Which skill is a major which every field supervisor should possess?

First must be a graduate of the University of Engineering Industry

And must be available when all the conditions leadership and oversight

It has to be alternatives to solve problems and work under pressure

A complete understanding of the field of work and its implementation

The speed of implementation and taking good decision

Order of workers and the use of time

Writing reports and inventory sites

It's good to have all skills But if I have to choose a skill that I believe that is importantI i would say the analysis,The spirit of the analysis allows you to effectively use the other skills. Analyze the words before saying them analyze peopel befor distribut tasks analyze the acts before producing them and so on

A supervisor sould have work knowledge in the fild and and have good knowledge of managment and good coordination between team members.

The major skill fo Supervisor IS A SAFETY.  Safety FIRST, it dosn't meter where are you working, To keep the Life and Heath of your people in safe. This is the main MAJOR SKILL! 

Fully understand the field of work to be implemented and executing it with reliable results

I believe as a leader one needs to various skills but i believe a team working leader who is hands on, leading by example with surbodinates is the that surpasses all

good management and communication skills are the most important when it comes to site supervision , a good supervisor needs good management skills and an abillity to communicate with his team in order to inforce safety rules , to handle workers eg, if you are too liniant workers mostly likely are going to become slower and stop listening to you and the opposite is true , so site management is the main skill that every supevisor must posses .

Executing work at site with highly efficiency , effectiveness and but with safety  

1. Possessed good skill and vast experiences in the related field of the job given to him. 

2. Good and effective communication skill - verbal and written.

3. Good safety knowledge wrt its legislative and statutory compliance  requirements.

1. The Supervisor is must be smart than good manner team and crews, he should know the program n plan how to do it.  They have good knowledge about the objectives and plans.
2. Following the safety rule and safety management
3. Good reporting and diplomation

partrolling of field & equipment also trouble shooting.