Field assessment of crusting on a tilled sandy clay loam

Nine different techniques were used to record the initial change in the physical and hydrological properties of a freshly tilled soil surface following successive cycles of wetting and drying. The study was made in the field on a sandy clay loam soil ploughed and harrowed and then exposed to three simulated rainfall events of 76 mm/h for 15 minutes. Although the degradation of the soil surface increased with each successive rainfall, the most significant changes were observed after the first rainfall. Qualitative observations of clod size distribution and crust development provide a good indication of the early stages of soil surface degradation. Complementary physical data were quickly obtained using a hand held shear vane. These techniques are simple and robust enough that they can be used in on-farm research programmes, where resources, both human and technical are at a premium. Tension infiltrometry provided hydrological information that complemented the physical information provided by the above techniques, but is not as simple.     

腐殖酸和溶液的pH对Na和Ca土壤粘土分散的影响

Dispersed soil clays have a negative impact on soil structure and contribute to soil erosion and contaminant movement.In this study,two typical soils from the south of China were chosen for investigating roles of pH and humic acid(HA) on dispersion of soil clays.Critical flocculation concentration (CFC) of the soil clay suspension was determined by using light transmission at a wavelength of 600 nm.The results indicated that effects of pH and HA on dispersion of the soil clays were closely related to the type of the major minerals makin up the soil and to the valence of the exchangeable cations as well.At four rates of pH(4,6,8and 10),the CFC for the Na-yellow-brown soil treated with H2O2 was increased from 0.32 to 0.56,6.0 to 14.0,10.0 to 24.6 and 26.0 to 52.0mmol L^-1 NaCl,respectively when Na-HA was added at the rate of from 0 to 40mgL^-1,With the same Na-HA addition and three pH(6,8and 10)treatments,the CFC for the Na-red soil was incresed from 0.5 to 20.0,1.0 to 40.0 and 6.0 to 141.0mmol L^-1 NaCl,respectively.Obviously,pH and HA has greater effects on clay dispersion of the red soil(dominated by 1:1 minerals and oxides) than on that of the yellow-brown soil(dominated by 2:1minerals).However,at three rates of pH(6,8and 10) and with the addition of Ca-HA from 0 to 40mg L^-1,the CFC of the Ca-yellow-brown soil and Ca-red soil treated with H2O2 was increased from 0.55 to 0.81,0.75 to 1.28,0.55 to 1.45and 0.038 to 0.266.0.25 to 0.62,0.7to 1.6mmol CaCl2 L^-1,respectively.So,Na-soil claye are more sensitive to pH and HA than Ca-soil clays.     

Role of Phenolics and Organic Acids in Phosphorus Mobilization in Calcareous and Acidic Soils

Abstract

Phenolic acids (caffeic, CAF; protocatechuic, PCA; p-coumaric, COU; and vanillic, VAN), catechol (CAT), poly-galacturonic acid (PGA), and citric acid (CIT) were compared for their effectiveness in phosphorus (P) mobilization in three soils differing in chemical properties. The addition of organic ligands at 100 μmol g^{? 1} soil increased the concentrations of resin P (P_r), water-extractable P (P_w), and bicarbonate-extractable inorganic P (P_bi), thus improving the phosphorus availability. The magnitude of P mobilization in the calcareous soil can be expressed in the following order: CAF > CAT > PCA = CIT > VAN > COU > PGA, which was consistent with the number of phenolic hydroxyl groups they contained and the position of carboxyl on the benzoic ring. In the two acid soils tested, the order of P mobilization was CIT > CAT > PCA > CAF after 24 h incubation, and CIT > PCA > CAF > CAT after a 14 d incubation. The mobilized P originated partly from the organic P fractions, which could be extracted by 0.5 M NaHCO₃. In addition, P_r decreased and P_w increased during incubation. The exceptions were that the CAF treatment increased P_r and the CIT treatment did not affect P_w. Calcium extraction from the soils after a 1 d or 14 d incubation could not fully account for the P mobilization. The results suggest that the inorganic P dissolution by the organic ligands was not the only mechanism of P mobilization in the calcareous soil, while in acid soils the chelation of metal cations by organic ligands is likely an important factor in P mobilization.     

腐植酸改良铜污染土壤对小麦生长与吸收利用养分的影响

为了评价腐植酸对铜污染土壤的改良效果,以冬小麦为研究对象,设置施加铜和腐植酸双因素田间盆栽试验,研究成熟期小麦的干物质积累与分配以及对氮、磷、铜素的吸收与利用。结果表明:(1)铜污染土壤中小麦器官的生长受到抑制,总生物量显著降低28.7%～66.9%;小麦吸收氮、磷量分别显著降低18.4%～61.5%、9.6%～65.5%,氮、磷素收获指数显著下降;尽管铜污染使小麦对铜素的吸收量显著增加40.5%～115.2%,但茎向叶和穗的迁移系数下降,使得收获指数无变化。(2)施用腐植酸明显改善铜污染造成的小麦根、茎、穗生长受到的抑制,缓解小麦吸收氮、磷素减少的不利影响;相比铜污染处理,腐植酸低(20g/kg干土)和高(40g/kg干土)用量可使小麦生物量分别提高25.0%和115.6%,促进小麦对氮(22.6%～111.9%)、磷(28.3%～161.9%)的吸收并提高氮、磷素的收获指数。高腐植酸用量更有助于小麦抵抗铜污染危害胁迫。(3)增施腐植酸能使小麦铜素收获指数显著降低7.2%～9.0%,但会显著增加铜素由茎向叶(12.2%～30.7%)和由茎向穗(46.8%～71.9%)的迁移,导致铜在穗中的积累量增加。由此可见,施用腐植酸改良铜污染土壤的农用效果仍需要进一步研究。     

硫酸铵与腐植酸及改性腐植酸配施对氨挥发的影响

通过室内连续培养试验,研究了石灰性褐土中硫酸铵与不同用量及改性腐植酸（HA）配施对氨挥发及氮素形态转化的影响。试验设置6个腐植酸用量处理,分别为CKⅠ、ASNⅠ（硫酸铵Ⅰ）、ASNⅠ+5%HA、ASNⅠ+10%HA、ASNⅠ+15%HA、ASNⅠ+20%HA(5%、10%、15%、20%为腐植酸占硫酸铵施用量的百分比)和6个改性腐植酸处理,分别为CKⅡ、ASNⅡ（硫酸铵Ⅱ）、ASNⅡ+W0、ASNⅡ+W400、ASNⅡ+W600、ASNⅡ+OHA(W0、W400、W600分别为含水量0%、400%、600%的改性腐植酸,OHA为干燥+过氧化氢氧化处理的改性腐植酸)。结果表明：培养32 d后,与单施硫酸铵处理（ASNⅠ）相比,ASNⅠ+10%HA～ASNⅠ+20%HA处理可以抑制氨挥发,其中ASNⅠ+20%HA处理抑制效果最佳,日平均氨挥发速率降幅为5.07%。腐植酸经不同改性处理后,按硫酸铵用量的20%与硫酸铵配施培养32 d后,与单施硫酸铵处理（ASNⅡ）相比,ASNⅡ+W400与ASNⅡ+W600处理加剧了土壤氨挥发,土壤氨挥发总量分别增加了50.69%和57.64%;ASNⅡ+O...     

Plant Response to Copper Toxicity as Affected by Plant Species and Soil Type

ABSTRACT

A greenhouse experiment was conducted to determine the bioavailability of copper (Cu) in clay loam and sandy clay loam soil. Lettuce (Lactuca sativa) and spinach (Spinacia oleracea) were grown in pots for 45 d. When mature, plants were treated for 15 additional days with 0, 100, 250, 500, or 1000 mg Cu kg^?1 as CuSO₄·5H₂O. After harvest, Cu in soils and plant tissues was determined. In soils, applied Cu raised total and EDTA-extractible Cu. Results also revealed that the amounts of Cu extracted from sandy clay loam soil (80%) were higher than those extracted from clay loam soil (70%). In plants, increasing soil Cu concentration increased plant concentration of the metal. Plant species vary in their capacity for Cu accumulation: Lettuce has a relatively higher potential for Cu uptake and translocation than does spinach. Cu accumulation also differs among plant organs. In lettuce, metal accumulation is higher in roots than in shoots, where 60% to 80% of the total Cu of the plant is located in the roots. However, in spinach, there is no significant difference in Cu content between roots and shoots. The transfer of the metal from soil to plant is higher for plants grown on sandy clay loam soil. For a given rate of applied Cu, metal content in plant tissues is higher on sandy clay loam soil due to its higher transfer coefficient (C_T) from soil to plant. Nevertheless, all crops studied showed a positive linear relationship between extractible soil Cu and plant Cu.     

土柱尺寸对扰动黏壤土饱和导水率的影响

土壤饱和导水率Ks是最基本的水力参数之一,而已知实验室内其值的确定受土柱尺寸的影响.以关中的塿土为研究对象,在室内,采用定水头法,研究5～30 cm内6个不同土柱尺寸对扰动黏壤土Ka测定的影响.结果表明：随着时间的延伸,Ks逐渐减小,其值最初降幅较大,其后趋于稳定,且在5 ～ 30 cm土柱直径范围内,Ks随着土柱直径的变大,扰动黏壤土的Ks递增,二者线性相关,y=0.000 4x＋0.003 7（R2=0.965 1）.研究结果可为测定Ks合理测定时间段及合理尺寸的选择提供参考.     

Nitrate leaching losses under Miscanthus grass planted on a silty clay loam soil

Abstract. Nitrate leaching under newly planted Miscanthus grass was measured for three years. The crop received either no fertilizer-N or an annual spring application of 60 kg or 120 kg N ha^-1. During three winters soil water was collected from porous cup probes installed 90 cm deep. Nitrate leaching was calculated from the mean drain flow recorded in two drain gauges multiplied by the mean nitrate-N concentration in the soil water solutions collected. In the first year soil water nitrate concentrations were high on all treatments and N losses were 154, 187 and 228 kg ha^-1 respectively on the unfertilized treatment and those that received 60 or 120 kg N ha^-1. Leaching losses in the second and third years were, in turn, 8, 24 and 87 kg ha^-1 and 3, 11 and 30 kg ha^-1 for the unfertilized treatment and for the 60 and 120 kg N ha^-1 treatments respectively. Leaching losses were closer to those recorded under extensively managed grassland than arable land. The large losses in the first year were probably due to the previous agricultural management at the site and excessive inputs of N on the fertilized plots. In the second and third year, lower drainage volumes may also have influenced losses. The results show that Miscanthus , once established, can lead to low levels of nitrate leaching and improved groundwater quality compared with growing arable crops.     

Organic and Inorganic Amendments Affect Soil Concentration and Accumulation of Cadmium and Lead in Wheat in Calcareous Alkaline Soils

Irrigation with untreated effluent in periurban agriculture could result in accumulation and bioconcentrations of cadmium (Cd) and lead (Pb). Different amendments were used to investigate their effect on availability, concentration, and uptake of metals by wheat in texturally different soils. Crop was irrigated with water containing Cd and Pb at 20 mg L^?1, thereby adding 260 mg pot^?1 of each metal. Amendments included calcium carbonate at 6 or 12%, gypsum at 50 or 100% of the soil gypsum requirement, farm manure at 7.50 or 15.00 g kg^?1 soil, and a control. Amendments decreased ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA)–extractable Cd and Pb concentrations and uptake by wheat. Dry matter, concentration, uptake, and extractability of Cd and Pb were greater in sandy loam soil compared with those in sandy clay loam soil irrespective of amendments. Sequential extraction showed that more metals were extracted from the control in all fractions and that predominantly metals were found in the carbonate fraction.     

Effects of ISPOLIN Fertilizer on Uptake of Macro- and Trace Elements by Wheat Grown in Two Different Soils

Variations in concentrations of 24 elements in soils with loam and sandy loam texture and in Triticum aestivum wheat seedlings grown in the soils under greenhouse conditions were studied. Initial soils differed significantly in concentrations of 20 elements. Elemental composition of wheat seedlings depended on the soil where the plants were grown. An application of ISPOLIN (fertilizer enriched with potassium) resulted in variations in soil pH, plant biomass, and concentrations of several elements both in soils and in plants. An excess of bioavailable potassium (K) in soil led to significant increase of K and deficiency of calcium (Ca) and magnesium (Mg) in all parts of T. aestivum. Concentrations of many other elements in the plants also changed. The effects of soil fertilization on plant biomass, leaf chlorophyll, and plant element concentrations were soil-dependent. Depending on the ratio of K/Mg in the soils, there was either an increase of plant yield and chlorophyll content or no effect at all.     

Total and carboxyl acidity and methoxyl groups of humic acid preparations of chernozemic soils

Abstract

Alkaline‐soluble, acid‐precipitable organic matter from the Ah and Bm horizons of Chernozemic soils developed on four parent materials in each of three soil zones was analyzed for total and carboxyl acidity, and methoxyl groups. The values are expressed as meq/g dry ash‐free organic matter.

Total acidity generally was higher in the Black Chernozems than in the Brown Chernozems and higher in the Bm horizon than in the Ah horizon. The distribution of carboxyl acidity between the Ah and companion Bm horizons of individual soils appeared to be related to texture and rainfall.

The. methoxyl group content of the Brown Chernozems was larger than that of the .Dark Brown Chernozems, which in turn had a larger methoxyl group content than that of the Black Chernozems. It was concluded that the organic matter in the Ah horizons of the Brown Chernozems was not as humified as that of the Black Chernozems. The pH value and a minimum clay content are possible determining factors as to the amounts of methoxyl carbon present.     

Evaluation of the Clay Fraction in some Danish Soils,Making Use of High-Gradrent Magnetic Separation (HGMS)

Abstract

After removal of the ‘free Fe-oxyhydroxides’, a high-gradient magnetic separation (HGMS) procedure was used to separate the minerals of the clay fraction in soil samples from different horizons of two Alfisols, a Mollisol, an Ultisol and a Spodosol into a magnetic and a non-magnetic fraction. The magnetic fraction constituted 12–19% of the total clay fraction in the Alfisols, 28–35% in the Mollisol, 9–10% in the Ultisol and 11–16% in the Spodosol. X-Ray diffraction (XRD), Mossbauer spectroscopy and total elemental analysis (TEA) were used for the characterization of the different fractions. The CBD-treated magnetic clay contained mainly paramagnetic 2:1 layer silicate clay minerals, including hydroxy-interlayered clay minerals (HICM) high in Fe. The nonmagnetic clay was composed of diamagnetic minerals such as quartz, feldspars, gibbsite, kaolinite and the diamagnetic 2:1 layer silicate clay minerals.     

不同耕作方式对中国东北黑土有机碳的短期影响

A tillage experiment, consisting of moldboard plow （MP）, ridge tillage （RT）, and no-tillage （NT）, was performed in a randomized complete block design with four replicates to study the effect of 3-year tillage management on SOC content and its distribution in surface layer （30 cm） of a clay loam soil in northeast China. NT did not lead to significant increase of SOC in topsoil （0-5 cm） compared with MP and RT; however, the SOC content in NT soil was remarkably reduced at a depth of 5-20 cm. Accordingly, short-term （3-year） NT management tended to stratify SOC concentration, but not necessarily increase its storage in the plow layer for the soil.     

重碳酸根对不同小麦基因型生长及锌营养的影响

石灰性土壤上小麦锌缺乏问题在世界范围内广泛存在,而高含量的HCO3-被认为是造成缺锌的主要原因之一。本试验采用土培试验方法,选用3种小麦基因型（中育6号、S02-8、远丰998）,研究了不同HCO3-浓度水平对小麦生长及Zn营养的影响。结果表明,HCO3-对小麦植株生长（尤其是对根系）及Zn吸收有一定的抑制作用,且在较低浓度（15 mmol/L）条件下表现更为明显。另外,高浓度HCO3-对土壤中有效锌含量及对锌从小麦根系向地上部的转运率均会产生不利的影响,在HCO3- 30 mmol/L条件下,与未进行HCO3-处理的对照相比,土壤有效锌及锌向地上部的转运率分别下降11.1%和5.0%,表明HCO3-对小麦锌营养的影响可能主要是通过以下途径实现的:1) 对土壤中有效锌的钝化;2) 对小麦根系生长的抑制;3) 抑制锌从小麦根系向地上部的转运,其中前两个途径可能起着更为重要的作用。总体来看,土壤中高含量的HCO3- 对供试的3种冬小麦基因型的生长及Zn吸收的抑制作用比较轻微,这可能与它们对高浓度的HCO3-具有较高的耐性有关。     

Effect of High Humic Substance Levels on Growth and Nutrient Concentration of Corn under Calcareous Conditions

This study investigated the effect of high humic substance (HS) levels (0, 500, 1000, and 2000 mg HS kg^?1) on growth and nutrient concentrations of corn grown on calcareous soils. For these, soil samples were collected from the six different provinces of Turkey. According to the average values, HS levels had no significant effect alone on dry weight, nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) concentrations. Soil differences significantly affected dry weight, N, Mg, and Cu concentrations (p ≤ 0.05). Looking at HSxsoil interactions on K, Ca, Fe, and Mn concentrations, it could be seen that there was no effect or that the effect was negative. Only plant Fe concentrations obtained from Konya and Urfa provinces were positively affected from HSxsoil interaction. It was concluded that high level of HS had no or negative effect on corn growth and some nutrient concentration under calcareous conditions.     

Integrative Soil Application of Humic Acid and Sulfur Improves Saline Calcareous Soil Properties and Barley Plant Performance

ABSTRACT

During the 2017 and 2018 seasons, two field experiments were conducted on newly reclaimed saline calcareous soil (7.13 dS m^?1, 16.9% CaCO₃) in the experimental farm of the Faculty of Agriculture, Demo, Fayoum Governorate, Egypt. The current work aimed at identifying the potential positive effects of applied humic acid (HA) and elemental sulfur (S) on some soil properties and barley plant performance. The results showed that the application of HA and/or S at different rates ameliorated the adverse effects of saline calcareous soil conditions and significantly reduced some chemical properties of the soil (e.g., pH, ECe, and CaCO₃%), while soil organic matter (OM%) and some nutrients (e.g., P, Fe, Mn, Cu, and Zn) contents were significantly increased. In addition, the contents of nutrients (e.g., P, Fe, Mn, Cu, and Zn) in barley plant and yielded grain, grain content of N and protein (%), and the performance (e.g., plant height, spike length, grain and straw yields, and weight of 1000-grain) of barley plant were significantly increased with the application of HA and/or S. The best results were obtained through the integrative application of 100 kg HA + 400 kg S ha^?1 to the tested saline calcareous soil. Therefore, the integrative soil application of 100 kg HA + 400 kg S ha^?1 can be recommended for the cultivation and sustainability of crop production in saline calcareous soil, in addition to rationalize the use of mineral fertilizers, which represent a surplus point for the sustainable agriculture system.     

Influence of soil pH and application of zinc on the yield and uptake of selected nutrient elements by rice

Abstract

Rice grown on a recently water‐leveled Crowley silt loam that contained less than 1.8 μg g^‐1 of 0.1 N HCl‐extractable Zn with pH levels ranging from 6.8 to 7.7, responded to Zn application. Each kg ha of applied Zn as Zn chelate, 14.2 % Zn, resulted in increases of +673, +477, and +2026 kg rice ha^‐1 at pH 6.8, 7.3, and 7.7, respectively. There was a critically low concentration of Zn in rice plants at the midtillering, first joint, and panicle differentiation stages of plant development when no Zn was applied. A yield response to applied Zn was obtained when the concentration of Zn in rice tissue was less than 15 μg g^‐1.

Application of Zn resulted in a significant increase in the uptake of N by rice plants at each of the three stages of plant development. Application of Zn also resulted in relatively large and significant increases in the uptake of Zn from the soil irrespective of soil pH. The uptake of Zn by rice plants at each of the growth stages showed a two‐ to three‐fold increase following Zn application when soil pH was 6.8 and 7.3. Also, the uptake of Zn by rice plants following Zn application showed a four‐fold increase at midtillering, a five‐fold increase at first joint, and a six‐fold increase at panicle differentiation, respectively, when soil pH was 7.7.