(1) According to the research steps of the subject, the following experimental steps can be determined by using appropriate scientific inquiry methods: First, go deep into social life investigation to obtain first-hand information, and you can go to market research to collect relevant information (such as price, purity, etc.). Different brands of the same or different nitrogen fertilizers; Then use the collected data and knowledge to calculate the cost performance of different brands of the same or different nitrogen fertilizers; Then analyze and summarize the survey results, analyze the cost performance of different brands of the same or different nitrogen fertilizers, determine the nitrogen fertilizer with the highest cost performance, and write relevant survey reports or small papers.

(2) the form of research results (that is, the final research conclusion and the expression form of research results): investigation reports and papers are the two main forms of research results.

So the answer is: (1)① Investigate and collect relevant information (such as price and purity). ) the same or different nitrogen fertilizers of different brands in the market; ② Using the collected data, find out the cost performance of different brands of the same or different nitrogen fertilizers; ③ Analyze the cost performance of different brands of the same or different nitrogen fertilizers, determine the nitrogen fertilizer with the highest cost performance, and write relevant investigation reports or small papers.

(2) investigation reports or documents.