While writing an academic paper, you may make use of bullet points. Now, in a list of bullet points, whether each item begins with a capital letter depends on the punctuation mark that comes before the item. A capital letter typically marks the beginning of a sentence. However, in lists of bullet points, the beginning of a point is also indicated by space and the item marker (whether a bullet, a number, or a letter). This is why capitalization of items that make up a list of bullet points is sometimes a matter of style.
Most often, the text that introduces such lists ends with a colon, as in "The value of soil for agriculture depends on the following factors:". If we take that only a full stop, a question mark, or an exclamation mark can mark the end of a sentence, it is only logical to begin the items that make up the list with small or lowercase letters because the sentence that began with "The value of soil" is yet to end.
However, many would consider this logic as being either too rigid or irrelevant, and it is very common to see lists of bullets points in which each item begins with a capital letter despite the colon that comes before the first point.
If each item in the list is a single word or runs to only two to three words, capitalizing the items seems excessive to me since each item begins on a new line and is preceded by an item marker, capitals serve no useful function either.
If a list is introduced by a complete sentence, each bullet point needs to begin with a capital letter. This is why it is better to use a colon to introduce a list in which each item is a single word or consists of only two or three words. On the other hand, if each item in the list runs to many words, often with commas and even semicolons, it is best to introduce the list with a complete sentence and make each item in the list also a complete sentence or a group of complete sentences in which case, each item will naturally begin with a capital letter.
When a list is introduced by an incomplete sentence, as in "Three main types of vegetative parts used for propagation are," leave the incomplete introduction "open" (no punctuation). Never use a capital letter to begin an item in such lists; instead, begin with a lowercase letter and end the last item with a full stop, thereby completing the sentence.
These guidelines will help you write a more presentable research paper.