【简答题】为什么说1mol/L NH 4 OAc是土壤交换性钾的标准浸提剂,并简述NH 4 OAc浸提-火焰光度法测定土壤速效钾的原理。
【判断题】Concise messages are essential.
【单选题】关于土壤速效钾的测定,下列说法中错误的是()
A.
如果用NH 4 OAc浸提,最好用四苯硼钠比浊法测定溶液中K +
B.
若采用钾离子选择性电极测定溶液中K + 用 BaCl 2 (石灰性土)或HCl(酸性、中性土)浸提,以消除NH 4 + 对测定K + 的干扰。
C.
在表述测定结果时,应说明浸提剂、液土比、浸提时间等
D.
选择土壤速效钾的浸提剂时要考虑溶液中钾的定量方法
【单选题】在用NH 4 OAc浸提-火焰光度法测定土壤速效钾时,下列操作中错误的是()
A.
用HOAc或NH 4 OH调节1mol/L NH 4 OAc溶液(提取剂)至pH7.0
B.
用1mol/L NH 4 OAc配制钾标准溶液
【单选题】What is an advantage of concise business messages?
A.
Concise messages are easier to read.
B.
Concise messages save reading time and, thus, money.
C.
Concise messages are easier to understand.
D.
All of these are advantages of concise business messages.
【单选题】在用 浸提-火焰光度法测定土壤速效钾时,下列操作中错误的是( )。
A.
用 或 调节 1mol·L -1 溶液(提取剂)至pH7.0。
【单选题】Effective business messages are
A.
Entertaining, blunt, and persuasive
B.
Practical, objective, concise, clear, and persuasive
C.
Personal, clear, and challenging
D.
Formal, clear, and blunt
【简答题】Fill in the blank with proper words. 选词填空15% dedicated; dramatically; accessible; components; access; expectations; concise 1It was linked to other networks around the world, and the APRAnet grew beyo...