吉林省主要耕作土壤中钾的固定与释放

通过X—射线衍射、室内模拟实验及常规分析研究了吉林省主要耕作土壤中钾的固定与释放。结果表明,土壤对钾的固定与释放与土壤的矿物组成有关,3种土壤的固钾量均随钾加入量的增加而增大,而固钾率则随施钾量的增加而逐渐下降。随钾加入量的增加,固钾量和固钾率均有黑土>白浆土>黑钙土的趋势。土壤释钾量有黑钙土>黑土>白浆土的趋势。相关分析表明,蒙脱石、蛭石为主要的固钾矿物,而伊利石为主要的释钾矿物。     

川西3种亚高山针叶林的养分和凋落物格局分析

Investigations were conducted to quantify litterfall, and litter and nutrient accumulation in forest floor, and to acquire information on litter decomposition and nitrogen and phosphorus release patterns in three different subalpine coniferous forests, a plantation （P1）, a secondary forest （SF）, and a primitive forest （PF）, in western Sichuan, China. The litter trap method was used to evaluate litterfall with the litterbag method being utilized for litter decomposition. Seasonal patterns of litterfall were similar in the three forests, with two peaks occurring in September-November and March-May. The plantation revealed an annual litterfall of 4.38 x 103 kg ha-1, which was similar to those of SF and PF, but P1 had a lower mass loss rate and a higher C/N ratio. The C/N ratio may be a sound predictor for the decomposition differences. N concentrations of leaf litter in both the secondary forest and primitive forest increased first and then decreased, and the percentages of their final/initial values were 108.9% and 99.9%, respectively. P concentration in the three forests increased by the end of the study. The results of litterfall and decomposition indicated that in the plantation the potential to provide nutrients for soil organic matter was similar to those of SF and PF; however, its slower decomposition rate could result in a somewhat transient accumulation of litter in the forest floor.     

茶树施用控释氮肥的产量和品质效应

采用盆栽和大田试验,研究了控释氮肥对茶树生长发育、茶叶产量和品质的影响。结果表明,控释氮肥能明显促进茶树的生长发育,茶树新梢数、百芽重、成熟叶片数量及叶绿素含量、树高和主杆直径等均有明显提高,从而使盆栽茶树根、茎和叶各部位的生物产量比施普通尿素分别提高了58.3%、36.9%和17.2%。10个大田试验的茶叶产量增加了4.2%￣24.1%,平均9.6%。茶叶品质成分氨基酸、咖啡碱和水浸出物含量有不同程度提高,其中氨基酸增幅明显,但对茶多酚含量的影响不大,茶叶酚氨比明显降低。可见,控释氮肥具有明显的增产提质效果。     

Short‐term potassium release and fixation in some calcareous soils

Potassium (K⁺) directly released from primary K‐bearing minerals can contribute to plant nutrition. The objective of this research was to assess short‐term K⁺ release and fixation on a range of intensively cropped calcareous soils. Potassium sorption and desorption properties and the contributions of exchangeable‐K⁺ (EK) and nonexchangeable‐K⁺ (NEK) pools to K⁺ dynamics of the soil‐solution system was measured using a modified quantity‐to‐intensity (Q : I) experiment. Release and fixation of K⁺ were varied among soils. The relation between the change in the amount of NEK during the experiment and the initial constrain was linear, and soil ability for K⁺ release and fixation (β) for all soils varied from 0.041 to 0.183, indicating that 4% to 18% of added K⁺ converted to NEK when fixation occurred. The equilibrium potential buffering capacity (PBC) for K⁺ derived from Q : I experiments had significant correlation (r = 0.75, p < 0.01) with β, indicating that PBC depends not only on exchange properties but also on release and fixation properties. The depleted soils showed higher β value than the other soils, indicating much of the added K⁺ was converted to NEK in case of positive constraint. The range of the amount of EK which was not in exchange equilibrium with Ca (E_min) in the experimental conditions was large and varied from 0.68 to 9.00 mmol kg^–1. On average, E_min amounted to 64% of EK. This fraction of EK may not be available to the plant. The parameters obtained from these short‐term K⁺ release and fixation experiments can be used in plant nutrition.     

Soil microbial biomass and activities in a Japanese Andisol as affected by controlled release and application depth of urea

This experiment was conducted in maize field plots to study the effects of controlled release and application depth of urea on soil microbial biomass and activities at two depths of surface soil of a Japanese Andisol from June to September, 2001. Three N amendment treatments and a Control were included in this experiment: deep application (8 cm) of controlled release urea; deep application (8 cm) of conventional urea; surface application of conventional urea; Control, without N application. Prior to this experiment, the field plots received the same N fertilizer treatments for two consecutive years under maize/barley rotation. Soil microbial biomass, dehydrogenase and nitrification activities exhibited great vertical and temporal variations during the maize growth season, and the microbial biomass was significantly correlated to soil water-filled pore space (p<0.01). N fertilization did not significantly affect the microbial biomass, but greatly increased the dehydrogenase and nitrification activities. The increase in the microbial activities following N fertilization was not attributed to the increase in microbial biomass but to the increase in intrinsic microbial activities. Controlled release urea was found to continuously affect the dehydrogenase activity over a shorter distance, while conventional urea could greatly increase the enzyme activity for a shorter period of time. Both controlled release and deep application of urea had potentials to reduce the nitrification activity and suggested that the nitrate production might be decreased in 0–10 cm surface soil. Deep application of urea increased aboveground N uptake by maize and then the recovery rate of N fertilizer, whereas controlled release of urea greatly increased grain yield and N uptake by grain.     

含硫尿素养分缓释释放测定方法的研究

包膜尿素肥料是提高肥料利用率，解决环境污染问题的一种新型肥料。针对目前对缓释肥料释放特性的研究集中在化工制作领域这一现状，采用不同的测定方法，阐明含硫尿素中的养分氮在水及土壤中的转化特点，确定养分的释放速率，以求找出适合农业生产应用的方法。研究表明，可以用电导率法快速准确地定性评价缓释肥料的供肥特性和供肥速度，用土壤培养法和水培法定量测定其供肥性能。     

低分子量有机酸对高岭石中铝释放的影响

选择了几种土壤中可能存在的低分子量脂肪羧酸 ,研究了它们对高岭石中铝释放的影响。结果表明 ,有机酸可以通过络合作用促进高岭石中铝的释放。几种有机酸对体系中可溶性铝影响的大小顺序为 :草酸 >柠檬酸 >丙二酸 >苹果酸 >乳酸。草酸、柠檬酸和乳酸对可溶性铝释放的促进作用随体系pH的升高而减小 ,其中草酸体系中可溶性铝随pH的变化幅度最大。在苹果酸体系中 ,可溶性铝随pH的升高而稍有增加。体系中的可溶性铝随有机酸浓度的增加而增加 ,而交换性铝随柠檬酸浓度的增加而减少 ,先随苹果酸浓度增加而增加 ,然后又逐渐减少。与对照相比 ,柠檬酸和草酸使交换性铝的量减小 ,苹果酸和乳酸在低pH下使交换性铝明显增加 ,而苹果酸在较高pH下使交换性铝减少。有机酸影响释放出的铝在固液相间的分配比 ,苹果酸在低pH下使体系中释放出的大部分铝以交换性形态存在 ,而在较高pH下 ,大部分铝以可溶形态存在。在草酸体系中 ,释放出铝的大部分都以可溶形态存在。不同有机酸的不同表现与体系中铝的溶解平衡、铝的吸附 -解吸平衡、有机酸的吸附 -解吸平衡、有机酸的离解平衡和铝与有机酸的络合 -离解平衡有关。     

腐殖酸对耕地棕壤固钾与释钾作用的影响研究

通过室内等温培养试验,研究了施用富里酸和胡敏酸对耕地棕壤钾素释放和固定作用的影响。结果表明,施用腐殖酸可以促进土壤钾素的释放,并有随腐殖酸用量提高而增高的趋势。其中,施用富里酸4%,在25℃条件下培养21d,土壤的钾素释放量增加了6.25%,而在相同条件下,施用胡敏酸土壤钾素的释放量仅增加了2.26%;施用腐殖酸可以降低土壤对外源钾的固定量,在施用外源钾400mgkg-1土条件下,与对照比较各处理的固钾量差异均达到了极显著水平。外源钾施用方式对腐殖酸降低土壤固钾作用的影响不同,腐殖酸与土壤恒温培养7d以后施用钾素的固钾量低于钾素与腐殖酸同时施用处理的。腐殖酸对土壤钾素释放和固定的影响是通过对含钾矿物的溶解和层间堵塞以及对钾素的吸附作用实现的。     

冻融循环作用对不同深度土壤各形态氮磷释放的影响

通过模拟实验研究了在冻融条件下,东北地区旱田、水田土壤中硝酸盐氮、铵氮、总溶解磷、无机磷及有机磷释放量的变化。研究表明,铵氮、硝酸盐氮的释放量主要产生在单次冻融条件下,多次冻融对氮的释放量没有显著的影响。单次冻融后,硝酸盐氮含量旱田和水田分别上升了50.2%~55.3%和27.1%~61.4%;铵氮的含量旱田及水田分别上升了46.6%~52.9%和26.5%~29.0%,不同深度水田土壤铵氮的释放有显著差异。土壤总溶解磷、无机磷及有机磷在5次冻融循环,释放量达到最大。总溶解磷、无机磷上升量旱田及水田分别为51.4%~57.1%及45.3%~50.3%;有机磷上升量旱田及水田为46.8%~47.3%及37.9%~47.8%。氮增加的主要原因是易矿化氮组分的矿化与团聚体破坏后吸附氮的解吸,磷的增加则是由于持续冻融对团聚体的破坏,导致原吸附点位磷暴露,随水分迁移流失。     

薄膜阀

薄膜阀是专为渠道塑膜加混凝土薄板防渗衬砌设计的,具有逆止特性的排水(气)阀。通过水工模型试验及黄材水库沙河干渠刁子潭渠段的实际运用,证明该阀具有动作灵敏、排水(气)流量大、逆止性能好、构造简单、施工方便、造价低廉、检修方便等优点,可有效地排除渠道外水(气)压力,保持衬砌的稳定和安全。