耕作方式对黄绵土无机磷形态的影响

以设置在陇中黄土高原并已经进行了5年的田间定位试验为基础,采用蒋-顾石灰性土壤无机磷分级法,研究了不同耕作方式对黄绵土无机磷形态的影响。结果表明,供试土壤中78.6%的磷以无机磷形式存在,且以Ca-P占绝大多数。无机磷各形态含量排列顺序为:Ca10-P Ca8-P O-PAl-P Fe-PCa2-P。与传统耕作不覆盖(T)相比,免耕秸秆覆盖(NTS)、免耕不覆盖(NT)、传统耕作结合秸秆还田(TS)均可降低土壤中的Ca8-P、O-P和0—5 cm土层中的Ca10-P含量,其中NTS最为明显;NTS处理可提高土壤中的Al-P、Fe-P含量。不同处理中,Ca2-P、Ca8-P、Al-P、Fe-P均以0—5 cm土层中含量最高,且随着土层的增加呈下降趋势;但是Ca10-P 以5—10 cm土层含量最高;各处理O-P在土壤剖面中的变化没有显著差异。     

Contributions of soil biota to C sequestration varied with aggregate fractions under different tillage systems

It is increasingly believed that substantial soil organic carbon (SOC) can be sequestered in conservation tillage system by manipulating the functional groups of soil biota. Soil aggregates of different size provide diverse microhabitats for soil biota and consequently influence C sequestration. Our objective was to evaluate the contributions of soil biota induced by tillage systems to C sequestration among different aggregate size fractions. Soil microbial and nematode communities were examined within four aggregate fractions: large macroaggregates (>2 mm), macroaggregates (2–1 mm), small macroaggregates (1–0.25 mm) and microaggregates (<0.25 mm) isolated from three tillage systems: no tillage (NT), ridge tillage (RT) and conventional tillage (CT) in Northeast China. Soil microbial and nematode communities varied across both tillage systems and aggregate fractions. The activity and abundance of microbes and nematodes were generally higher under NT and RT than under CT. Among the four aggregate fractions, soil microbial biomass and diversity were higher in microaggregates, while soil nematode abundance and diversity were higher in large macroaggregates. Structural equation modelling (SEM) revealed that the linkage between microbial and nematode communities and their contributions to soil C accumulation in >1 mm aggregate fractions were different from those in <1 mm aggregate fractions. Higher abundance of arbuscular mycorrhizal fungi (AMF) could enhance C retention within >1 mm aggregates, while more gram-positive bacteria and plant-parasitic nematodes might increase C accumulation within <1 mm aggregates. Our findings suggested that the increase in microbial biomass and nematode abundance and the alteration in their community composition at the micro-niche within aggregates could contribute to the higher C sequestration in conservation tillage systems (NT and RT).     

Phosphorus losses from a structured clay soil in relation to tillage practices

Abstract. Preferential flow may enhance phosphorus transport through the soil profile and thereby increase the risks for eutrophication of watercourses. Destruction of continuous macropores in topsoil by tillage provides the possibility for better contact between soil particles and P fertilizer. This is facilitated by incorporation rather than surface application of fertilizer, which should reduce the risk of rapid P transport from the soil surface through the unsaturated zone. To test this hypothesis, undisturbed soil monoliths (0.295 m in diameter and 1.2 m in length) were collected at a field site with a clay soil in which preferential flow is the dominant solute transport mechanism. After three years of observation, average total P loads reached 1.86, 1.59 and 1.25 kg ha^–1for no-tillage, conventional tillage, and conventional tillage where the P fertilizer was incorporated, respectively. More than 80% of total losses were in the form of dissolved P. The tillage treatment had no significant effect on P leaching loads compared to no-tillage, but the improved contact between soil particles and P fertilizer resulting from fertilizer incorporation significantly reduced P loads during the first year after application of 100 kg P ha^–1. However, after further application of 100 kg P ha^–1 two years later, there were no significant differences between the treatments.     

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。     

Conservation tillage induced changes in organic carbon, total nitrogen and available phosphorus in a semi-arid alkaline subtropical soil

A multi-year experiment was conducted to compare the effects of conservation tillage (no-till and ridge-till) with conventional plow tillage on organic C, N, and resin-extractable P in an alkaline semi-arid subtropical soil (Hidalgo sandy clay loam, a fine-loamy, mixed, hyperthermic Typic Calciustoll) at Weslaco, TX (26°9′N 97°57′W). Tillage comparisons were established on irrigated plots in 1992 as a randomized block design with four replications. Soil samples were collected for analyses 1 month before cotton planting of the eighth year of annual cotton (planted in March) followed by corn (planted in August).

No-till resulted in significantly (p<0.01) greater soil organic C in the top 4 cm of soil, where the organic C concentration was 58% greater than in the top 4 cm of the plow-till treatment. In the 4–8 cm depth, organic C was 15% greater than the plow-till control. The differences were relatively modest, but consistent with organic C gains observed in hot climates where conservation tillage has been adopted. Higher concentrations of total soil N occurred in the same treatments, however a significant (p<0.01) reduction in N was detected below 12 cm in the ridge-till treatment. The relatively low amount of readily oxidizable C (ROC) in all tillage treatments suggests that much of the soil organic C gained is humic in nature which would be expected to improve C sequestration in this soil.

Against the background of improved soil organic C and N, bicarbonate extractable P was greater in the top 8 cm of soil. Some of the improvement, however, appeared to come from a redistribution or “mining” of P at lower soil depths. The results indicate that stratification and redistribution of nutrients were consistent with known effects of tillage modification and that slow improvements in soil fertility are being realized.     

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.     

不同施肥和耕作制度下土壤微生物多样性研究进展

本文主要介绍了运用Biolog GN、磷脂脂肪酸(PLFA)、核酸分析法进行土壤微生物群落分析的优缺点,综述了施肥、耕作两种农业措施对土壤微生物多样性影响的研究进展。指出不同施肥处理对微生物影响效果不同,合理施用有机肥有利于维持土壤微生物的多样性及活性;由于受其他环境因素(如土壤类型、农作制度、残茬量等)的影响,不同耕作措施对土壤微生物多样性影响有差异,但是大多试验结果显示免耕、少耕能增加微生物多样性和生物量,保持系统的稳定性。文章还指出了目前研究中存在的问题,并对今后的研究方向做了展望。     

Effects of tillage and management practices on soil crust morphology under a Mediterranean environment

Soil crust formation can be affected by soil tillage. Alternative soil conservation practices consisting of reduced tillage were tested against traditional tillage, which involves mechanical weeding by frequent ploughing in rainfed vineyard soils in Catalonia, Spain. After 2 years of the experiment (1994–1996), thin sections of the surface crusts were studied to evaluate the effects of the soil management treatments on crust morphology and genesis, using micromorphological observations and pore characterisation with image analysis. Reduced tillage caused thicker and more complex crusts consisting of layers with different degrees of sorting and pore types, compared to traditional tillage. Total porosity of crusts did not differ from that of non-crusted areas, but pores in crusts were less interconnected, more horizontally distributed and more elongated than in the underlying non-crusted material. The soil type, especially structure and texture, affected crust morphology and played an important role in the process of crusting. The results show that reduced tillage may be limited as an alternative management practice when used to reduce crust formation in Mediterranean conditions, due to the difficulty to establish an effective groundcover.     

Effects of fertilizer placement on solute leaching under ridge tillage and no tillage

Elevated nitrate concentrations in ground water can be a problem in agricultural areas, especially where soils are sandy. Tillage operations, such as ridge tillage (RT) and no tillage (NT) can reduce runoff and erosion but leaching of soluble nutrients could adversely impact groundwater. In a 2-year study, Br was used to trace the effects of fertilizer placement on solute movement under corn (Zea mays L.) in RT and NT systems on a Monmouth fine sandy loam (Typic Hapludult) in Maryland. Treatments included 120 kg ha⁻¹ of Br⁻ or NO₃⁻-N applied in a narrow band near the ridge top (RT-RA) or in the furrow (RT-FA) with ridge tillage, or in the inter-row with NT. Two-dimensional arrays of tensiometers and suction lysimeters were used to follow the movement of water and solutes during and after the corn-growing season. Tillage and fertilizer placement did not significantly affect N uptake when averaged across years. A pronounced argillic horizon beginning at 60 cm depth caused lateral movement of Br. It appears that Br leaching in RT-RA increased slightly due to the crop canopy funneling rain towards the ridge top. Therefore, when fertilizer is applied near the row, rain occurring after full corn canopy may cause greater solute leaching in RT-RA compared to other treatments. Rain during the beginning of the growing season or after harvest caused less leaching in RT-RA. Corn yield could be maximized and N leaching minimized by applying fertilizer to the upper portion of the ridge in RT.     

黄土坡耕地耕作方式不同时微地形分布特征及水土保持效应

 利用GIS技术模拟黄土坡耕地微地形空间分布特征,并对其水土保持效应进行研究。结果表明：1)地表微地形起伏大小依次为等髙耕作 > 人工掏挖 >人工锄耕 > 直线坡面（CK),和CK相比,人工锄耕与人工掏挖微地形呈随机相间的坑洼特征,等高耕作呈沟垄相间的空间特征;雨后CK、人工锄耕、人工掏挖与等商耕作方式下地表髙程平均分别降低0.015、0.014、0.018和0.015 m。2)除CK地表填洼量为增大外,其余方式均为减小;地表产流时间依次为直线坡面 < 人工掏挖< 人工锄耕< 等髙耕作。3)产流量随降雨时间呈先增大,后趋于平稳的过程。4)与CK相比,等高耕作、人工锄耕和人工掏挖产流量分别减小38. 17%、17.88%和9.43%。5)产沙最随降雨时间呈先增大,后减小并逐渐趋于稳定的过程,与CK相比,等高耕作、人工锄耕和人工掏挖产沙量分别减小65.6%、36.3%和23.4%。6)坡度对产流产沙的影响主要是坡度越大,产流时间越早,产流产沙量也越大。因此,不同耕作方式的水土保持效应与其形成的地表微地形空间特征密切相关。     

Duration of tillage management affects carbon and phosphorus stratification in phosphatic Paleudalfs

Surface accumulation of soil organic carbon (SOC) under conservation tillage has significant effects on stratification of other nutrients, on crop productivity and in ameliorating the greenhouse effect via atmospheric CO₂ sequestration. A measure of SOC stratification relative to deeper soil layers has been proposed as a soil quality index. Our objective was to determine the effects of the duration of tillage practices upon the SOC and extractable P distribution with depth in Maury silt loams (Typic Paleudalfs) at similar levels of corn (Zea mays L.) productivity without P fertilization. Soil samples (0–20.0 cm in 2.5 cm increments) were collected under moldboard tillage (MT), chisel tillage (CT) and no-tillage (NT) and in surrounding tall fescue (Festuca arundinacea L.) sods selected from three tillage experiments (1–2-, 8- and 29-year durations) in Kentucky. SOC stratification was greater under conservation tillage (CT and NT) and sods than under MT. SOC and soil-test-extractable P stratification were positively related. Increasing the duration under NT caused the thickness of C stratification to increase. In NT soils, C stratification ratio (CSR) approached CSR in the nearby long-term sods with time. Conservation tillage rapidly promoted the occurrence of CSR greater than 2 while MT always resulted in values lower than 2. The rapid initial change in CSR suggests characterization of thin soil layers (i.e. 2.5 cm depth increments) is desirable under conservation tillage.     

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.     

Physical and mechanical properties of a clayey soil as affected by tillage systems for wheat growth

Abstract

The effect of tillage systems on soil physical properties of a clayey soil was studied. Tillage systems consisting of conventional tillage I (CT₁), conventional tillage II (CT₂), reduced conventional tillage (RCT), reduced tillage (RT) and no tillage (NT) were carried out in autumn after harvest of sugar beet. Significant differences between tillage systems were recorded on the measured properties, apart from moisture content, at 15–30 cm soil layer. The CT₁, CT₂ and RCT systems resulted in similar penetration resistance and bulk density values below the 15 cm soil depth, while the RT and NT systems resulted in higher but similar values. The mean penetration resistance values were less than 1 MPa in the CT₁, CT₂ and RCT systems at the 0–15 cm depth, while they were 1.41, 1.84 MPa in RT and NT, respectively. The mean total porosity increased with tillage from 8.2 to 28% when compared with NT. The CT₁, CT₂ and RCT systems resulted in lower moisture content at the 0–15 cm depth. The lowest moisture content occurred in RCT (24.4%) and the highest in NT (30.9%), while it was 30.3% in RT system. The lowest and highest mean weight diameter values were reported for the RT (1.36 mm) and NT (2.37 mm) systems, respectively. The lowest wheat grain yield was obtained in NT (4.14) and the highest in CT₁ (5.24 Mg ha^?1). A significant difference occurred between only NT and the other systems. When both grain yield and advantages of reduced tillage are considered, the RT system is recommended.     

Phosphorus sequestration in soil aggregates after long-term tillage and cropping

Cultivated soils in the Everglades are being converted to their historic use as pastures or seasonally flooded prairies as parts of restoration efforts, but long-term cultivation may have altered soil P distribution and availability which may pose eutrophication hazards upon change in land use. The objectives of this study were to determine the distribution of P in soil chemical and physical fractions for contrasting long-term land management practices. The distribution of P in labile, Fe–Al bound, Ca bound, humic–fulvic acid, and residual pools in five aggregate-size fractions were measured for fields under sugarcane (Saccharum sp.) cropping for 50 years and perennial pasture for 100 years. Both land uses were characterized by a high degree of macroaggregation, as aggregates >0.25 mm contained 76 and 83% of the total soil under cultivation and pasture, respectively. Soils under sugarcane sequestered a total of 77 kg ha⁻¹ more P than pasture at 0–15 cm. The distribution of P in chemical fractions significantly varied between land uses as cultivation increased P sequestration in Ca-bound fractions more for sugarcane (244 kg P ha⁻¹) than pasture (65 kg P ha⁻¹). Pasture sequestered more P in organic pools, as storage in humic–fulvic acid and residual fractions were 26 and 25%, respectively, higher than sugarcane. Labile P was 100% higher for pasture than sugarcane, but Fe–Al bound P storage did not differ between land uses. Aggregation increased P sequestration in humic–fulvic acid and residual fractions, and P storage in organic pools increased with increasing aggregate size. In contrast, cultivation decreased aggregation and increased P accumulation in inorganic fractions. Long-term cultivation altered the distribution of soil P from organic to inorganic pools. The P stored in inorganic pools is stable under current land use, but may be unstable and pose eutrophication hazards upon onset of future land use change to the seasonally flooded prairie ecosystem.     

不同耕作措施下土壤孔隙的多重分形特征

首先利用数字图像处理技术提取了东北黑土区长期免耕(no tillage,NT)和翻耕(moldboardtillage,MT)制度下土壤切片中的孔隙信息,然后应用矩方法研究了两种耕作制度下土壤孔隙结构的多重分形特征。结果表明,免耕降低了表层(0~5 cm)大孔隙度(500μm),但是提高了10~15 cm和20~25 cm深度的孔隙度和大孔隙度。土壤孔隙结构在64~1 024像素尺度上具有多重分形特征。广义维(Dq)和多重分形谱(f(α))及相关参数能够反映切片中孔隙结构的特征。表层土壤孔隙多重分形谱明显右偏,随深度增加趋于对称。在同一深度下,免耕处理的Δα(α-10-α10)和ΔD(D-10-D10)均大于翻耕处理,免耕处理增加了孔隙结构的复杂程度,尤其是10~15 cm和20~25 cm深度下的孔隙结构。     

Short-term effects of tillage practices on soil aggregate fractions in a Chinese Mollisol

Abstract

Soil aggregate-size distribution and soil aggregate stability are used to characterize soil structure. Quantifying the changes of structural stability of soil is an important element in assessing soil and crop management practices. A 5-year tillage experiment consisting of no till (NT), moldboard plow (MP) and ridge tillage (RT), was used to study soil water-stable aggregate size distribution, aggregate stability and aggregate-associated soil organic carbon (SOC) at four soil depths (0–5, 5–10, 10–20 and 20–30 cm) of a clay loam soil in northeast China. Nonlinear fractal dimension (D_m) was used to characterize soil aggregate stability. No tillage led to a significantly greater aggregation for >1 mm aggregate and significant SOC changes in this fraction at 0–5 cm depth. There were significant positive relationships between SOC and >1 mm aggregate, SOC in each aggregate fraction, but there was no relationship between soil aggregate parameters (the proportion of soil aggregates, aggregate-associated SOC and soil stability) and soil bulk density. After 5 years, there was no difference in D_m of soil aggregate size distribution among tillage treatments, which suggested that D_m could not be used as an indicator to assess short-term effects of tillage practices on soil aggregation. In the short term, > 1 mm soil aggregate was a better indicator to characterize the impacts of tillage practices on quality of a Chinese Mollisol, particularly in the near-surface layer of the soil.     

转变耕作方式对长期旋免耕农田土壤有机碳库的影响

土壤深松是解决长期旋免耕农田耕层浅薄化、亚表层（>15～30 cm）容重增加等问题的有效方法之一,而将长期旋免耕农田进行深松必然导致农业生态系统中土壤有机碳（soil organic carbon,SOC）及碳固定速率的变化。因此,为对比将长期旋免耕转变为深松前后农田土壤有机碳库变化,该研究利用连续12a 的旋耕和免耕长期定位试验以及在此基础上连续6 a旋耕-深松和免耕-深松定位试验,对比了转变耕作方式对农田土壤0～30 cm有机碳含量、周年累积速率及其固碳量的影响。研究结果表明,经过连续12 a的旋耕和免耕处理（2002－2014）,2014年免耕处理土壤0～30 cm有机碳储量比试验初期（2002年）提高38%,旋耕处理降低了30%,而对照常规处理无显著差异。免耕处理土壤0～30 cm有机碳储量比旋耕处理高约2.6倍（2014年）。长期免耕显著提高了土壤0～30 cm的有机碳含量,2002~2014年其土壤0～30 cm固碳量为16.69 t/hm2,但长期旋耕导致土壤0～30 cm SOC含量显著降低,表现为土壤有机碳的净损耗,年损耗速率为?0.75 t/hm2。而长期旋耕后进行深松（旋耕-深松处理）6年其土壤0～30 cm的有机碳含量较原旋耕处理提高32%～67%,且显著提高了土壤固碳量及周年累积速率;免耕-深松土壤0～30 cm的有机碳周年累积速率较免耕处理下降了42%。长期旋耕造成有机碳水平下降的条件下,将旋耕处理转变为深松处理在短期内更有利于促进土壤有机碳的积累,而将长期免耕处理转变为深松措施,降低了土壤有机碳的累积速率和固碳量。     

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.     

长期不同施肥条件下黑土水稳性团聚体中磷的分布及其有效性

利用中国科学院海伦农业生态实验站的长期定位试验,研究了长期不同施肥条件下[对照(CK)、施用化学氮磷肥(NP)、化学氮磷肥配施有机肥(NP+OM)]农田黑土不同粒径水稳性团聚体中磷的分布及其有效性。结果表明,施肥增加了黑土各粒级水稳性团聚体中全磷含量,其中,NP处理比对照(CK)全磷含量增加28.9%~37.8%,NP+OM处理比NP处理增加44.0%~63.9%。施肥增加了黑土各粒级水稳性团聚体中有效磷含量,NP处理比CK处理有效磷含量增加146%~183%,NP+OM处理有效磷含量是NP处理的3.4~5.3倍。各处理水稳性团聚体全磷和有效磷均表现为较均匀地分布在0.053mm的各粒级水稳性团聚体中,而0.053mm粒级水稳性团聚体内全磷和有效磷均显著降低。施磷可显著增加土壤磷的有效率,且以化肥配施有机肥处理表现更为明显。NP处理不同粒径水稳性团聚体中磷的有效率是CK处理的1.94~2.32倍,NP+OM处理是NP处理的2.13~2.83倍。     

Soil sustainability indicators following conservation tillage practices under subtropical maize and bean crops

Conservation management systems such as no tillage may enhance sequestration of soil C. The soil properties that contribute to soil C storage under such systems are still largely unknown, especially in subtropical agroecosystems. We investigated the influence of tillage [mouldboard plough (MP) and no tillage (NT)] on soil organic C, microbial biomass and activity, structural stability and mycorrhizal status of a field cultivated with maize (Zea mays L.) or bean (Phaseolus vulgaris L.) on a Vertisol in Northern Tamaulipas, Mexico. Crop type, tillage system and soil depth had a significant effect on soil organic C, aggregate stability and bulk density. Soil organic C, microbial biomass C and N and dehydrogenase and phosphatase activities were greater with NT than with MP, particularly under bean cultivation. In the 0–5 cm layer, microbial biomass C and N were, on average, about 87 and 51% greater in the soils cultivated with bean and maize, respectively, under NT than under MP. Higher levels of mycorrhizal propagules, glomalin related soil protein (GRSP) and stable aggregates were produced under NT than under MP in both crops. The no-tillage system can be considered an effective management practice for carrying out sustainable agriculture under subtropical conditions, due to its improvement of soil physical and biochemical quality and soil C sequestration.