投放鱼种四关键

提高鱼种放养质量是池塘高产养鱼的一项重要措施,应把握好以下关键四点。一、放养时间 冬至后惊蛰前是最佳投放鱼种时间,此时水温都在5℃—12℃,有利鱼种捕捉运输和放养中的分拣挑选。但宜选择晴天操作,遇雨雪风冻天气不宜放养,以防冻伤鱼种,影响下塘鱼的成活率。二、选好鱼种 俗话说:“种好鱼满塘。”优质的鱼种,肉质肥满结实,体形正常,鳞片完整,体表光滑,体色和眼睛明亮,拿在手中跳动激烈。

Effects of Plant Age and Rock Phosphate on Quality and Nutrient Release of Legume Residue

An incubation experiment was carried out on plateau and slope fields to investigate the effect of plant age and rock phosphate （RP） on the organic resource （OR） quality and available N and P release of the legume residues, including standing biomass and surface litter. The legumes, Mueuna pruriens （L.） and Lablab purpureus （L.）, were treated with or without Togo rock phosphate （RP） and were sampled at 12, 18, 24 and 30 weeks after planting. Results showed that the application of RP significantly affected the P content of the legume residues on the plateau field for the first 18 weeks, but not the other OR quality parameters, nor their N mineralization, or P release parameters. Although application of RP led to higher P contents in both legumes on the plateau field, the P contents were still far below those observed on the slope field. For both species, the biomass age appeared to have a major impact on their N, P, and polyphenol contents, but not on the liguin content. At 24 weeks, both legume N and P contents dropped to about half their values at 12 weeks of age. Residue age also significantly affected N mineralization both with and without RP addition and the net Olsen-P with RP addition. The younger residues generally led to higher N mineralization and net Olsen-P content than the older residues. The best immediate responses to herbaceous legume addition were expected from younger materials, but often at the cost of the total biomass produced and the possibility to produce seeds. The production of seeds, however, could be potentially implemented on a small area of legumes, thus invariably allowing for maturity and seed production.

河蟹暂养管理技术

河蟹暂养是指每年的9月份前后把成蟹捕捞上来,再用池塘分规格进行育肥饲养、待价而售的养殖方式。近年来,已普遍为养殖户所采用,这对提高养蟹的经济效益,保证养殖成功起到了重要的作用。1.池塘条件选择离河蟹养殖水面较近、水源充足、水质良好、排灌方便、环境安静、用电方便的地方。

Warming and grazing enhance litter decomposition and nutrient release independent of litter quality in an alpine meadow

Warming and grazing,and ltter quality jointly determine liter decomposition and nutrient releases in grazing ecosystems.However,their effects have previously been studied in isolation.We conducted a two factorial experiment with asymmetric warming using infrared heaters and moderate grazing in an alpine meadow.Litter samples were collected from all plots in each treatment,among which some subsamples were placed in their original plots and other samples were translocated to other treatment plots to test the relative effects of each treatment on litter decomposition and nutrient releases.We found that warming rather than grazing alone significantly increased total losses of litter mass,total organic carbon,total nitrogen(TN)and total phosphorus(TP)per unit area due to increases in both mass loss rates and ltter biomass.However,grazing with warming did not affect their total mass losses because increased mass loss was offset by decreased litter biomass compared with the control.Seasonal mean soil temperature better predicted litter decomposition than litter lignin content or carbon to nitrogen ratio.There were interactions between warming and grazing,but there were no interactions between them and litter quality on litter decomposition.The temperature sensitivity of TN loss was higher than that of TP loss per unit area.Our results suggest that increased temperature has a greater effect on litter decomposition and nutrient release than change in litter quality,and that more N release from litter could result in greater P deficiency in the alpine meadow.

Soil burial has a greater effect on litter decomposition rate than nitrogen enrichment in alpine grasslands

Aims Litter is frequently buried in the soil in alpine grasslands due to grassland degradation,serious rodent infestation and frequent strong winds.However,the effects of various litter positions on litter decomposition rates and nutrient dynamics under nitrogen(N)enrichment in such areas remain unknown.Methods A field experiment was performed in the alpine grasslands of northwest China to investigate the influence of litter position(surface,buried in the soil and standing)and N enrichment on litter decomposition,using data from two dominant grass species(Festuca ovina and Leymus tianschanicus)in control and N-enriched plots.Important Findings Litter decomposition rates were much faster in buried litter and slower in standing litter than in surface litter.N enrichment significantly affected litter quality and then influenced decomposition.But no significant differences in litter mass remaining were observed between control and N-enriched soil burial.These results indicated that N enrichment significantly affected litter decomposition by changes in litter quality.In addition,all litter exhibited net carbon(C)and phosphorus(P)release regardless of treatments.Litter exhibited net N accumulation for litter from the control plots but showed N release for litter from N enrichment plots.These suggested that litter decomposition can be limited by N and N enrichment influenced N cycling of litter.Current study presented direct evidence that soil buried litter exhibited faster mass loss and C release,and that soil burial can be a candidate explanation why litter decomposes faster than expected in dryland.