Changes in soil chemical characteristics with different tillage practices in a semi-arid environment

We examined the effects of various tillage intensities: no-tillage (NT), minimum tillage with chisel plow (MT), conventional tillage with mouldboard plow (CT), and zone-tillage subsoiling with a paraplow (ZT) applied in alternate years in rotation with NT, on the topsoil profile distribution (0–30 cm) of pH, soil organic carbon (SOC), organic N and available nutrients on a semi-arid soil from Central Spain. The equivalent depth approach was used to compare SOC, N and nutrient stocks in the various tillage treatments. Measurements made at the end of 5 years showed that in the 0–30 cm depth, SOC and N had increased under NT and ZT compared with MT and CT. Most dramatic changes occurred within the 0–5 cm depth where plots under NT and ZT had respectively 7.0 Mg ha⁻¹ and 6.2 Mg ha⁻¹ more SOC and 0.5 Mg ha⁻¹ and 0.3 Mg ha⁻¹ more N than under MT or CT. No-tillage and ZT plots, however, exhibited strong vertical gradients of SOC and N with concentrations decreasing from 0–5 to 20–30 cm. In the 0–20 cm layer, higher concentrations of P and K under NT and ZT than under MT or CT were also found. Soil pH under NT and ZT was 0.3 units lower than under MT or CT at a depth of 0–5 cm. This acidifying effect was restricted at the surface layer and in the 20–30 cm interval, pH values under NT and ZT were higher than in MT and CT plots. These results suggest that in the soil studied, ZT in rotation with NT maintain most advantages associated with NT, and present a definite potential for use as a partial-width rotational tillage practice.     

Soil structure and the effect of management practices

To evaluate the impact of management practices on the soil environment, it is necessary to quantify the modifications to the soil structure. Soil structure conditions were evaluated by characterizing porosity using a combination of mercury intrusion porosimetry, image analysis and micromorphological observations. Saturated hydraulic conductivity and aggregate stability were also analysed.

In soils tilled by alternative tillage systems, like ripper subsoiling, the macroporosity was generally higher and homogeneously distributed through the profile while the conventional tillage systems, like the mouldboard ploughing, showed a significant reduction of porosity both in the surface layer (0–100 mm) and at the lower cultivation depth (400–500 mm). The higher macroporosity in soils under alternative tillage systems was due to a larger number of elongated transmission pores. Also, the microporosity within the aggregates, measured by mercury intrusion porosimetry, increased in the soil tilled by ripper subsoiling and disc harrow (minimum tillage). The resulting soil structure was more open and more homogeneous, thus allowing better water movement, as confirmed by the higher hydraulic conductivity in the soil tilled by ripper subsoiling. Aggregates were less stable in ploughed soils and this resulted in a more pronounced tendency to form surface crust compared with soils under minimum tillage and ripper subsoiling.

The application of compost and manure improved the soil porosity and the soil aggregation. A better aggregation indicated that the addition of organic materials plays an important role in preventing soil crust formation.

These results confirm that it is possible to adopt alternative tillage systems to prevent soil physical degradation and that the application of organic materials is essential to improve the soil structure quality.     

耕作方式对耕层土壤结构性能及有机碳含量的影响

为了寻求能够提高土壤结构稳定性的耕作模式,在陇中黄土高原半干旱区连续7年的定位试验研究基础上,采用常规分析方法(湿筛法、重铬酸钾容量法、环刀法),研究了不同耕作方式对耕层土壤结构性能及有机碳含量的影响.结果表明:与传统耕作(T)相比,免耕无覆盖(NT)、传统耕作+秸秆还田(TS)和免耕+秸秆覆盖(NTS)3种保护性耕作方式均能不同程度地增加耕层土壤的有机碳和不同粒径水稳性团聚体的含量,其中免耕+秸秆覆盖(NTS)处理效果最佳.在0～10 cm土层中,NTS处理的土壤容重低、孔隙度大,土壤结构得到了较大改善.不同耕作方式下0～5 cm、5～10 cm和10～30 cm土层粒径1～0.5 mm水稳性团聚体的含量最高,粒径>0.25 mm水稳性团聚体含量与有机碳含量和孔隙度呈显著正相关,与容重呈显著负相关.     

基于因子和聚类分析的保护性耕作土壤质量评价研究

基于长期定位试验,选择12项反映土壤质量特性的定量因子作为评价指标,采用因子分析对不同耕作模式的土壤质量进行综合评价,并运用欧氏距离最短法对其进行聚类分析。12项理化及生物属性指标归纳为5个公因子:保肥供肥因子、有机质因子、容重因子、磷素因子、酶活性因子。因子得分的结果表明:不同耕作模式的5个公因子优势差异明显。相比较而言传统耕作的土壤质量综合得分最低,说明在研究区保护性耕作模式条件下土壤在物理、化学、生物学性质方面都有所改善,土壤质量有所提高。土壤质量综合得分最高的前3种处理为隔年深松(NS2)、秸秆覆盖联合浅松、旋耕(SR2)、连年深松(NS3),说明深松、旋耕及秸秆还田与旋耕技术联合作业在改善土壤结构和培肥土壤方面优势更突出。聚类分析结果表明,同一耕作措施的不同模式土壤质量差异较小,说明在本研究试验条件下,耕作措施是影响土壤质量的关键因素。     

Effects of intensifying organic manuring and tillage practices on penetration resistance and infiltration rate

Soil erosion, along with the contributing factors of soil crusting and sealing, have received minimal scientific attention to date in Latin America. This study was conducted in an Andean hillside environment to determine how the local organic manuring and tillage practices influence the development of soil crusting and sealing, and the extent to which these practices influence soil water infiltration. The aim of this study was to identify treatments that prevented superficial soil structural constraints, i.e. treatments which maintain infiltration and therefore reduce potential soil erosion and run-off.

Treatment results were measured with a pocket penetrometer and a mini-rain simulator on nine different cropping systems, mainly based on cassava (Manihot esculenta Crantz), from February to November 2000 and 2001. The cropping systems were laid out on a Ferrallic Cambisol, an acid, vulcanically influenced soil of the Andean region.

In both cropping cycles, treatments with chicken manure application developed superficial soil crusts during the dry season. For a treatment manured with 8 t ha⁻¹ chicken manure, this crust meant an increase in penetration resistance from 2.3 kg cm⁻² in April 2000 to 16.2 kg cm⁻² in July 2000. The change in superficial soil structure created a notable reduction in final infiltration from 92 to 42.2 mm h⁻¹. A minimum tillage treatment which displayed the highest penetration resistance during the dry periods of up to 46.4 kg cm⁻² presented no restricting effects on soil water intake (76.2 mm h⁻¹ final infiltration in 2000) due to an optimal aggregate development during 10 years of consecutive conservation practice.

Measurements of penetration resistance and infiltration showed that soil conserving treatments, such as minimum tillage and crop rotations, improved the physical soil status and prevented soil crusting developing along with its negative effects on infiltration. These methods can therefore be strongly recommended to farmers.     

长期保护性耕作对黄土高原旱地土壤肥力质量的影响

长期定位试验研究了黄土高原西部旱农区传统耕作措施和5种保护性耕作措施对豌豆-小麦(P→W)和小麦-豌豆(W→P)轮作序列的耕层土壤肥力质量的影响。结果表明,与传统耕作(T)处理相比,传统耕作秸秆还田(TS)和免耕秸秆覆盖(NTS)处理有机质含量分别提高11.61%～12.21%和12.13%～16.99%,全氮提高7.29%～8.42%和11.58%～12.95%,全磷提高10.35%～14.63%和13.79%～18.29%,全钾提高7.32%～7.51%和8.78%～9.15%,速效磷提高11.10%～12.41%和16.29%～20.99%,速效钾提高25.11%～43.26%和31.62%～44.22%,pH降低0.11～0.17个单位和0.09～0.16个单位。进一步利用加乘法则和加权综合法两种模型评价不同耕作方式下的土壤肥力质量,结果表明,土壤肥力质量指数排序为NTS处理TS处理NTP处理NT处理T处理TP处理(P→W轮作序列)和NTS处理TS处理NT处理NTP处理TP处理T处理(W→P轮作序列)。在黄土高原雨养农作系统中,实施免耕结合秸秆覆盖,对促进和维持土壤养分平衡,提高土壤肥力质量具有重要意义。     

Long-term tillage effects on soil quality

Public interest in soil quality is increasing, but assessment is difficult because soil quality evaluations are often purpose- and site-specific. Our objective was to use a systems engineering methodology to evaluate soil quality with data collected following a long-term tillage study on continuous corn (Zea mays L.). Aggregate characteristics, penetration resistance, bulk density, volumetric water content, earthworm populations, respiration, microbial biomass, ergosterol concentrations, and several soil-test parameters (pH, P, K, Ca, Mg, Total-N, Total-C, NH₄-N, and NO₃-N) were measured on Orthic Luvisol soil samples collected from Rozetta and Palsgrove silt loam (fine-silty, mixed, mesic Typic Hapludalfs) soils. Plots managed using no-till practices for 12 years before samples were collected for this study had surface soil aggregates that were more stable in water and had higher total carbon, microbial activity, ergosterol concentrations, and earthworm populations than either the chisel or plow treatments. Selected parameters were combined in the proposed soil quality index and gave ratings of 0.48, 0.49, or 0.68 for plow, chisel, or no-till treatments, respectively. This indicated that long-term no-till management had improved soil quality. The prediction was supported by using a sprinkler infiltration study to measure the amount of soil loss from plots that had been managed using no-till or mold-board plow tillage. We conclude that no-till practices on these soils can improve soil quality and that the systems engineering methodology may be useful for developing a more comprehensive soil quality index that includes factors such as pesticide and leaching potentials.     

Changes in some soil properties in a Vertic Argiudoll under short-term conservation tillage

The purpose of this work was to determine whether some soil physical and chemical properties, and microbial activity were affected by two conservation tillage systems in a Chernozemic clay loam soil (Vertic Argiudoll), after 5 years of trial initiation. Two crop sequences, corn (Zea mays L.)–wheat (Triticum aestivum L.)/soybean (Glycine max (L.) Merr.) and wheat/soybean, under chisel plowing (ChP) and no till (NT) were evaluated. Physical and chemical properties were also analyzed taking the same soil without disturbance as reference. The Hénin instability index (HI) was larger in ChP than in NT in both corn–wheat/soybean (C–W/S) and wheat/soybean (W/S) sequences (P≤0.05). The C–W/S sequence differed from W/S (P≤0.01) in total organic carbon (TOC). As regards organic carbon fractions, no differences were found in labile organic carbon (LOC), while W/S under ChP showed the lowest value (P≤0.01) of humified organic carbon (HOC). No differences were found in microbial respiration either in crop sequences or in tillage systems. Soil physical and chemical properties differentiated crop sequences and tillage treatments from the undisturbed soil when a Student’s t-test was performed. Five years elapsed since the beginning of this trial was time enough to detect changes in some of the soil properties as a consequence of management practices. An important reduction in the soil structural stability was observed as related to the undisturbed soil. However, the C–W/S sequence under NT resulted in lower soil degradation with respect to the other treatments.     

Effect of mulch and tillage system on soil porosity under wheat (Triticum aestivum)

Crop residues and reduced tillage become current tendency in modifying tillage due to better water management, organic and nutrient supply and increasing crop production. This study was carried out to quantify the effect of fodder radish mulching and different tillage systems in wheat production. In 2004–2006 the field trial was set up on Luvic Chernozems derived from loess. This experiment consisted of two factors: tillage system (conventional or reduced) and mulch (with or without). The air–water properties of soil with particular focus on macropore characteristics were investigated.The tillage system and mulch application significantly influenced physical properties of investigated soil. Reduced tillage, without mouldboard plough, increased the soil density with respect to conventional tillage. However, in the upper soil layer (0–10 cm) with mulch residues the bulk density decreased and reached the similar value as those obtained at conventional tillage (1.25 g cm⁻³). The macroporosity of soil with conventional tillage (14.79%) was significantly higher in comparison with reduced tillage (6.55%). The mulch of fodder radish added at reduced tillage increased the macroporosity in pore diameter range of 50–500 μm. These changes referred to all shape classes: regular, irregular and elongated pores. The lowest transmission pores content (0.078 cm³ cm⁻³) was noticed at the reduced tillage without mulch at the 0–10 cm layer. Due to lack of differences in storage pores the tillage and mulching had no effect on both AWC (available water content) and PWC (productive water content) values. The higher value of AWC was noticed in the upper soil layer (0.198 cm³ cm⁻³ in average), whereas in the 10–20 cm soil layer it was 0.186 cm³ cm⁻³. Similar relation was recorded in PWC values, 0.165 and 0.154 cm³ cm⁻³, respectively. The results obtained in physical properties of soil reflected in wheat yields. The yields obtained at reduced tillage system without mulch (5.54 t ha⁻¹) were significant lower with respect to treatment when mulch applied (6.79 t ha⁻¹). The mulch residues did not affect yields at conventional tillage (6.53 t ha⁻¹ without mulch and 7.00 t ha⁻¹ with mulch). The main conclusion is that the mulching can help to avoid yield reduction in wheat production when reduced tillage is used.     

紫色土丘陵区保护性耕作下旱地土壤呼吸及影响因素

为了探讨保护性耕作对旱作农田土壤呼吸的影响,采用LI6400XT便携式光合作用测量系统自带的土壤呼吸室(6400-09)在重庆北碚西南大学试验农场对传统耕作(T,traditional farming)、垄作(R,ridge planting)、传统耕作+秸秆覆盖(TS,traditional farming+straw mulching)、垄作+秸秆覆盖(RS,ridge planting+straw mulching)、传统耕作+秸秆覆盖+秸秆速腐剂(TSD,traditional farming+straw mulching+decomposing agent)、垄作+秸秆覆盖+秸秆速腐剂(RSD,ridge planting+straw mulching+decomposing agent)6种处理下的西南紫色土丘陵区小麦/玉米/大豆套作体系中作物生长季节的土壤呼吸及其水热因子进行了测定和分析。结果表明,6种处理中土壤呼吸速率的季节变化明显,各处理日均土壤呼吸速率差异显著。其中在小麦-大豆条带,小麦土壤呼吸速率均值为1.53μmol m-2s-1,大豆土壤呼吸速率日均值为4.10μmol m-2s-1,各处理日平均土壤呼吸速率大小排序为TRTSTSDRSRSD。在空地-玉米-空地条带,玉米土壤呼吸日均值为2.56μmol m-2s-1,介于小麦和大豆土壤呼吸速率之间,各处理日平均土壤呼吸大小排序为RTRSTSRSDTSD。整个套作体系土壤呼吸总量C为1 543~2 134 g m-2,表现为TRRSTSTSDRSD。研究结果还显示土壤温度和土壤水分是影响旱地农田土壤呼吸的主要因素,二者分别解释了土壤呼吸季节变化的28.9%~53.7%和13.7%~42.0%。水热因子与土壤呼吸速率的回归分析表明,指数方程较好地模拟了土壤呼吸与10 cm土温的关系,土壤呼吸的温度敏感性指标Q10值在2.25~2.69之间;而土壤呼吸与5 cm土壤水分的关系以抛物线型函数模拟最优。土壤呼吸对土壤水分的响应阈值为14.94%。该研究为明确农田生态系统土壤呼吸变化规律及影响因素的控制机理提高参考,对估算全球碳平衡、评估区域碳源汇具有重要意义。     

Effects of tillage systems on soil characteristics, glomalin and mycorrhizal propagules in a Chilean Ultisol

Tillage affects the soil physical and chemical environment in which soil microorganisms live, thereby affecting their number, diversity and activity. However, soil disturbance generally has the greatest impact on biological properties, including both free and symbiotic fungal populations. Interest in more ecologically sustainable agricultural systems is rising with increasing recognition that agricultural intensification can adversely affect environmental quality. This paper discusses the effect of tillage system on some soil characteristics, such as pH, C, N and S levels, total and Olsen-P contents including some P forms associated with organic matter, glomalin contents and arbuscular mycorrhizae (AM) parameters, such as root colonization, spore number and total and active hyphal length. Measurements were in the sixth year of an on-going tillage-rotation experiment conducted on an Ultisol under no-till (NT), reduced tillage (RT) and conventional tillage with stubble mixed into the soil (CTS) or stubble burnt (CTB). Soil was sampled at two dates; after wheat (Triticum aestivum) harvest (autumn) and 6 months after subsequent grassland seeding (spring). Higher C, N, S, total P and fulvic acid-P concentrations and pH occurred under NT and RT than under CTS and CTB after wheat harvest. However, results at the second sampling were not consistent. AM spore number and active hyphal length were highest under NT having the greatest incidence on AM root colonization and P concentration in shoots of the pasture. Glomalin concentration was higher under NT and RT than under CTS and CTB but no differences in calculated glomalin to total C (ca. 5%) were found. It is concluded that a less disruptive effect of NT influences positively all soil characteristics and also increases P acquisition by the following crop in the rotation system.     

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.     

Characterization of soil physical properties and organic matter under long-term primary tillage in a humid climate

Chisel ploughing is considered to be a potential conservation tillage method to replace mouldboard ploughing for annual crops in the cool-humid climate of eastern Canada. To assess possible changes in some soil physical and biological properties due to differences in annual primary tillage, a study was conducted for 9 years in Prince Edward Island on a Tignish loam, a well-drained Podzoluvisol, to characterize several mouldboard and chisel ploughing systems (at 25 cm), under conditions of similar crop productivity. The influence of primary tillage on the degree of soil loosening, soil permeability, and both organic matter distribution throughout the soil profile and organic matter content in soil particle size fractions was determined. At the time of tillage, chisel ploughing provided a coarser soil macrostructure than mouldboard ploughing. Mouldboard ploughing increased soil loosening at the lower depth of the tillage zone compared to chisel ploughing. These transient differences between primary tillage treatments had little effect on overall soil profile permeability and hydraulic properties of the tilled/non-tilled interface at the 15–30 cm soil depth. Although soil microbial biomass, on a volume basis, was increased by 30% at the 0–10 cm soil depth under chisel ploughing, no differences were evident between tillage systems over the total tillage depth. Mouldboard ploughing increased total orgainc carbon by 43% at the 20–30 cm soil depth, and the carbon and nitrogen in the organic matter fraction ≤ 53 μm by 18–44% at the 10–30 cm soil depth, compared to chisel ploughing.     

Energy use efficiency of deficit-irrigated silage maize in different soil tillage practices on a high plain with a semi-arid climate

ABSTRACT

Energy requirement increases rapidly in agriculture due to the increase in mechanization. The aim of the present study is to evaluate the energy use efficiency of silage maize under three different tillage practices (conventional, reduced, no-tillage) combined with four different irrigation levels (full and three deficit irrigations). The no-tillage and reduced tillage practices provided savings in input energy at the rate of 17.4 and 9.1%, respectively compared to the conventional tillage. The highest silage yields in all irrigation levels were obtained in the no-tillage practice. Therefore, in full and deficit irrigated silage maize, the highest energy ratio, energy productivity and net energy and the lowest specific energy values were manifested in the no-tillage practice. Energy rates in the no-tillage practice were higher by 34.2 and 22.9% than the conventional and the reduced tillage practices, respectively. Moreover, the direct and non-renewable energy requirements were the lowest in the no-tillage practice. In conclusion, the fully-irrigated no-tillage practice can be recommended to obtain the highest energy use ratio and productivity. However, no-tillage irrigated with up to 50% less water amount could be a better alternative for areas with a water shortage by improving the energy use ratio with better water and fuel savings.     

Aggregate breakdown during tillage in a Mediterranean loamy soil

Long-term tillage negatively affects soil aggregation, but little is known about the short-term effects of tillage. We investigated the effects of intensive tillage (moldboard plowing) and conservation tillage (chisel plowing) on aggregate breakage during tillage in a long-term study located in the semiarid Ebro river valley (NE Spain). The type of tillage resulted in different soil aggregate distributions. In the 0–5-cm and 5–10-cm soil layers, chisel plowing decreased dry mean weight diameter (DMWD) 29% and 35%, respectively, while moldboard plowing decreased DMWD by only 2% and 16%, respectively. The decrease in DMWD was mainly due to breaking of large aggregates ranging (2–8 mm) into small aggregates (<0.5 mm). Tillage method had no effect on water stability of 1–2 mm aggregates. The differences in DMWD demonstrate that the choice of the tillage implement can be a key factor in improving soil management and productivity. The surprising result that aggregate breakdown was greater with chisel than moldboard plowing needs further research to determine the mechanisms controlling aggregate breaking during tillage.     

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。     

Crop yield and soil fertility response to reduced tillage under organic management

Conservation tillage (no-till and reduced tillage) brings many benefits with respect to soil fertility and energy use, but it also has drawbacks regarding the need for synthetic fertilizers and herbicides. Our objective was to adapt reduced tillage to organic farming by quantifying effects of tillage (plough versus chisel), fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators and crop yield. The experiment was initiated in 2002 on a Stagnic Eutric Cambisol (45% clay content) near Frick (Switzerland) where the average annual precipitation is 1000 mm. This report focuses on the conversion period and examines changes as tillage intensity was reduced. Soil samples were taken from the 0–10 and 10–20 cm depths and analysed for soil organic carbon (C_org), microbial biomass (C_mic), dehydrogenase activity (DHA) and earthworm density and biomass. Among the components tested, only tillage had any influence on these soil fertility indicators. C_org in the 0–10 cm soil layer increased by 7.4% (1.5 g C_org kg⁻¹ soil, p < 0.001) with reduced tillage between 2002 and 2005, but remained constant with conventional tillage. Similarly, C_mic was 28% higher and DHA 27% (p < 0.001) higher with reduced than with conventional tillage in the soil layer 0–10 cm. In the 10–20 cm layer, there were no significant differences for these soil parameters between the tillage treatments. Tillage had no significant effect on total earthworm density and biomass. The abundance of endogeic, horizontally burrowing adult earthworms was 70% higher under reduced than conventional tillage but their biomass was 53% lower with reduced tillage. Wheat (Triticum aestivum L.) and spelt (Triticum spelta L.) yield decreased by 14% (p < 0.001) and 8% (p < 0.05), respectively, with reduced tillage, but sunflower (Helianthus annuus L.) yield was slightly higher with reduced tillage. Slurry fertilization enhanced wheat yield by 5% (p < 0.001) compared to compost fertilization. Overall, C_org, C_mic, and DHA improved and yields showed only a small reduction with reduced tillage under organic management, but long-term effects such as weed competition remain unknown.     

Seasonal variations in soil erosion resistance during concentrated flow for a loess-derived soil under two contrasting tillage practices

Soil erodibilty during concentrated flow (K_c) and critical flow shear stress (τ_cr), both reflecting the soil's resistance to erosion by concentrated runoff, are important input parameters in many physically-based soil erosion models. Field data on the spatial and temporal variability of these parameters is limited but crucial for accurate prediction of soil loss by rill or gully erosion. In this study, the temporal variations in K_c and τ_cr for a winter wheat field on a silt loam soil under three different tillage practices (conventional ploughing, CP; shallow non-inversion tillage, ST; deep non-inversion tillage, DT) in the Belgian Loess Belt were monitored during one growing season. Undisturbed topsoil samples (0.003 m³) were taken every three weeks and subjected to five different flow shear stresses (τ = 4–45 Pa) in a laboratory flume to simulate soil detachment by concentrated flow. To explain the observed variation, relevant soil and environmental parameters were measured at the time of sampling. Results indicated that after two years of conservation tillage, K_c(CP) > K_c(DT) > K_c(ST). K_c values can be up to 10 times smaller for ST compared to CP but differences strongly vary over time, with an increasing difference with decreasing soil moisture content. The beneficial effects of no-tillage are not reflected in τ_cr. K_c values vary from 0.006 to 0.05 sm⁻¹ for CP and from 0.0008 to 0.01 sm⁻¹ for ST over time. Temporal variations in K_c can be mainly explained by variations in soil moisture content but consolidation effects, root growth, residue decomposition and the presence of microbiotic soil crusts as well play a role. τ_cr values increase with increasing soil shear strength but K_c seems more appropriate to represent the temporal variability in soil erosion resistance during concentrated flow. The large intra-seasonal variations in K_c, which are shown to be at least equally important as differences between different soil types reported in literature, demonstrate the importance of incorporating temporal variability in soil erosion resistance when modelling soil erosion by concentrated flow.     

Effects of soil management practices and tillage systems on surface soil water conservation and crust formation on a sandy loam in semi-arid Kenya

The effect of different soil management practices on crust strength and thickness, soil water conservation and crop performance was investigated on a ferric lixisol in a semi-arid environment of eastern Kenya.

The study proved that manure and mulching with minimum tillage have a greater effect on the water balance of crusted soils and maize emergence. There was increase in steady infiltration rates, amount of soil water stored in the soil and better drainage. The physical effect of mulch was less important in the rehabilitation of crusted soils in the study site when it was incorporated into the soil. Manure and surface mulch with minimum tillage should therefore be taken into account in land management and water conservation in the semi-arid areas of Kenya. The response of crops to the improved water availability due to manure with minimum and with conventional tillage and surface mulch was very clear. These management practices should be recommended when considering the effectiveness of soil and water management techniques in the study area.     

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。