广西壮族自治区土地利用与土壤侵蚀的关系

[目的]对广西壮族自治区的土壤侵蚀现状进行定量分析,分析土地利用类型与土壤侵蚀的关系,为科学防治土壤侵蚀提供决策依据。[方法]以RUSLE模型为基础,引入喀斯特石漠化修正因子M,构建适合广西地区的土壤侵蚀模型。[结果](1)2015年,研究区土壤侵蚀模数为135.51t/(km~2·a),土壤侵蚀厚度达0.08mm/a,土壤侵蚀面积2.52×10~4 km~2,土壤侵蚀量3.21×10~7 t。其中,喀斯特地区土壤侵蚀面积1.86×10~4 km~2,占土壤侵蚀面积的73.81%,占总侵蚀量的31.01%。(2)土壤侵蚀量占总侵蚀量的大小顺序为:耕地(37.58%)林地(30.94%)草地(16.10%)园地(6.39%)工矿用地(4.09%)裸地(2.16%)。[结论]人类活动干扰强烈的土地利用影响全区土壤侵蚀空间分布格局。     

长期施肥对栗褐土有机碳矿化的影响

【目的】 土壤有机碳矿化是土壤中重要的生物化学过程,与土壤养分的释放、土壤质量的保持以及温室气体的形成密切相关。本文以 25 年长期定位施肥试验为依托,对栗褐土土壤有机碳矿化速率、有机碳累积矿化量的动态变化进行研究,为科学管理土壤肥力、增加栗褐土碳汇、减少温室气体排放提供依据。 【方法】 田间试验开始于 1988,共设置 8 个施肥处理:不施肥 (CK);单施氮肥 (N);氮磷肥合施 (NP);单施低量有机肥(M₁);低量有机肥与氮肥合施 (M₁N);低量有机肥与氮磷肥合施(M₁NP);高量有机肥与氮肥合施 (M₂N);高量有机肥与氮磷肥合施 (M₂NP)。于 2013 年玉米播种前,采集耕层 (0—20 cm) 土壤样品,采用室内培养方法,对土壤碳矿化释放 CO₂ 的数量和速率进行测定,并利用一级动力学方程计算出土壤有机碳库潜在矿化势和周转速率。 【结果】 各肥料处理不同程度地提高了栗褐土总有机碳含量,以高量有机肥与化肥配施作用最为显著。与 CK 相比,M₂N、M₂NP 处理土壤总有机碳含量增加了 121.1%、166.8%。不同处理土壤样品培养有机碳矿化速率均在第一天达到峰值,随后急剧下降。5 d 后,下降趋缓,不同处理 CO₂ 产生速率趋于一致。培养期间,各处理矿化速率变化符合对数函数关系。长期施用不同肥料均可以提高栗褐土有机碳的矿化速率,其大小顺序为:有机肥与化肥配施 > 单施有机肥 > 单施化肥 > 对照。培养 57 d 后,各处理土壤有机碳累积矿化量为 555.0～980.3 mg/kg,以 M₂NP、M₁N 的累积量较高,为对照的 1.77 倍、1.73 倍。长期施肥栗褐土有机碳矿化率呈下降趋势,以处理 M₂NP 下降最明显,与对照相比,降低了 6.3 个百分点。施肥处理土壤的潜在矿化势均高于对照,M₁N、M₂NP 最高,为 923.7 mg/kg 和 926.4 mg/kg,较对照增加了 74.0% 和 74.5%。不同施肥处理均可明显提升土壤有机碳的周转速率,减少周转时间,其中处理 M₁NP、M₂NP 效果最为明显。 【结论】 长期施用化肥、有机肥及有机无机肥配施可有效促进栗褐土有机碳的积累,提高有机碳的矿化速率和周转速率,降低有机碳的矿化率 (累积矿化量占有机碳总量的比率),加强了土壤的固碳能力,以 M₂NP 处理的效果更佳。      

适量有机肥与氮肥配施方可提高河西绿洲土壤肥力及作物生产效益

【目的】 河西绿洲灌溉农业区是我国主要的商品粮生产及玉米制种基地,结合当地耕作制度进行土壤有效培肥是提高农业生产效益和可持续发展的基础。本研究以河西灌漠土长期定位试验为依托,探讨了长期施用一种或者多种有机肥以及有机无机肥配合对土壤养分、土壤酶活性及产量的影响,为筛选出适于当地农业可持续发展的施肥模式提供理论依据。 【方法】 试验采用随机区组排列,除对照外,在施磷肥 (P₂O₅) 150 kg/hm2 的基础上,再设 12 个处理:单施用农家肥 120 t/hm2 (M);单施绿肥 45 t/hm2 (G);单施秸秆 10.5 t/hm2 (S);单施氮肥 375 kg/hm2 (N);农家肥 60 t/hm2 + 绿肥 22.5 t/hm2 (1/2MG);农家肥 60 t/hm2 + 秸秆 5.25 t/hm2 (1/2MS);农家肥 60 t/hm2 + 氮肥 187.5 kg/hm2 (1/2MN);绿肥 22.5 t/hm2 + 氮肥 187.5 kg/hm2 (1/2GN);秸秆 60 t/hm2 + 氮肥 187.5 kg/hm2 (1/2SN);农家肥 40 t/hm2 + 绿肥 15 t/hm2 + 氮肥 124.5 kg/hm2 (1/3MGN);农家肥 40 t/hm2 + 秸秆 3495 kg/hm2 + 氮肥 124.5 kg/hm2 (1/3MSN);农家肥 30 t/hm2 + 秸秆 2625 kg/hm2 + 绿肥 11.25 t/hm2 + 氮肥 94.5 kg/hm2 (1/4MGSN)。调查了耕层土壤有机质和速效养分含量变化以及几种主要土壤酶活力,采用主成分分析、聚类分析、经济效益分析综合比较了不同施肥方式对土壤质量与经济收益的影响。 【结果】 长期不施肥、单施氮肥(N)、氮肥配施绿肥或者秸秆均会造成土壤钾素匮缺,较 1988 年初测土土壤速效钾含量分别下降了 16.59%、39.37%、25.04%、23.31%;M、G、S 三种有机肥单施或与氮配施均能提高土壤碱解氮、土壤有效磷、土壤有效钾、土壤有机质(SOM)含量,不同施肥方式下,其含量大小总体表现为高量有机肥 > 减量有机肥 + 减量 N > N > CK;M、G、S、N 单施或 1/2MN、1/2GN、1/2SN 处理均能提高蔗糖酶、磷酸酶、脲酶、过氧化氢酶活性,以 G、1/2GN 处理对提高土壤蔗糖酶、脲酶的活性的效果最显著,M、G、MN、GN 处理对提高碱性磷酸酶活性的效果最显著;主成分得分进行聚类分析,不同处理培肥土壤质量效果由高到低分成四类,分别为一类高量有机肥 M、G、1/2MG > 二种有机肥与氮肥减量配施 1/2MN、1/3MSN、1/3MGN、1/2GN、1/2MS、1/4MSGN > 三类氮肥、秸秆、秸秆与氮肥 N、1/2SN、S > 四类不施肥(CK);各施肥方式均能提高作物产量,与不施肥(CK)相比,增产幅度为 12.21%～235.4%,肥料贡献率在 10.89%～70.18% 之间,单施肥增产总趋势为 N > G > M > S,减量配施肥增产总趋势为 1/2GN > 1/2MN>1/2MS,施肥方式以有机肥配施 N 对产量贡献最大;经济效益分析表明施 N 或有机肥与 N 配施对于提高净收益作用较大。 【结论】 通过主成分分析与聚类分析、经济效益与产量综合比较,农家肥、绿肥和秸秆长期单施成本高,产量和经济效益低,维持土壤养分和产量需要的用量大。因此,提倡适量有机肥与氮肥配施,达到提高作物产量,增加经济效益,保证土壤肥力可持续发展。      

施用常规磷水平的80%可实现玉米高产、磷素高效利用和土壤磷平衡

【目的】近年来,黑土有效磷含量呈逐年增加趋势。研究田间条件下,黑土的玉米产量及构成因素、磷素的吸收利用和土壤有效磷含量变化对不同施磷水平的响应,为黑土区的磷肥合理施用和地力培育提供理论依据。【方法】在土壤有效磷初始含量较高（30.15 mg/kg）的吉林公主岭黑土区,进行了3年的田间试验,以不施磷肥为对照（P0）,设置当地磷肥用量的80%（P₂O₅ 60 kg/hm2,P60）和当地施肥量（P₂O₅75 kg/hm2,P75）,研究不同施磷水平对玉米产量及产量性状、磷素吸收分配、磷肥利用效率的影响,并分析了土壤表观磷平衡和有效磷含量的变化。【结果】连续三年（2009~2011年）不同施磷水平下,玉米的产量随施磷水平的提高而增加,到第三年施磷处理的玉米产量显著高于不施磷处理,随施肥年限增加,P60与P75处理的增产效应差距缩小。P75处理吸收的磷素高于P60,但分配到籽粒中的磷素比例逐年下降,说明其吸收的磷素未高效转移到籽粒中,存在磷素奢侈吸收现象。两个施磷处理的磷肥利用率均为P75>P60,磷肥偏生产力均为P60>P75,说明P60处理中土壤基础养分和施入磷肥的综合效应更大。2009~2011年,土壤的表观磷平衡,P0处理一直处于亏缺状态,P60和P75处理均有盈余。P0、P60和P75处理的土壤有效磷的变化量为-15.4、-0.19和3.50 mg/kg。有效磷含量变化与表观磷盈余量呈极显著线性正相关,土壤P盈余每增加100 kg/hm2,有效磷含量增加9.6 mg/kg。【结论】在有效磷含量较高的黑土区,适当减少磷肥用量（60 kg/hm2 P₂O₅,比传统施肥减少20%）能获得与传统施磷相当的产量,维持土壤适宜的有效磷含量和供磷水平,并能保证磷肥的高效利用。可以考虑将P₂O₅ 60 kg/hm2作为黑土区的推荐施磷水平。     

Effect of Citrate Concentration on the Extraction Efficiency of Selected Micronutrients from Soil

This study was carried out with the objective of evaluating the effect of citrate concentration on the extraction efficiency of some micronutrients from soil. Composite surface soil samples (0–20 cm) were collected from Eastern Harage Zone (Babile and Haramaya Districts), Wolaita Zone (Damot Sore, Boloso Bombe, Damot Pulasa and Humbo Districts) and Dire Dawa Administrative Council in purposive sampling. The treatments were arranged in completely randomized design (CRD) with three replications. A greenhouse pot experiment with soybean plant was conducted to determine the correlation between soil test methods and the selected micronutrients, such as iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn) in the leaves of the plant. The results showed that, among the different citrate concentrations with strontium chloride (SrCl₂) tested for the determination of available Fe, Mn and Zn, the highest correlation coefficients (r = 0.82, p < 0.05), (r = 0.96, p < 0.001) and (r = 0.98, p < 0.001) were found between the diethylenetriamine pentaacetic acid (DTPA) method and 0.02 M strontium chloride (SrCl₂)-0.025 M citric acid extractant, respectively. Therefore, 0.02 M SrCl₂-0.025 M citric acid extractant is considered to be the most effective for the determination of Fe, Mn and Zn in soils of the studied areas. Similarly, high correlation coefficients (r = 0.97, p < 0.001) were found between DTPA and 0.02 M SrCl₂-0.05 M citric acid and (r = 0.88, p < 0.01) between DTPA and 0.02 M SrCl₂-0.025 M citric acid extractants for the determination of available Cu from soils. Hence, the 0.02 M SrCl₂-0.05 M citric acid extractant was shown to be the best for the determination of Cu in soils of the studied areas. However, considering the use of universal extractant, the 0.02 M SrCl₂-0.025 M citric acid extractant could easily be adopted as a procedure for the determination of Fe, Cu, Mn and Zn for both agricultural and environmental purposes. The greenhouse experiment confirmed the result.     

Mycorrhizal (Rhizophagus Intraradices) Symbiosis and Fe and Zn Availability in Calcareous Soil

Greenhouse experiment was conducted to assess the iron (Fe) and zinc (Zn) fractionation patterns in soils of arbuscular mycorrhizal (AM) fungus-inoculated and uninoculated maize plants fertilized with varying levels of Fe and Zn. Soil samples were collected for Fe and Zn fractions and available Fe, Zn and phosphorus (P) contents besides organic and biomass carbon (BMC), soil enzymes and glomalin. Major portion of Fe and Zn fractionations was found to occur in the residual form. Mycorrhizal symbiosis increased the organically bound forms of Fe and Zn while reducing the crystalline oxide, residual Fe and Zn fractions, indicating the transformation of unavailable forms into available forms. Soil enzymes, viz. dehydrogenase and acid phosphatase activities in M+ soils, were significantly higher than M? soil consistently. Overall, the data suggest that mycorrhizal symbiosis enhanced the availability of Fe and Zn as a result of preferential fractionation and biochemical changes that may alleviate micronutrient deficiencies in calcareous soil.

Abbreviations: AM: arbuscular mycorrhiza; Fe: Iron; Zn: Zinc; P: Phosphorous; Amox-Zn: amorphous oxide bound zinc; Cryox-Zn: crystalline oxide bound zinc; DAS: days after sowing; DTPA: diethylene Triamine Penta Acetic Acid; MnO₂-Zn: manganese oxide bound zinc; OC-Zn: organically bound zinc; WSEX: water soluble plus exchangeable zinc; MnO₂ Fe: manganese oxide bound iron; OC-Fe: Organically bound iron; WSEX Fe: water soluble plus exchangeable iron.     

Effects of Soil Characteristics on Spring-Harvested Switchgrass Biomass Composition

Switchgrass (Panicum virgatum L.) is a promising bioenergy crop for temperate regions. Overwintering has been used to improve biomass quality, resulting in a more efficient combustion, partially due to a reduction in minerals concentration. This study examines the effects of soil composition on overwintered switchgrass composition. Samples were collected in the spring from 58 environments in Southern Quebec to determine possible relationships between soil composition and biomass quality. Principal component analysis and stepwise regressions were used to identify relationships between soil and biomass compositions. Soil parameters monitored explained 74% of the variation in biomass silicon (Si) concentration, 45% of the variation in ash, and 32% of the variation in magnesium (Mg). Soil composition had limited effects on the concentration of other elements in switchgrass biomass. Switchgrass biomass quality is influenced by soil composition and appears well suited to biomass combustion when overwintered and harvested in the spring.     

Minimizing ammonia volatilization from urea,improving lowland rice (cv. MR219) seed germination,plant growth variables,nutrient uptake,and nutrient recovery using clinoptilolite zeolite

The anionic nature and high cation exchange capacity (CEC) of clinoptilolite zeolite can be exploited to reduce ammonia (NH₃) loss from urea and to improve soil chemical properties to increase nutrient utilization efficiency in lowland rice cultivation. A closed-dynamic airflow system was used to determine NH₃ loss from treatments (20, 40, and 60 g clinoptilolite zeolite pot^?1). Seed germination study was conducted to evaluate the effects of clinoptilolite zeolite on rice seed germination. A pot study was conducted to determine the effects of clinoptilolite zeolite on rice plant growth variables, nutrient uptake, nutrient recovery, and soil chemical properties. Standard procedures were used to determine NH₃ loss, rice plant height, number of leaves, number of tillers, dry matter production, nutrient uptake, nutrient recovery, and soil chemical properties. Application of clinoptilolite zeolite (15%) increased shoot elongation of seedlings and significantly reduced NH₃ loss (up to 26% with 60 g zeolite pot^?1), and increased number of leaves, total dry matter, nutrient uptake, nutrient recovery, soil pH, CEC, and exchangeable Na⁺. Amending acid soils with clinoptilolite zeolite can significantly minimize NH₃ loss and improve rice plant growth variables, nutrient uptake, nutrient recovery, and soil chemical properties. These findings are being validated in our ongoing field trials.     

Diversity and abundance of springtails (Hexapoda: Collembola) in soil under 90-year potato monoculture in relation to crop rotation

The monoculture cropping system causes significant changes within the soil ecosystem, which constitutes a habitat for soil-dwelling springtails. Focusing on the response of soil fauna to 90 years of potato cultivation in monoculture the study investigates the abundance and diversity of soil-dwelling springtails, considering changes in the soil environment in relation to five-crop rotation. Another point was the soil quality evaluation using Collembola as bioindicators (QBS-c index). A long-term monoculture experiment was established in Poland in 1923 and has continued uninterruptedly to the present time. Soil samples were taken over a period of three years (2011–2013) to determine collembolan abundance and composition, as well as physical and chemical soil properties.

The study demonstrated that there were greater numbers of Collembola in the long-term monoculture of potatoes, especially before planting time, compared to numbers in a five-field crop rotation. At the same time apparently greater species diversity was found in potato culture within crop rotation. The biological indicator of soil quality based on the occurrence of springtails (QBS-c) has proved useful in assessing changes in soil caused by agrotechnical activities. This index indicated better biological soil quality in the five-field rotation system compared to monoculture.     

Roughness of biopores and cracks in Bt‐horizons assessed by confocal laser scanning microscopy

In structured soils, water and reactive solutes can preferentially move through larger inter‐aggregate pores, cracks, and biopores. The surface roughness of such macropores is crucial for describing microbial habitats and the exchange of water and solutes between macropores and the soil matrix together with other properties. The objective of this study was to compare the roughness of intact structural surfaces from the Bt‐horizons of five Luvisols developed on loess and glacial till and to test the applicability of confocal laser scanning microscopy. Samples of 5 to 10 cm edge length with intact structural surfaces including cracks with and without clay‐organic coatings, earthworm burrow walls, and root channels were prepared manually. The surface roughness of these structures was determined with a confocal laser scanning microscope of the type Keyence VK‐X100K. The root‐mean‐squared roughness (R_q) the curvature (R_cu) and the ratio between surface area and base area (R_A) were calculated from selected surface regions of interest of 0.342 mm² with an elevation resolution of 0.02 µm. The roughness was smaller for coated as compared to uncoated cracks and earthworm burrows of the Bt‐horizons. This reduction of roughness by the illuviation of clayey material was similar for the structural surfaces of the coarser textured till‐Bt and the finer‐textured loess‐Bt. This similarity suggested a dominant effect of pedogenesis and a minor effect of the parent material on the roughness levels of structural surfaces in the Bt‐horizons. An expected “smoothing” effect of burrow wall surfaces by earthworm activity was not reflected in the roughness values compared to those of uncoated cracks at the chosen spatial scale. However, for root channel walls from one loess‐Bt, the roughness was reduced as compared to that of other structures. These results suggest that the surface roughness of the structural surface types should separately be considered when describing preferential flow and macropore‐matrix exchange or analysing root growth, microbial habitats, and colloidal transport in structured soils. The confocal laser scanning microscopy technique was found useful for characterizing the roughness of intact structural surfaces.