Okies, tis a bit hard to give you a definite answer without knowing your method and what you were trying to show by your experiment, but generally in writing up a report you should have:
* introduction - what have similar experiments shown, background research and the like. Similar to a literary review.
* hypothesis - why do you think is going to happen? (for example: "i think that the NPK fertiliser will ensure the fastest growth rate of potatoes". It doesn't matter if what you think will happen doesn't turn out to be what did happen - thats why you are doing the experiment!!)
* aim - what are you trying to show by your experiment. (for example: the aim of this experiment is to determine the effect of different types of fertiliser on the growth rate of potatoes", or whatever)
* method - just write out the steps that you took in conducting the experiment. Include any relevant diagrams such as pot placement etc..
* variables - what variables did you control, measure, change?
* results - usually best to have a table for this. Include averages. Graphs are good too, but make sure you explain them, don't just leave them to explain themselves. For example: "graph #1 shows that the NPK fertiliser exhibited a faster growth rate when compared to the Aquasol fertiliser solution.")
* discussion - ok, so what do your results mean? why is that going to affect us? (for example: the potato plants treated with NPK fertiliser exhibited a much higher growth rate over the 6 week trial, and had a final average height that was 12.3cm and 6.5cm taller than the aquasol and compost treatments repectively. This is important, because it shows that farmers can increase their yield through the application of NPK fertiliser.")(yes, plant height is not an indicator of yield for potatoes, given that the 'yield' is the underground but, but you get what i mean...) Also proably discuss any unusual things that you found in your results, and if their were any outlying results, mention why they may have occurred. You should also mention the standard deviation of your treatments. If your average height for NPK fert was 45cm and the standard deviation was 20, then it is a very unreliable treatment, and another treatment that may have given results of (for example) average height 40cm (lower than NPK) and standard deviation of 3 (very good SD, much lower) then this would be the better treatment, as it is much more reliable. SD is a measure of how far most of the scores are from the average. The SD also lets you discuss the reliability of your results.
* conclusion - what has your experiment shown?
and then you're done!
In regard to your second question, I don't really understand what you are asking, but as a general rule, write your results out as they occurred.
If some of the seedlings didn't emerge until the third week then the measurements for weeks 1 and 2 are zero. don't start the measurements from when the plant started growing, start them from when you started your trial.
Hope this helps.
Good luck with your assignment!!
