Long-term variation in brown trout, Salmo trutta L., stocking success in a large lake: interplay between availability of suitable prey and size at release

Abstract –  Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974–1991 and in summer (late June to early July) in 1992–2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series.     

自压喷灌系统管道减压的研究

本文对自压喷灌系统的合理减压方式和布置形式进行了分析。用递推法导出确定减压池级数及位置的计算公式。根据减压池的工况分析,探讨了减压池调节容积的计算方法。本文为自压喷灌系统的减压设计提供了方法和依据。     

Release of sulphate-sulphur, potassium, calcium and magnesium from spent mushroom compost under field conditions

 The release of SO₄ ^2–-S, K⁺, Ca²⁺ and Mg²⁺ from soil amended with spent mushroom compost (SMC), a byproduct of mushroom production, was measured in leachate from field lysimeters for 30 weeks. Rates of application were 0 and 80 t ha^–1 moist SMC. The SMC contained 1.7% K, 6.5% Ca, 0.4% Mg and 1.2% S (of which 87% is SO₄ ^2–-S), and has a C : S ratio of 26. The break-through curves of ion leaching were polymodal indicating the preservation of soil structure in the lysimeters and its influence on leaching. SO₄ ^2–-S release from SMC was rapid (first-order exponential) and was very similar to the release from a laboratory incubation. The release of K⁺, Ca²⁺ and Mg²⁺ was described using first/zero-order models which were also used to describe their release in the laboratory. The rate and amount of Ca²⁺ release was similar in the field and laboratory, but the amount of K⁺ (and to a lesser extent Mg²⁺) release was less in the field than in the laboratory. Recoveries of SMC applied nutrients in leachate were 80% of S (263 kg ha^–1), 3% of K (14 kg ha^–1), 16% of Ca (284 kg ha^–1) and 37% of Mg (40 kg ha^–1). Little if any S was mineralised. Using SMC could provide plants with S, K, Ca and Mg but there is potential for SO₄ ^2–-S losses via leaching. Received: 7 April 1999     

不同工艺肥料对夏玉米植物学性状和经济性状的影响

[目的]研究不同工艺肥料对夏玉米植物学和经济性状影响。[方法]以郑单958为试验材料,通过田间试验研究不同肥料对玉米植株高度、茎粗、果穗、产量、经济效益等方面的影响。[结果]在所选的4种肥料中,长效控释肥能显著提高夏玉米郑单958的产量,与施入相同养分用量的尿素处理相比,增幅8.8%。[结论]玉米施用长效控释肥后可不再追肥,省工省时省钱,具有较好的推广前景。     

包膜控释肥料在水旱2种模式下的释放率研究

比较了包膜控释肥料在水旱2种模拟形式下的释放率变化情况。结果表明：在同等条件下,包膜控释肥料在水田的养分累计释放率大于旱田。包膜控释肥料前期的释放速率是水田明显高于旱田,而后期的释放速率则为旱田略高于水田。土壤物理形态的差异对包膜控释肥料的养分释放有很大影响。     

基质在热带兰栽培过程中的养分释放研究

采用PT法探究几种常见热带兰栽培基质有效氮、磷、钾释放及pH变化情况。结果表明:整个试验阶段所有处理基质pH变化在5.24～6.88,适合大多数花卉生长,水苔受外界环境影响最大,有着较大的pH变化,不适宜热带兰长期栽培。各基质的养分释放并不是按一定规律来进行,混合基质养分释放量低于纯基质,混合基质可以避免纯基质养分释放量大的弊端。NH4+-N的释放遵循类似\"U\"型曲线变化,火山石与松树皮混合有利于NO3--N的释放。前60d内,A与B处理磷的释放变化较大,60d后磷含量表现为下降变化,直至趋于平缓,不过混合基质整体磷含量水平较低。A与B处理的钾释放量分别在第15和45天降至平缓释放水平,以后一直维持在该平缓水平上释放钾。     

控释尿素氮素释放特征及其在番茄上的应用研究

应用室内恒温培养试验研究了释放曲线为抛物线型(L)和S型(S)的包膜控释尿素(L120d和S80d)在4种温度条件下(10、15、25、35℃)的氮素释放规律,并依托SUGIHARA和LOGISTIC模型探明了L120d和S80d氮素释放速率常数。在此基础上通过设施番茄试验,进一步验证了田间条件下控释氮素释放特征及其对番茄的效果影响。结果表明：室内培养条件下L120d和S80d氮素释放速率显著受温度影响,4种温度条件下释放速率常数分别为0.0022~0.0212/d和0.043~0.279/d,释放曲线分别呈现出抛物线型和S型特点。田间设施土壤条件下L120d氮素释放特征与之吻合,S80d释放周期差异达到30天以上,L120d和S80d氮素释放规律迥异。与普通尿素底施加3次追肥相比,施用L120d和S80d控释尿素的番茄产量较等氮量普通尿素(N 200 kg/hm2)和常规施氮量(N 400 kg/hm2)处理分别增加了7.8%、7.2%和5.4%、4.8%;氮素利用率提高了5.5~10.1个百分点;经济效益分别增加22817、13375元/hm2。此研究为控释肥料在设施农业上的应用和推广提供了科学依据。