10 cm 土层SMBC 翻耕、旋耕处理分别增加30.2%和20.7%(P<0.01),10~20 cm 土层SMBC 翻耕、旋耕处理比免耕增加48.1%(P<0.01)和10.5%(P<0.05)。在冬小麦生育期内, 0~20 cm土层SMBC 稳定性表现为翻耕>旋耕>免耕, 20~30 cm 土层SMBC 稳定性表现为免耕>翻耕>旋耕。