密云水库北京集水区油松水源保护林主要养分元素积累与分配研究

对密云水库北京集水区油松水源保护林主要养分元素积累与分配的研究结果表明:29年生油松林的生物量为92 627 kg/hm².油松林不同器官中各养分元素的含量差异较大,在叶、枝和干中各养分元素的含量顺序分别为N(K)>K(N、Ca)>Ca(K)>Mg(P)>P(Mg).根系中的养分元素随着根系直径的增加呈各养分元素的含量降低.油松林生态系统5种养分元素的贮存量为695.17 kg/hm².若以各养分元素在油松林生态系统中的贮存量来计,则N的贮存量最大,P的最小,不同养分元素贮存量的顺序N>Ca>K>Mg>P.油松林生态系统对N元素的富集能力最强,不同器官中各养分元素的富集系数排序均为N>P>K>Ca>Mg.油松林每积累1 t干物质需N、P、K、Ca和Mg等5种养分元素共计7.51 kg.     

Phosphorus,calcium, and magnesium fertilization effects on upland rice in an ultisol

Abstract

Acid‐related soil infertility is the major constraint to crop production on low‐activity clay soils in the tropics. We investigated the role of phosphorus (P), calcium (Ca), and magnesium (Mg) in alleviating the acid‐related fertility problem in upland rice on an Ultisol in the humid forest zone of West Africa. A field experiment was conducted in 1994 under rainfed condition to determine the response of an acid‐tolerant, upland rice cultivar (WAB 56–50) to the application of P, Ca, and Mg nutrient combinations. Phosphorus alone or in combination with Ca and Mg significantly increased yield and agronomic and physiological P efficiencies and improved harvest index of the crop. Application of Ca and Mg alone or together had a non‐significant effect on yield, elemental composition of plant tissue at tillering, and the uptake of macro‐ and micronutrients at harvest. The results indicate that P deficiency was the most important nutrient disorder in the Ultisol and that the application of Ca and Mg as plant nutrients was initially not as important to the growth, yield, and plant nutrient status of an acid‐tolerant upland rice cultivar.     

荔枝年度枝梢和花果发育养分需求特性

【目的】荔枝（Litchi chinensis Sonn.）通常在夏季采果后进行修剪,抽生秋梢作为翌年结果母枝。生产中常有见花后或见果后才施肥现象,不重视对结果母枝的培育,对荔枝的成花和座果可能产生不良影响。本文研究荔枝采果修剪后新梢抽生、花穗萌发及果实膨大成熟年生长周期间树体吸收累积养分特性,为荔枝年度枝梢和花果发育的养分管理提供科学依据。【方法】妃子笑是我国最广泛种植的荔枝品种,通常在采后抽生2~3次秋梢,以末次梢为结果母枝。本文在妃子笑末次梢老熟期、初花期及果实成熟期分别收获三株妃子笑抽生的三次秋梢、秋梢+花穗、秋梢+果实,测定植株各种养分含量,研究妃子笑年度枝梢和花果发育养分需求量及养分转移特点。【结果】妃子笑末次梢生物量及各种养分（Ca例外）累积量均约为前两次梢之和。为获得（55.27.8）kg/tree的产量,每株妃子笑需抽生秋梢（39.782.60）kg,秋梢累积养分量为N（259.528.4）g、P（28.32.6）g、K（186.519.6）g、Ca（41.69.2）g、Mg（36.14.7）g、S（12.436.1）g、Zn（316.853.4）mg、B（201.129.0）mg和Mo（1.40.3）mg。妃子笑花穗累积的N、P、K、Mg、S、Mo养分全部来自于末次梢,67.5%的Zn和20.2%的B也来自末次梢。但是,末次梢吸收Ca能力弱,而且向花穗及果实转移Ca能力低。妃子笑秋梢与花穗N、P、K、Ca、Mg养分累积比例在1:0.11~0.12:0.72~0.75:0.16~0.44:0.13~0.14之间,在果实比例为1:0.13:1.06:0.16:0.12。【结论】荔枝在末次梢老熟至开花初期,树体除继续累积Ca、Zn、B外,基本不吸收其他养分。果实累积的N、K、Ca、Zn、S养分基本全部来自果实膨大期树体的吸收,而P、Mg、B、Mo则部分来自于第一和第二梢的养分转移。故健壮秋梢是荔枝成花的关键,也是获得高产的物质基础,应避免见花施肥或见果施肥。秋梢及花穗发育期以施用氮肥为主,果实发育期以施用钾肥为主。     

Decomposition rates of forest residues and soil fertility after clear‐cutting of Eucalyptus grandis stands in response to site management and fertilizer application

Forest residues (i.e. harvest residues and litter) are important nutrient sources for trees because soils of poor fertility are used for eucalypt plantations in Brazil. Understanding the dynamics of decomposition for these residues and their effects on soil fertility are relevant for the management of forest plantations. The objectives with this study were to assess the effects of forest residue management and fertilizer, both applied in the establishment of a Eucalyptus grandis Hill ex Maiden stand, on the decomposition rate (k), nutrient release and soil fertility after harvest of this stand. The treatments were applied to a plantation (R1). After 8 yr, R1 was clear‐cut and all of the treatments were reapplied to a new planting (R2). At the end of R1 (age of 8 yr), there was a reduction of 10% in the wood volume in the treatment with the forest residues removed and 36% reduction with no fertilizer application. At the end of 1 yr for plantation R2, these reductions were 30 and 57%, respectively. Residue decomposition under R2 was assessed by a new approach that involved collecting samples directly on the site without using litter bags. The k of forest residues was 3.6 for leaves, 1.2 for bark and 0.8 for branches. The application of small rates of N and P fertilizer did not influence the k of forest residues. In the first 300 days after clear‐cutting, approximately 50% of N, P, Ca, Mg and S and 80% of K in the forest residues were released. Even so, this did not result in significant changes in soil fertility levels. Only small reductions in soil N and P contents over time and changes in topsoil pH resulted from forest residue removal.     

Foliar nutrient status in three boreal species for three years following hexazinone application

Abstract

Effects of hexazinone on the dynamics of macronutrients were studied in the foliage of trembling aspen, showy aster and marsh reed grass for three years after broadcast application of 10% granular formulation of hexazinone at 0, 2, and 4 kg ai/ha rates in August 1986 in a 3‐year‐old mixedwood cutover in a boreal forest. In untreated plots, nutrient concentrations followed normal patterns: calcium (Ca) increased from spring to late summer; potassium (K), phosphorus (P), sulfur (S), and nitrogen (N) peaked in early summer and declined towards fall; and magnesium (Mg) did not show any definite trends. At each sampling date, the coefficient of variation ranged from <10% for Ca, Mg, K and total N to 10–20% for P and S. Seasonal variations in the concentrations of each element were greater than the year‐to‐year variations. In treated plots, hexazinone application resulted in elevated concentrations of total Ca, Mg, K, P, S, and N during the first growing season, but these changes were only significant (P<0.05) at the 4 kg rate. The intensity of the effects declined by the end of the second growing season following herbicide application. In 1989, differences between nutrient levels in foliage from control and treated sites were significant (P<0.05) only for total N. Consequently, any changes in the nutrient status of hexazinone‐treated sites (beyond two years post‐treatment) are not expected to result from changes in foliar nutrient levels, but rather from changes in litter fall quantities, species dominance and total vegetation cover. Nutrient quality of forage for wildlife would not be affected beyond two years post‐treatment.     

Ripening season affects tissue mineral concentration and nutrient partitioning in peach trees

The objective of this research was to determine the influence of ripening season on nutrient concentration and nutrient partitioning of peach trees (Prunus persica L. Batsch). We selected peach trees from three different ripening seasons and measured: (1) the concentration of macronutrients in pruned wood, thinned fruitlets, harvested fruit, and leaves fallen in autumn and (2) the total amount of macronutrients at each of these removal events. Our results showed that early‐season cultivars had more K in pruned wood, more P and K in fallen leaves, and more N, P, K, and Mg in mature fruits than mid‐ and late‐season cultivars. Also, early‐season cultivars removed more dry weight from pruned wood and fallen leaves but less from fruit than mid‐ and late‐season cultivars. These results suggest that different ripening season can affect peach tree nutrient concentration and nutrient partitioning and, consequently, peach cultivars harvested at different times of the year may benefit from specific fertilization programs rather than uniform, calendar‐based fertilization programs.     

Wood Ash Effects on Soil Solution and Nutrient Budgets in A Willow Bioenergy Plantation

The management of wood ash is an important factor in the environmental and economic analysis of wood burning. Wood ash can be applied to energy crops as a fertilizer, which can help replace nutrients removed during harvest. The objectives of this study were to examine the temporal and spatial dynamics of nutrient elements applied in wood ash to an intensively cultured, short-rotation willow bioenergy system. Wood ash was applied at the rates of 10 and 20 Mg ha^–1 yr^–1 to coppiced willow, Salix purpurea, clone SP3, from 1992 to 1994. The relative abundance of nutrients in applied wood ash was Ca > K > Mg > P > N. There was little effect of wood ash on N or P concentrations in soil solution measured at 20 and 40 cm depth. Soil solution concentrations of base cations were elevated in the last two years of the study by 30 to 90%, depending on the element and treatment, in plots receiving wood ash. Wood ash treatments had little influence on foliar leaching. Wood ash treatment also had few significant effects on willow growth or on the contents of N, P, K, Ca, and Mg in foliage and stems. The addition of P, K, Ca, and Mg in wood ash was more than enough to compensate for harvest removals and leaching losses. This study demonstrated that wood ash can supply most nutrients removed during harvest in willow plantations, with the exception of N, without adverse effects on groundwater or vegetation.     

Seasonal variation in nutrient concentration in leaves and inflorescences of Avocado

The concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were determined in leaves from the north and south sides of the tree canopy, and in apical and basal parts of winter and fall inflorescences of 20‐year‐old ‘Colin V‐33’ avocado (Persea americana Mill.) trees, to observe the seasonal variation of all these nutrients in leaves and in inflorescences. The concentration of all the elements evaluated did not change considerably during the months of flowering and vegetative growth, but it changed with leaf age. The concentration of Ca and Mg were 14 and 7% higher, in the leaves on the south side of the canopy than in those on the north side. Inflorescences had higher P and K, and lower Ca and Mg concentrations than leaves. The concentration of Ca and Mg was higher in the winter inflorescences than in the autumn ones. The concentration of P was significantly higher in the apical part of the inflorescence than in the basal part.     

Effect of fertilization and harvest frequency on yield and quality of tall fescue and smooth bromegrass

Abstract

Fertilization and harvest frequency affect yield and quality of forages. The purposes of this experiment were to determine (i) the effects of fertilization and frequent harvesting on yield and quality of tall fescue (Festuca arundinacea Schreb.) and smooth bromegrass (Bromus inermis Leyss.) and (ii) the efficiency of N in animal waste as compared with inorganic N fertilizer for forage production of these cool season grasses. ‘Fawn’ tall fescue and ‘Southland’ smooth bromegrass were grown in the greenhouse on Pullman clay loam topsoil (fine, mixed thermic Torrertic Paleustoll) under eleven fertilizer treatments and two harvest regimes. Nitrogen fertilizer increased yields, N and K concentrations and K/(Ca + Mg) ratios and decreased P, Ca, and Mg concentrations. Phosphorus and K fertilizers did not affect yields but applied P increased P and tended to decrease N and Ca concentrations. Applied K tended to increase Ca concentrations. Recovery of N from feedlot manure ranged from 0.8 to 14%, whereas, recovery from NH₄NO₃ averaged 64%. Harvesting at 3‐week rather than at 6‐week intervals reduced yields 25%; however, N and P removal were higher under the 3‐week harvest regime. Even though forage production was reduced under heavy utilization, the grasses required more N fertilizer under heavy than under lighter utilization. The two grasses produced similar yields under the 3‐week cutting regime and at N rates through 340 kg/ha under the 6‐week cutting regime. Tall fescue yields were higher with the higher N rates under the 6‐week cutting regime. Smooth bromegrass forage was higher than tall fescue forage in N, K, and Ca, whereas tall fescue forage was higher in P and Mg.     

Contribution of decomposing harvest residues to nutrient cycling in a second rotation Eucalyptus globulus plantation in south-western Australia

Amounts of nutrients in harvest residues and their contribution to nutrient cycling were quantified following logging of a Eucalyptus globulus plantation in south-western Australia. An estimated 64 t ha^–1 of leaf, bark and branch material less than 3 cm in diameter was deposited on the forest floor during harvesting. Leaves contributed about one-third of the residue dry weight but accounted for almost three-quarters of residue-N stores (299 of 428 kg N ha^–1) and 36% to 52% of P, K, Ca, and Mg stores. Stores of nutrients in slash were significant in comparison to amounts in surface soil (0–20 cm). Residue-N amounted to 11% of total surface soil N and cations stored in residues were equivalent to 23–114% of surface soil exchangeable cations. Decomposition of the leaf fraction of slash was rapid with more than 90% of dry weight released during the 105-week study. Bark and branch fractions of diameters 0.5, 1 and 2 cm lost 39%, 37%, 32% and 29% of dry weight, respectively, during the same period. Single and double exponential decay models fitted to the data indicated half lives ranging from 20 weeks for leaves and from 3 to 4 years for bark and the branch fractions. During decomposition, K was leached rapidly from all residue fractions, Mg and P were released at similar rates to dry weight, and Ca and N were released more slowly than dry weight. In the 105-week study period, 250 kg ha^–1 of N, 20 kg ha^–1 of P, 213 kg ha^–1 of Ca, 298 kg ha^–1 of K, and 63 kg ha^–1 of Mg were returned to the soil from decomposing harvest slash. The leaf fraction was the major contributor to nutrient cycling, accounting for almost all of the N and Ca release and from half to three-quarters of the K, Mg and P released. Amounts of nutrients released from residues in the year following logging greatly exceeded quantities likely to be taken up by the newly established tree crop.     

Application of lime and wood ash to decrease acidification of forest soils

Liming and wood ash application are measures to decrease acidification of forests soils. The assessment of lime requirement can be based on that base saturation, which indicates a low risk of acid toxicity. Because of a wide spread Mg deficiency in Central European forests, Mg containing lime is normally applied. Ash from untreated wood is applied to decrease soil acidity as well as to improve K and P nutrition. In wood ash, K is the most soluble nutrient, follwed by Ca and Mg. The overall dissolution rate of lime applied to the forest floor is about 1t ha^?1 a^?1. After liming, soil solution alkalinity and Mg concentrations increase markedly, while changes of Ca, H ions and Al concentrations are less pronounced. After the application of wood ash, K concentrations increase due to the high K content and the high solubility of K in wood ash. After the application of a sufficiently high dosage of lime to the forest floor, the decrease of acidity in deeper soil layers may need decades because of the low solubility of lime. Nitrification and nitrate leaching induced by lime or wood ash may reduce their acid buffering efficiency.     

De‐eutrophication of a nitrogen‐saturated Scots pine forest by prescribed litter‐raking

Short‐term (<7 years) effects of prescribed litter‐raking on forest‐floor nutrient pools, stand nutrition, and seepage water chemistry were studied in an N‐saturated Scots pine (Pinus sylvestris L.) forest in Southern Germany subject to high atmospheric‐nitrogen deposition. The study was based on a comparison of plots with and without annual prescribed litter raking at three sites with different N‐deposition levels. Prescribed litter‐raking resulted in a considerable reduction of forest‐floor thickness and mass, as well as of forest‐floor C, N, P, K, Mg, and Ca pools. Furthermore, it induced a significant decrease of the foliar N content in current‐year needles of the pines and a more balanced nutritional status of the stand. Particularly on the site subject to the highest N deposition, but to a lesser degree also at the other sites, the mean NO concentration in the subsoil seepage water and the N export into the groundwater were substantially reduced on the litter‐raked plots. The results show that in N‐saturated Scots pine ecosystems prescribed litter‐raking on areas of limited size, which are used as sources of groundwater‐derived drinking water and/or serve as habitat for endangered plant species, is a quick and effective method to achieve a more balanced nutritional status of the trees and to reduce seepage‐water NO concentrations and N export into the groundwater. In terms of sustainable ecosystem nutrient management, the conversion of conifer monocultures into broadleaf‐rich mixed stands is the better, yet less immediately effective method to reduce the seepage‐water N export from conifer forests subject to high atmospheric‐N deposition.     

Seasonal fluctuations in microbial populations and available nutrients in forest soils

Viable microorganisms, soil respiration, and available N, Ca, Mg, Na, K, and P contents were determined in samples of five different forest soils collected in spring, summer, autumn, and winter. Viable microorganisms and soil respiration were positively correlated and showed a clear seasonal trend. The soils exhibited high microbial population values in spring and autumn and low values in summer and winter; total respiration values were largely higher in autumn than in the other seasons. Seasonal variations in available Ca, Na, and K contents were much more marked than those found for available N, Mg, and P. Available N and K and the microbial population showed similar seasonal trends whereas available Ca, Mg, Na, and P did not exhibit a distinguishable and uniform seasonal pattern. The quantities of available nutrients in soils followed the order Ca>K=Na>Mg>P>N. Soils developed over basic rocks showed higher values of both microbial density and microbial activity than those in soils developed over acid rocks. All the variables analysed were clearly related to the type of soil but varied with the date of sampling; a significant seasonal effect on the microbial population, microbial activity and available nutrients was detected in all the soils studied.     

Nutrient uptake and removal by Christmas tree harvest

Writing nutrient management plans for Christmas tree production requires accurate values for nutrient removal and harvest records. Freshly cut trees of each of Norway spruce (Picea abies), Canaan fir (Abies balsamea var. phanerolepis), and Douglas fir (Pseudotsuga menziesii) were collected in December 2005. Minimum, maximum, and mean cut tree size measurements were documented. Nutrient contents were calculated and there were no significant differences in nutrient uptake values among species. In a spacing of 1.5 m × 1.5 m (4302 trees per hectare), a clear-cut harvest would remove on average (kg/ha) 560 nitrogen (N), 60.87 phosphorus (P), 168 potassium (K), 243.51 calcium (Ca), 37.75 magnesium (Mg), 28.25 sulfur (S), 0.54 boron (B), 3.39 iron (Fe), 4.74 manganese (Mn), 0.11 copper (Cu), 2.79 zinc (Zn), 2.92 aluminum (Al), 105.85 chlorine (Cl), 0.02 molybdenum (Mo), and 1.44 sodium (Na). Except for Mn and Na, nutrient removal increased linearly as dry weight of whole tree increased.     

Seasonal dynamics of mineral nutrients by walnut tree fruits

Walnut (Juglans regia L.) tree fruit showed after the endocarp lignification a fast growing stage during which fresh and dry weights increased abruptly. From the beginning of fruit ripening and during the fast sperm growing stage, fresh weight started to decrease while dry weight continued to increase with a reduced growth rate. Dry weights increased in sperm and decreased in exocarp‐mesocarp tissues during the fast sperm growing stage. The material exit from pericarp tissues was completed in the ripe fruit. By contrast, fresh weight continued to decrease in the tissue. Patterns of nutrient accumulation per fruit increased continuously during the fruit growth period. The observed reductions of nutrient accumulations for total nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in the fruit individuals during the very late fruit stage after fruit ripening, and in conjunction with the pericarp tissues senescence, are supposed to represent mineral nutrient returns from the ripe fruit. Patterns of total N, P, Mg, Fe, and Zn accumulations increased in the exocarp‐mesocarp tissue during the slow sperm growing stage and decreased during the fast sperm growing stage. Potassium accumulation in the tissue increased continuously up to the fruit ripening time. Calcium, Mn, and Cu increased continuously. Patterns of all nutrients in endocarp tissue increased during the slow sperm growing stage and decreased at the fast sperm growing stage. In the sperm tissues, total N, P, Mg, and Ca accumulations increased during the sperm development and slightly decreased in a late stage. The increasing trend of Ca accumulation was temporarily interrupted during the fast sperm growing stage. Iron, Mn, Cu, and Zn accumulations showed no reductions at all. Potassium accumulation was drastically restricted in the tissue with the approach of fruit ripening. Sperm tissues are extraordinary rich in mineral nutrients. Sperm total N, P, Mg, Mn, Zn, Cu, and Fe accumulations represented the 98.1%, 88.2%, 59.2%, 81.5%, 72.3%, 65.6%, and 52.5% of the total nutrients accumulation in the fruit, respectively. Sperm K and Ca accumulations represented only the 13% and 11.6%, respectively. Exocarp‐mesocarp K, Ca, and Mg accumulations represented the 76%, 72% and 37.1% of the total nutrients accumulation in the fruit individual, respectively. Total N and P accumulation in the tissue were detected in very low levels 1.3% and 7%, respectively. Iron, Cu, Zn, and Mn accumulations were detected in the same tissue in ratio values of 27.5%, 22%, 5.4%, and 11%, respectively. Macro‐ and micro‐nutrient accumulations of the endocarp tissues were detected in the lower levels as compared to the other fruit tissues. The estimated values of mineral nutrient returns from the mature fruit individuals were 2.8% for total N, 13% for P, 16.5% for K, 23% for Ca, 12% for Mg, 28.5% for Fe, and 21% for Zn. Manganese and Cu showed no returns at all. The estimated nutrient returns from the sperm tissues were 60% for total N, 67% for P, 22% for K, and 50% for Mg of the total returned nutrient from the fruit individual. The estimated nutrient returns from exocarp‐mesocarp were 100% for Zn, Fe, and Ca, 50% for Mg, 78% for K, 33% for P, and 40% for total N. Calcium, Fe, Mn, Cu, and Zn in the sperm and Mn and Cu accumulations in pericarp tissues showed no returns at all. A restricted nutrient diffusion from exocarp‐mesocarp and sperm tissues to the endocarp tissues is supposed to be possible. These results suggested a pericarp tissue behaviour similar to the old senescing leaves.     

Seasonal dynamics of mineral nutrients and carbohydrates by walnut tree leaves

The dry weight accumulation per leaf as well as the concentration per gram of dry weight and the accumulation of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were determined in walnut tree leaves (Juglans regia L.) during a complete life cycle. Additionally, the dynamics of plant nutrient concentration in leaf petiole sap and carbohydrate accumulation in leaves were studied in relation to the main life cycle events of the walnut tree. Total N, P, K, Cu, and Zn concentrations decreased, whereas that of Ca, Mg, and Mn increased during the season. Iron concentration fluctuated around a mean value. Total N, P, K, Mg, and Cu concentrations detected in younger mature leaves were at the sufficient level, whereas Ca, Fe, Mn, and Zn concentrations were at higher levels as compared to those previously reported. All the detected nutrient accumulations increased abruptly during leaf ontogeny and leaf maturation until a maximum level was attained in the younger mature leaves. Similarly, sucrose, glucose, and fructose accumulation were observed at the same period. The rates of total N, P, Cu, and Zn accumulation were lower than the rates of the observed dry matter accumulation and nutrient concentration dilution. Potassium and Mn accumulation rates were almost equal, whereas those for Ca and Mg were higher as compared to the dry matter accumulation rate. The fast embryo growing phase resulted in a considerable decrease in dry weight, total N, P, K, Cu, Zn, and carbohydrate accumulation, and to a lesser degree in Ca, Mg, and Mn accumulation. Nutrient accumulation reduction in leaves by the influence of the growing fruits were estimated to be: total N 52%, K 48%, P 29.5%, Mg 16.3%, Ca 15%, Fe 51.2%, Cu 55.2%, Zn 37.3%, and Mn 5.4% of the maximum nutrient value of the younger mature leaves. Old leaves preserved nutrients before leaf fall as follows: total N 25.4%, P 45%, K 31%, Ca 74.8%, Mg 76.5%, Mn 89.2%, Fe and Zn 50%, and Cu 37%. Nutrient remobilization from the senescing old leaves before leaf fall were: total N 22.6%, P 25.5%, K 21%, Ca 10.2%, Mg 7%, Fe 3.2%, Mn 5.4%, Cu 8%, and Zn 13.3% of the maximum value in the younger mature leaves. In early spring, the absorption rates of N, P, and Ca were low while those of Mg, Fe, Mn, Cu, and Zn were high. During the fast growing pollen phase, the N, P, Fe, Mn, Cu, and Zn concentrations were reduced. Calcium concentration is supposed to be more affected by the rate of transpiration rather than during the growing of embryo. Calcium and Mg concentrations in the sap were negatively correlated. The detected K concentration level in the sap was as high as 33 to 50 times that of soluble N, 12 to 21 times to that of P, 5 times to that of Ca, and 10 to 20 times to that of Mg. The first maximum of starch accumulation in mature leaves was observed during the slow growing embryo phase and a second one after fruit ripening. Old senescing leaves showed an extensive carbohydrate depletion before leaf fall.     

Metal,nutrient and biomass accumulation during the growing cycle of Miscanthus established on metal‐contaminated soils

The energy crop Miscanthus presents high potentials for phytomanagement. Its shoot yield and nutrient accumulation has been extensively characterized in uncontaminated agricultural soils, while very little is known for metal‐contaminated conditions. This study aimed at assessing potential differences in dry matter and metal and nutrient accumulation of the standing aerial biomass in Miscanthus (M. × giganteus) growing in situ on agricultural plots presenting different soil Cd, Pb, and Zn concentrations. Plant samplings were conducted monthly along the growing period from May to December. Cadmium, Pb, Zn, and the concentrations of the nutrients N, P, K, Ca, Mg, and Na were determined in leaves and stems separately. During the growing phase, the maximum dry matter was reached in early in autumn. Whatever the organ, Cd and Zn concentrations were higher on contaminated than on uncontaminated plots. During summer and autumn, Zn and Pb concentrations were higher in leaves than in stems whereas Cd concentrations did not significantly differ between the organs. Concentrations of N, P, K, and Mg decreased across the study period whereas those of Ca and Na increased. Overall, metal and nutrient concentrations depended on plant organ and its development stage. The dry matter and nutrient accumulation patterns were not different between contaminated and uncontaminated plots. The significance of these findings is discussed in light of best phytomanagement practices and potential uses of Miscanthus biomass.     

Effect of potassium and boron upon yield and nutrient concentration of alfalfa

An alfalfa experiment was conducted to determine the effect of rates of K applied in the fall and rates of K applied, one‐half in the fall and one‐half after first harvest, upon yield and chemical composition. Three rates of B applied in the fall and also one‐half in the fall and one‐half after first harvest at the highest K rate (560 kg/ha) were also included. Herbage samples were taken from each plot at each harvest and analyzed for N, P, K, Ca, Mg, B, Cu, Fe, Mn and Zn. Significant effects of fertility upon yield and nutrient content were observed. Harvest x fertility interactions also affected many parameters. The Cu concentration of herbage was relatively uniform and not significantly affected by any factors studied.     

Relationship between Norway Spruce Status and Soil Water Base Cations/Aluminum Ratios in the Czech Republic

There is a concern that soil acidification by acidic deposition, along with the resulting depletion of the labile pool of nutrient cations (e.g. Ca, Mg) and enhanced leaching of Al from soil may contribute to forest dieback. The molar ratios of Ca/Al or (Ca+Mg+K)/Al in the soil solution have been widely used as a criterion for risk of tree damage due to acidification. Intensity and quality of the crown and branch structure transformation due to formation of secondary shoots in successive series is a very sensitive indicator of long-term tree damage, and the subsequent regenerative processes. Soil water chemistry and crown structure transformation of Norway spruce were observed at 16 forest plots within the Czech Republic with the following results: parameters, expressing degradation processes in the crown (defoliation of primary structure), regeneration processes (percentage of secondary shoots) or synthetic stages of crown structure transformation showed high correlation with soil water (Ca+Mg+K)/Al ratio in organic horizons. No relationships were found for mineral horizons. The correlations between soil water and crown status parameters were considerably stronger when using the (Ca+Mg+K)/Al ratio rather than the Ca/Al ratio.     

Dry‐matter production,mineral nutrient concentrations,and nutrient distribution and redistribution in irrigated spring wheat

A field study was made of the seasonal changes in dry‐matter production, and the uptake, distribution, and redistribution of 12 mineral nutrients in the semi‐dwarf spring wheat, Egret, grown under typical irrigation farming conditions. Most of the dry‐matter production and nutrient uptake had occurred by anthesis, with 75–100% of the final content of magnesium (Mg), copper (Cu), chloride (Cl), sulfur (S), phosphorus (P), nitrogen (N), and potassium (K) being taken up in the pre‐anthesis period. The above‐ground dry‐matter harvest index was 37%, and grain made up 76% of the head dry matter. Redistributed dry matter from stems and leaves could have provided 29% of the grain dry matter. Concentrations of phloemmobile nutrients, such as N and P, decreased in the leaves and stems throughout the season, whereas concentrations of phloem‐immobile nutrients, such as calcium (Ca) and iron (Fe), generally increased. The decline in the N concentration in stems and leaves was not prevented by N fertilizer applied just before anthesis. Leaves had the major proportion of most nutrients in young plants, but stems had the major proportion of these nutrients at anthesis. Grain had over 70% of the N and P, and 31–64% of the Mg, manganese (Mn), S, and zinc (Zn), but less than 20% of the K, Ca, sodium (Na), Cl, and Fe in the plant. Over 70% of the N and P, and from 15 to 51% of the Mg, K, Cu, S, and Zn was apparently redistributed from stems and leaves to developing grain. There was negligible redistribution of Ca, Na, Cl, Fe, and Mn from vegetative organs. Redistribution from stems and leaves could have provided 100% of the K, 68–72% of the N and P, and 33–48% of the Zn, Cu, Mg, and S accumulated by grain. It was concluded that the distribution patterns of some key nutrients such as N, P, and K have not changed much in the transition from tall to semi‐dwarf wheats, and that the capacity of wheat to redistribute dry matter and nutrients to grain is a valuable trait when nutrient uptake is severely restricted in the post‐anthesis period.