Fertilizers and biological nitrogen fixation as sources of plant nutrients: Perspectives for future agriculture

Biological nitrogen fixation (BNF) has an assured place in agriculture, mainly as a source of nitrogen for legumes. Legumes are currently grown mostly as a source of vegetable oil and as food for humans and animals, but not as nitrogen source.Other crops with BNF capability may be eventually be developed eventually. Such crops will also need mineral fertilizers to maintain a good status of soil nutrients, but their possible effects to the environment is also a concern. Fertilizers, however, will remain a necessary and sustainable input to agriculture to feed the present and increasing human population. It is not a case of whether BNF is better or worse than mineral fertilizers because both plays an important role in agriculture.     

城市居民食物氮消费变化及其环境负荷——以厦门市为例

食物消费是城市养分流动的重要环节,以厦门市为例,分析了1988—2009年居民食物氮素消费的变化特点,分析与其变化相关的经济、社会因素,并探讨了居民食物氮素消费变化所带来的环境负荷。研究结果表明,厦门市人均食物氮消费量变化与食物消费量变化并不完全一致,人均氮消费量2000年以前维持在3.29 kg N.人-1.a-1,2000年以后呈现波动性的增长,2004年达到最高值4.00 kg N.人-1.a-1。厦门市食物氮素消费总量增长幅度较大,由1988年的0.54万t增至2009年的1.50万t。同时,粮食在食物氮消费量中所占比例由45.5%下降到15.9%。畜禽肉、奶制品所占比例分别由25.0%和0.4%上升至29.8%和8.8%。通过将相关经济、社会因素与居民食物氮消费量进行相关性分析表明,人均可支配收入、食物价格指数、具有大学学历以上人口比重均与其联系较为密切,呈正相关;恩格尔系数、平均家庭人口数与居民食物氮消费量呈负相关。通过选取1988、1994、2001、2008年分析居民食物氮素消费造成的环境氮负荷发现,由其带来的环境氮负荷量由3509.12t增加至7629.36t,约90%的氮素进入了土壤和水体。其中,进入土壤的氮素占进入环境氮总量的比例由37%增长到60%,进入水体的氮素比例由57%降至35%。     

Plant nutrition research: Priorities to meet human needs for food in sustainable ways

The world population is expanding rapidly and will likely be 10 billion by the year 2050. Limited availability of additional arable land and water resources, and the declining trend in crop yields globally make food security a major challenge in the 21st century. According to the projections, food production on presently used land must be doubled in the next two decades to meet food demand of the growing world population. To achieve the required massive increase in food production, large enhancements in application of fertilizers and improvements of soil fertility are indispensable approaches. Presently, in many developing countries, poor soil fertility, low levels of available mineral nutrients in soil, improper nutrient management, along with the lack of plant genotypes having high tolerance to nutrient deficiencies or toxicities are major constraints contributing to food insecurity, malnutrition (i.e., micronutrient deficiencies) and ecosystem degradation. Plant nutrition research provides invaluable information highly useful in elimination of these constraints, and thus, sustaining food security and well-being of humans without harming the environment. The fact that at least 60% of cultivated soils have growth-limiting problems with mineral-nutrient deficiencies and toxicities, and about 50% of the world population suffers from micronutrient deficiencies make plant nutrition research a major promising area in meeting the global demand for sufficient food production with enhanced nutritional value in this millennium. Integration of plant nutrition research with plant genetics and molecular biology is indispensable in developing plant genotypes with high genetic ability to adapt to nutrient deficient and toxic soil conditions and to allocate more micronutrients into edible plant products such as cereal grains.     

Effects of atmospheric CO(2) enrichment on plant constituents related to animal and human health

Atmospheric CO(2) enrichment is known to significantly enhance the growth and development of nearly all plants, implying a potential for elevated levels of CO(2) to alter the concentrations of plant constituents related to animal and human health. Our review of this subject indicates that increases in the air's CO(2) content typically lead to reductions in the nitrogen and protein concentrations of animal-sustaining forage and human-sustaining cereal grains when soil nitrogen levels are sub-optimal. When plants are supplied with all the nitrogen they can use, however, no such reductions are observed. CO(2)-enriched plants growing in the natural environment also tend to overcome initial reductions in plant mineral concentrations as time progresses, possibly due to development of larger root systems and consequent enhanced abilities to locate and absorb mineral nutrients. Atmospheric CO(2) enrichment additionally appears to reduce oxidative stresses in plants; and it has been shown to increase the concentration of vitamin C in certain fruits and vegetables. Elevated CO(2) has also been demonstrated to increase the biomass of plants grown for medicinal purposes while simultaneously increasing the concentrations of the disease-fighting substances produced within them. It is likely, therefore, that the ongoing rise in the air's CO(2) content will continue to increase food production around the world, while maintaining the nutritive quality of that food and enhancing the production of certain disease-inhibiting plant compounds.     

Nutrient flow in a major urban settlement: Hong Kong

A nutrient balance is established for the contemporary urban ecosystem of Hong Kong. The flow of nutrients in the Hong Kong food system in particular is examined, including current and potential nutrient recycling patterns. Losses of nutrients in food for human consumption are found to be up to 20% for major nutrients. The flow of mineral phosphorus in the Hong Kong food system is examined in detail. About 3600 tonnes of phosphorus are lost from the Hong Kong food system each year. A comparison is made between the land-based forage area demand of the Hong Kong population and a similar-sized Western population, that of Sydney, Australia. It is estimated that the average Hong Kong person consumes a diet which requires only half the land area needed to produce the diet of the average Sydney person. However, Hong Kong relies on the ocean for 25% of its animal protein supply compared with 2.5% for Sydney. Patterns of food production and nutrient recycling are proposed, with the aim of optimizing resource utilization in close association with contemporary urban settlements.     

Potential for increasing protein production by legume inoculation

Summary and Conclusions The world food problem has been discussed in terms of food production for a rapidly expanding population, a large portion of which is already undernourished. Evidence has been presented that legumes are more efficient producers of essential amino acids than either non-legumes or animal sources. A wider use of legumes has been suggested as an aid to the solution of the protein deficiency problem. Legumes are useful in conserving soil and moisture by increasing infiltration and decreasing runoff, and in improving the physical condition and fertility status of soils by stabilizing soil structure and decreasing the leaching of plant nutrients. The nitrogen status of a soil may be greatly improved by the decomposition of nitrogen-rich leguminous residues. Yields of edible legumes in the developing regions of the world are generally much lower than in the technologically developed regions. This suggests a considerable potential for increasing protein production by the application of modern technology to legume production in the developing countries. Legume production can, in many instances, be improved quantitatively and qualitatively by proper inoculation.     

联合固氮菌的合成生物学研究进展

氮素是作物生长过程中最重要的元素,氮素缺乏将会严重影响作物生长。随着人类对粮食的需求量增加,化学氮肥的施用量越来越多。生物固氮在全球氮素循环中有着重要的作用,60%的氮来源于生物固氮。因此,生物固氮,尤其是能够在作物中定殖的联合固氮菌,最有可能代替氮肥成为粮食作物的主要氮源。长期以来,如何提高生物固氮效率以及在作物中实现生物固氮是生物学家的重要研究方向。合成生物学的出现和发展为能够生物固氮的研究带了新的机遇,有望缓解粮食作物对化学氮肥的大量需求。本文概述了固氮菌的种类、联合固氮菌中固氮基因岛的组成以及转录调控机理,阐述了合成生物学在生物固氮领域中的研究现状,对未来的联合固氮菌合成生物学的发展方向作出了展望。     

Nutrient resources for crop production in the tropics

For the foreseeable future a majority of the population, and almost all the mal- and under-nourished, will continue to be found in the tropics and subtropics. Food security in these parts of the world will have to be met largely from local resources. The productivity of the land is to a large extent determined by the fertlity of the soil, which in turn is mostly determined by its organic matter content and stored nutrients. Soil organic matter is readily lost when organic matter inputs are reduced upon cultivation and more so upon intensification. The concomitant loss of topsoil and possible exposure of subsoil acidity may cause further soil degradation.<br>Plant nutrients to replenish what is yearly taken from the soil to meet the demands for food and fibre amount to 230 million tonnes (Mt). Current fertilizer consumption stands at about 130 Mt of N, P₂O₅,and K₂O, supplemented by an estimated 90 Mt of N from biological nitrogen fixation worldwide. Although 80 per cent of the population lives in the developing world, only half the world''s fertilizer is consumed there. Yet, as much as 50% of the increase in agricultural productivity in the developing world is due to the adoption of fertilizers. World population growth will cause a doubling in these nutrients requirements for the developing world by 2020, which, in the likely case of inadequate production, will need to be met from soil reserves. Because expansion of the cultivable land area is reaching its limits, the reliance on nutrient inputs and their efficient use is bound to grow.<br>With current urban expansion, nutrients in harvested products are increasingly lost from the rural environment as a whole. Estimates of soil nutrient depletion rates for sub-Saharan Africa (SSA) are alarmingly high. The situation may be more favourable in Latin America and Asia where fertilizer inputs are tenfold those of SSA. Closing the nutrient cycle at a community level in rural areas may be tedious; on an inter-regional level it is associated with considerable costs of collection, detoxification and transportation to the farms. Yet, at the rate at which some of the non-renewable resources such as phosphorus and potassium are being exploited, recycling of these nutrients will soon be required. <br>     

喀斯特峰丛洼地不同生态系统的土壤肥力变化特征

基于喀斯特峰丛洼地坡耕地、草丛、灌丛、人工林、次生林、原生林6种典型生态系统的土壤主要养分、矿质养分和微生物这3组变量共计20个指标的调查、取样和分析,运用多重比较分析、主成分分析和典范相关分析探讨了其土壤肥力变化特征、主要影响因子及两两之间的相互关系。结果表明,喀斯特峰丛洼地土壤pH值为6.60—7.75,土壤主要养分、微生物种群数量和微生物生物量明显高于同纬度地区地带性红壤,矿质养分含量相对较低,其中SiO2、Al2O3、Fe2O3占矿质全量的90%以上。土壤肥力的总体趋势为原生林>次生林>灌丛>草丛>坡耕地>人工林。喀斯特石漠化地区实行林草结合的退耕还林还草模式更有利于土壤生态系统的环境改善,坡耕地应多施有机肥和氮肥,人工林应多施氮肥。原生林植物与养分之间达到了良好的平衡状态,主要应加强森林抚育管理,改善森林环境,保障植物、土壤养分及微生物之间的良好协调关系。确保土壤资源的合理利用,促进喀斯特峰丛洼地乃至整个西南喀斯特区域植被的迅速恢复和生态重建。     

Ecology of Soil Erosion in Ecosystems

Each year, about 75 billion tons of soil are eroded from the world's terrestrial ecosystems. Most agricultural land in the world is losing soil at rates ranging from 13 tons/ha/year to 40 tons/ha/year. Because soil is formed very slowly, this means that soil is being lost 13–40 times faster than the rate of renewal and sustainability. Rain and wind energy are the two prime causes of erosion from tilled or bare land. Erosion occurs when the soil lacks protective vegetative cover. Soil erosion reduces the productivity of the land by loss of water, soil organic matter, nutrients, biota, and depth of soil. The greatest threat to providing food for a rapidly growing human population is soil erosion. Abandoned, eroded agricultural land is replaced by clearing forested ecosystems. Received 17 February 1998; accepted 26 May 1998.     

The nitrogen fertilization of spring barley

Summary From 1971 to 1979 field trials with increasing rates of fertilizer nitrogen on spring barley with sugar beet as the preceding crop were conducted on a farm on sandy loam in the south western part of The Netherlands. Prior to sowing and fertilizing soil samples were taken and analysed for mineral nitrogen (N_min). The average yield increase through application of fertilizer nitrogen was only 750 kg of grain per ha per year, the maximum yield being about 5 tonnes per ha. In the case of a fixed rate of fertilizer nitrogen per annum it can be derived from the response curves that 60 kg of N would have given the smallest average yield deficit (170 kg grain per ha) in comparison with maximum yields. With an N-advisory system based on soil analysis the average yield deficit would be at a minimum (163 kg of grain per ha) with a value for mineral soil nitrogen+fertilizer nitrogen totalling 120 kg N per ha.No relationship was found between optimum rate of fertilizer nitrogen and the amount of mineral soil nitrogen at the end of the winter. This was ascribed to the relatively small variation in mineral soil nitrogen and the weak response of the crop to fertilizer nitrogen.Promising results from nitrogen fertilizing systems based on soil analysis can be expected from more responsive crops like winter wheat, sugar beets and potatoes.With the average yield deficit compared with maximum yield as a characteristic, the usefulness of any N-advisory system can be compared, taking a fixed rate of nitrogen system as a standard.Seconded by the Agricultural Bureau of the Netherlands Fertilizer Industry (LBNM).     

The opening of Pandora’s Box: climate change impacts on soil fertility and crop nutrition in developing countries

Feeding the world’s growing population is a serious challenge. Food insecurity is concentrated in developing nations, where drought and low soil fertility are primary constraints to food production. Many crops in developing countries are supported by weathered soils in which nutrient deficiencies and ion toxicities are common. Many systems have declining soil fertility due to inadequate use of fertility inputs, ongoing soil degradation, and increasingly intense resource use by burgeoning populations. Climate models predict that warmer temperatures and increases in the frequency and duration of drought during the 21st century will have net negative effects on agricultural productivity. The potential effects of climate change on soil fertility and the ability of crops to acquire and utilize soil nutrients is poorly understood, but is essential for understanding the future of global agriculture. This paper explores how rising temperature, drought and more intense precipitation events projected in climate change scenarios for the 21st century might affect soil fertility and the mineral nutrition of crops in developing countries. The effects of climate change on erosion rates, soil organic carbon losses, soil moisture, root growth and function, root-microbe associations and plant phenology as they relate to mineral nutrition are discussed. Our analysis suggests that the negative impacts of climate change on soil fertility and mineral nutrition of crops will far exceed beneficial effects, which would intensify food insecurity, particularly in developing countries.     

The Circulation of Minerals in Plantations of Pinus sylvestris L.

The dry weights and amounts of sodium, potassium, calcium, magnesium,phosphorus, and nitrogen in the ground flora and organic layersformed over the mineral soil are recorded for an age seriesof plantations of Pinus sylvestris. From these data, the distributionof mineral nutrients within the plantations is deter-mined andcalculations are made of the annual circulation of nutrientsthrough the ecosystem. After 55 years of afforestation the amountof organic matter accumulated over the forest floor is onlyequivalent to the litter fall of the last 6 years. Thus, althoughafforestation results in a progressive accumulation of organicmatter, the woodland community is characterized by a large andrapid transfer of nutrients between the plants and mineral soil.     

模拟氮沉降对华西雨屏区苦竹林土壤有机碳和养分的影响

从2007年11月至2009年10月, 对华西雨屏区苦竹(Pleioblastus amarus)人工林进行了模拟氮(N)沉降试验, N沉降水平分别为对照(CK, 0 g N·m^-2·a^-1)、低N (5 g N·m^-2·a^-1)、中N (15 g N·m^-2·a^-1)和高N (30 g N·m^-2·a^-1)。在N沉降进行1年后, 每月采集各样方0-20 cm的土壤样品, 连续采集12个月, 测定其土壤总有机C、微生物生物量C、浸提性溶解有机C、活性C、全N、微生物生物量N、NH₄⁺-N、NO₃^--N、有效P和速效K。结果表明: N沉降显著增加了土壤总有机C、微生物生物量C、全N、微生物生物量N、NH₄⁺-N和有效P含量, 对其余几个指标无显著影响。土壤微生物生物量C和微生物生物量N的季节变化明显, 并与气温极显著正相关。土壤有效P、速效K与微生物生物量C、微生物生物量N呈极显著负相关关系。N沉降提高了土壤中C、N、P元素的活性, 并通过微生物的转化固定作用使得C、N、P元素在土壤中的含量增加。苦竹林生态系统处于N限制状态, 土壤有机C和养分对N沉降呈正响应, N沉降的增加可能会提高土壤肥力并促进植被的生长, 进而促进生态系统对C的固定。     

Seasonal hyperphagia does not reduce digestive efficiency in an Arctic grazer

Muskoxen (Ovibos moschatus) consume fibrous plants that grow rapidly over the short Arctic summer. We studied responses of eight castrated male muskoxen to a diet of grass hay and mineral supplements during spring, autumn, and winter. Animals gained body mass in spring (239+/-39 kg) as body fat content increased from 26% to 38% of ingesta-free mass in winter without changes in lean mass and protein. Intakes of dry matter (DM) increased by 74% between spring and autumn as digestible energy increased from 554 to 923 kJ kg(-0.75) d(-1) during mass gain. Digestibility of cellulose (72%-76%) was not affected by increasing food intake between spring and autumn but was reduced to 65% in winter. Digestibility of nitrogen compounds was 61%-66%, even though intake increased by 134% between spring and autumn. Excess dietary nitrogen from hay and supplements increased urea concentrations in plasma and urine. High loads of solutes such as potassium did not affect plasma or urinary osmolality but were associated with increased rates of glomerular filtration and urinary excretion. Low intakes of sodium from grasses may limit intake and digestion during summer, but high food intakes can support deposition of nitrogen, calcium, magnesium, copper, and zinc in body tissue even when dietary concentrations are low. Seasonal increases in digestive and metabolic functions allow muskoxen to rapidly accumulate energy and nutrients in body tissue during the short season of plant growth.     

Effects of food quality on life history of the rotifer Brachionus calyciflorus Pallas

1. Herbivorous zooplankton face considerable temporal and spatial variation in food quality, to which they respond by adapting their life histories. Zooplankton may even take up mineral nutrients directly, and use these to counter the effects of algal nutrient limitation (mineral compensation). This study examined the life history of the rotifer Brachionus calyciflorus fed phosphorus‐, and nitrogen‐limited Scenedesmus obliquus (Chlorophyta), and investigated whether B. calyciflorus was capable of mineral compensation. 2. Both phosphorus‐ and nitrogen‐limited algae gave similar life history responses: somatic growth and reproduction were reduced, whereas lifespan remained unaffected. 3. No evidence was found for mineral compensation in B. calyciflorus in relation to detrimental life history effects, so mineral compensation does not seem to be relevant for this species under field conditions. 4. The similarity in life history responses of B. calyciflorus and the low levels of ω‐3 PUFAs in both phosphorus‐ and nitrogen‐depleted algae suggest that ω‐3 PUFAs were limiting to B. calyciflorus, although other (bio)chemicals or mineral nutrients may also have been important. 5. No trade‐off was observed between life span and reproduction during algal nutrient limitation. Reduced population growth rates of B. calyciflorus were caused by shorter reproductive periods.     

Nutrient Cycling in Hampsfell Bracken Grassland Ecosystem,England

The nutrient flow in bracken stands during year showed an inerement of nutrients in standing crop from winter to autumn, reabsorbing the nutrients by plants from soil. In autumn the senescence of live fronds results in a loss of nutrients to standing dead and the nutrients in some below ground standing crop is lost to dead rhizomes. Annual uptakes were estimated to be 17.6 g/m2 potassium, 16.4 g/m2 nitrogen, 12.8 g/m2 calcium, 3.14 g/m2 manganese, 2.47 g/m2 iron, 2.12 g/m2 phosphorus. Compared the annual uptake of elements by bracken with nutrient budget in soil, the efficiency of elements absorbed from soil varied from 0.012 for nitrogen to 1.36 for iron.     

Theoretical and practical approaches to the genetic specificity of mineral nutrition of plants

Summary Mineral nutrition of plants is one of the most important factors controlling biomass production. However, the efficiency of utilizing certain elements of mineral nutrition in biomass production is highly related to the genetic specificity of plants. The present paper deals with problems and former results regarding plant mineral nutrition presented from the genetic aspects. Particular attention has been devoted to the increased efficiency of using both the natural fertility of soils and mineral fertilizers by creating and utilizing suitable cultivars and hybrids, increased efficiency of using mineral nutrients under certain ecological conditions, plant-specific role of microorganisms in enriching soil with nitrogen and soluble forms of other elements, role of genetic specificity of mineral nutrition in plants in solving the problems of environmental pollution, principles of evaluating the genetic specificity of mineral nutrition in plants, genotype features influencing uptake of mineral nutrients, criteria for evaluating the genetic specificity of mineral nutrition of plants, and also to the methods for selecting genotypes for specific soil types, and mineral nutrition.     

Fertilisation practice changes rhizosphere microbial community structure in the agroecosystem

Rhizosphere microbial community is important for the acquisition of soil nutrients and closely related to plant species. Fertilisation practice changed soil quality. With the hypothesis of stronger rhizosphere effect of plant on rhizosphere microbial community than fertilisation management, we designed this research based on a long‐term field experiment (1982–present). This study consists of no fertilisation (NF), mineral fertilisers (NPK), mineral fertilisers plus 7,500 kg/ha of wheat straw addition (WS) and mineral fertilisers plus 30,000 kg/ha of cow manure (CM). After analysing, we found that fertilisation management not only elevated crop yield but also affected crop rhizosphere microbial community structure. The influence of fertilisation practice on wheat rhizosphere microbial structure was stronger than that of wheat. For wheat rhizosphere bacterial community, it was significantly affected by soil water content (SWC), nitrogen (TN), phosphorus (TP), pH, available phosphorus (AVP) and nitrogen (AVN), dissolved organic nitrogen (DON) and carbon (DOC). Besides SWC, pH, AVP, AVN, TN, TP and DOC, the wheat rhizosphere fungi community was also significantly affected by soil organic matter (SOM) and available potassium (AVK). Moreover, compared to rhizosphere bacterial community, the influences of soil physiochemical properties on rhizosphere fungal community was stronger. In conclusion, fertilisation practice was the primary factor structuring rhizosphere microbial community by changing soil nutrients availabilities in the agroecosystem.     

Accumulation and Retranslocation of Mineral Nutrients in Developing Needles in Relation to Seasonal Growth of Young Radiata Pine Trees

The growth, accumulation and movement of mineral nutrients (nitrogen,phosphorus, potassium (calcium) and chlorophyll in needles ofyoung radiata pine trees (Pinus radiata D. Don) were examined,from bud break in spring through the following year. Retranslocationof nutrients from needles was measured and is discussed in relationto nutrient requirements for seasonal growth. During the first 4–5 months after bud break when mostneedle growth occurred, all nutrients and chlorophyll accumulatedprogressively, although the concentrations of nitrogen, phosphorusand potassium decreased. During summer, substantial amounts of phosphorus were withdrawnfrom needles less than 6 months old, regardless of positionon the tree and silvicultural practice. In young needles andunder certain environmental conditions, this led to a markedtemporary decline in concentrations, even in fertilized treeson a fertile site. However, the phosphorus content of needleswas quickly restored following autumn rains. Similar fluctuations,including nutrient withdrawal in summer, occurred for nitrogenand potassium, but these were smaller than those observed forphosphorus. Phosphorus was also withdrawn from relatively olderneedles during summer. It was estimated that on a tree basis 86, 48 and 39 per centof the phosphorus, nitrogen and potassium, respectively, insummer shoots could have come from the retranslocation of nutrientsfrom young needles formed during the preceding spring. These results highlight the importance of nutrients stored inneedles to meet the nutrient requirements for growth when environmentalfactors may not be conducive to nutrient uptake from the soil. Pinus radiata D. Don, mineral nutrition, retranslocation, phosphorus, nitrogen, seasonal effects, pine needle growth