Long-term availability of nutients in forest soil derived from fast- and slow-release fertilizers

The availability of P, K and Mg was studied in boreal forest soil treated 10 years earlier with slow- and fast-release fertilizers. Fast release superphosphate, potassium chloride and magnesium sulphate and slow-release apatite (P) and biotite (K, Mg) were applied alone or together with urea or urea+limestone. The concentrations of total and exchangeable nutrients in the organic horizon and the concentration of exchangeable nutrients in the uppermost mineral horizon were measured. CO₂ production during aerobic laboratory incubation was used to estimate the microbial activity and substrate-induced respiration to determine the microbial biomass C in soil. Biotite caused a moderate but persistent increase in pH in the organic horizon, but this increase was smaller than with lime. The fast-release fertilizers had no effects on the nutrient status of the soil 10 years after the fertilization. However, apatite and biotite still increased the total content of Mg, K and P and the concentrations of exchangeable Mg and soluble P in soil. On the other hand, simultaneous addition of lime and biotite reduced the release of soluble P from apatite. The reduction in soil microbial activity found with urea and the fast-release salts soon after application was no longer evident 10 years later. There was no increase in nitrification in the fertilized soils, not even with the urea+lime treatment. The previous results right after the application and the results presented here do not indicate major leaching of nutrients from the slow-release fertilizers to the deeper soil profiles.     

Mineralization of carbon and nitrogen in acid forest soil treated with fast and slow-release nutrients

The effects of slow (apatite, biotite) and fast-release nutrients (P, K, Mg) on C and N mineralization in acid forest soil were studied. These nutrients were applied alone or together with urea or urea and limestone. The production of CO₂ in the soil samples taken one and three growing seasons after the application was lower in the soils treated with the fast-release nutrients than in the untreated soils. Similar reduction of microbial activity was not seen after the apatite and apatite+biotite treatments. In the first growing season, urea and urea+limestone enhanced CO₂ production, but after three growing seasons, the opposite was true. Apatite and apatite+biotite added together with urea did not compensate for the decreasing effect of urea on the CO₂ production. The addition of fast-release salts increased somewhat the concentration of NH _inf4 ^sup+ in the soil and more NH₄ ⁺ accumulated during laboratory incubation in the soil samples taken one growing season after the application. The urea addition immediately increased the concentrations of NH₄ ⁺ and of NO₃ ⁻ in the soil, but, three growing seasons after application, urea had only a slight increasing effect on mineral N content of the soil. Slow-release nutrients seem to have a more favourable effect than fast-release salts on nutrient turnover in acid forest soil.     

Seasonal variation in nutrient concentration in leaves and branches of Quercus pyrenaica

Abstract. Seasonal variation in nutrient concentration in leaves and branches of Quercus pyrenaica was studied in natural Q. pyrenaica forest in the Sierra de Gata (Salamanca Province, Spain). Two permanent plots were established at the two extremes of a rainfall gradient in this area: annual mean precipitation from 720 mm at Fuenteguinaldo (granite bedrock) to 1580 mm at Navasfrias (schists and graywackes). Leaf and branch samples were collected every three weeks during the growing season from May to October, at three height levels of the tree canopy. Seasonal changes and internal nutrient dynamics were investigated for N, Ca, Mg, K, Na, Mn, Fe and P during a two-year period. The concentrations of all nutrients varied among the seasons; these variations were related to nutrient mobility and the annual physiological cycle. Nutrient concentrations decrease in the case of K and P, while the sparse mobile nutrients Ca, Mg, Mn and Fe gradually accumulated during each growing season. In Navasfrias a considerable resorption of P from senescing leaves was detected. Different patterns were found for the other nutrients studied (Na and N).     

长白山林线主要木本植物叶片养分的季节动态及回收效率

植物叶片养分含量的季节动态和回收效率对植被生态系统的养分循环和植物生长策略具有重要意义。以长白山高山林线上分布的3种主要木本植物——岳桦(Betula ermanii),牛皮杜鹃(Rhododendron aureum)和笃斯越橘(Vaccinium uliginosum)为研究对象,通过测定叶片中N、P、K、Ca、Mg、Fe等6种养分元素含量,分析在林线处植物叶片养分含量的季节动态及其与土壤养分含量的关系。结果表明岳桦和笃斯越橘叶片中养分元素的季节动态基本一致,即:N、P、K含量在生长季内逐渐降低,而Ca的含量逐渐增加;Mg在生长季旺盛期最低,而Fe含量却最高。牛皮杜鹃作为常绿灌木,叶片养分的季节动态与其余两种植物明显不同,表现为在生长季初期6种养分元素含量最低。岳桦和笃斯越橘植物叶片中N、P、K、Fe都有一定程度的回收,但笃斯越橘叶片的养分回收率更高,反映了笃斯越橘更能适应相对贫瘠的环境。3种林线植物叶片中养分含量与土壤养分并不存在显著的相关性,说明长白山林线上土壤中养分的分布没有对林线上3种主要的木本植物的生长和分布产生直接的影响。     

桂北丰水梨园土壤养分与叶片营养的相关性分析

选取桂北地区有生理异常现象发生的丰水梨园,以成年结果树为研究对象,通过检测年生长周期内梨树叶片矿质营养元素、土壤养分的含量,分析不同时期梨树叶片营养元素和土壤养分含量及其动态变化规律,探讨年生长季内叶片营养与土壤养分之间的相关关系。结果表明:(1)在生长季节内,丰水梨叶片中N、P、K含量丰富;营养元素含量随时间的变化幅度均为P最大,N、K较小,但均未达到显著水平(P>0.05)。(2)梨园土壤中有机质、水解性N含量丰富,有效P、速效K含量普遍偏高;年生长周期内土壤速效N、P、K含量随时间的推移变化较大,均达显著水平(P<0.05),而有机质含量则相对稳定。(3)梨树叶片N含量与土壤有机质、水解性N、有效P、速效K含量呈显著正相关关系(P<0.05);叶片P和K含量与土壤水解性N含量分别呈显著负相关和正相关关系(P<0.05),而与土壤有机质、有效P、速效K相关关系不明显。     

Temporal Asynchrony in Soil Nutrient Dynamics and Plant Production in a Semiarid Ecosystem

A central goal of ecosystem ecology is to understand how the cycling of nutrients and the growth of organisms are linked. Ecologists have repeatedly observed that nutrient mineralization and plant production are closely coupled in time in many terrestrial ecosystems. Typically, mineralization rates of limiting nutrients, particularly of nitrogen, during the growing season determine nutrient availability while pools of mineral nutrients remain low and relatively constant. Although several previous reports suggest nitrogen mineralization has the potential to vary seasonally and out of phase with plant production, such a phenomenon has been poorly documented. Here we report results from a semiarid savanna ecosystem characterized by distinct temporal asynchrony in rates of soil nitrogen cycling and plant production. Periods of positive plant growth following the onset of rains coincide with periods of low N turnover rates, whereas higher rates occur late in the wet season following plant senescence and throughout dry seasons. Plant uptake from the substantial mineral N pool present early in the growing season is sufficient to explain most of the N allocation to aboveground plant biomass during the growing season, even in the absence of any wet-season mineralization. The mineral N pool is subsequently recharged by late wet- and dry-season mineralization, plus urine inputs at sites with high levels of ungulate activity. These findings suggest fundamental changes in the quality of substrates available to decomposers over a seasonal cycle, with significant implications for the partitioning of limiting nutrients by plant species, the seasonal pattern of nutrient limitations of aboveground production, and the effective use of N fertilizers in semiarid ecosystems.     

Shoot and root growth and nutrients uptake of wheat as affected by soil layers

The effect of soil layering on the growth and nutrient content of wheat shoots and roots was studied. PVC containers (120 cm long and 25 cm inside diameter) were filled with layers of loam and loamy sand. Both roots and shoots dry weight increased as the thickness of loam layer increased. The root:shoot ratios decreased throughout the growing season. The N, P and K content of the shoots peaked at two weeks before anthesis, while shoot dry weight peaked at anthesis. The ranges of shoot content of N, P and K at anthesis for the different treatments were 6–25, 8–25 and 5–25% of the total plant nutrients, respectively. Late in the season the translocation rate of nutrients from the shoots to the seeds were in the following order N>P>K.     

Temporal patterns of soil nutrients in a Panamanian moist forest revealed by ion-exchange resin and experimental irrigation

The effect of seasonal water availability on soil nutrients and soil N transformations was investigated by irrigating two large plots of mature tropical forest on Barro Colorado Island (BCI), Panama, during the dry season for five consecutive years. Methods included (i) nutrient accumulation by ion-exchange resins placed on the surface of the mineral soil for contiguous 21-day periods, (ii) monthly mineral soil (0–10 cm) extractions and incubations for inorganic N and P concentrations, and (iii) leaching loss of nutrients from leaf litter samples. Rates of nutrient accumulation by the resins showed a great deal of variation between sampling dates and among years in control plots; albeit, seasonal patterns were slight, except for the highest Ca values near the end of the wet season and inorganic P (P_i) and SO₄ values that peaked during the dry season. Irrigation had remarkably little effect on nutrient accumulation rates by resins, except for an increase in Mg and Na values, but did affect the timing in the temporal variation in K, Na, N_i and P_i values. In contrast, inorganic N (N_i) and P_i pools and N transformation rates in the mineral soil hardly varied among sampling dates and did not show any response to irrigation. We hypothesize that the timing of leaf litterfall and nutrient leaching from forest floor litter can set up temporal patterns in the levels of soil nutrient at the surface of the mineral soil, but the temporal patterns essentially disappear with depth in the mineral soil.     

Mineralization of carbon and nitrogen in soil samples taken from three fertilized pine stands: Long-term effects

Seven years after fertilization the rate of CO₂ production in the soil samples taken from the organic horizons of a poor pine forest site (Calluna vulgaris site type), treated with urea or ammonium nitrate with lime, was lower than that in the unfertilized soil. The same trend was also observed in samples of theEmpetrum-Calluna site type 14 years after fertilization. In the more fertileVaccinium myrtillus site type these rapidly-soluble N fertilizers had a long-term enhancing effect on the production of CO₂. Apatite and biotite eliminated the decreasing effect of urea on the production of CO₂. One reason for this might be the long-term increase in soil pH caused by apatite and biotite, or their constituents (Ca, Mg, K, P). Nitroform (a slow-releasing N fertilizer) had no statistically significant effect on the production of CO₂ in soil samples from any of the forest types. Despite the high N mineralization in the samples from nitroform fertilized soils there was no nitrification, and the high content of total N indicated that after nitroform fertilization the losses of N were low.The correlation between the net mineralization values for C (CO₂ production) and N was poor. However, multiple linear regression analysis, which also took into account the effect of nutrients and pH, indicated that there was a link between the mineralization of C and N.     

Applications of mineral nutrients to heavily N-fertilized Scots pine trees: Effects on arginine and mineral nutrient concentrations

The aim of the investigation was to study if improved nutrient status in Scots pine (Pinus sylvestris L) trees would be reflected in decreased concentrations of arginine in the needles. The studies trees had imbalanced mineral nutrient composition and elevated needle arginine concentrations caused by long-term fertilization with N. Concentrations of arginine and mineral nutrients in needles were followed over three consecutive years of additional fertilization with N alone or with P, K, Mg and micronutrients in combination with and without N.Analysis of needle mineral concentrations suggested that there were deficiencies only in K and Mg. The N concentration increased both in trees fertilized with N alone and in trees fertilized with N in combination with mineral nutrients. In the control treatment and in trees fertilized with mineral nutrients other than N the N concentration remained fairly constant. The highest Ca/N, K/N and P/N ratios were found in trees fertilized with mineral nutrients other than N while the lowest ratios were found in trees fertilized with N alone. Arginine concentrations in needles from trees fertilized with N alone remained at a high level throughout the experiment while arginine concentrations in trees given the other treatments decreased.The results show that the mineral nutrient balance can be improved with appropriate fertilization and that this improvement is reflected in decreasing arginine levels. Furthermore the study demonstrates that when N supply is reduced the arginine concentration also decreases also as an effect of reduced N supply per se. The study also indicates that arginine may be a better measure of the N status in pine trees than total N.     

Seasonal variation in the growth and nutrient content of yellow-birch replacement roots

Summary Modified air layers were established on lateral long roots of 9 yellow birch (Betula alleghniensis Britton) trees, and all replacement roots >. 5 cm long were harvested periodically during the 1971 and 1972 growing seasons. The first replacement roots grew 6 weeks after layer establishment. Root layers were inactive from 29 Oct. 71 to 5 May 72. Active root layers produced an average of 208 mg per tree during the first season and 198 mg per tree during the second season. Concentrations of N, P, K, Ca, Mg, Fe, Mn, Zn, and Al all varied within growing season, and average concentration of some elements—Ca in particular—varied between growing seasons. This technique shows promise for studying the nutrient status of root systems of forest trees.     

Fertilizer applications and the organic matter status in the agege experimental field in Nigeria

Summary The influence of 14 years application of mineral fertilizers on the organic carbon content of the Agege sandy soil was appraised. The fertilizer treatments in comparison to unfertilized plots led to higher as well as lower organic carbon. The sole applications of N. P, and K were compared, while N alone increased the organic carbon content of the soil, P alone tended to decrease it, but K alone especially decreased the soil organic carbon. Increased P application, however, could compensate this decrease, whereas increased K-accelerated the decrease. NP and NK combinations showed similar trends to decrease the organic carbon but this decrease was more with NK than NP. But PK fertilizer combinations in contrast to the effect of each of these nutrients alone influenced the organic carbon positively, whereby higher P contents showed again favourable effects than higher K. The fertilizer combinations of the three nutrients (NPK) showed in comparison to unfertilized variants not much higher carbon contents. The complete fertilizer decreased the organic carbon as against unfertilized variants. It was therefore concluded that not always and everywhere can harmonious fertilizer lead to higher organic carbon in the soil, this depends on the type of soil and kinds of cations available in the soil concerned.Ammonium sulphate and urea influenced the content of organic carbon in the soil differently, owing to their different influences on P and K in the soil. Ammonium sulphate in contrast to urea led to mobility of organic carbon in the soil, therefore for better results split application of ammonium sulphate will minimize this effect. For better results of the organic carbon in the soil, mineral fertilizer should not be applied alone but in combination with organic manure. It is also very essential not only to assess the quantity but also qualitative aspect of organic matter as influenced by 14 years of applications.     

Mineralization and distribution of nutrients in plants and microbes in four arctic ecosystems: responses to warming

Mineralization and nutrient distribution in plants and microbes were studied in four arctic ecosystems at Abisko, Northern Sweden and Toolik Lake, Alaska, which have been subjected to long-term warming with plastic greenhouses. Net mineralization and microbial immobilization were studied by the buried bag method and ecosystem pool sizes of C, N and P were determined by harvest methods. The highest amounts of organic N and P were bound in the soil organic matter. Microbial N and P constituted the largest labile pools often equal to (N) or exceeding (P) the amounts stored in the vegetation. Despite large pools of N and P in the soil, net mineralization of N and P was generally low during the growing season, except in the wet sedge tundra, and in most cases lower than the plant uptake requirement. In contrast, the microorganisms immobilized high amounts of nutrients in the buried bags during incubation. The same high immobilization was not observed in the surrounding soil, where the microbial nutrient content in most cases remained constant or decreased over the growing season. This suggests that the low mineralization measured in many arctic ecosystems over the growing season is due to increased immobilization by soil microbes when competition from plant roots is prevented. Furthermore, it suggests that plants compete well with microbes for nutrients in these four ecosystems. Warming increased net mineralization in several cases, which led to increased assimilation of nutrients by plants but not by the microbes.     

长期不同施肥方式对麦田杂草群落的影响

以太湖地区农业科学研究所31a的长期肥料定位试验田为材料,分别于2011—2012年小麦苗期、拔节期和收获期进行了杂草群落调查,研究杂草类型与密度的分布、杂草多样性指数的变化,并对杂草种群分布与土壤养分因子进行冗余分析。结果表明:小飞蓬、看麦娘、大巢菜、稻槎菜、通泉草是本地区小麦生长期的主要杂草类型;随着小麦的生长以及氮肥、有机肥的施入,杂草密度呈下降趋势;施入有机肥降低了麦季杂草的群落多样性指数,在小麦生长的不同时期均衡施肥的CNPK处理以及不施肥的C0处理的群落各项多样性指数能维持在一个较高的水平。RDA分析显示土壤氮含量以及有机质含量与第一排序轴相关性大,是对杂草分布影响最大的两个土壤养分因子。太湖地区稻麦两熟制条件下,长期有机无机肥料单一或配合投入可显著影响麦田杂草的群落组成,其中氮肥和有机肥的施入能显著降低杂草密度;土壤养分的差异影响田面杂草密度和优势种群,均衡施肥能降低优势杂草种群的优势地位,抑制其发生危害程度,提高农田生态系统的生产力及稳定性。     

Use of plant residues for improving soil fertility, pod nutrients, root growth and pod weight of okra (Abelmoschus esculentum L)

The effect of wood ash, sawdust, ground cocoa husk, spent grain and rice bran upon root development, ash content, pod yield and nutrient status and soil fertility for okra (Abelmoschus esculentum L NHAe 47 variety) was studied. The five organic fertilizer treatments were compared to chemical fertilizer (400kg/ha/crop NPK 15-15-15) and unfertilized controls in four field experiments replicated four times in a randomized complete block design. The results showed that the application of 6tha(-1) of plant residues increased (P<0.05) the soil N, P, K, Ca, Mg, pH, and SOM; pod N, P, K, Ca, Mg and ash; root length; and pod yield of okra in all four experiments relative to the control treatment. For instance, spent grain treatment increased the okra pod yield by 99%, 33%, 50%, 49%, 65% and 67% compared to control, NPK, wood ash, cocoa husk, rice bran and sawdust treatments respectively. In the stepwise regression, out of the total R(2) value of 0.83 for the soil nutrients to the pod yield of okra; soil N accounted for 50% of the soil fertility improvement and yield of okra. Spent grain, wood ash and cocoa husk were the most effective in improving okra pod weight, pod nutrients, ash content, root length and soil fertility whereas the rice bran and sawdust were the least effective. This was because the spent grain, wood ash and cocoa husk had lower C/N ratio and higher nutrient composition than rice bran and sawdust, thus, the former enhanced an increase in pod nutrients, composition for better human dietary intake, increased the root length, pod weight of okra and improved soil fertility and plant nutrition crop. The significance of the increases in okra mineral nutrition concentration by plant residues is that consumers will consume more of these minerals in their meals and monetarily spend less for purchasing vitamins and mineral supplement drugs to meet health requirements. In addition, the increase in plant nutrition and soil fertility would help to reduce the high cost of buying synthetic inorganic fertilizers and maintain the long term productivity of soils for sustainable cultivation of okra.     

Nutrient retention by Pseudoscleropodium purum and its relation to growth

Abstract

A complete mineral nutrient fertilizer solution was added to carpets of Pseudoseleropodium purum growing in Windsor Forest, Berkshire, to study the efficiency of nutrient capture from dilute solutions and its effect on growth. In the experiment different frequencies of application were balanced by employing different concentrations of fertilizer so that all treatment plots received the same quantities of nutrients over a six-month period. At the end of the experiment the concentrations of macronutrients (N, P, K, Mg, Ca) within the moss tissues were determined and shoot growth was assessed by the tagged shoot method.

Significant luxury uptake occurred only in the case of P where shoot concentrations in fertilized plots were 50% above the control. Smaller net increases were noted for other elements, particularly Mg. Shoot N concentration was hardly affected by fertilizer application possibly due to efficient internal recycling of the element in P. purum. Levels of exchange ably held cations were not markedly increased by fertilizer addition in the field experiment but when shoots were incubated with fertilizers in the laboratory for 30 min the concentrations of exchangeable Ca and Mg rose appreciably and exchangeable K fell. These changes appear to be quickly reversed under field conditions without transfer of cations to the protoplasts. The importance of elevated cation exchange capacity in the initial sequestration of nutrient cations is, therefore, questioned. Growth stimulation due to fertilizer treatment was negligible. Maximum net uptake of P, Mg and Ca occurred when plots were watered at weekly intervals with a dilute fertilizer and least occurred where a concentrated solution was applied at less frequent intervals implying that contact time between P. purum and its potential nutrients is an important factor. The period elapsing between fertilizer additions may also have significance, however, due to leaching away of nutrients and the re-establishment of a natural ionic balance at the cell wall exchange sites. Levels of nutrient absorption and growth were greatest at a site where the moss remained moist longest. This result indicates that the ability of P. purum to absorb and utilize additional nutrients is governed by general metabolic performance which is itself restricted by water supply in Windsor Forest.     

Significance of sequential leaf development for nutrient balance of the cotton sedge,Eriophorum vaginatum L.

Summary The sedgeEriophorum vaginatum in an interior Alaskan muskeg site produced leaves sequentially at about 1.5-month intervals. Each leaf remained active for two growing seasons. Young leaves (even those initiated late in the season) always had high concentrations of N, P, K and Mg and were low in Ca. Stems had high concentrations of nutrients, sugar, amino acid N and soluble organic P in autumn and spring but low concentrations in summer. Growth of leaves in spring was strongly supported by translocation from storage. Leaves approached their maximum nutrient pool before nutrient uptake began in late spring, one month before maximum biomass. Retranslocation of nutrients from aging leaves could support nutrient input into new, actively growing leaves as a consequence of the sequential leaf development. For instance retranslocation from aging leaves accounted for more than 90 and 85% of P and N input to new leaves appearing in early summer and 100% to leaves that appeared later. Leaching losses were negligible. Half time for decay of standing dead litter was 10 years. We suggest that sequential leaf development paired with highly efficient remobilization of nutrients from senescing leaves enables plants to recycle nutrients within the shoot and minimize dependence upon soil nutrients. This may be an important mechanism enablingEriophorum vaginatum to dominate nutrient-poor sites. This may also explain why graminoids with sequential leaf production cooccur with evergreen shrubs and dominate over forbs and deciduous shrubs in nutrient-poor sites in the boreal forest (e.g., in bogs) and at the northern limit of the tundra zone.     

小麦籽粒不同部位的矿质元素组成与其含量差异

采用X-射线能谱仪测定非糯与糯性等品种小麦籽粒不同部位的矿质元素组成(H和He元素除外)和含量的结果表明:小麦籽粒中除含有大量C、O外,皮层富含K、P、se,其次是Cl、Si、S、Mg和Ca等;糊粉层富含P、K和Mg,其次是Si、Se、S、Ca、Cl和Fe等;胚乳层中相应的矿质元素含量比皮层和糊粉层低。不同品种籽粒各部位的矿质元素含量存在遗传性差异。据此认为籽粒磨成粉时应减少糊粉层的损失,以提高面粉的矿质价值。     

不同施肥模式下潮棕壤稻田的速效养分状况和水稻的养分分配

研究了不同施肥模式下下辽河平原潮棕壤稻田土壤速效养分的供应能力及水稻的养分分配.结果表明:各处理0～20 cm速效养分供应能力均高于20～40 cm,其变异也大于20～40 cm(速效氮除外);有机、无机肥相结合有利于提高土壤速效养分的供应能力;水稻氮和磷的分配主要集中在籽实中,钾的分配则主要集中在秸秆中.采用秸秆还田措施有利于缓解钾肥资源的不足,保持钾素的循环再利用,维持土壤钾库,减少钾肥投入,降低农业生产成本,减轻环境污染.     

Disproportionate allocation of mineral nutrients and carbon between vegetative and reproductive structures in Banksia hookeriana

We compared above-ground allocation patterns in mature shrubs of Banksia hookeriana from three 13-year-old populations, growing on nutrient-impoverished sands to determine whether C (dry mass) could be a substitute for mineral nutrients (N, P, K, Ca, Mg and NA). The percentage of reproductive structures to total above-ground growth (reproductive effort; RE) was integrated over nine successive reproductive cycles. Only 0.5% of above-ground dry mass was allocated to seeds compared with 31% to total RE. Allocations of N (24%) and P (48%) to seeds, and N (44%) and P (65%) to RE were much higher. Allocations of K, Ca, Mg and Na to seeds (<1–3%), and RE (21–35%) were closer to that of dry mass. Relative allocation (RA) is defined as the proportion of a nutrient element allocated to a structure relative to its dry mass. RA of P to seeds was 91 and N was 44, but for K, Ca, Mg and Na ranged from only 6 for K to<1 for Na. Thus P, and to a lesser extent N, provide a much more sensitive measure of the relative cost of reproduction than C in this nutrient-limited system.