问题 问答题 简答题

简述提高池塘养殖水体中溶氧量的措施和“肥、活、嫩、爽”的意义。

答案

参考答案:

措施:减少耗氧因子:减少池底淤泥厚度(过多的淤泥会增加氧债形成的可能);控制施肥量(少量多次);降低放养密度;使用腐熟的有机肥(以减少中间产物的存积和氧债形成);增加溶氧,施无机肥(特别是P肥改善池塘N、P比,促进浮游植物生长;及时加新水(以增加池水透明度和补偿深度);合理使用增氧机;化学药物增氧;使用微生态制剂(如光合细菌);增加水体透明度,黄泥浆+食盐、明矾、生石灰注新水;保持池面良好的日照和通风条件;适当扩大池塘面积(以增大空气和水的接触面积)。

“肥”表示水中浮游生物量大,有机物与营养盐类丰富。

“活”表示水色经常在变化。水色有月变化和日变化(即上下午和上下风的变化),表明浮游植物优势种群交替出现,特别是鱼类容易消化的浮游植物数量多,质量好,且出现频率高。透明度不再变化

“嫩”表示池水透明度适中(25-40cm),水中溶氧条件好。

“爽”表示池水呈油绿色,黄褐色,表明浮游生物组成好。

阅读理解

A new plan for getting children to and from school is being started by a local government in Eastern England. This could end the worries of many parents fear ful for their children's safety on the roads.

Until now the local government have only been prepared to provide bus services for children living more than three miles from their school, or sometimes less if special reasons existed. Now it has been decided that if a group of parents ask for help in organizing transport they will be prepared to go ahead, as long as the arrangement will not lose money and children taking part will be attending their nearest school.

The new plan is to be tried out this term for children living at Milton who attend Impington School. The children live just without the three mile limit and the local government have said in the past that they will not undertake to provide free transport to the school. But now they have agreed to offer a sum of money for a bus service from Milton to Impington and back, a plan which has the support of the school's headmaster.

Between 50 and 60 parents have said they would like their children to take part. Final calculations have still to be carried out, but a government official has said the cost to parents should be less than £ 20 a term.

They have been able to arrange the service at a low cost because there is already an agreement with the bus company for a bus to take children who live further away to Impington. The same bus would now just make one more journey to pick up the Milton children. The official said they would get in touch with other groups of parents who in the past had asked if transport could be provided for their children, to see if they would like to take part in the new plan.

1.What is the aim of the plan?

A.To prevent the students' road accident.        

B.To relieve the traffic pressure.

C.To save time for the parents and students.        

D.To help the parents save money. 

2.How can the local government arrange the new bus service at a low cost?

A.By letting the bus run in the morning only.

B.By limiting the number of the students.

C.By obtaining the support from the headmaster.

D.By lining the new bus service with the existing one. 

3.The new bus service will be paid for by  ________ .

A. the parents             B. the local government

C. the bus company         D. the local government and the parents 

4.Which of the following is possible if the plan is carried out?

A.The bus company will make much more money.

B.The children can choose whatever school they like.

C.The parents can get rid of their worries.

D.The students in Impington School can have free bus rides. 

5.This passage is most probably ________  .

A.a personal letter         B. a headmaster's report

C.an advertisement          D. a newspaper article 

单项选择题