施肥对幼蟹池塘养殖水质影响的初步探究

Preliminary study on the effect of fertilization on the water quality of crab culture pond

摘要:

为了探究施肥对河蟹幼蟹养殖水质的影响，于2016年6-10月在上海崇明幼蟹培育基地选择6口池塘进行研究。实验设置不施肥处理组和施肥处理组，并对以上处理组和水源的水温（T）、溶解氧（DO）、pH、化学需氧量（COD_Mn）、总磷（TP）、磷酸盐（PO₄^3--P）、总氮（TN）、铵态氮（NH₄⁺-N）、硝酸盐（NO₃^--N）、亚硝酸盐（NO₂^--N）、钙镁总硬度和叶绿素a（Chl.a）进行监测。结果表明，幼蟹池塘水质变化具有明显季节特征，其中6月和9月两组池塘水质因子较为平稳，7-8月两组池塘COD_Mn、Chl.a出现显著升高而DO显著下降，养殖末期（10月）两组池塘除总硬度和DO大幅下降，剩余水质因子显著升高。实验中水源和两组池塘的水温和pH差异不显著（P > 0.05）。水源DO和NO₃^--N显著高于施肥与不施肥池塘（P < 0.05），不施肥池塘的TP、PO₄^3--P、Chl.a和总硬度均显著低于施肥池塘（P < 0.05）。幼蟹池塘施肥后会引起TN、NH₄⁺-N、NO₂^--N、NO₃^--N和COD_Mn短暂性显著升高（P < 0.05）。研究发现，对比两组池塘的综合效益，得出两者差异不显著。池塘施肥会因N、P营养元素积累过多，造成施肥池塘水质劣于不施肥池塘。因此，池塘养蟹采用不施肥的策略更符合生态养殖的理念。

Abstract:

To explore the effect of fertilization on the water quality of juvenile crab culture ponds, a field experiment was carried out in Chongming, Shanghai from June to October, 2016. Two groups with three replications each were set:(1) unfertilized group and (2) fertilized group. Water temperature(T), dissolved oxygen (DO), pH, chemical oxygen demand(COD_Mn), total phosphorus (TP), phosphate(PO₄^3--P), total nitrogen (TN), nitrate (NO₃^--N), nitrite (NO₂^--N), ammonia nitrogen (NH₄⁺-N), total hardness and chlorophyll a(Chl. a) of headwaters were monitored seasonally. The result indicated that water quality in the ponds had significant seasonal variation. The water quality factors were comparatively steady in June and September. COD_Mn and Chl. a increased significantly in July and August, while the DO decreased markedly. In the end of crab cultivation, most of the water quality factors increased significantly in two groups, but the total hardness and DO decreased greatly. There was no significant difference in T and pH between headwater and pond water (P > 0.05). DO and NO₃^--N of headwater were higher than ponds(P < 0.05). TP,PO₄^3--P, Chl. a and total hardness in unfertilized ponds were lower than fertilized ponds(P < 0.05). The juvenile crab ponds after fertilizing would cause temporary increase of of TN,NH₄⁺-N,NO₂^--N,NO₃^--N and COD_Mn. The study found that the difference of comprehensive benefits of two groups is not obvious. The fertilized group increased the N and P accumulation in pond and then aggravated the water pollution, having no more benefits than unfertilized group. Therefore, non-fertilization is more suitable for ecological cultivation.