Growth and carbon sequestration by ectomycorrhizal fungi in intensively fertilized Norway spruce forests

A substantial portion of the carbon (C) fixed by the trees is allocated belowground to ectomycorrhizal (EM) symbionts, but this fraction usually declines after fertilization. The aim of the present study was to estimate the effect of optimal fertilization (including all the necessary nutrients) on the growth of EM fungi in young Norway spruce forests over a three year period. In addition, the amount of carbon sequestered by EM mycelia was estimated using a method based on the difference in δ¹³C between C₃ and C₄ plants. Sand-filled ingrowth mesh bags were used to estimate EM growth, and similar bags amended with compost made from maize leaves (a C₄ plant) were used to estimate C sequestration. Fertilizers had been applied either every year or every second year since 2002 and the estimates of EM growth started in 2007. The application of fertilizer reduced EM growth to between 0% and 40% of the growth in the control plots at one site (Ebbegärde), while no significant effect was found at the other three sites studied. The effect of the fertilizer was similar in sand-filled and maize-compost-amended mesh bags, but the total production of EM fungi was 3-4 times higher in maize-compost-amended mesh bags. The fertilizer tended to reduce EM growth more when applied every year than when applied every second year. The amount of C sequestered in maize-compost-amended mesh bags collected from unfertilized treatments was estimated to be between 0.2 and 0.7 mg C g sand⁻¹ at Ebbegärde and between 0.2 and 0.5 mg C g sand⁻¹ at Grängshammar. This corresponds to between 300 and 1100 kg C per ha, assuming a similar production in the soil as in the mesh bags. Fertilization at the Ebbegärde site reduced carbon sequestration, which confirmed the results based on estimates of fungal growth (ergosterol levels). A correlation was found between fungal biomass and δ¹³C in mesh bags amended with maize compost. Based on this, it was estimated that a fungal production of 1 μg ergosterol corresponded to 0.33 mg of sequestered carbon. In conclusion, the effect of the fertilizer on EM growth seemed to be dependent on the effect of the fertilizer on tree growth. Thus, at Ebbegärde, were tree growth was less stimulated by the fertilizer, EM growth was reduced upon fertilization. At other sites, where tree growth was more stimulated, the fertilizer did not influence EM growth. The large amounts of carbon sequestered during the experiment may be a result of fungal residues remaining in the soil after the death of the hyphae.     

Sitka spruce site index in response to varying soil moisture and nutrients in three different climate regions in Ireland

We examined the relationships between Sitka spruce (Picea sitchensis (Bong.) Carr.) site index, windspeed, former land use, soil moisture and soil nutrients with a view to identifying factors limiting the growth potential of the species in three climate regions in Ireland. We selected plantations covering three climate regions (delineated on the basis of ‘growing season’ balance of precipitation and potential evapotranspiration; representing dry, moist and wet climate regions) located on sites representing the range of soil moisture regimes (SMR), soil nutrient regimes (SNR), and land use types found throughout Ireland. Site index of Sitka spruce varied among climate region, with significantly lower site index associated with the wet climate region mainly due to the deterioration in edaphic conditions and adverse climatic conditions. The effect of edaphic variables (SMR, SNR) on site index was consistent across climate regions, site index increasing with increasing SNR, and decreasing with excess moisture or moisture deficit. Site index reached a maximum on fresh/very rich sites in the dry and moist climate regions and on moist/rich sites in the wet climate region. In the dry climate region, water supply (SMR) was the most important variable regulating growth, in wetter windier climates nutrient supply (SNR) was the most important factor, accounting for 69% of the variation in site index. The study has allowed region-specific recommendations to be made for successful plantation establishment in Ireland and for countries with similar climatic regions.     

德惠市农田黑土肥力评价及施肥措施研究

对吉林省德惠市黑土农田土壤5项指标综合评价的结果表明,土壤速效钾含量、阳离子交换量处于良好级,速效磷含量、土壤有机质含量处于中等级,全N含量处于差级,pH在不同地块差异明显。土壤保肥、耐肥性能好,但土壤肥力严重退化。因此,在施肥上应遵循增施有机肥,增N、控P、保K,配合施用中微量元素的原则,保持黑土的持续生产能力。     

辽宁省水稻生产中硅肥施用技术的研究 Ⅰ钢渣硅肥的施用技术

探讨了田间条件下钢渣硅肥的用量和施用方法。结果表明:供试土壤的水浸态硅含量低于85mgkg-1,施用钢渣硅肥能够显著提高水稻的产量;依据产量和肥料用量关系的效应方程,除康平地区的碱性水稻土外,供试的其它地区比较合理的钢渣施用量为1500kghm-2;钢渣硅肥可明显提高水稻植株体内SiO2含量,根据水稻植株体内SiO2含量随钢渣硅肥施入量的变化情况,沈阳市康平县最佳的施入量也应为1500kghm-2,钢渣基施更有利于水稻对SiO2吸收和利用;钢渣硅肥对土壤pH值影响不大,钢渣硅肥具有一定的后效。     

Influence of management practices on soil organic matter changes in the Northern China plain and Northeastern China

Soil organic matter (SOM) is strongly related to soil type and management practices. Changes in government policy have brought drastic changes in farm management practices in the last two decades in rural China. This study investigates changes in SOM in two different soils: Ustepts and Udolls. Ustepts, in the North China Plain where the climate is warm and sub-humid, developed from an alluvial flood plain with organic matter <10 g kg⁻¹. Udolls, in Northeastern China where the climate is cool and sub-humid, developed from loess-like materials with organic matter >20 g kg⁻¹. Two locations for Ustepts and three locations for Udolls were used to collect 567 soil samples in 1980–1982 and again in 2000 for SOM analysis. Soil organic matter increased for Ustepts and decreased for Udolls soils over the sampling period, resulting from differences in fertilizer rates and crop residue input to soil. Higher fertilizer input and crop intensity and initially very low SOM content in Ustepts all contributed to greater OM input than oxidation release. In contrast, lower fertilizer input and crop intensity, and initially high SOM content in the Udolls, led to lower OM input than oxidation release. Increasing SOM content through higher mineral fertilizer input is a valuable option for sustainable agriculture production in areas where SOM is low and there is a shortage or potential shortage of food supply.     

灌溉入渗条件下农田土壤水盐动态简化模型及应用

率先采用线性简化式 ,并引入优先流系数来表示计算土层下边界渗漏水流通量 ;然后导出了计算土层入渗前后土壤储水量变化公式 ,在此基础上又引入淋洗系数 ,导出了入渗前后土壤储盐量变化公式。通过对公式的讨论 ,提出了灌溉水矿化度临界方程 ,讨论了淋洗系数和优先流系数的物理意义和影响因素。本文所建模型简单适用 ,而且与田间实测灌溉水矿化度临界方程极其吻合 ,可为农田灌溉水矿化度的选择提供参考     

Simplified N fertilization strategies for winter wheat. Part 1: plants: compensation capacity of modern wheat varieties

ABSTRACT

Winter wheat in northwestern Europe is often fertilized with several doses of calcium-ammonium-nitrate (CAN). For economy, farmers fertilize using a combination of N-doses. Here, we examined the necessity of N splitting (1–3) and application timing in experiments conducted in 2010 using a one-factorial fully randomized block design, and in 2011–2012 using a two-factorial split-plot design (four replicates). The study site, in southwestern Germany, had silty loam soil, and modern cultivars (2010: one cultivar, 2011–2012: three cultivars) with different genetic abilities to develop the yield components of interest were tested. A late first or single N application at stage BBCH 29/31 did not lead to differences in grain yields or protein contents compared to three N applications. However, a single N application at stage BBCH 25/27 resulted in a reduced protein content. Yield component development did not significantly differ among the cultivars. Early N application increased plant density but not yield. In two years, low plant densities were compensated by higher numbers of kernels per spike. Hence, under the tested conditions, the number of N applications could be reduced, as the high compensation ability of modern cultivars allows N fertilization consisting of two or even one application.     

不同施肥措施对白土腐殖质组成的影响

以白土稻区4年大田定位试验为基础,设置2种翻耕深度(10 cm、20 cm,分别标记为T10、T20)和4种施肥措施(单施化肥、化肥+畜禽粪肥、化肥+秸秆还田、化肥+绿肥,分别标记为F、F+M、F+S、F+G),通过腐殖质组成修改法分别提取表层土壤水溶性物质、胡敏酸、富里酸和胡敏素,研究不同施肥措施对白土腐殖质各组分碳含量的影响。结果表明:单施化肥措施下,翻耕20 cm处理(T20+F)土壤总有机碳和腐殖质各组分碳含量均低于翻耕10 cm处理(T10+F),但差异未达显著水平。在翻耕20 cm的基础上增施有机肥能显著提高土壤总有机碳和腐殖质各组分碳含量,增施畜禽粪(T20+F+M)、秸秆还田(T20+F+S)和增施绿肥(T20+F+G)3处理的土壤总有机碳、胡敏酸、富里酸和水溶性物质碳含量较T20+F处理分别提高14.57%~30.64%、10.36%~30.57%、0.74%~12.31%和14.25%~26.80%。增施有机肥显著提高胡敏素碳含量,T20+F+M、T20+F+S和T20+F+G处理较T20+F处理提高18.87%~35.78%。4年不同翻耕与施肥措施对白土腐殖质性质未产生显著影响。增施有机肥能一定程度上提高土壤PQ值、胡富比、E4/E6值和色调系数。相关性分析表明,胡敏素、胡敏酸、富里酸碳含量与总有机碳含量间均存在显著或极显著正相关,与水溶性物质碳含量间无明显相关性。     

施肥对丹参产量及丹参根主要有效成份含量的影响

研究了苏北中药材种植基地常用有机肥及化肥对丹参产量和丹参根主要有效成份丹参酮ⅡA、丹参酮Ⅰ、隐丹参酮、丹酚酸B含量的影响。结果表明,施肥可以提高丹参根产量,影响三种丹参酮及丹酚酸B的含量。有机肥对丹参产量和丹参酮、丹酚酸B含量的影响优于化肥,三种有机肥常规施肥水平处理均优于相对应的两倍施用量处理;三种有机肥中猪粪较菜籽饼和鸡粪更有利于丹参酮和丹酚酸B的累积。根膨大期的丹参根中三种丹参酮、丹酚酸B的含量高于成熟期。为了提高丹参产量,稳定其有效成分含量,建议大田生产中合理施用有机肥,适度密植,适当提早采收期。     

Estimation of associative nitrogen fixation in relation to water regime and plant nutrition in a long-term pot experiment with rice (Oryza sativa L.)

Summary The contribution of associative N₂ fixation to the N nutrition of lowland rice was estimated in a long-term pot experiment with ten consecutive crops of rice. The experiment comprised two N and two K levels with wet (WF) and dry fallow (DF) between the cropping seasons. Growth of N₂-fixing cyanobacteria was prevented. Greatest yields were obtained in the high NK fertilizer treatment, but with continuation of the experiment yields responsed more to DF than to WF. Nitrogenase activity, however, was favoured by WF. Higher K application increased and higher N application decreased nitrogenase activity. Under WF treatments the organic C and total N contents of the soil remained unchanged during the experimental period, but alternate drying and flooding in DF treatments caused a decline. Lower N fertilizer rates in the second five-crop period did not affect yields, but increased the ratio of N removed to N applied. For the ten-crop period the estimated N balance was positive in the low-N and negative in the high-N treatments. N balances were also established separately for both the first and the second halves of the ten-crop period. In the first period N losses were higher, and the N balance was mostly negative. In the second period only high-N combined with low-K fertilization resulted in a negative N balance. DF favoured N losses in the first but not in the second period. The highest N gain in the second period was found in the DF treatment with low-N and high-K application. In this treatment, nearly one-quarter of the N taken up by the above-ground parts of the plants could be ascribed to associative N₂ fixation. In the corresponding treatment with the higher N level and a 49% higher yield, the contribution of fixed N declined to less than 5%. When harvested straw contained more than 10 mg N g^–1, the N balance was mostly negative, while at N contents less than 10 mg N g^–1, the N balance was generally positive.