Carbon-allocation dynamics in reed canary grass as affected by soil type and fertilization rates in northern Sweden

Abstract

A field experiment was conducted in northern Sweden between 1995 and 1997, with the objectives (1) to quantify the dynamics of carbon accumulation in above- and belowground crop components of reed canary grass (RCG) during the second and third year after sowing and (2) to examine the effect of fertilization and soil type (mineral vs. organic) on C allocation. Across all treatments, carbon accumulation in belowground organs in the top 20 cm was on average 3 and 3.4 Mg C by the end of the second and third year, respectively, with roots and rhizomes accounting for up to 80%. Roots contributed most to belowground C mass during the second growing season but during the preceding winter, root biomass C decreased by 44–67%, and, thereafter, during the third growing season, the proportion of rhizome C increased. The dynamics of root biomass was considerably high, suggesting high root turnover rates. Rhizomes support re-growth during spring and rhizome biomass seems to increase with crop age. Thus, early harvesting before October may impact on the productivity during the following season.

Among the factors studied, harvest date was the most influential and affected C allocation in all crop components considerably. Fertilization stimulated growth of shoots, rhizomes, and BSBs (belowground shoot bases) but not that of roots. However, root biomass was higher in the organic than in the mineral soil. In this study, we considered only plant components above 20 cm depth. More detailed studies are needed to calculate more complete soil C balances. However, high belowground biomass production and root turnover indicate a high C input to the soil, which may result in positive soil C balances. Therefore, RCG cropping could have considerable carbon-sequestration potential.     

Nutrient Bioaccumulation in Phragmites australis: Management Tool for Reduction of Pollution in the Mar Menor

We studied nutrient removal by Phragmites australis in the Albujón rambla, the main drainage system that discharges into the Mar Menor, a Mediterranean coastal lagoon of high conservation interest, but highly threatened by point and nonpoint pollution derived from tourism and agricultural activities. We measured aerial biomass and N and P concentrations in both aboveground and belowground tissues of common reed during an annual cycle that included two cutting events and two periods of reed growth (one at the end of summer after cutting and another at the beginning of spring, following their natural cycle). The temporal variation of N and P concentrations was related to the phenology of the plant and cutting events. The maximum nutrient concentrations were recorded in young stems in the initial stages of the autumn growing season (35.86 mg N g^?1 and 2.38 mg P g^?1). The phosphorus dynamics showed evidence of translocation processes related with growth activity, although no evidence of N translocation was found. In November and in summer, when aerial growth ceases because of the hard conditions, the P concentration in rhizomes was higher than in stems, while in spring and in September, the period of maximal growth, the reverse relation was found. The highest total amounts of the two elements in the aboveground biomass (0.54 Tm N ha^?1 and 0.25 Tm P ha^?1) were reached in July, coinciding with the highest biomass (3.72 kg DW m^?2), which then decreased to approximately half in August. Nutrient content in the aboveground tissues was highly dependent on the ammonium and nitrate water concentrations. In addition, the N content was inversely related to the C_org/N of sediments, while the P content was influenced positively by the phosphorous concentration of the water. Common reed of the Albujón rambla corresponds to the assimilation type, adapted to nutrient-rich habitats, which is characterized by a pronounced external N cycle and P internal reserves. Based on the results obtained, we propose a management plan for common reed to help control eutrophication of the Mar Menor lagoon. This would bring forward reed cutting to the beginning of summer, instead of August, coinciding with the time of maximum aerial biomass, greater nutrient retention, and lower risk of strong precipitation.     

Nitrogen uptake,nitrate leaching and root development in winter‐grown wheat and fodder radish

Early seeding of winter wheat (Triticum aestivum L.) has been proposed as a means to reduce N leaching as an alternative to growing cover crops like fodder radish (Raphanus sativus L.). The objective of this study was to quantify the effect of winter wheat, seeded early and normally, and of fodder radish on N dynamics and root growth. Field experiments were carried out on a humid temperate sandy loam soil. Aboveground biomass and soil inorganic N were determined in late autumn; N uptake and grain yield of winter wheat were measured at harvest. Nitrate leaching was estimated from soil water samples taken at 1 m depth. Root growth was measured late autumn using the core break and root washing methods. Winter wheat root growth dynamics were followed during the growing season using the minirhizotron method. The 2013–2014 results showed that early seeding of wheat improved autumn growth and N uptake and reduced N leaching during the winter compared with the normal seeding time. Early‐seeded wheat (WW_early) was, however, not as efficient as fodder radish at reducing N leaching. Proper establishment of WW_early was a prerequisite for benefiting from early seeding, as indicated by the 2012–2013 results. Early seeding improved root growth throughout the 2013–2014 growing season compared with normal seeding time, but had no significant effect on crop grain yield. Our results indicate the potential of using early seeding as a tool to limit drought susceptibility and increase nutrient uptake from the subsoil.     

A glass house trial to investigate the impact of water treatment sludge and green waste compost to enhance the revegetation of contaminated sites

This study investigated the use of waste amendments (green waste compost (GWC) and water treatment sludge (WTS) cake) in improving the nutrient and revegetation status of contaminated soil obtained from a former industrial site that has heavy metal and hydrocarbon contamination. The waste amendments were mixed with the contaminated soil at application rates equivalent to 90 and 180 t ha^?1 (wet weight) and placed in plastic pots. The unamended soil serves as the control. Reed canary grass and white mustard were allowed to grow on the amended and unamended contaminated soil in the glass house. After a 30- day growth period, soil nutrient status was observed and was found to be higher in the amended contaminated soil than the control. In the amended soil, organic matter, total nitrogen, total potassium and soil nitrate were highest in contaminated soil amended with GWC at 180 t ha^?1 and lowest in contaminated soil amended with WTS cake at 90 t ha^?1. Above-ground dry mass of reed canary grass and white mustard grown on amended contaminated soil increased by 120–222% and 130–337%, respectively, as compared to the control, showing that improved fertility of contaminated soils thereafter, enhanced revegetation.     

Elevated CO2 differentially alters belowground plant and soil microbial community structure in reed canary grass-invaded experimental wetlands

Several recent studies have indicated that an enriched atmosphere of carbon dioxide (CO₂) could exacerbate the intensity of plant invasions within natural ecosystems, but little is known of how rising CO₂ impacts the belowground characteristics of these invaded systems. In this study, we examined the effects of elevated CO₂ and nitrogen (N) inputs on plant and soil microbial community characteristics of plant communities invaded by reed canary grass, Phalaris arundinacea L. We grew the invasive grass under two levels of invasion: the invader was either dominant (high invasion) at >90% plant cover or sub-dominant (low invasion) at <50% plant cover. Experimental wetland communities were grown for four months in greenhouses that received either 600 or 365 μl l⁻¹ (ambient) CO₂. Within each of three replicate rooms per CO₂ treatment, the plant communities were grown under high (30 mg l⁻¹) or low (5 mg l⁻¹) N. In contrast to what is often predicted under N limitation, we found that elevated CO₂ increased native graminoid biomass at low N, but not at high N. The aboveground biomass of reed canary grass did not respond to elevated CO₂, despite it being a fast-growing C3 species. Although elevated CO₂ had no impact on the plant biomass of heavily invaded communities, the relative abundance of several soil microbial indicators increased. In contrast, the moderately invaded plant communities displayed increased total root biomass under elevated CO_2, while little impact occurred on the relative abundance of soil microbial indicators. Principal components analysis indicated that overall soil microbial community structure was distinct by CO₂ level for the varying N and invasion treatments. This study demonstrates that even when elevated CO₂ does not have visible effects on aboveground plant biomass, it can have large impacts belowground.     

Nitrate leaching: modifying the loss from mineralized organic matter

The impact on nitrate leaching of agronomic practices designed to immobilize nitrogen in autumn and winter was investigated over 4 years. Experimental treatments (reducing tillage depth, incorporating harvest residues, reducing fertilizer N by growing unfertilized grass or by spring-sown rather than autumn-sown crops) were compared with a control treatment in which autumn crops were sown after burning harvest residues, mouldboard ploughing and seedbed preparation. Winter cover cropping was also compared with winter fallowing. In the first year, incorporation of harvest residues or reducing tillage depth significantly decreased nitrate leaching compared with the control. Unfertilized grass did not affect leaching in the first winter but significantly decreased it in years 2 and 3. When winter cover crops were grown, nitrate leaching was never less than that under an autumn-sown cereal, and in the subsequent year leaching could be significantly greater. Winter fallowing caused the most nitrate leaching over the year. In the winter following a spring-sown crop, leaching under an autumn-sown crop greatly increased. Summed over 4 years, most leaching occurred with the winter fallow—spring cropping treatment; it was 18% more than where a winter cover crop preceded the spring crop. Reducing tillage depth or incorporating harvest residues did not significantly decrease leaching. Unfertilized grass ley followed by an autumn-sown cereal in the fourth year was the only treatment that significantly decrease leaching. Unfertilized grass ley followed by an autumn-sown cereal in the fourth year was the only treatment that significantly reduced leaching loss compared with the control. Incorporating harvest residues resulted in a balance between annual N inputs and outputs. All other treatments required substantial net annual N mineralization to balance annual inputs and outputs.     

Nitrous oxide emissions and nitrogen cycling in managed grassland in Southern Hokkaido,Japan

Abstract

Nitrous oxide (N₂O) emissions were measured and nitrogen (N) budgets were estimated for 2?years in the fertilizer, manure, control and bare plots established in a reed canary grass (Phalaris arundinacea L.) grassland in Southern Hokkaido, Japan. In the manure plot, beef cattle manure with bark was applied at a rate of 43–44?Mg fresh matter (236–310?kg?N)?ha^?1?year^?1, and a supplement of chemical fertilizer was also added to equalize the application rate of mineral N to that in the fertilizer plots (164–184?kg?N?ha^?1?year^?1). Grass was harvested twice per year. The total mineral N supply was estimated as the sum of the N deposition, chemical fertilizer application and gross mineralization of manure (GMm), soil (GMs), and root-litter (GMl). GMm, GMs and GMl were estimated by dividing the carbon dioxide production derived from the decomposition of soil organic matter, root-litter and manure by each C?:?N ratio (11.1 for soil, 15.5 for root-litter and 23.5 for manure). The N uptake in aboveground biomass for each growing season was equivalent to or greater than the external mineral N supply, which is composed of N deposition, chemical fertilizer application and GMm. However, there was a positive correlation between the N uptake in aboveground biomass and the total mineral N supply. It was assumed that 58% of the total mineral N supply was taken up by the grass. The N supply rates from soil and root-litter were estimated to be 331–384?kg?N?ha^?1?year^?1 and 94–165?kg?N?ha^?1?year^?1, respectively. These results indicated that the GMs and GMl also were significant inputs in the grassland N budget. The cumulative N₂O flux for each season showed a significant positive correlation with mineral N surplus, which was calculated as the difference between the total mineral N supply and N uptake in aboveground biomass. The emission factor of N₂O to mineral N surplus was estimated to be 1.2%. Furthermore, multiple regression analysis suggested that the N₂O emission factor increased with an increase in precipitation. Consequently, soil and root-litter as well as chemical fertilizer and manure were found to be major sources of mineral N supply in the grassland, and an optimum balance between mineral N supply and N uptake is required for reducing N₂O emission.     

Effects of nitrogen supply on growth and nitrogen uptake by Miscanthus sinensis during establishment

The effect of nitrogen (N) supply on growth and N uptake of Miscanthus sinensis during the establishment was determined. Seven different N addition regimes were compared in a nutrient solution experiment. In the treatments N111 (severe deficient), N222 (moderate deficient), N333 and N444 (optimal for maximum growth) different N concentration ranges were held constant during the entire growing season. In the treatments N144, N414 and N441 plants were subjected to low (1) N concentration in one of three experimental periods, whereas the N concentration was high (4) in the other two periods. Depending on the N demand of the plants, N concentrations were adjusted to 250–500 μM (N1), 500–1000 μM (N2), 1250–2500 μM (N3) and 2500–5000 μM (N4) when the N concentration in the N222 treatment had dropped below 100 μM. The other elements in the solution were replenished according to the estimated element ratios in the plants. As a reference the potassium concentration in the solution was measured regularly. During the first year plants with a non-limited N supply (N444) produced new tillers and increased the length of individual tillers until the end of the growing season. This resulted in a 48% shoot dry matter increase late in the growing season between August and October and a linear increase of cumulative N uptake between July and October. Limited N supply during the entire growing season (N111, N222) caused lower shoot yields but rhizome and particularly root dry weights were less affected. Significant final yield losses were also observed when the N supply was limited only during the first 7 weeks of growth (N144). By contrast, final shoot yield was hardly affected when the plants were exposed to limited N supply over a period of 9 weeks at the end of the growing season (N441). In the second year regrowth of shoots in spring was affected by the previous year's N supply, since five weeks after the beginning of regrowth, shoot dry matter was significantly positively correlated with N contents in rhizomes and shoots in the previous October. Our results show, that N supply at the beginning of the growing season has a major effect on final yield in the first establishment year of M. sinensis. However, from the second year on, the capacity of N reserves in rhizomes and roots affects spring growth much more than current N supply.     

Biogas digestates based on lignin-rich feedstock – potential as fertilizer and soil amendment

With advances in biogas technology, lignocellulosic material may be increasingly included in feedstock due to the abundance of raw materials. The main goal of this study was to evaluate fertilizing and soil amendment effects of digestates based on lignin-rich feedstock. The digestates originated from reactors fed with manure co-digested with Salix, wheat straw or sugarcane bagasse, respectively. In pot experiments with three different soils, Italian ryegrass and reed canary grass were grown with 120 kg ha^?1 total nitrogen or 150 kg ha^?1 available nitrogen, respectively, given as either mineral fertilizer or digestate. Soil chemical and physical characteristics were determined after ended experiments. Additionally, an incubation study was carried out to estimate N mineralization from one digestate over time. Digestate addition resulted in similar yields compared to mineral fertilizer, varying from 0.5 (loam) to 1 kg dry matter m^?2 (silt) for Italian ryegrass and 1.2 (loam) to 2.3 kg m^?2 (silt) for reed canary grass. Digestates contributed to a favourable pH for plant growth, reduced bulk density in the loam and improved water retention characteristics in the sand. Biogas digestates based on lignin-rich feedstock appear promising as fertilizers and for soil amelioration but results have to be verified in field experiments.     

Nitrate leaching after cut grass/clover leys as affected by time of ploughing

Abstract. Nitrate leaching after one year of a cut grass/clover ley was measured in two succeeding years to investigate how the postponing of ploughing leys from early to late autumn or spring, in combination with spring or winter cereals affected leaching of nitrate. The experiment was conducted as three field trials, two on a coarse sandy soil and one on a sandy loam soil. For calculation of nitrate leaching, soil water samples were taken using ceramic suction cups. The experiments started in spring in a first year ley and ended in spring three years later. Total nitrate leaching for the three year periods for each trial ranged between 160–254 and 189–254 kg N/ha on the coarse sand and 129–233 kg N/ha on the sandy loam. The results showed that winter wheat ( Triticum aestivum L.) did not have the potential for taking up the mineralized N in autumn after early autumn ploughing of grass/clover leys, and that the least leaching was generally found when ploughing was postponed until spring, and when winter rye ( Secale cereale L.) was grown as the second crop rather than spring barley ( Hordeum vulgare L.). Nevertheless, leaching was generally high in the winter period even when winter rye was grown. On these soil types ploughing out should be postponed, whenever possible, to spring. Crop systems that maximize the utilization of mineralized N and thereby minimize nitrate leaching need to be further developed. Based on N balances, the data were further used to estimate the biological N fixation by the clover.     

Effects of elevated CO2 concentration on rhizodeposition from Lolium perenne grown on soil exposed to 9 years of CO2 enrichment

The effects of enriched CO₂ atmosphere on partitioning of recently assimilated carbon were investigated in a plant-soil-microorganism system in which Lolium perenne seedlings were planted into cores inserted into the resident soil within a sward that had been treated with elevated CO₂ for 9 consecutive years, under two N fertilisation levels (Swiss FACE experiment). The planted cores were excavated from the ambient (35 Pa pCO₂) and enriched (60 Pa pCO₂) rings at two dates, in spring and autumn, during the growing season. The cores were brought back to the laboratory for ¹⁴C labelling of shoots in order to trace the transfer of recently assimilated C both within the plant and to the soil and microbial biomass. At the spring sampling, high N supply stimulated shoot and total dry matter production. Consistently, high N enhanced the allocation of recently fixed C to shoots, and reduced it to belowground compartments. Elevated CO₂ had no consequences for DM or the pattern of C allocation. At the autumn sampling, at high N plot, yield of L. perenne was stimulated by elevated CO₂. Consistently, ¹⁴C was preferentially allocated aboveground and, consequently belowground recent C allocation was depressed and rhizodeposition reduced. At both experimental periods, total soil C content was similar in all treatments, providing no evidence for soil carbon sequestration in the Swiss Free Air CO₂ Enrichment experiment (FACE) after 9 years of enrichment. Recently assimilated C and soil C were mineralised faster in soils from enriched rings, suggesting a CO₂-induced shift in the microbial biomass characteristics (structure, diversity, activity) and/or in the quality of the root-released organic compounds.     

Seed Yield of meadow fescue (Festuca pratensis Huds.) in Norway and Denmark: The effects of locations,cultivars and autumn management

In order to determine genetic differences in seed yield potential, the optimal locations for seed production and optimal management after the first seed harvest, experiments with different timing of cutting and nitrogen application in autumn were conducted in three Scandinavian cultivars of meadow fescue (Saiten—origin 67° N, Fure—origin 61° N, and Senu Pajbjerg—origin 56° N) at the Norwegian locations Kvithamar (63.3° N), Staur (60.5° N), Landvik (58.2° N) and the Danish location Roskilde (55.4° N). The relative seed yields of ‘Saiten’, ‘Fure’ and ‘Senu Pajbjerg’ were 100, 171 and 175 on average for the first ley year, 100, 126 and 141 on average for the second ley year and 100, 115 and 116 on average for third ley year, respectively. A higher seed yield potential of the predominant Danish cultivar probably explains the commonly reported difference in seed yield between Norway and Denmark. Within Norway, seed yields normally decreased from south to north, with the lowest seed yields produced at Kvithamar and the highest at Staur or Landvik. At the coastal locations Kvithamar and, in particular, Landvik, cutting immediately after seed harvest (stubble removal) was necessary in order to maximize seed yields of ‘Fure’ and ‘Saiten’. Cutting at the end of the growing season (10 October) reduced the winter survival and seed yield of ‘Fure’ and ‘Saiten’ at these locations but was favourable at the inland location Staur, which had more stable snow cover. ‘Senu Pajbjerg’ was especially vulnerable to winter damage and did not benefit from cutting of stubble or regrowth at any location. Compared with inputs later in autumn, nitrogen application immediately after seed harvest increased both DM production in autumn and the next year's seed yield at all Norwegian locations.     

Seasonal Changes of Shoot Nitrogen Concentrations and 15N/14N Ratios in Common Reed in a Constructed Wetland

Abstract

Nitrogen (N) concentrations and stable N isotope abundances (δ¹⁵N) of common reed (Phragmites australis) planted in a constructed wetland were measured periodically between July 2001 and May 2002 to examine their seasonal variations in relation to N uptake and N translocation within common reed. Nitrogen concentrations in P. australis shoots were higher in the growing stage (7.5 to 24.8 g N kg^?1) than in the senescence stage (4.2 to 6.8 g N kg^?1), indicating N translocation from shoots to rhizomes. Meanwhile, the corresponding δ¹⁵N values were higher in the senescence stage (+12.2 to +22.4‰) than in the growing stage (+5.1 to +11.3‰). Coupled with the negative correlation (R²=0.24, P<0.05, n=18) between N concentrations and δ¹⁵N values of shoots in the senescence stage, our results suggested that shoot N became enriched in ¹⁵N due to N isotopic fractionation (with an isotopic fractionation factor, α_s/p, of 1.012) during N translocation to rhizomes. However, the positive correlation between N concentrations and δ¹⁵N values in the growing stage (R²=0.19, P<0.001, n=54) suggested that P. australis relies on N re‐translocated from rhizome in the early growing stage and on mineral N in the sediment during the active growing stage. Therefore, seasonal δ¹⁵N variations provide N‐isotopic evidence of N translocation within and N uptake from external N sources by common reed.     

Long-term soil feedback on plant N allocation in defoliated grassland miniecosystems

Defoliation of plants is known to have effects on soil organisms and nutrient availability in grassland communities, but few studies have examined whether changes in soil attributes can further feed back to plant growth and plant nutrient content. To examine defoliation-induced soil feedbacks, we established replicated miniecosystems with a grass Phleum pratense, defoliated half of the systems, collected soil from both defoliated and non-defoliated systems and planted new seedlings into each soil. The two soils did not differ in promoting shoot and root growth. However, seedlings that grew in the soil collected from defoliated systems had higher shoot N content, allocated relatively more N to shoots and had lower root N concentration than those growing in the soil collected from non-defoliated systems. Our study provides novel evidence that defoliation can generate long-lasting changes in grassland soil that in turn can affect plant N allocation.     

Temporal course of net N mineralization and immobilization in topsoil following incorporation of crop residues of winter oilseed rape,peas and oats in a northern climate

The impact of incorporated residues of winter oilseed rape, peas and oats on soil N availability and the risk of N leaching during autumn and winter in a northern climate is not clear. Therefore, the aim was to determine the influence of incorporated residues on net N mineralization–immobilization in topsoil during autumn and winter. A field experiment carried out at three sites in South Sweden provided soil samples and crop residues for an interpretive, in situ incubation study. Topsoil corresponding to a 7‐cm soil layer from each site used for the field experiment was incubated with and without aboveground residues under natural temperature conditions at a single field location. On the basis of the incubation study, we concluded that in the field experiment, soil N dynamics during autumn and winter trials were the combined outcome of net N mineralization in the topsoil fraction not affected by aboveground residues and net N immobilization in the fraction in contact with aboveground crop residues. In the absence of aboveground residues, the net rate of N mineralization during early autumn was similar after both oilseed rape and peas, but values were larger than that after oats. After incorporation, aboveground residues of winter oilseed rape and peas made no contribution to soil mineral N in late autumn and thus did not increase the risk of N losses during winter. In fact, the residues of oilseed rape, peas and oats reduced the amount of soil mineral N by 7–14 kg N/ha during the main drainage period (October–March). Therefore, incorporating chopped aboveground residues should be encouraged before sowing winter wheat after peas and winter oilseed rape.     

Chicory (Cichorium intybus L.) and dandelion (Taraxacum officinale Web.) as phytoindicators of cadmium contamination

Chicory (Cichorium intybus L.) and dandelion (Taraxacum officinale Web.) were demonstrated to be potential indicator plants for heavy metal contaminated sites. Chicory, grown with 0.5–50 μM cadmium (Cd) in nutrient solution, accumulated 10–300 μM Cd g^?1 in shoots and 10–890 μg Cd μg^?1 in roots and rhizomes. With dandelion, 20–410 μg Cd μg^?1 was found in shoots and 20–1360 μg Cd μg^?1 in roots and rhizomes. An inverse correlation existed between chlorophyll and Cd concentrations in shoots of both species. Accumulation of Cd from nutrient solution was similar with the counter-anions SO₄ ^2?, Cl^1? and NO₃ ^? in chicory. In chicory grown in Cd-amended (11.2 kg Cd ha^?1 applied five years previously) soils, Cd concentrations were substantially higher than in controls in all plant parts following the order: leaf > caudex > stem > root and rhizome. The above trend was the opposite of that observed in solution culture, where Cd accumulation was higher in roots and rhizomes than in shoots. Higher cadmium accumulation was found from a Cd-treated sand (Grossarenic Paleudult) than from a loamy sand (Typic Kandiudult) soil type. Chicory and dandelion are proposed indicator plants of cadmium contamination, and both have the potential to be an international standard heavy phytomonitor species of heavy metal contaminantion.     

氮硫配施对生姜生长和氮素吸收的影响

【目的】施肥显著影响生姜的产量及品质,在施氮的基础上合理增施硫肥可通过协调氮代谢的能力,促进干物质的合成与积累,从而提高生姜产量。本文在砂姜黑土区采用田间试验,研究氮硫配施对生姜不同生育期干物质积累、产量及氮素吸收的影响,为提高生姜产量及养分吸收提供理论依据。【方法】试验设置4个N水平(0、300、450、600 kg/hm2)和2个S水平(S 0、50 kg/hm2),在发棵期、根茎膨大期和收获期取样,测定茎、叶及根茎的干物质量及含氮量。【结果】生姜的茎和叶生长主要集中在前期,根茎膨大期时的茎和叶干物质量分别为5.49.3 g/plant和7.0 11.6 g/plant;根茎则在后期快速积累,至收获期时根茎干物质量达20.0 36.8 g/plant。随施氮量的增加,不同生育期茎和叶的干物质量均随之增加。适宜施氮量内,生姜根茎干物质量和产量表现出随施氮量增加而增加的趋势,以N450S50处理最高。相较于N0S0处理和N0S50处理,不同施氮量处理生姜增产率分别在33.1%74.3%和25.4%64.2%之间。同一施氮量下,增施硫肥处理的生姜干物质量和产量较高。氮硫配施对生姜根茎、茎和叶氮含量有不同影响。各器官中叶的氮含量在不同生育时期均高于根茎和茎,其中以根茎膨大期较高,为24.3 28.4 g/kg;而根茎和茎的氮含量均在发棵期较高,分别为18.3 24.5和16.3 22.2 g/kg。不同处理中,根茎氮含量在N600S50处理中较高,而茎和叶氮含量则是在N450S50处理中最高。收获期生姜各器官氮累积量表现为根茎叶茎,其中N450S50处理的根茎氮累积量高于其他处理,而茎和叶中则是N600S50处理的氮累积量最高。整株氮累积量随施氮量的增加而增加,N450S50处理最高,较N0S0处理和N0S50处理分别上升116.2%和99.0%,过量施氮反而降低氮素累积。增施硫肥能提高氮累积量,增加幅度在8.1%15.8%之间。【结论】生姜根茎干物质量主要在根茎膨大期积累,实际生产中在这一时期追施氮、钾肥,对于提高生姜根茎生物量,获得高产具有重要作用。氮和硫存在很强的内在联系,适宜施氮量下增施硫肥能够促进同化产物的形成,使养分向生长旺盛部位转移,从而提高生姜干物质积累和产量,促进植株对氮素的吸收。过量施氮或氮硫比例不合理则会导致产量提升受限。     

Nitrogen fertilizer requirements of cereals following grass

Abstract. The effect of increasing rates of nitrogen (N) fertilizer on the yield response of 3 or 4 consecutive winter cereal crops after ploughing out grass was investigated at six field sites on commercial farms in England and Wales. Amounts of N required for an economically optimum yield (>3 kg of grain for each kg of fertilizer N applied) ranged from 0 to 265 kg ha⁻¹ and were dependent on soil N supply, but not on crop yield. Optimum N rates were large (mean 197 kg N ha⁻¹) at three sites: two sites where cereals followed 2-year grass leys receiving low N inputs (<200 kg N ha⁻¹), and at one site where a cut and grazed 4-year ley had received c . 315 kg N ha⁻¹ of fertilizer N annually. At the other three sites where 4 and 5-year grass leys had received large regular amounts of organic manures (20–30 t or m³ ha⁻¹) plus fertilizer N ( c . 300 kg ha⁻¹ each year), optimum N rates were low (mean 93 kg N ha⁻¹) and consistently over-estimated by the farmer by an average of 107 kg N ha⁻¹. Optimum N rates generally increased in successive years after ploughing as the N supply from the soil declined. Determination of soil C:N ratio and mineral N (NO₃N+NH₄N) to 90 cm depth in autumn were helpful in assessing fertilizer N need. The results suggest there is scope to improve current fertilizer recommendations for cereals after grass by removing crop yield as a determinant and including an assessment of soil mineralizable N during the growing season.     

石柱黄连不同生长期植株营养特性的研究

采用大田调查和室内化学分析方法研究了石柱黄连不同生长期植株养分含量、吸收、比例以及养分含量与土壤有效养分的关系。结果表明,1～5年生黄连生物量、叶片重和根茎重(产量)与生长年份呈极好的二次回归关系,叶片12种营养元素含量和吸收量均以NKSCaMgPFeMnZnCuBMo,根茎养分含量和吸收量的大小序列不一致。黄连叶片和植株养分吸收量与年份呈良好的二次回归关系,根茎养分吸收量的变化可用幂函数(y=axb)表征,叶片养分吸收量成倍(4.29～11.4倍)高于根茎。黄连土壤有机质、有效氮、硫、钙、锌含量丰富,其余8种养分含量低,不同年份黄连叶片(镁、铁、铜除外)和根茎(镁、钼除外)养分含量与土壤有效养分间呈很好的三次回归关系。     

Comparison of isothiocyanate yield from wasabi rhizome tissues grown in soil or water

The isothiocyanate (ITC) yield of wasabi, the Japanese horseradish (Wasabi japonica), was measured on its release from glucosinolates in the rhizomes of plants grown in two traditional ways. Mature plants of 18 months old were harvested from two different commercial farms located in the South Island of New Zealand. At one farm, the plants were grown in raised soil beds, while the plants at the other farm were grown in gravel irrigated by river water. Following harvest, the rhizomes from each growth medium were divided into five size groups based on the weight and length of the rhizomes. The different sized rhizomes were also subdivided into proximal, medial, and distal portions of the rhizomes and each portion was further subdivided into epidermis plus cortex, and vascular plus pith. The individual and total ITC contents of each portion (proximal, medial, and distal) of the rhizomes were measured using dichloromethane extraction followed by the GC-FPD. The total ITC content of the rhizomes grown in soil increased (13 times) linearly from 6 to 114 g of rhizome weight, while the mean ITC content of the water-grown wasabi increased (10 times) nonlinearly for similar sized rhizomes. Water-grown rhizomes in the weight range from 18 to 45 g gave significantly (P = 0.030) higher total ITC (1-2 times) than similarly sized soil-grown rhizomes. Analysis of the tissues showed that the total and the individual ITCs were found in significantly higher levels (73 and 64%, respectively) in the skin and cortex tissue compared to the vascular and pith tissues. Analysis of the ITC content of the different locations of the wasabi rhizome showed that the distal portion of the rhizome contained significantly higher levels of both total and individual ITCs compared to the medial and proximal portions of the rhizome.