Continuous Fertilization Research Articles

Assessment of sulphur demand of crops under permanent fertilization experiment

The aim of the study was to determine plant needs with regard to sulphur fertilization based on the assessments of sulphur in the soil profile carried out in the early spring. The study was founded on the continuous fertilization experiment established in 1985 at the Experimental Station of the Faculty of Agriculture and Biology, Warsaw University of Life Sciences-SGGW, which is located in Skierniewice. Soil samples were collected in the years 2009–2011 in the early spring (February/March) at low soil temperatures. The samples were taken at three soil depths: 0–30, 30–60, 60–90 cm. The content of sulfate sulphur was assessed in fresh soil samples after extraction in 0.01 mol/L CaCl<sub>2</sub>. The plants cultivated during the study were spring barley and yellow lupine. The amount of sulphur in soil profile was too small and not sufficient to fulfill yellow lupine nutritional needs, thus could be a limiting factor for successful yield production. Regardless the fertilizer treatment, the amount of sulfate sulphur found in 0–60 cm soil layer fully covered nutritional needs of spring barley.

Soil CO2 and N2O Emissions in Maize Growing Season Under Different Fertilizer Regimes in an Upland Red Soil Region of South China

Upland red soils have been identified as major CO2 and N2O sources induced by human activities such as fertilization. To monitor characteristics of soil surface CO2 and N2O fluxes in cropland ecosystems after continuous fertilizer applications over decades and to separate the respective contributions of root and heterotrophic respiration to the total soil CO2 and N2O fluxes, the measurements of soil surface CO2 and N2O fluxes throughout the maize growing season in 2009 were carried out based on a fertilization experiment (from 1990) through of the maize (Zea mays L.) growing season in red soil in southern China. Five fertilization treatments were chosen from the experiment for study: zero-fertilizer application (CK), nitrogen-phosphorus-potassium (NPK) fertilizer application only, pig manure (M), NPK plus pig manure (NPKM) and NPK with straw (NPKS). Six chambers were installed in each plot. Three of them are in the inter-row soil (NR) and the others are in the soil within the row (R). Each fertilizer treatment received the same amount of N (300 kg ha−1 yr−1). Results showed that cumulative soil CO2 fluxes in NR or R were both following the order: NPKS>M, NPKM>NPK>CK. The contributions of root respiration to soil CO2 fluxes was 40, 44, 50, 47 and 35% in CK, NPK, NPKM, M and NPKS treatments, respectively, with the mean value of 43%. Cumulative soil N2O fluxes in NR or R were both following the order: NPKS, NPKM>M>NPK>CK, and soil N2O fluxes in R were 18, 20 and 30% higher than that in NR in NPKM, M and NPKS treatments, respectively, but with no difference between NR and R in NPK treatment. Furthermore, combine with soil temperature at −5 cm depth and soil moisture (0–20 cm) together could explain 55–70% and 42–59% of soil CO2 and N2O emissions with root interference and 62–78% and 44–63% of that without root interference, respectively. In addition, soil CO2 and N2O fluxes per unit yield in NPKM (0.55 and 0.10 kg C t−1) and M (0.65 and 0.13 g N t−1) treatments were lower than those in other treatments. Therefore, manure application could be a preferred fertilization strategy in red soils in South China.

The influence of winter wheat continuous cropping and fertilization on the crop yields and microbial soil diversity

The possibilities of the elimination of continuous cropping negative implications on the grain yield and microbial soil diversity were investigated. A stationary field experiment was established on Luvi-Haplic Chernozem. Statistically higher grain yield was found in the variant with mineral fertilization and straw and organic fertiliser Veget® incorporation (5.58 t.ha−1) compared with the variant with mineral fertilization only (4.87 t.ha−1) and with the variant with mineral fertilization and straw incorporation (4.90 t.ha−1). Statistically higher straw yield was found in the variant with mineral fertilization and straw and organic fertiliser Veget® incorporation (6.21 t.ha−1) compared with the variant with mineral fertilization only (4.41 t.ha−1). By cultivar Ebi, the grain yield was significantly higher in comparison to the cultivar Petrana. The lowest metabolic diversity of microbial communities and their respiration activity was found out in the variant with mineral fertilizer. On the other hand, the increase of functional diversity of microorganisms, their respiration activity and the number of cultivable bacteria was found in the variant with mineral fertilization and straw incorporation as well as in the variant with mineral fertilization and straw and organic fertiliser Veget® incorporation.

Effects of fertilization on the relations of diameter at breast height between different-aged ramets of Phyllostachys edulis population

Aims Clonal plants are physiologically integrated, allowing translocation of photosynthates, water, nutrients and other substances between connected ramets within a clone. This suggests that the sizes of ramets of different ages may be correlated. So far, however, little is known about the effects of fertilization on the size relationships between ramets of different ages. In this study, we aim to examine how fertilization affects the relations of diameter at breast height(DBH) between ramets of different ages in the giant clonal bamboo Phyllostachys edulis. Methods We established 112 20 m × 30 m plots of P. edulis in Longquan City, Zhejiang Province, China. Among them, 46 plots were fertilized only in 2008, 49 fertilized in five consecutive years from 2004 to 2008, and 17 unfertilized(the control). We measured DBH of ramets of one, three and five years old in each plot in 2009. The relations of DBH between ramets of different ages in different fertilization treatments were examined using allometric scaling by the standardized major axis(SMA) analysis, and that were also analyzed by multiple linear regression. Important findings The DBH of the 1-year-old ramets was significantly greater than that of the 5-year-old ones in the 5-year fertilization plots, while no significant difference was found in the 1-year fertilization plots. Under different fertilization treatments, the slopes of SMA(0.88–1.10) for the relations of DBH between ramets of one, three and five years old were not significantly different from 1.00(p 0.05), suggesting isomeric growth relationships. Compared to the control(unfertilization), fertilization in one or five years did not change the slope of SMA. However, fertilization in five years increased the intercept of SMA, indicating that continuous fertilization could result in greater DBH increment in the 1-year-old ramets. The multiple linear stepwise regression analysis indicated that 3-year-old ramets could greatly influence DBH of the newly produced ramets, and that the effect of DBH of the 5-year-old ramets on that of the 1-year-old ramets increased after five years of continuous fertilization.

Influence of Long-Term Fertilizer Treatments on the Fluorescence Spectroscopic Characterization of DOM Leached by Acid Rain From Red Soil

Dissolved organic matter (DOM) is the most reactive fraction of the soil organic matter pool; that is, its structural characteristics affect its biodegradation and flux. Acid rain has deleterious effects on terrestrial ecosystems, including soil and surface water acidification, which also changes the composition of leaching DOM. In this work, we used three-dimensional excitation/emission matrix spectroscopy and gel permeation chromatography to investigate the fluorescence characteristics and molecular weight distribution of DOM leached by simulated acid rain (SAR) from red soil. Samples were taken from red soil under 22 years of five continuous fertilization treatments: chemical fertilizer (NPK), NPK plus organic manure (NPKM), organic manure (M), without fertilizers (CK), and fallow (F). Results from the fluorescence regional integration analysis showed that humic acid–like substances (Region V) in the NPKM, M, and F treatments were greater than those in the CK and NPK treatments at SAR pH 3.5 and 2.5, but the tryptophan-like compounds (Region II) in the NPKM, M, and F treatments were less than those in the CK and NPK treatments. The results of excitation/emission matrix–fluorescence regional integration and gel permeation chromatography analysis showed that the leaching DOM from NPKM, M, and F treatments was relatively stable and had a higher molecular weight than that from NPK and CK treatments at SAR pH 3.5 and 2.5. Results suggest that the structure and composition of the leaching DOM not only depend on the acid rain pH but also on the fertilizer treatments in soil.

How do environmental factors and different fertilizer strategies affect soil CO2 emission and carbon sequestration in the upland soils of southern China?

Upland soils have been identified as a major CO2 source induced by human activities, such as fertilizer applications. The aim of this study is to identify the characteristics of soil CO2 emission and carbon balance in cropland ecosystems after continuous fertilizer applications over decades. The measurements of soil surface CO2 fluxes throughout the years of 2009 and 2010 were carried out based on a fertilization experiment (from 1990) in a double cropping system rotated with winter wheat (Triticum aestivum L.) and maize (Zea mays L.) in upland soil in southern China. Four treatments were chosen from the experiment for this study: no-fertilizer application (SR), nitrogen–phosphorus–potassium chemical fertilizers (NPK), NPK plus pig manure (NPKM) and pig manure alone (M). Results showed that the mean value of soil CO2 fluxes from 08:00 to 10:00 am could represent its daily mean value in summer period (June–August) and that from 09:00 am to 12:00 pm for the rest season of a year. Soil temperature and moisture combined together could explain 70–83% of variations of CO2 emission. Annual cumulative soil CO2 fluxes in the treatments with manure applications (8.2±0.8 and 11.0±1.2tCha−1 in 2009, and 7.9±0.9 and 11.1±1.2tCha−1 in 2010 in NPKM and M, respectively) were significantly higher than those in the treatments with non-manure addition (2.5±0.2 and 3.4±0.2tCha−1 in 2009, and 2.1±0.2 and 3.7±0.3tCha−1 in 2010 in SR and NPK, respectively). However, the treatments with manure applications represented a carbon sink in the soil (carbon output/input ratio<1.0), which demonstrated potential for carbon sequestration.

Cumulative effects of a 17‐year chemical fertilization on the soil quality of cropping system in the Loess Hilly Region, China

AbstractSoil‐quality assessment provides a tool for evaluating the sustainability of alternative soil‐management practices. Understanding the effects of the long‐term use of chemical fertilizers on soil quality is essential for sustaining soil productivity. The cumulative effect of a 17‐y‐old chemical‐fertilizer application on integrated soil quality was investigated in the surface (0–15 cm) and subsurface (15–30 cm) soils of a soy–broomcorn–millet cropping system with an experiment design of two factors with three levels for each factor. The treatments were N0P0, N0P1, N0P2, N1P0, N1P1 (local farmer' fertilization strategy), N1P2, N2P0, N2P1, N2P2, and a control NF. The objectives were to describe and quantify the effect of continuous applications of chemical fertilizer through soil‐quality index (SQI) and attempt to offer an efficient and appropriate nutrient‐supply strategy for the local region. Following 17 y of chemical fertilization, the SQI increased markedly in the studied soil layers, and soil chemical indicators changed more significantly than physical properties. The soil‐quality indicators in the surface soil layer were more variable and sensitive to fertilizer application than the subsurface layer. The indicators that sensitively responded to long‐term fertilization could be classified into three types: soil‐fertility indicators (soil organic matter [SOM], total P, and available N), soil‐texture indicators (clay, silt), and soil‐structure indicators (bulk density, mean weight diameter [MWD]). The simplified indicators (SOM, sand, available N, bulk density, and total P in the surface soil and SOM, MWD, and silt content in the subsurface soil) preferably reflected the status of the integrated soil quality as influenced by continuous fertilization. Among the fertilized treatments, the combined‐fertilizer treatments maintained a higher SQI than the single‐fertilizer treatments in the surface and subsurface soils. The N1P2 treatment maintained the highest SQI in both soil layers, followed by N1P1 treatment. However, for the slope cropland, given the relative costs, soil resource, and environmental protection, the traditional treatment of N1P1 may be the optimal fertilizer treatment in the local region.

Water-dispersible clay in bare fallow soils after 80 years of continuous fertilizer addition

The 42 plots of the Versailles long-term bare fallow experiment offer exceptional opportunities to study the impacts of fertilizers and amendments on soil physical properties. In this experiment, continuous annual applications since 1928 of 16 different treatments – including nitrates, phosphates, manure, ammonium, calcium, and potassium salts – have led to strongly diverging physical and chemical properties in the soil's surface layer. In this work, the proportion of water dispersible clay (WDC), which is considered a good indicator of soil structural stability and sensitivity to crusting and erosion, was determined in all plots of the experiment. The results showed the influence of the valence of cations and pH on soil structure and clay dispersability. Application of sodium or potassium salts deteriorated the degree of soil aggregation, with increased bulk density and WDC values, whereas amendment with manure or calcium salts ameliorated soil aggregation, with decreasing bulk density and WDC. The strong acidification of the soils receiving ammonium-based fertilizers was another factor related to the increase of water dispersible clay, and therefore the deterioration of soil structure. This study emphasizes the role of potassium and ammonium, associated with fertilizer additions, on the deterioration of soil structure and on the increase of the risk of erosion.

Assessment of phosphorus fertilizer practices in altered wetland soils using uncertainty analysis

AbstractIntensive P fertilizer application is widely practised in East Mediterranean altered wetland soils, even when results from the Olsen‐P extract indicate sufficiency (&gt;10 mg P/kg). To reduce or even eliminate this practice we conducted a large field study to test the feasibility of a major reduction in the use of P fertilizers. A total of 90 sample sites were evenly spaced with respect to their parent material (deep peat, shallow peat, marl). Soils were analysed for Olsen‐P, bulk density, pH, electrical conductivity, and nitrate, chloride and sulphate in saturated paste extracts. We determined variograms and estimated the spatial structure of Olsen‐P data by ordinary kriging. We then used a sequential Gaussian model to produce 100 alternative simulations to measure the joint spatial uncertainty of P concentrations in the study area (ca. 1500 ha). Finally, we post‐processed the simulation results to compute the probability of exceeding the threshold Olsen‐P value of 10 mg/kg. The simulation results indicate a high probability of exceeding the 10 mg/kg threshold in most peat soils supporting an earlier recommendation to reduce or even eliminate P fertilizer application in these fields. On the other hand, a very low probability of exceeding this threshold was observed in most marl soils justifying continued fertilizer application. However, the added P is likely to affect adjacent waterways and increase potential downstream eutrophication due to high conductance and flow continuity between the marl soils and adjacent waterways.

Calcium Induces Long-Term Legacy Effects in a Subalpine Ecosystem

Human activities have transformed a significant proportion of the world’s land surface, with profound effects on ecosystem processes. Soil applications of macronutrients such as nitrate, phosphorus, potassium or calcium are routinely used in the management of croplands, grasslands and forests to improve plant health or increase productivity. However, while the effects of continuous fertilization and liming on terrestrial ecosystems are well documented, remarkably little is known about the legacy effect of historical fertilization and liming events in terrestrial ecosystems and of the mechanisms involved. Here, we show that more than 70 years after the last application of lime on a subalpine grassland, all major soil and plant calcium pools were still significantly larger in limed than in unlimed plots, and that the resulting shift in the soil calcium/aluminium ratio continues to affect ecosystem services such as primary production. The difference in the calcium content of the vegetation and the topmost 10 cm of the soil in limed vs. unlimed plots amounts to approximately 19.5 g m−2, equivalent to 16.3% of the amount that was added to the plots some 70 years ago. In contrast, plots that were treated with nitrogen-phosphorus-potassium fertilizer in the 1930s did not differ from unfertilized plots in any of the soil and vegetation characteristics measured. Our findings suggest that the long-term legacy effect of historical liming is due to long-term storage of added calcium in stable soil pools, rather than a general increase in nutrient availability. Our results demonstrate that single applications of calcium in its carbonated form can profoundly and persistently alter ecosystem processes and services in mountain ecosystems.

Arbuscular mycorrhizal fungal diversity, external mycelium length, and glomalin-related soil protein content in response to long-term fertilizer management

Arbuscular mycorrhizal (AM) fungi are crucial for ecosystem functioning and can contribute to the formation and maintenance of soil aggregates through the exudation of glomalin by extraradical hyphae. Monitoring fertilization effects on AM fungi may help us to develop sound management strategies. The objectives of this study were to investigate the impacts of long-term fertilization on AM fungal parameters and to find out the key factor that affects the diversity and function of AM fungi. A long-term fertilization experiment established in a sandy loam soil at northern China has received continuous fertilization treatments for 21 years, including control; mineral fertilizers of NK, PK, NP, and NPK; organic manure (OM); and half organic manure N plus half mineral fertilizer N (1/2 OMN). Top soil samples (0–15 cm) from three individual plots per treatment were collected for the analysis of chemical properties and fungal parameters. The population size of soil AM fungi was determined by real-time PCR, and the community composition was analyzed using PCR-denature gradient gel electrophoresis (DGGE), cloning, and sequencing techniques. The external mycelium of AM fungi was assessed using the grid-line intersect method, and the glomalin-related soil protein (GRSP) was extracted with citrate solution using bovine serum albumin as a standard. Long-term fertilization significantly increased (P < 0.05) soil organic C content, AM fungal population, species richness (R), Shannon–Wiener index (H), and GRSP content, except for the P-deficiency (NK) fertilization treatment. OM had a significantly greater (P < 0.05) impact on AM fungal population and GRSP content compared to mineral fertilizers but significantly decreased the length of external mycelium compared to the control (P < 0.05). Fertilization also changed the community composition of AM fungi, and the P-deficiency treatment again had the slightest influence. In addition, most species recovered from the DGGE profiles belonged to three genera, Glomus, Diversispora, and Archaeospora. Redundancy analysis showed that the population size and species richness of AM fungi and the GRSP content all significantly correlated to soil organic C content (P < 0.05). Long-term P-containing fertilization, especially the application of OM, greatly increased the population size, species richness, and species diversity of AM fungi, as well as the contents of GRSP and soil organic C, but tended to decrease the length of external mycelium, while the P-deficiency fertilization had no such effect, suggesting that P was the key factor to maintain soil fertility as well as soil AM fungal diversity in this sandy loam soil.

Soil productivity from the sandy pampas region under the present agricultural conditions

During the last decade, major changes in the organization, extension and intensifi cation of the agricultural systems from the sandy pampas region are observed. Crop production is mostly performed under continuous zero tillage and with the application of fertilizers. In this region, strong relationships between crop yields and soil properties, mostly related to water and nutrient storage, have been described. The purpose of this presentation is to discuss, supported by specifi c local long-term fi eld trials, about several of the changes in the productivity of the soils of the region under the present management practices. Soil organic matter levels decrease under continuous tillage practices after systems with pastures. But, the application of zero tillage practices contributed to maintain the original soil productivity properties. Production systems established on degraded soils frequently show less water use effi ciency, mainly when are cropped with maize (Zea mays L.). The establishment of continuous fertilization programs based on the suffi ciency for low mobility nutrients (e.g. Phosphorus) shows reduction in the soil extractable levels of the nutrient and lower mean crop production compared with maintenance fertilization programs. The use of winter cover crops in soybean [Glycine max (L.) Merrill] monoculture enhances physical soil properties without benefi ts on crop yields. The crop and soil management practices widely performed during this period have contributed to the soil conservation and to the water use effi ciency. However, the application of suffi ciency fertilization programs could conduct to the reduction in the levels of soil extractable nutrients and in crop productivity. The present agricultural land use in the region requires to intensify in the use of indexes for the diagnosis of soils productivity independently of the actual relationships with today`s yields. The delimitation of homogeneous areas for the application of effi cient soil management practices is needed for the conservation and enhancement of soils productivity capability.

Soil productivity from the sandy pampas region under the present agricultural conditions

During the last decade, major changes in the organization, extension and intensifi cation of the agricultural systems from the sandy pampas region are observed. Crop production is mostly performed under continuous zero tillage and with the application of fertilizers. In this region, strong relationships between crop yields and soil properties, mostly related to water and nutrient storage, have been described. The purpose of this presentation is to discuss, supported by specifi c local long-term fi eld trials, about several of the changes in the productivity of the soils of the region under the present management practices. Soil organic matter levels decrease under continuous tillage practices after systems with pastures. But, the application of zero tillage practices contributed to maintain the original soil productivity properties. Production systems established on degraded soils frequently show less water use effi ciency, mainly when are cropped with maize ( Zea mays L.). The establishment of continuous fertilization programs based on the suffi ciency for low mobility nutrients (e.g. Phosphorus) shows reduction in the soil extractable levels of the nutrient and lower mean crop production compared with maintenance fertilization programs. The use of winter cover crops in soybean [ Glycine max (L.) Merrill] monoculture enhances physical soil properties without benefi ts on crop yields. The crop and soil management practices widely performed during this period have contributed to the soil conservation and to the water use effi ciency. However, the application of suffi ciency fertilization programs could conduct to the reduction in the levels of soil extractable nutrients and in crop productivity. The present agricultural land use in the region requires to intensify in the use of indexes for the diagnosis of soils productivity independently of the actual relationships with today`s yields. The delimitation of homogeneous areas for the application of effi cient soil management practices is needed for the conservation and enhancement of soils productivity capability.

长期施肥对玉米生育期土壤微生物量碳氮及酶活性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 长期施肥对玉米生育期土壤微生物量碳氮及酶活性的影响 DOI: 10.5846/stxb201110191555 作者: 作者单位: 西北农林科技大学/农业部西北植物营养与农业环境重点实验室,陕西杨凌,西北农林科技大学/农业部西北植物营养与农业环境重点实验室,陕西杨凌,陕西省土壤肥料工作站,西北农林科技大学/农业部西北植物营养与农业环境重点实验室,陕西杨凌,西北农林科技大学/农业部西北植物营养与农业环境重点实验室,陕西杨凌,西北农林科技大学/农业部西北植物营养与农业环境重点实验室,陕西杨凌,西北农林科技大学/农业部西北植物营养与农业环境重点实验室,陕西杨凌 作者简介: 通讯作者: 中图分类号: 基金项目: 公益性行业(农业)科研专项(201203030)资助;西北农林科技大学创新团队项目资助 Effects of long-term fertilization on soil microbial biomass carbon and nitrogen and enzyme activities during maize growing season Author: Affiliation: Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Northwest A & F University, Yangling,,,,,,Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Northwest A & F University, Yangling Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以小麦-玉米轮作长期肥料定位试验为平台,探讨不同养分管理对玉米生育期塿土微生物量碳、氮和酶活性动态变化的影响。试验包括6个处理,分别为不施肥(CK)、单施氮肥(N)、氮磷配合(NP)、氮磷钾配合(NPK)、NPK+秸秆(SNPK)以及有机肥+NPK(MNPK)。结果表明玉米生育期土壤微生物量碳、氮变化显著。不同施肥管理下土壤微生物量碳、氮的高低显著性分别为MNPK > SNPK、NP、NPK > N、CK。玉米生育期内土壤酶活性也变化显著,蔗糖酶、脲酶和纤维素酶在玉米抽雄期达到活性高峰,而磷酸酶在玉米拔节期出现活性高峰。不同施肥管理对土壤酶活性的影响总体表现为MNPK处理最高,其次为SNPK处理,再次为NPK和NP处理,N和CK处理最低。不同施肥处理间土壤微生物量碳、氮以及酶活性与土壤有机碳、全氮、速效磷水平密切相关。塿土长期施用氮磷或氮磷钾化肥可以提高土壤微生物量碳、氮以及酶活性。一季作物秸秆还田配合氮磷钾化肥与氮磷钾相比有提高土壤微生物量碳、氮以及酶活性的趋势。在等氮量下,有机肥配合化肥与其他施肥模式相比,均显著提升土壤化学肥力因素、微生物量碳氮和酶活性。因此,塿土上建议进行有机无机肥配合以提高土壤肥力,保持土壤生物健康。 Abstract:This study was designed to examine the effects of continuous fertilization, straw incorporation, and manuring on the soil microbial biomass and activities of enzymes by a long-term fertilizer field trial with winter wheat and summer maize rotation system under temperate conditions in a loess soil in Shaanxi of China. Treatments at the site included application of recommended doses of nitrogen (N), nitrogen and phosphorus (NP), nitrogen, phosphorus and potassium (NPK), wheat/maize straw (S) with NPK (SNPK), dairy manure (M) with NPK (MNPK) and un-amended control (CK), totally six treatments. The results showed that soil microbial biomass carbon and nitrogen changed significantly during maize growing season. The effects of fertilization regimes on soil microbial biomass carbon and nitrogen can be arranged (based on statistical significance) in the following orders: MNPK > SNPK, NP, NPK > N, CK. Soil enzyme activities also significantly changed with maize development stage. Invertse, urease and cellulase activities reached the peak at the silk stage, but alkaline phosphatase activities was the highest at the jonting stage. The effects of fertilization regimes on soil enzyme activity generally followed the order: MNPK > SNPK > NPK, NP > N, CK. The difference in soil microbial biomass carbon, nitrogen and enzyme activity was related to the levels of organic carbon, total nitrogen and Olsen P in soils. Overall, long-term application of NP or NPK could significantly increase soil microbial biomass carbon, nitrogen and enzyme activity relative to CK. Compared with NPK, SNPK treated soil had a tendency to increase microbial biomass and enzyme activity. At the same N application rate, manure combined with chemical fertilizer significantly enhanced soil chemical and biochemical fertility compared with the other fertilization regimes. It is, therefore, recommended that NP application combined with crop straw could be a suitable way in the loess soil in order to improve soil fertility and maintain land productivity if organic manure were not applicable. 参考文献 相似文献 引证文献

Measuring the Effect of Fertility Decline on the Maternal Mortality Ratio

This article proposes a simple method to decompose the overall decline in the maternal mortality ratio (MMR) observed between 1990 and 2008 into two components: decline attributable to fertility decline and decline attributable to safe motherhood programs. This method--illustrated here for three South Asian countries (India, Pakistan, and Bangladesh)--is aimed at helping to properly assess the impact of safe motherhood initiatives on the MMR. The methodology is also applied to estimate the 2015 MMR level implied by low, medium, and high variants of fertility decline assumed by the United Nations, and thus to assess the contribution of future fertility decline in these countries to the achievement of MDG 5 by 2015. The results show that fertility decline in these countries between 1990 and 2008 has made a substantial contribution to the reduction of the MMR and that continued fertility decline between 2008 and 2015 will contribute to the achievement of MDG 5.

Hydrologic and biogeochemical functioning of intensively managed catchments: A synthesis of top‐down analyses

This paper synthesizes a 3‐year collaborative effort to characterize the biogeochemical and hydrological features of intensively managed agricultural catchments by combining data analysis, modeling, and preliminary hypothesis testing. The specific focus was on the Midwestern region of the United States. The results suggest that: (1) water management, specifically the homogenization of evapotranspiration losses driven by mono‐cultural vegetation cover, and the homogenization of runoff generation driven by artificial drainage, has created engineered, predictable hydrologic systems; (2) nutrient and pesticide management, specifically their regular applications have created two kinds of biogeochemical export regimes: chemostatic (low variability in concentration as exhibited by nitrate) and episodic (high variability in concentration as exhibited by pesticides); (3) coupled mass‐balance models for water and solutes reproduce these two regimes as a function of chemical rate constants. Phosphorus transport regimes were found to be episodic at smaller spatial scales, but chemostatic at larger scales. Chemostatic response dominates in transport‐limited catchments that have internal sources of the solute to buffer the periodicity in episodic inputs, while episodic response dominates in source‐limited catchments. The shift from episodic nitrate export in pristine catchments to chemostatic regimes in managed watersheds was attributed to legacy stores of nitrogen (built from continued fertilizer applications) that buffer interannual variations in biogeochemical processing. Fast degradation kinetics of pesticides prevents the build‐up of legacy sources, and leads to episodic export. Analytical expressions were derived for the probability density functions of solute delivery ratio as a function of the stochastics of rainfall‐runoff events and biogeochemical controls.

Nitrogen fertilization does not affect micronutrient uptake in grain maize (Zea mays L.)

Due to continuous single nitrogen fertilization, we hypothesized a built-up deficiency of micronutrients in crops that would limit plant growth and crop quality. In 2-year field experiments using urea-N fertilized grain maize (Zea mays L.), hybrid KWS 2376 at 0, 120 and 240 kg N ha−1 crop uptake of Zn, Mn, Cu and Fe was studied at DC 32, DC 61 and in the grain harvested. Micronutrient contents at DC 32 stage – 1st node (aboveground phytomass) and DC 61 – flowering (ear leaf) were all at levels indicative of adequate micronutrient supply to the crop. At both sampling occasions the Fe:Zn and Fe:Mn ratios were adequate implying that Fe did not inhibit the uptake of Zn and Mn. The application of nitrogen increased the Fe content at the 1st sampling in both years; in the second year the same was also the case for the Zn content. Nitrogen nutrition increased the contents of Mn and Fe at the 2nd sampling only in year 2; in the other treatments no changes were observed in the micronutrient contents. Micronutrient correlations in the grain were discovered between Zn and Mn contents and between Fe and Mn contents. In the second year the highest N-rate significantly increased the Fe and Zn content of the grain compared with the lower rates of nitrogen fertilization. Grain yields were not affected by the rate of nitrogen and ranged between 13.65 and 14.34 t ha−1 (1st year) and between 13.68 and 14.18 t ha−1 (2nd year). Nitrogen fertilization did not reduce the content of micronutrients in the plant or grain of maize. It is evident that the continuous single use of N fertilization so far has not resulted in a micronutrient deficiency of the plants limiting the nutrient density of the grain or reducing its quality.

Mechanisms of Sperm Storage in the Female Reproductive Tract: an Interspecies Comparison

Once semen has been collected for artificial insemination, it is diluted into extenders designed to prevent its deterioration over the period prior to insemination. If the semen is not frozen, the extenders provide protection for a period of a few hours to a few days, depending on species. Despite the efforts of biotechnologists to increase the duration of storage without compromising fertility, there has been relatively little progress for many years. However, comparative studies in diverse species have revealed that long-term sperm storage (up to months and years) within the female reproductive tract is relatively commonplace in reptiles, fishes, birds and amphibians. Even among mammals, some species of bat have evolved mechanisms for storing spermatozoa for several months in the uterus or oviduct so that they can mate in the autumn but postpone fertilization until the spring. We currently know little about the mechanisms that support such long-term sperm storage, mainly because evidence from such species is either absent or fragmentary. Nevertheless, parallels between mammalian and other systems, where spermatozoa are sequestered in sperm storage tubules, suggest that the enclosure of spermatozoa within pockets of epithelial cells may be sufficient to achieve long-term sperm storage. In addition, recent evidence from sperm-storing bats has suggested an alternative, or additional, hypothesis that the modulation of apoptosis within epithelial cells is important in controlling sperm survival. Despite a lack of direct experimental evidence from a wide variety of species, I propose that there is now enough evidence to warrant investigation of these hypotheses.

Differentiated Response of Denitrifying Communities to Fertilization Regime in Paddy Soil

The impact of fertilization regimes on sequential denitrifying communities was investigated in a rice paddy field with 17 years continuous fertilization, located in Taoyuan Agro-ecosystem Research Station (110°72″ E, 28°52″ N), China. The diversity, community composition, and size of denitrifying genes of narG, qnorB, and nosZ were determined using molecular tools including terminal restriction fragment length polymorphism, quantitative polymerase chain reaction (qPCR), cloning, and sequencing analysis. Soil samples were collected from the plots with no fertilizer (NF), urea (UR), balanced mineral fertilizers (BM), and BM combined with rice straw (BMR). UR and BM caused marked increase in the community size of the denitrifying genes; however, BMR resulted in the highest abundance. The community size of narG was the most affected by the fertilization regimes, while qnorB was the least. Fertilization also induced some shifts in the composition of denitrifying genes, but the responses of different genes varied. However, fertilization regimes caused no significant changes to the diversity of the denitrifying genes. Potential denitrification activity (PDA) was significantly correlated with the abundance of narG and nosZ rather than qnorB, but there were no such correlations between PDA and the composition and diversity of denitrifying communities. Conclusively, long-term fertilization significantly affected denitrifying community size and composition, but not diversity. Among the sequential denitrifying genes, narG was the most, while qnorB was the least sensitive communities to fertilization regimes.

Quality of shallow water table as affected by long-term fertilizer use in the rice-wheat system

In India, the increase in foodgrain production from 50.8 million t (1951-52) to 203.6 million t (1998-99) is mainly attributed to the adoption of high-yielding crop varieties and use of fertilizers. Consequently, fertilizer consumption during the corresponding period increased from a mere 0.55 kg ha-1 to 90.04 kg ha-1 (FAI 1999). The increased use Quality of shallow water table as affected by long-term fertilizer use in the rice-wheat system and/or misuse of fertilizers had frequently been cited as the cause of water quality deterioration (Miller 1979). Nitrate leaching can occur in intensively cultivated areas with a shallow water table (Bajwa et al 1992). In the face of increasing food demand of the burgeoning population, efficient fertilizer use in crops and the prevention of groundwater pollution are critical (Singh and Sekhon 1976). In the tarai region of Uttaranchal, the water table is shallow (about 1 m deep) and rice-wheat is the predominant cropping system. Since the inception of this long-term experiment, no study on groundwater quality has so far been conducted. This study aimed to monitor the impact of continuous fertilizer use (more than 30 y) under intensive cropping on the nutrient enrichment of groundwater.