共查询到20条相似文献,搜索用时 15 毫秒
1.
A. P. Gupta 《中国科学C辑(英文版)》2005,48(Z2)
Nitrogen is one of the major plant nutrients without which the agricultural production is not possible. Nitrogen use in Indian agriculture was nearly 55000 tons in 1950-1951 that increased to 11.31 million tons in 2001-2002. The total food production of the country has also experienced the similar increase from 50.83 to 222 million tons in the respective years. Interestingly the N fertilizer consumption of India remained almost constant during the last six years indicating the possibility of reducing N consumption. The highest N consumption is in North zone owing to the introduction of rice-wheat cropping system followed by West, South and East.The N use efficiency has been reported to be varying between 30% to 50% depending on the crops and the management. But in most of the cases, N use efficiency has been calculated based on the total N removed by the crops (above ground part only) ignoring the N content left in the roots. It has been observed in controlled experiments that the total N uptake by roots varied from 18% to 44% of the total N removed by the above ground parts, i.e. grain and straw. If the root N is also accounted, the N use efficiency will be higher than reported. The management of other organic sources has to be improved so as to increase the fertilizer use efficiency as well as to check the direct release of N in the atmosphere. In this review all these issues will be dealt. 相似文献
2.
Micronutrient status and fertilizer use scenario in India 总被引:1,自引:0,他引:1
India was dependent on external food supplies in the early 1960s. To meet the growing demand for food, fiber and fuel, high yielding cultivars were introduced. These high yielding crop cultivars were highly responsive to fertilizers. Thus, slowly the soils were exhausted of their nutrients. Application of major nutrients (nitrogen, phosphorus, potassium) became common, therefore the crops started responding to micronutrient fertilizers. Concerted efforts have been made through the All India Coordinated Research Project on Micronutrients to delineate the soils of India regarding the deficiency of micronutrients. At present about 48.1% of Indian soils are deficient in diethylenetriaminepentaacetate (DTPA) extractable zinc, 11.2% in iron, 7% in copper and 5.1% in manganese. Apart from the deficiency of these micronutrients, deficiencies of boron and molybdenum have also been reported in some areas. Areas with multi-micronutrient deficiencies are limited, thus simple fertilizers are sufficient to exploit the potential of crops and cropping systems. Based on the extent of deficiency, cultivated area, and crop removal, the micronutrient fertilizer demand in 2025 is projected using sufficiency and maintenance approaches. 相似文献
3.
A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management. 相似文献
4.
Nitrogen uptake and use of two contrasting maize hybrids differing in leaf senescence 总被引:22,自引:2,他引:22
In eastern Canada, the use of fertilizer N has been identified as the most energy-consuming component of maize (Zea mays L.) grain production. As the economic and environmental costs of excessive N fertilization rise, there is an increased emphasis on selection of hybrids with greater N use efficiency (NUE; defined as the ratio of the amount of 15N recovered in grain or stover dry matter to the amount of fertilizer 15N applied to the soil in this study). Using an 15N-labelling approach, a field study was conducted on a tile-drained Brandon loam soil (Typic Endoaquoll) on the Central Experimental Farm at Ottawa, Canada (45°22 N, 75°43 W) in 1993 and 1994. Fertilizer N uptake and partitioning within the plant in relation to dry matter changes were monitored during development of a current stay-green maize hybrid and an older early-senescing hybrid grown with three fertilizer N levels (0, 100, 200 kg N ha-1). Dry matter, N concentration and15 N atom% enrichment of plant components were determined at five growth stages. The current stay-green hybrid, Pioneer 3902 had greater NUE than the old early-senescing hybrid, Pride 5, which was associated with 24% more dry matter production and 20% more N uptake during grain fill for Pioneer 3902. There was no indication of greater allocation of N to the grain in Pioneer 3902. Our data suggest that prolonged maintenance of green leaf area for photosynthate production during grain fill and the ability to take up available soil N later in grain filling are characteristics of maize hybrids with greater NUE. 相似文献
5.
以大田试验获得的大麦氮敏感基因型BI-45为材料,利用溶液培养方法,测定了苗期株高、根长、叶绿素含量、含氮量、谷氨酰胺合成酶和硝酸还原酶活性,以及与氮代谢相关的基因(GSI-GSl-2、GSI-3、GS2、Narl、NRT2.J、NRT2-2、NRT2-3和NRT2-4)的表达。结果表明:相对于正常供氮,氮饥饿胁迫下,BI-45根和叶中的氮素利用率提高,含氮量降低,叶绿素含量减少,根冠比增加;叶片中的谷氨酰胺合成酶活性和硝酸还原酶的活性高于根,但是,与叶中的相比,根中的谷氨酰胺合成酶活性升高及硝酸还原酶活性降低的差异性更显著;与正常供氮相比,氮饥饿处理下,根中基因傩家族,基Narl和硝酸盐转运蛋白基因NRT2家族的相对表达量皆达到显著性差异,其中GSl-I、GSl-2和NRT2-2在苗期大麦氮饥饿处理下表现尤为突出,并且在6h都有上调表达。 相似文献
6.
Current scenario of malaria in India 总被引:4,自引:0,他引:4
Sharma VP 《Parassitologia》1999,41(1-3):349-353
The Indian National Malaria Eradication Programme (NMEP) is reporting 2.5 to 3 million malaria cases, and about 1,000 malaria deaths annually. Malaria in the northeastern states is stable and in the peninsular India unstable. There are six major and three minor malaria vectors, of which Anopheles culicifacies transmits malaria in rural areas and An. stephensi in the towns. Other vectors are of local importance. Plasmodium vivax is the dominant infection and accounts for 60-65% cases whereas P. falciparum contributes 30-35% cases. Field operations to control malaria are impeded by resistance and/or exophilic vector behavior, parasite resistance to antimalarial drugs, operational problems in spraying, failure to search breeding of mosquitoes at weekly intervals, staff shortages and financial constraints. Resurgent malaria invaded new ecotypes created by green revolution, industrial growth and urban development resulting in paradigm shift towards man-made malaria. NMEP has launched a world bank-assisted enhanced malaria control project with primary emphasis to protect 62.2 million high risk population in 7 states. 相似文献
7.
Animal production systems convert plant protein into animal protein. Depending on animal species, ration and management, between 5% and 45 % of the nitrogen (N) in plant protein is converted to and deposited in animal protein. The other 55%-95% is excreted via urine and feces, and can be used as nutrient source for plant (= often animal feed) production. The estimated global amount of N voided by animals ranges between 80 and 130 Tg N per year, and is as large as or larger than the global annual N fertilizer consumption. Cattle (60%), sheep (12%) and pigs (6%) have the largest share in animal manure N production. The conversion of plant N into animal N is on average more efficient in poultry and pork production than in dairy production, which is higher than in beef and sheep production. However, differences within a type of animal production system can be as large as differences between types of animal production systems, due to large effects of the genetic potential of animals, animal feed and management. The management of animals and animal feed, together with the genetic potential of the animals, are key factors to a high efficiency of conversion of plant protein into animal protein. The efficiency of the conversion of N from animal manure, following application to land, into plant protein ranges between 0 and 60%, while the estimated global mean is about 15%. The other 40%-100% is lost to the wider environment via NH3 volatilization, denitrification, leaching and run-off in pastures or during storage and/or following application of the animal manure to land. On a global scale, only 40%-50% of the amount of N voided is collected in barns, stables and paddocks, and only half of this amount is recycled to crop land. The N losses from animal manure collected in barns, stables and paddocks depend on the animal manure management system. Relative large losses occur in confined animal feeding operations, as these often lack the land base to utilize the N from animal manure effectively. Losses will be relatively low when all manure are collected rapidly in water-tight and covered basins, and when they are subsequently applied to the land in proper amounts and at the proper time, and using the proper method (low-emission techniques). There is opportunity for improving the N conversion in animal production systems by improving the genetic production potential of the herd, the composition of the animal feed, and the management of the animal manure. Coupling of crop and animal production systems, at least at a regional scale, is one way to high N use efficiency in the whole system. Clustering of confined animal production systems with other intensive agricultural production systems on the basis of concepts from industrial ecology with manure processing is another possible way to improve N use efficiency. 相似文献
8.
Agrama H.A.S. Zakaria A.G. Said F.B. Tuinstra M. 《Molecular breeding : new strategies in plant improvement》1999,5(2):187-195
Intensively managed crop systems are normally dependent on nitrogen input to maximize yield potential. Improvements in nitrogen-
use efficiency (NUE) in crop plants may support the development of cropping systems that are more economically efficient and
environment friendly. The objective of this study was to map and characterize quantitative trait loci (QTL) for NUE in a maize
population. In preliminary experiments, inbred lines contrasting for NUE were identified and were used to generate populations
of F2:3 families for genetic study. A total of 214 F2:3 families were evaluated in replicated trials under high nitrogen (280
kg/ha) and low nitrogen (30 kg/ha) conditions in 1996 and 1997. Analysis of ear-leaf area, plant height, grain yield, ears
per plant, kernels number per ear, and kernel weight indicated significant genetic variation among F2:3 families. The heritability
of these traits was found to be high (h2=0.57–0.81). The mapping population were genotyped using a set of 99 restriction fragment
length polymorphism (RFLP) markers. A linkage map of these markers was developed and used to identify QTL. Between two and
six loci were found to be associated with each trait. The correspondence of several genomic regions with traits measured under
nitrogen limited conditions suggests the presence of QTL associated with NUE. QTLs will help breeders to improve their maize
ideotype of a low-nitrogen efficiency by identifying those constitutive and adaptive traits involved in the expression of
traits significantly correlated with yield, such as ear leaf area and number of ears per plant.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Nitrogen Mediates Flowering Time and Nitrogen Use Efficiency via Floral Regulators in Rice 总被引:2,自引:0,他引:2
Shunan Zhang Yuyi Zhang Kangning Li Ming Yan Jinfei Zhang Ming Yu Shuo Tang Luyang Wang Hongye Qu Le Luo Wei Xuan Guohua Xu 《Current biology : CB》2021,31(4):671-683.e5
- Download : Download high-res image (179KB)
- Download : Download full-size image
11.
This paper gives a quantitative analysis on the non-CO2 emissions related to energy demand, energy activities and land use change of six scenarios with different development pattern in 2030 and 2050 based on IPAC emission model. The various mitigation technologies and policies are assessed to understand the corresponding non-CO2 emission reduction effect. The research shows that the future non-CO2 emissions of China will grow along with increasing energy demand, in which thermal power and transportation will be the major emission and mitigation sectors. During the cause of future social and economic development, the control and mitigation of non-CO2 emissions is a problem as challenging and pressing as that of CO2 emissions. This study indicates that the energy efficiency improvement, renewable energy, advanced nuclear power generation, fuel cell, coal-fired combined cycle, clean coal and motor vehicle emission control technologies will contribute to non-CO2 emissions control and mitigation. 相似文献
12.
Nitrogen use strategies of neotropical rainforest trees in threatened Atlantic Forest 总被引:1,自引:0,他引:1
M. P. M. AIDAR S. SCHMIDT G. MOSS G. R. STEWART & C. A. JOLY 《Plant, cell & environment》2003,26(3):389-399
The characteristics of nitrogen acquisition, transport and assimilation were investigated in species of an Atlantic Forest succession over calcareous soil in south‐eastern Brazil. Differences in behaviour were observed within the regeneration guilds. Pioneer species showed high leaf nitrogen contents, a high capacity to respond to increased soil nitrogen availability, a high capacity for leaf nitrate assimilation and were characterized by the transport of nitrate + asparagine. At the other end of the succession, late secondary species had low leaf nitrogen contents, little capacity to respond to increased soil nitrogen availability, low leaf nitrate assimilation and were active in the transport of asparagine + arginine. The characteristics of nitrogen nutrition in some early secondary species showed similarities to those of pioneer species whereas others more closely resembled late secondary species. Average leaf δ15N values increased along the successional gradient. The results indicate that the nitrogen metabolism characteristics of species may be an additional ecophysiological tool in classifying tropical forest tree species into ecological guilds, and may have implications for regeneration programmes in degraded areas. 相似文献
13.
Ashis Mukhopadhya 《Journal of biosciences》2008,33(4):465-473
Hepatitis C is an emerging infection in India and an important pathogen causing liver disease in India. The high risk of chronicity of this blood-borne infection and its association with hepatocellular carcinoma underscores its public health importance. Blood transfusion and unsafe therapeutic interventions by infected needles are two preventable modalities of spread of hepatitis C infection. In addition, risk factor modification by reducing the number of intravenous drug users will help curtail the prevalence of this infection. This review summarizes the extent, nature and implications of this relatively new pathogen in causing disease in India. 相似文献
14.
Cereal area and nitrogen use efficiency are drivers of future nitrogen fertilizer consumption 总被引:1,自引:0,他引:1
At a global scale, cereal yields and fertilizer N consumption have increased in a near-linear fashion during the past 40 years and are highly correlated with one another. However, large differences exist in historical trends of N fertilizer usage and nitrogen use efficiency (NUE) among regions, countries, and crops. The reasons for these differences must be understood to estimate future N fertilizer requirements. Global nitrogen needs will depend on: (i) changes in cropped cereal area and the associated yield increases required to meet increasing cereal demand from population and income growth, and (ii) changes in NUE at the farm level. Our analysis indicates that the anticipated 38% increase in global cereal demand by 2025 can be met by a 30% increase in N use on cereals, provided that the steady decline in cereal harvest area is halted and the yield response to applied N can be increased by 20%. If losses of cereal cropping area continue at the rate of the past 20 years (-0.33% per year) and NUE cannot be increased substantially, a 60% increase in global N use on cereals would be required to meet cereal demand. Interventions to increase NUE and reduce N losses to the environment must be accomplished at the farm- or field-scale through a combination of improved technologies and carefully crafted local policies that contribute to the adoption of improved N management; uniform regional or national directives are unlikey to be effective at both sustaining yield increases and improving NUE. Examples from several countries show that increases in NUE at rates of 1% per year or more can be achieved if adequate investments are made in research and extension. Failure to arrest the decrease in cereal crop area and to improve NUE in the world's most important agricultural systems will likely cause severe damage to environmental services at local, regional, and global scales due to a large increase in reactive N load in the environment. 相似文献
15.
A species of Stenior isolated from freshwater ponds and tanks in and around Bangalore, India, showed striking differences from those that have been described so far. The ciliate is red in color and has 2 spherical macronuclei and 2 small micronuclei. On the basis of the nuclear apparatus and pigmentation of the body, it is believed to be a new species, named in honor of Professor Vance Tartar as Stentor tartari. n. sp. 相似文献
16.
Agricultural soils in North America can be a sink for rising atmospheric CO2 concentrations through the formation of soil organic matter (SOM) or humus. Humification is limited by the availability of nutrients such as nitrogen (N). Recommended management practices (RMPs) that optimize N availability foster humus formation. This review examines the management practices that contribute to maximizing N availability for optimizing sequestration of atmospheric CO2 into soil humus. Farming practices that enhance nutrient use, reduce or eliminate tillage, and increase crop intensity, together, affect N availability and, therefore, C sequestration. N additions, from especially, livestock manure and leguminous cover crops are necessary for increasing grain and biomass yields and returning crop residues to the soil thereby increasing soil organic carbon (SOC) concentration. Conservation tillage practices enhance also the availability of N and increase SOC concentration. Increase in cropping intensity and/or crop rotations produce higher quantity and quality of residues, increase availability of N, and therefore foster increase in C sequestration. The benefit of C sequestration from N additions may be negated by CO2 and N2O emissions associated with production and application of N fertilizers. More studies need to be conducted to ascertain the benefits of adding N via manuring versus N fertilizer additions. Furthermore, site specific adaptive research is needed to identify RMPs that optimize soil N use efficiency while improving crop yield and C sequestration thereby curbing greenhouse gas (GHG) emissions. Due to the wide range of climate in North America, there is a large range of C sequestration potential in agricultural soils through N management. Humid croplands may have the potential to sequester 8–298 Tg C yr?1 while dry croplands may sequester 1–35 Tg C yr?1. These estimates, however, are highly uncertain and wide-ranging. Clearly, more research is needed to quantify, more precisely, the C sequestration potential across different N management scenarios especially in Mexico and Canada. 相似文献
17.
18.
H. Walter 《International Journal of Anthropology》1986,1(4):297-306
The genetic variability in Indian populations is examined on the basis of the study of Tf, Gc, Gm, and Km polymorphisms. This variability is not associated with fluctuations, but is related to population history (mainly to migrations, hybrydization and caste endogamy). When genetic distances are calculated, Northern, Southern and Western Indian poplations show closer resemblances to Western Asian populations, while Eastern Indian populations are more similar to Mongoloid peoples. 相似文献
19.
不同功能型植物叶氮含量与光合特性的关系研究 总被引:3,自引:0,他引:3
在山西南部的霍山七里峪林场,确定乔木、灌木和草本物种共26个,用Li-3000A叶面积测定仪测量了叶面积的大小、用Li-6400便携式光合作用测定系统测定了叶光饱和速率(Aarea),计算了比叶重(LMA)、单位重量的光饱和光合速率(Amass)、单位面积叶氮含量(Narea)、单位重量叶氮含量(Nmass)及光合氮利用效率(PNUE),研究了它们之间的不同和相互作用关系。结果表明:不同功能型植物的Nmass、Aarea、Amass、Narea和PNUE差异显著(p<0.05),植物叶片氮含量与植物光合生理特性具有显著相关关系,Nmass与Aarea、Amass和PNUE呈线性显著的正相关(p<0.05);Narea与Aarea、Amass、PNUE之间呈极显著的负相关(p<0.01)。 相似文献
20.
Nitrogen reallocation and photosynthetic acclimation in response to partial shading in soybean plants 总被引:11,自引:0,他引:11
The first trifoliate of soybean was shaded when fully expanded, while the plant remained in high light; a situation representative for plants growing in a closed crop. Leaf mass and respiration rate per unit area declined sharply in the first few days upon shading and remained rather constant during the further 12 days of the shading treatment. Leaf nitrogen per unit area decreased gradually until the leaves were shed. Leaf senescence was enhanced by the shading treatment in contrast to control plants growing in low light. Shaded leaves on plants grown at low nutrient availability senesced earlier than shaded leaves on plants grown at high nutrient availability. The light saturated rate of photosynthesis decreased also gradually during the shading treatment, but somewhat faster than leaf N, whereas chlorophyll contents declined somewhat slower than leaf N.
Partitioning of N in the leaf over main photosynthetic functions was estimated from parameters derived from the response of photosynthesis to CO2 . It appeared that the N exported from the leaf was more at the expense of compounds that make up photosynthetic capacity than of those involved in photon absorption, resulting in a change in partitioning of N within the photosynthetic apparatus. Photosynthetic nitrogen use efficiency increased during the shading treatment, which was for the largest part due to the decrease in leaf N content, to some extent to the decrease in respiration rate and only for a small part to change in partitioning of N within the photosynthetic apparatus. 相似文献
Partitioning of N in the leaf over main photosynthetic functions was estimated from parameters derived from the response of photosynthesis to CO