酸雨对黄土磷的淋溶效应

采用室内土柱模拟淋溶试验,分析了陕西省杨凌区3种土壤在5个酸雨梯度的侵蚀作用下,土壤磷的释放和迁移规律.结果表明,酸雨会使土壤受到一定程度的酸化,而土壤的酸化程度与酸雨的pH值、土壤的类型、土壤的pH值、阳离子交换量、有机质含量有关.土壤对酸雨的缓冲能力由大到小的顺序为:腐殖质层＞母质层＞黏化层.随着酸雨累积淋溶量的增加,土壤磷的释放总量呈增加趋势,但淋失率会下降.酸雨的pH值为5时土壤磷的累积淋失量最大,土壤磷的累积淋失量和淋失率顺序为:腐殖质层＞黏化层＞母质层.酸雨对腐殖质层的磷具有最强侵蚀效应.母质层和黏化层的酸化主要发生在土壤表层,而腐殖质层酸化主要发生在土壤底层,酸雨侵蚀后腐殖质层酸化最严重.长期的酸雨侵蚀会导致土壤磷流失,造成土壤养分贫瘠化.     

NURSERY RESPONSE OF ACACIA KOA SEEDLINGS TO CONTAINER SIZE,IRRIGATION METHOD,AND FERTILIZATION RATE

Planting koa (Acacia koa A. Gray) in Hawai‘i, USA aids in restoration of disturbed sites essential to conservation of endemic species. Survival and growth of planted seedlings under vegetative competition typically increases with initial plant size. Increasing container size and fertilizer rate may produce larger seedlings, but high fertilization can lead to surface and groundwater pollution and relatively low fertilizer use efficiency. Subirrigation systems may help mitigate this problem. Our study objective was to evaluate koa seedling growth with overhead or subirrigation over a range of container volumes (50 to 656 mL) and fertilizer rates (0 to 9.6 kg·m^?3). Increasing container volume from 50 to 656 mL yielded koa seedlings with 200% more height and stem diameter growth. Subirrigation resulted in less nutrient leaching losses and yielded seedlings of similar vigor as overhead irrigated seedlings. Subirrigation helps optimize fertilizer delivery, which may improve fertilizer use efficiency and reduce environmental contamination.     

Evaluation of slag application to decrease methane emission from paddy soil and fate of iron

Abstract

Organic carbon in paddy soil is oxidized to carbon dioxide by reducing electron acceptors for a certain period after submerging. Methane production commences after the reduction of iron oxide which is the most important electron acceptor in the soil. We aimed to study the long-term suppression of the methane emission from the paddy soil by single application of iron slag. A revolving furnace slag (RFS; 248 g Fe kg^?1) was applied to the potted soil at the rate of 0 (control) or 20 ton ha^?1 in 2000. Rice plants were successively cultivated on the potted soils for 3 years without further application of the RFS. Methane emissions from the potted soils with rice plants were measured by the closed chamber method during these cultivation periods. Total flux of CH₄ emission from the pot applied with ,FS decreased by 5–30% compared with the control. The RFS supplied free iron oxide to the potted soil, and its iron acted as the oxidizing agent as evidenced by the increase in ferrous iron content in the soil. The amount of iron lost from leaching at the bottom of the pots was estimated as 54–59 kg Fe ha^?1 year^?1 at the percolation rate of 20 mm d^?1. Accordingly, half-life of the iron in the applied RFS was calculated as 42–46 years. Therefore, there is a possibility that the suppressing effect of RFS on CH₄ emission is sustained for a half-century, Contents of heavy metals (Cd, Cu, and Zn) in the brown rice harvested from the pot applied with RFS were not significantly different with those from the control pot.     

亚热带不同林龄次生林与杉木林土壤氮淋溶损失特征

为分析不同林龄亚热带常绿阔叶次生林和杉木(Cunninghamia lanceolata)种植对土壤氮淋溶的影响,采用土柱微宇宙原位培养,分别比较9年生和45年生次生林(以米槠Castanopsis carlesii为建群种)之间、米槠和杉木人工林(均为9年生)之间的土壤总氮、硝态氮和铵态氮浓度及通量。结果表明：(1)4种类型森林土壤总氮和硝态氮浓度均表现为45年生次生林>9年生次生林>杉木人工林>米槠人工林;铵态氮浓度则为45年生次生林>杉木人工林>9年生次生林>米槠人工林。(2)4种类型森林土壤总氮和硝态氮的淋溶通量在整个试验期表现为9年生次生林>45年生次生林>杉木人工林>米槠人工林;5—8月4种类型森林土壤氨态氮淋溶通量差异较大,但大体上表现为杉木人工林>45年生次生林>9年生次生林>米槠人工林。(3)9年生和45年生次生林、米槠人工林、杉木人工林土壤总氮年淋溶量分别为14.24,13.27,7.26,10.97 [g/(m²·a)],硝态氮年淋溶量分别为10.88,9.97,5.35...     

引黄灌区灌淤土氮素淋失特征土柱模拟研究

采取土柱模拟实验的方法研究了不同施氮强度对宁夏引黄灌区灌淤土中氮素淋洗损失特征,以期为氮素淋失控制和合理施用提供科学依据。试验设5个氮水平,分别为对照处理(N0)、常规氮水平300 kg·hm^-2(N300)、优化氮水平(N240)、2倍常规氮水平(N600)、2倍优化氮水平(N480)。试验结果表明:不同施氮水平淋洗液中NO₃^--N的浓度表现出先升高后降低的趋势,浓度峰值出现的时间随施氮水平增加逐渐后移,NO₃^--N是氮素淋洗损失的主要形态,而NH₄⁺-N的淋失损失主要出现在淋洗前期,增加施氮量可以推迟各形态氮素峰值出现时间,增加淋失风险。N240,N300,N480和N600处理总氮累积淋失量分别为94.53、128.02、222.06 kg·hm^-2和268.6 kg·hm^-2,淋洗损失比例分别为39.38%、42.67%、46.26%和44.77%,当季施入稻田土壤的氮肥极易淋洗到100 cm深度以下,成为浅层地下水的潜在威胁。施入到灌淤土的氮素有39.38%～46.26%通过淋洗途径损失,各处理总氮累积量淋失规律服从对数方程Yt=a+blnt(R²=0.927～0.975)。     

喹诺酮类抗生素在土壤中的迁移行为及影响因素研究

通过土柱淋溶实验探讨了4种典型喹诺酮类抗生素诺氟沙星(NOR)、环丙沙星(CIP)、洛美沙星(LOM)、恩诺沙星(ENR)在土壤中的迁移行为及影响因素(污染程度、淋溶液pH和淋溶时间)。结果表明,喹诺酮类抗生素在低污染程度(≤4 mg·kg-1)下只迁移至40~50 cm层(0.2μg·kg-1),在高污染程度(20 mg·kg-1)下可迁移至90~100 cm层(4.7μg·kg-1),不同化合物的迁移能力强弱顺序为NORCIPLOMENR;在酸性条件(pH=5)下各化合物的迁移能力最强,可迁移至70~80 cm层(3.0μg·kg-1),在其余条件(pH=3、7、9)下只迁移至40~50 cm层(0.3μg·kg-1);淋溶时间较短(≤3 d)时只迁移至30~40 cm层(0.1μg·kg-1),淋溶时间为5 d时可迁移至90~100cm层(4.0μg·kg-1)。因此,土壤中喹诺酮类抗生素在污染较严重、长时间降水尤其是弱酸性降水时易于迁移。     

引黄灌区设施菜田硝态氮淋失的季节性特征

以宁夏引黄灌区设施菜田番茄-黄瓜轮作体系为研究对象,采用田间定位试验与实地观测相结合的研究方法,对设施菜田硝态氮淋洗的季节特征及其环境因子和施肥管理对硝态氮淋洗的影响进行研究。研究结果表明:硝态氮淋失呈现明显的季节变化,峰值出现在7月夏季休闲期,黄瓜季(秋冬茬)淋洗显著高于番茄季(冬春季),常规施肥周年硝态氮淋洗量平均为185.7 kg·hm-2,优化施肥和调节碳氮比两处理硝态氮淋洗量比常规处理分别降低了10.6%和8.3%。设施菜田硝态氮淋失与浅层地下水位、土壤温度、土壤水分等环境因子季节性变化关系密切,浅层地下水位与硝态氮的淋失量呈极显著负相关,浅层地下水位埋深越浅,硝态氮淋失量越大;土壤水分和温度与硝态氮的淋失量呈显著正相关,随着土壤表层温度和含水量升高,硝态氮淋失增多。     

Dietary arginine requirement of juvenile kuruma shrimp Marsupenaeus japonicus (Bate)

The requirements for essential amino acids by kuruma shrimp, Marsupenaeus japonicus (Bate) have not yet been determined using the dose–response method due to poor utilization of crystalline amino acids (CAA). In a previous study, we produced coated CAA that could be used to retard leaching losses. Therefore, to determine the arginine requirement of juvenile kuruma shrimp, a growth study was conducted using test diets containing six levels of coated arginine (from 1.20% to 3.19% of diet) for 42 days. Crystalline amino acids was supplemented to correspond to the amino acid pattern in the whole body protein of the kuruma shrimp except for arginine. To reduce leaching losses, CAA were coated with carboxymethylcellulose (CMC) and diets were further bound with CMC and k‐carrageenan. Test diets were fed to triplicate groups of juveniles (0.25±0.02 g) twice a day. Proximate composition and the amino acid composition of shrimp whole bodies were analysed at the end of the feeding trial. Percent body weight gain (WG), specific growth rate, feed intake, feed efficiency ratio and protein retention efficiency were significantly affected by the dietary arginine concentrations. Estimating the arginine requirement of kuruma shrimp using broken‐line analysis of percent WG resulted in a value of 2.66% of diet or 5.32% of protein. After correcting for leaching of arginine from the diets, the optimum dietary value of arginine for kuruma shrimp was a little lower than the estimated value.     

Influence of binder type on leaching rate and ingestion of microbound diets by mud crab, Scylla serrata (Forsskål), larvae

Microbound diets (MBD), composed of nutrients held within a matrix or binder, were shown to be readily ingested by larvae of the mud crab, Scylla serrata (Forsskål). In an effort to improve experimental MBD developed for S. serrata larvae, this study determined the effects of various binders on estimated larval ingestion of MBD as well as their leaching rates. Microbound diets with the same dietary compositions were bound with either agar, alginate, carrageenan, gelatin or zein. All diets contained ¹⁴C‐labelled rotifers and were fed to Zoea I, III, V larvae and megalopae. The ¹⁴C content of larvae fed ¹⁴C‐labelled MBD for 2 h was used to estimate the relative ingestion rates of MBD. For all larval stages tested, the estimated mean larval ingestion of MBD did not differ significantly between binder types (P>0.05). Determination of the amount of ¹⁴C‐labelled nutrient leaching from MBD bound with various binders after 30, 60 and 240 min of immersion showed that for all types of binders, ¹⁴C leaching occurred primarily within the first 30 min of immersion. Zein‐bound MBD consistently showed the lowest numerical leaching rate among the five binders tested for all immersion periods examined, and the differences compared with other binders were often significant, particularly after 60 and 240 min of immersion. Larval feeding experiments showed that MBD prepared with binders showing higher rates of leaching were not utilized to a greater degree by S. serrata larvae. Furthermore, unnecessary leaching from MBD particles wastes dietary nutrients and is likely to impact on water quality. On this basis, our results suggest that because of its consistently lower leaching rates, zein is probably a more suitable binder for MBD developed for S. serrata larvae.