First you want to use this day to get all pikmin over 100. You also have to get a part from here so I recommand you go here after you get the blue pikmin.

                                   Getting the part
First you go to impact site. You first want to get 100 pikmin on the feild. But have atleast 20 blue pikmin. Get pikmin from all colors.You now want to to where you moved that box on Day one. Get 3 yellow pikmin with bombs inside of the box. Blast the wall that blocks the way to the only part their. Their are 3 Clamp Clamps. The one furtest to the left holds the piece. What you need to kill it with vlue pikmin. Now if you have only 20 blue pikmin becareful not to lose any. Once the part is out and is taken to the ship pikmin harvest day will begin

                              Getting easy pikmin
First you will wantto kill the clamp clamps. You can kill one with bomb rocks. Than give the pearl to any pikmin that needs a boast in numbers.
Note these pearls give 50 pikmin. So be wise on who you use it on. Than grab the three 20 pellets. Make sure the color of the pellet is being carried by the pikimin of that color so you can get more. Their is also 3 10's food pellets  right of the red onion. So you'll want to get those like the 20's. Their are also toins of 1 food pellets. Like the 20's make sure is being carried by the right color pikmin

                          Tips for other places
Sometimes you don't have time to spend on getting more pikmin. So I reccommand you carry back the corpes back to the onion. That's the overall. Though you may want to get the one that's the most helpful

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                                                                        killeryoshis