有机肥对水稻根际土壤中微生物和酶活性的影响

利用根际箱在红壤上研究了有机肥对水稻根际有效磷、根际微生物和土壤酶活性的影响。试验结果表明,有机肥明显地提高水稻根际和非根际土壤真菌、放线菌和细菌的数量及土壤有效磷的含量。根际土壤各类微生物的数量大于非根际土壤,表现出明显的根际效应。施用有机肥使根际效应增加,其效应为细菌 放线菌 真菌。有机肥还明显地促进水稻根际无机磷溶解菌和有机磷分解数量以及磷酸酶和脲酶的活性,同时对水稻根际土壤磷转化速率有明显的提高,从而加速了土壤养分的转化。     

Improved management of Vertisols in the semiarid tropics for increased productivity and soil carbon sequestration

Abstract. This study was undertaken to test the hypothesis that an improved system of catchment management in combination with appropriate cropping practices can sustain increased crop production and improve soil quality of Vertisols, compared with prevailing traditional farming practices. Initiated in 1976, the improved system consisted of integrated land management to conserve soil and water, with excess rainwater being removed in a controlled manner. This was combined with improved crop rotation (legume based) and integrated nutrient management. In the traditional system, sorghum or chickpea was grown in the post-rainy season with organic fertilizers, and in the rainy season the field was maintained as a cultivated fallow. The average grain yield of the improved system over 24 years was 4.7 t ha⁻¹ yr⁻¹, nearly a five-fold increase over the traditional system (about 1 t ha⁻¹ yr⁻¹). There was also evidence of increased organic C, total N and P, available N, P and K, microbial biomass C and N in the soil of the improved system. A positive relationship between soil available P and soil organic C suggested that application of P to Vertisols increased carbon sequestration by 7.4 t C ha⁻¹ and, in turn, the productivity of the legume-based system, thus ultimately enhancing soil quality.     

Rice-soil interactions in Vietnamese acid sulphate soils: impacts of submergence depth on soil solution chemistry and yields

Abstract. The aim of this study was to investigate the effects of water submergence depth on radial oxygen loss (ROL), soil solution chemistry and rice growth performance in acid sulphate soils in southern Vietnam. ROL was measured in a solution culture. In a separate pot experiment the impact of water submergence depth on rice growth and soil solution chemistry was studied. Three submergence depths were used in the two experiments (5, 10 and 15 cm). ROL declined with submergence depth and was significantly greater in young roots (with no root hairs) than in older roots. In the pot experiment rice growth and soil solution chemistry were clearly affected by the submergence depth. During the first crop at 5 cm submergence, there was a significantly higher yield and a higher oxidation state (pe+pH) compared to 10 or 15 cm submergence. The Fe concentration was significantly greater at the 5 cm depth compared to the 10 or 15 cm depth. SO₄^2– reduction was delayed at the 5 cm depth. Rice yield was c. 25% less at the 15 cm than at the 5 cm depth. During a second crop, there was a substantial SO₄^2- reduction and H₂S formation and almost no significant effects of submergence depth on either soil solution chemistry or crop yield. In a field experiment with a dry-season rice crop, yield and Fe, Al and SO₄^2– concentrations were higher at a shallow submergence depth than at greater depths in the same field, showing similar depth trends to those found during the first crop in the pot experiment. Farmers should be advised to use a shallow submergence depth and, if possible, avoid deep-rooted rice varieties. A conceptual model is suggested, which summarizes the relationships between ROL and soil solution chemistry.     

干湿交替灌溉改善稻田根际氧环境进而促进氮素转化和水稻氮素吸收

[目的]阐明不同水氮管理模式下水稻根际内外氧环境变化特征及其对土壤碳氮转化和水稻氮吸收利用的影响,以期从稻田"根际氧环境"调控角度揭示适宜水氮耦合促进水稻生长和提高氮素利用效率的内在机制.[方法]在长期定位试验基础上,采用根箱模拟培养以及Unisense微电极系统和15N同位素示踪相结合的研究方法,以常规粳稻日本晴和常...     

一株耐盐溶磷真菌的筛选、鉴定及其生物肥料的应用效果

【目的】 从内蒙古种植向日葵的盐碱地中筛选高效溶磷真菌，为农业生产中增产节肥，开发耐盐、溶磷微生物肥料提供菌种资源。 【方法】 利用形态特征和ITS rDNA序列鉴定菌株；LC-MS技术测定菌株M2在液体培养基中分泌有机酸和植物激素含量，明确菌株M2的溶磷和促生机理。采用液体摇床培养试验测定了鉴定菌株的溶磷能力。试验处理包括:在磷酸三钙、磷酸铝和5个磷矿的磷矿粉制备的100 mL难溶磷磷源 (含5 g/L难溶磷) 中，接入1 mL灭菌培养液对照，和分别接种1 mL斜卧青霉菌P83和草酸青霉菌M2共15个处理。置于28℃、160 r/min摇床培养，分别于3、6和9 d，取菌液5 mL，在12000 r/min、4℃离心5 min，取上清液测定有效磷含量。采用含NaCl的固体培养基测定菌株的耐盐性。NaCl含量分别为0%、5%、7.5%、10%和12.5%的PDA平板中接入溶磷菌，置于28℃恒温培养箱中5 d，观察并记录菌丝的生长状况。采用盆栽试验方法检验了菌株的溶磷能力。以玉米种子 (郑单958) 为供试作物，以水稻土、黏性潮土、盐潮土和石灰性潮土为供试土壤，以Ca₃(PO₄)₂、AlPO₄ 和昆阳磷矿粉 (RP) 为供试磷源 (磷源用量为1.0 g/kg土壤)。设置只加入灭菌草炭和Pikovskaya培养液对照，分别接种溶磷菌P83、M2，共计38个处理，144盆。玉米播种40天后收获，测定植株鲜重、干重和玉米根际土壤有效磷含量。田间试验以花生为供试作物，设置只加灭菌草炭和Pikovskaya培养液对照和分别接种ATCC20851、P83、M2溶磷菌剂三个处理。花生生长155 d后收获，称量花生植株鲜重和干重、花生果实鲜重和干重，同时采集花生根部土壤测定有效磷含量。 【结果】 溶磷菌株M2鉴定为草酸青霉 (Penicillium oxalicum)。液体培养基摇床培养6 d后，接种菌株M2，以Ca₃(PO₄)₂为磷源的上清液中有效磷含量达972 mg/L，Ca₃(PO₄)₂溶解率为59.2%；以AlPO₄为磷源的有效磷含量达988 mg/L，溶解率为48.2%；以江苏锦屏、贵州开阳、云南晋宁、河北钒山和云南昆阳磷矿粉为磷源的有效磷释放量达21.0～556 mg/L。菌株M2在7.5%NaCl培养基中正常生长。盆栽试验结果发现，菌株M2对玉米植株促生效果显著，玉米植株鲜重比不接种菌剂 (CK) 提高26.4%～99.2%、干重增加20.0%～262.9%，土壤有效磷提高19.2～25.3 mg/kg。菌株M2与4种土壤的适配性均高于对照菌株P83。田间小区花生产量结果显示，接种溶磷菌剂M2增产效果最好，花生果实产量达4.50 t/hm2，比CK增加0.85 t/hm2，增产23.29%。菌株M2 在含有磷酸三钙、磷酸铝和开阳磷矿粉3种难溶磷培养液中经过6 d培养，均产生7种有机酸，其中草酸和柠檬酸含量最高，分别为653.46 mg/L和269.61 mg/L；培养液中均能检测到吲哚乙酸 (IAA) 和玉米素，IAA含量为32.38～66.17 mg/L，玉米素浓度为0.05～0.07 mg/L。 【结论】 获得了一株耐盐、高效溶解多种难溶磷的草酸青霉菌M2，可显著增加土壤有效磷，促进玉米生长和花生增产，与4种典型土壤适配性好，具有良好的农业应用前景。      

Effects of Inoculation of Phototrophic Purple Bacteria on Grain Yield of Rice and Nitrogenase Activity of Paddy Soil in a Pot Experiment

Phototrophic purple bacteria (PPB) are one group of dinitrogen (N₂)-fixing bacteria often found in the anoxic and photic zone of paddy soil. In the present study, the effects of inoculation of PPB on grain yield of rice and changes in their populations and nitrogenase activity were investigated with and without surface application of rice straw in a pot experiment. As an inoculant, Rhodopseudomonas palustris strain KN122 isolated from a paddy soil was selected, and the cell suspension was inoculated into the floodwater once or three times during the cultivation. As a result, the inoculation of PPB increased the grain yield of rice. Compared to the control, the grain yield was 9% higher in the inoculated plot without rice straw application. The treatment was more effective in combination with rice straw application. In the plots where PPB were inoculated with rice straw, grain yields were 21% (single inoculation) and 29% (triple inoculation) higher. Populations of PPB in the plots without rice straw application significantly increased by the inoculation, unlike those in the plots with rice straw application, except for the bulk soil. Phototrophic and heterotrophic nitrogenase activities (acetylene-reducing activity) associated with the soils or residues of the rice straw were not affected by PPB inoculation throughout the experiment. This indicates that the inoculation of PPB into floodwater may not be effective for enhancing N₂ fixation in paddy soils and that the beneficial effect of PPB inoculation on the grain yield of rice may be due to unidentified functions of PPB other than biological N₂ fixation.     

Simple phosphorus saturation index to estimate risk of dissolved P in runoff from arable soils

Abstract. There is increasing evidence that phosphorus has been accumulating in the surface horizons of agricultural soils to the extent that some soils represent a potential diffuse source of pollution to surface waters. The relationships between equilibrium phosphorus concentration at zero sorption (EPC ₀) of soil and a number of soil physicochemical variables were investigated in the surface layers of arable and grassland agricultural soils sampled from the Thame catchment, England. Soil EPC₀ could be predicted from an equation including soil test (Olsen) P, soil phosphate sorption index (PSI) and organic matter content (OM) (R²=0.88; P <0.001) across a range of soil types and land use. The simple index Olsen P/PSI was found to be a good predictor of EPC₀ (R²=0.77; P <0.001) and readily desorbable (0.02 m KCl extractable) P (R²=0.73; P <0.001) across a range of soil types under arable having soil organic matter contents of <10%.     

The phosphorus requirement of Amaranthus mangostanus L. exceeds the 'change point' of P loss

Due to the high economic value of vegetables, farmers in China often apply more fertilizer than is required for plant growth. This leads to phosphorus accumulation in soils, which can pollute the aquatic environment. This conflict arises because vegetables often use nutrients inefficiently, and require high phosphorus levels in the growth medium. In this study, amaranth ( Amaranthus mangostanus L.) was grown in soils with 14.7, 23.8, 45.3, 54.6, 74.2, 101 or 116 mg Olsen-P/kg, and with and without phosphorus fertilizer (175 mg P/kg or equivalent to 385 kg P/ha). The yield of amaranth was positively correlated with soil Olsen-P content. CaCl₂-P content was positively correlated with Olsen-P content and CaCl₂-P markedly increased at Olsen-P contents exceeding 53.8 mg P/kg in the pot experiment or 55.9 mg P/kg in the field survey. These values were regarded as the 'change points' for phosphorus loss; to achieve 85 or 95% of maximum amaranth yield, the amaranth crop required 91or 101 mg Olsen-P/kg soil, respectively, and application of 175 mg P/kg was still able to significantly increase amaranth yield at an Olsen-P level of 74.2 mg P/kg soil. These results indicated that the phosphorus requirement of amaranth exceeded the 'change point' (53.8 or 55.9 mg Olsen-P/kg); the C _min (minimum concentration in the media at which no net influx occurs) of phosphorus for 3-week-old amaranth was 1.55 μ m . This value is much higher than that reported for other crops, and may explain the inefficient P use of amaranth. The high C _min value also indicates that the phosphorus requirement of amaranth is beyond the 'change point' of P loss.     

Role of soil redox in growth and fertilizer nitrogen uptake by rice in Thailand paddy soils

Abstract. In a laboratory study, ¹⁵N ammonium fertilizer uptake and rice growth was determined in a non-acid sulphate marine soil (Typic Tropaquept) and an acid sulphate soil (Sulfic Tropaquept). Acid sulphate sensitive (IR 26) and acid sulphate tolerant (IR 46) rice varieties were grown in soil suspensions incubated at four Eh levels (+500, +250, +50, and -150 mV) in microcosms for three weeks. The results showed that rice grown in non-acid sulphate marine soils gave slightly better dry matter weight of 1.8g/pot, greater ¹⁵N uptake of 12.8 mg N/pot, and higher total N uptake of 38.4 mg N/pot than under acid sulphate soil conditions indicating the non-acid marine soil is more favourable to rice culture. Growth as measured by weight of dry matter was significantly reduced from 2.1g/pot under oxidized condition (+500 mV) to 0.8g/pot under highly reduced condition (-150 mV). N uptake by rice was significantly reduced from 16.9 mg/pot at + 500 mV to 4.5 mg N/pot at -150 mV Total N uptake also decreased with decreasing Eh. Growth, ¹⁵N uptake and total N uptake by acid sulphate tolerant rice, IR 46 were significantly higher than the acid sulphate sensitive rice variety, IR 26. Under highly reduced soil conditions (-150 mV), growing rice in acid sulphate soil would require additions of lime, intermittent irrigation and/or mid season drainage in order to increase soil redox potential and remove toxic substances.     

Liquid organic fertilizer sprayed on shoots of Phaseolus vulgaris stimulates arbuscular mycorrhiza colonization and phosphate solubilizing microorganisms in soil

Processed organic agricultural byproducts such as liquid organic fertilizer (LOF) are promising alternatives that can improve crop productivity while reducing mineral fertilizer use and improving sustainability. The effects on beneficial soil organisms, such as arbuscular mycorrhizal (AM) fungi and phosphate solubilizing microorganisms (PSM), caused by LOF spraying on shoots is poorly understood. Therefore, we evaluated how AM colonization and soil PSM are affected by LOF spraying on common beans (Phaseolus vulgaris L.) grown in a greenhouse. The LOF was obtained by anaerobically fermenting a mixture of fresh water, cattle manure, bovine milk, sugarcane molasses and mineral salts. LOF was applied twice on the plant shoots. Fresh and dry mass of root and shoot, P content, P accumulation in the shoots and AMF spore counts in the soil were not LOF dose dependent. However, we found that a 5% LOF application stimulated AM colonization and led to dose-dependence for calcium and aluminium phosphate solubilizing bacteria and fungi. These results show that LOF sprayed on shoots causes responses on soil communities. We therefore endorse the use of LOF in low input agriculture.     

烤烟根际土壤微生物对根系酚酸类物质的响应

【目的】烟草连作导致化感物质累积,探索化感物质中主要的酚酸类物质对根际土壤微生物的影响,可为克服烟草连作障碍提供理论依据。【方法】采用盆栽试验方法,将前期分离、鉴定出的烟草根系分泌物中主要酚酸类物质苯甲酸和3-苯丙酸接种到土壤中,模拟烟草多年连作土壤。试验设4个处理:对照(T0),向土壤中加入等量灭菌去离子水;添加苯甲酸3μg/kg土(T1);3-苯丙酸8μg/kg土(T2);同时添加苯甲酸3μg/kg土和3-苯丙酸8μg/kg土(T3),每处理5次重复。以MiSeq测序平台对根际土壤微生物进行高通量测序,探索其对根际土壤微生物的影响,同时采用荧光定量PCR法检测土壤中的茄科劳尔氏菌、短短芽孢杆菌、固氮菌、无机磷细菌、硅酸盐细菌等功能微生物及细菌和真菌的数量变化。【结果】T 1、 T 2处理土壤细菌OTUs(Operational Taxonomic Units)数目分别比对照T0降低了21.5%和17.0%,T3处理OTU数量低于T1和T2处理;T2处理土壤中优势微生物种群增多,结构平衡性降低,门上分类构成和微生物群落构成显著不同于对照。主成分分析与聚类分析显示,T2或T3处理土壤微生物聚类关系较近,都与T0处理较远;T3处理土壤中病原菌数量显著提高,拮抗菌、固氮菌、无机磷细菌、硅酸盐细菌、细菌和真菌数量显著减少,且减少幅度大于T1、T2处理。【结论】根系分泌物中主要酚酸类物质苯甲酸和3-苯丙酸均能明显改变根际土壤微生物区系,降低土壤微生群落多样性,显著增加有害微生物数量的同时大大降低有益微生物数量。两种酚类同时存在的危害效果远大于单一酚类。     

Mediterranean natural forest living at elevated carbon dioxide: soil biological properties and plant biomass growth

Abstract. Biomass productivity and soil microbial responses to long-term CO₂ enrichment have been investigated in a Mediterranean natural forest ecosystem. Several biochemical parameters have been measured on soil samples taken from six open top chambers (OTCs), enclosing clumps of natural Mediterranean woody vegetation including: Quercus ilex L., Phillyrea angustifolia L., Pistacia lentiscus L. and Myrtus communis L. The CO₂ concentration of the air inside the OTCs was either ambient or ambient plus 350 μmol mol^–1 ( c . 710 ppm as mean daily value). Microbial C biomass, microbial respiration, dehydrogenase, β-glucosidase, acid phosphatase and protease activities, inorganic N and soluble P, were tested in order to evaluate soil microbial size and activity. Statistically correlated seasonal patterns have been identified in some biochemical parameters in response to climatic conditions, soil nutritional status and the physiology of the vegetative cover. In situ soil respiration and above- and below-ground productivity were also measured. Microbial responses to CO₂ enrichment were observed only at the beginning of the study and a general progressive reduction of the CO₂ effect was recorded as monitoring continued. These results are in agreement with data from literature regarding similar studies on natural complex communities.     

The effect of soil texture on the dissolution of North Carolina phosphate rock

Laboratory investigations of the dissolution of North Carolina phosphate rock (PR) in soil, as affected by soil texture, were conducted using soils created by mixing various proportions of the <45 μm and >45 μm fractions of a lateritic soil. The dissolution of PR in soil, and the resulting changes in plant available P, were estimated by measuring increases in exchangeable Ca (ΔCa) and NaHCO₃-extractable P (ΔP_b), respectively. The total fertilizer phosphate dissolved (ΔP) was calculated from δCa values based on the assumption that dissolution of PR released amounts of Ca and P in a constant ratio determined by the stoichiometry of the PR. δP increased with increasing content of <45 μm particles. AP_b also increased with the percentage of <45μ fraction, with about 20% of AP being recovered as AP_b. A smaller proportion of dissolved P was soluble in NaHCO₃ for the soil comprising only the <45μ particles. The increase in δP with increased percentage of <45 μn soil was probably due inter alia to the greater P-sorption, Ca-sorption and the pH buffering capacity of the fine grained soil constituents.     

Effect of organic manure on the biological activities associated with insoluble phosphorus release in a blue purple paddy soil

Abstract

This study examined the effects of organic manure and chemical fertilizer on soil microflora, soil respiration, number of inorganic phosphate solubilizing bacteria, and organic phosphorus (P) mineralizing bacteria. The inorganic phosphate solubilizing rate, organic P mineralizing rate, and selected enzyme activities in a blue purple paddy soil were also studied. The results showed that organic manure significantly increased the total number of fungi, actinomyces, bacteria, P solubilizing bacteria, organic P mineralizing bacteria, P solubilizing rate and organic P mineralizing rate, soil respiration rate, and selected enzyme activities, whereas chemical fertilizer resulted in a smaller effect, and bacteria were affected more than fungi and actinomyces by organic manure. The enhancement of biological activities caused by organic manure might be due to the introduction of a large amount of living microorganisms and readily‐utilizable carbon source on which microorganisms live. This study showed that the augment of inorganic phosphate solubilizing bacteria and organic P mineralizing bacteria was one of the reasons that organic manure increased the avilability of P in a blue purple paddy soil.     

Soil respiration and carbon inputs from crops in a wheat—soyabean rotation under different tillage systems

Abstract. The production of CO₂ in the field and the contribution of carbon from crops to the soil were evaluated for the double crop wheat-soyabean rotation on a typical soil of the Rolling Pampa to assess the effects of two tillage systems, mouldboard ploughing and shallow discing, on the soil carbon balance. Microbial biomass and respiration under controlled conditions were also determined.
No differences in soil microbial biomass contents were detected between tillage systems after two years, but the biological activity of incubated soils and the mineralized fraction of organic carbon were greater ( P = 0.05) at the 0–5 cm depth in disc tillage. This suggested an increase in the labile fraction of organic matter in that layer, though the total carbon content of the soil did not vary significantly.
Soil moisture was not a limiting factor at any time of the year and production of CO₂ in the field was regulated by temperature ( r > 0.89, P = 0.01). There were no differences between tillage systems in the emission of CO₂ to the atmosphere, which was estimated at 11.6 t C/ha/yr. The contribution in dry matter from the crops ranged from 15.3 to 17.0 t/ha/yr, and the carbon input was approximately 7.0 t/ha/yr. Consequently, the soil lost carbon with the wheat—soyabean rotation but tillage systems did not affect carbon inputs and losses from the agrosystem.     

Changes in the N Recovery Process from 15N-Labeled Swine Manure Compost and Rice Bran in Direct-Seeded Rice by Simultaneous Application of Cattle Manure Compost

The N recovery from ¹⁵N-labeled swine manure compost and rice bran with or without simultaneous application of unlabeled cattle manure compost was examined in a paddy field with direct-seeded rice during a 1-year period (1 crop season). In all the ¹⁵N-labeled materials including (¹⁵NH₄)₂SO₄, the processes of N recovery from the ¹⁵N materials by rice plants were different between the plots with and without application of cattle manure compost. At the tillering stage, the N recovery rates from the ¹⁵N materials in the plots with application of cattle manure compost were significantly lower than those in the plots without application of cattle manure compost. These recovery rates, however, became close and no significant differences were observed at the maturity stage. Thus, simultaneous application of cattle manure compost could impede the N recovery from swine manure compost, rice bran as well as (NH₄)₂SO₄.     

Recovery of 15N-labelled fertilizer in crops, drainage water and soil using monolith lysimeters in south-east Nigeria

Labelled urea was applied to monolith lysimeters in the 1st year of a 2-year experiment at Onne in south-east Nigeria. On eight lysimeters maize and rice were grown in each of the 2 years. Four lysimeters were similarly cropped in the 2nd year after being uncropped in the 1st year. Measurements were made over the 2-year period of labelled and unlabelled mineral nitrogen in the drainage water, and labelled and unlabelled nitrogen in the crops. At the end of the experiment, weeds and the soil were also analysed for labelled and unlabelled nitrogen.
The total recovery of ¹⁵N in crop, soil and leachate varied between 70 and 93%. It was lowest when applied to the second season rice crop, which recovered only 15%, and highest when it was leached in the 1st year or was taken up by the maize crop. The highest crop uptake was 31%. The results indicate that, depending on the treatment, between 10 and 30% of the ¹⁵N was immobilized in the soil, lysimeters cropped in the 1st year lost between 22 and 29% of the ¹⁵N in drainage water, and between 7 and 30% was lost by denitrification. The accuracy of these figures is discussed.     

紫云英与稻秸还田对稻田土壤硝化潜势的影响

  【目的】  种植利用绿肥和稻秸还田是水稻土培肥的重要措施。硝化作用是氮循环中的关键过程,我们研究了绿肥与稻秸还田对土壤硝化作用的影响,以明确紫云英–稻秸联合还田下的稻田硝化作用机制。  【方法】  水稻盆栽试验共设8个处理,分别为:对照(CK)、单独紫云英(MV)、单独稻秸(RS)、紫云英+稻秸(MV+RS)、单施氮肥(N)、紫云英+氮肥(MV+N)、稻秸+氮肥(RS+N)、紫云英+稻秸+氮肥(MV+RS+N)。研究了在不施氮和施氮条件下,紫云英、稻秸不同利用方式对土壤性状及硝化作用的影响,并通过特异性细菌抑制剂(卡那霉素和大观霉素)研究了氨氧化细菌(AOB)和氨氧化古菌(AOA)对硝化作用的相对贡献。  【结果】  MV+RS+N处理提高了土壤全氮和有机质含量,降低了碱性水稻土的pH。在早稻分蘖期,MV+RS+N处理显著提高了土壤中铵态氮和硝态氮含量。早稻移栽前,MV+RS 处理显著增加了土壤硝化潜势(NP), 而MV处理相较CK降低了NP。早稻分蘖期,氮肥添加显著提高了NP。早稻拔节期和晚稻收获期,RS和MV+RS处理均降低了NP。早稻移栽前,MV+RS处理同时降低了土壤恢复硝化强度(RNP),以及AOA和AOB在恢复硝化强度中的贡献(RNP_AOA和RNP_AOB),并降低了RNP_AOB在RNP中的占比。早稻分蘖期,CK和N处理,MV+N处理提高了RNP_AOB,而在早稻拔节期,MV+RS+N处理相比MV+RS处理提高了土壤RNP及RNP_AOB。早稻收获期,MV、RS及MV+RS处理均降低了稻田土壤RNP。在不同生育期中,早稻分蘖期的NP与硝态氮含量显著正相关,其他时期相关不显著。土壤NP与土壤 pH 和硝态氮含量呈显著正相关,与土壤微生物量碳 (SMBC) 和土壤微生物量氮 (SMBN) 含量呈显著负相关。RNP_AOA与土壤pH和铵态氮含量呈显著正相关。  【结论】  紫云英–稻秸联合还田降低了碱性水稻土pH,并在水稻生育早期显著提高而在生育后期显著降低了土壤硝化潜势。硝化潜势与土壤pH和硝态氮含量呈显著正相关。早稻分蘖期和早稻拔节期以RNP_AOB占主导,紫云英–稻秸联合利用较CK降低了RNP_AOB;早稻和晚稻收获期则以RNP_AOA占主导,紫云英–稻秸联合还田相较于单独还田提高了RNP_AOA。     

田间陈化生物质炭提高稻田土壤团聚体稳定性和磷素利用率

  【目的】  生物质炭因其巨大的比表面积和稳定的结构而被用作土壤改良剂。然而关于田间陈化生物质炭对土壤肥力和养分利用效率影响的研究相对缺乏。通过定位试验，分析田间不同陈化年限的生物质炭对水稻产量和养分利用效率的影响。  【方法】  田间定位试验设在江苏南京，供试土壤为粘质水稻土。共设置5个处理，分别是不施磷肥对照 (CK)、施用磷肥 (P) 及磷肥配施新鲜生物质炭 (PB_0y，2017年施入)、2年陈化生物质炭 (PB_2y，2015年施入) 和5年陈化生物质炭 (PB_5y，2012年施入)。在水稻收获后采集土壤样品进行团聚体分级，测定大团聚体 (250～2000 μm)、微团聚体 (53～250 μm)、粉粒 (2～53 μm)、粘粒 (< 2 μm) 含量以有效磷含量和基本理化性质，同时测定水稻产量和磷素利用效率。  【结果】  与P处理相比，PB_2y和PB_5y处理显著提高250～2000 μm大团聚体的比例 (69.2%～107.8%) ，降低2～53 μm粉粒 (13.1%～14.7%) 和 < 2 μm粘粒 (6.9%～41.9%) 的比例，而PB_0y与P处理相比各粒级比例均无显著差异；PB_0y、PB_2y和PB_5y处理土壤有机碳 (SOC) 提高了18.5%～58.5%，全磷含量提高了5.7%～17.1%，但2～53 μm粒级SOC含量无显著差异。与P处理相比，PB_0y处理对水稻产量和磷素利用效率影响不显著，PB_2y和PB_5y处理均可显著提高水稻产量 (13.7%和16.3%) 和磷素利用率 (35.4%和45.5%)。由结构方程模型可知，陈化生物质炭 (PB_2y和PB_5y) 通过改善土壤养分状况 (SOC、全磷含量、碳磷比等) 和土壤结构 (250～2000 μm大团聚体比例增加)，保证了水稻产量和磷储量。  【结论】  与新鲜生物质炭相比，陈化生物质炭可有效增加250～2000 μm大团聚体比例以及土壤有效磷和全磷的保护，从而促进植物对磷的吸收利用，达到增加产量和磷素利用效率的目的。5年陈化生物质炭的改良效果好于2年陈化生物质炭。     

Effects of ridging on crop performance and symbiotic N2 fixation of fababean (Vicia faba L.)

Abstract. The success of organic cropping systems depends on symbiotic N₂ fixation by leguminous crops, and it is important to explore new management systems to improve the nitrogen input through N₂ fixation. During two growing seasons the possible advantage of growing fababean ( Vicia faba L.) in ridges was studied in comparison to the traditional method on flat soil. Differences in soil physical parameters resulted in a significantly greater microbial activity and a deeper root system at the flowering stage when grown in the ridge than on the flat. Consequently, the amount of fixed N at flowering was significantly greater in ridges than in flat soil. However, during the period from flowering until harvest, when the major part of the N uptake and N₂ fixation took place, the differences between the treatments disappeared. Average values for the growing season of fluorescein diacetate hydrolysis, arylamidase activity and arylsulphatase activity were significantly greater in the ridge than on the flat, and the microbial biomass-C, derived from substrate induced respiration (SIR), was on average 232 and 223 μg C g⁻¹ soil in the ridge and on the flat, respectively. Measured total-N uptake, including root N (0–30 cm depth), ranged from 206 to 247 kg N ha⁻¹, of which 182–201 kg N ha⁻¹ was fixed N. From 154 to 173 kg N ha⁻¹ was removed in grain resulting in a soil-N balance of +28 kg N ha⁻¹ in both years. However, by including estimates of total root N and rhizodeposition-N the soil-N balance ranged from +52 to +62 kg N ha⁻¹.