Is the same old work-a-day world of HayDay starting to lose some of it's fire? Are you a higher level player who has unlocked all your machines and wondering - What's Next?
Then try the newly updated
HAY DAY SCORCHED EARTH CHALLENGE! (ver 3.0)
The Challenge - How long will it take you to go from almost NOTHING to a FULLY STOCKED barn and silo? This challenge asks you to strip down your farm, sell virtually everything you have, and start over! Staring from only 1 of each crop and USING NO DIAMONDS, you must rebuild your Hay Day empire from SCRATCH!
NOTE! - In order to participate in the full challenge, a player must be at least Level 79 and have unlocked the Lobster Pasta. However, feel free to begin at any time and complete as much as you can with your available items. The guidelines listed below are my own, and I encourage you to make it more or less challenging as you see fit. The point is to have fun!
The Goal - Using the rules outlined below, the goal is to build 10 or more of EVERY ITEM available in the game. How many Crops/fruit you produce doesn't matter for completing the challenge.
The Set Up - Players start the challenge whenever they like, but everyone must start from the same initial position. There are a few variables here, some of which matter for the challenge, and others that might help but are not required. Each contestant must do the following:
Stop producing anything in your machines, and allow your production queues to run completely empty.
Completely exhaust ALL fruit trees and bushes on your farm (you don't have to remove the dead ones, just make sure they cannot produce any more fruit). If this seems particularly onerous or wasteful, feel free to simply move the plants to a remote corner of your farm and ignore them as though they are not there until you are done with the challenge as this is often the step that takes longest to prepare.
Sell off ALL of your berries, cocoa, coffee and other fruits from trees and bushes.
Sell off ALL but ONE of each of the 14 crops: Wheat, Corn, Carrot, Soy, Sugar Cane, Tomato, Strawberry, Pumpkin, Pepper, Indigo, Cotton, Rice, Lettuce, Potato
Sell off ALL the items, product, mining equipment and animal feed in your barn (you may keep expansion materials for your farm, land and town if you like, as well as saws and axes, though they WILL take up valuable space towards the end of the challenge).
Empty your tackle box of lures, nets and duck/lobster traps, clear your fishing holes, and your Feather and Lobster Tail machines.
All your animals (including pets!) must be awake and hungry.
Dismiss all the visitors in your Town, and make sure there are none lingering in shops waiting for requests to be filled.
The Variables - Your individual silo/barn capacity must be at least 1,300 to complete the basic challenge (see below), but having more space will definitely make it easier; how many pets you start with also does not matter, unless you are doing Metal Illness Mode, as they do not produce any items that will make the challenge easier; the amount of land you've expanded, or the amount of fishing spots unlocked are likewise largely irrelevant to the challenge (though having more fishing spots might give you a slight advantage).
It is advisable that you have as many animals as possible, though you can technically complete the challenge with only one of each. It is also advisable that you gain as many mastery stars on your machines as possible before attempting the challenge as the final mastery will reduce production times. And finally, the more slots in your productions queues the better!
The Rules -
You may NOT purchase ANY items or crops from the newspaper or roadside shops - EXCEPTION you may buy anything in Greg's shop!
You may NOT use diamonds to speed up the production of any items.
You may NOT use diamonds to ask Tom to fetch items for you.
You MAY spin the Wheel of Fortune, or order anything from the catalog with gift vouchers, but you must sell it immediately if it is one of the items needed to complete the Challenge. Participants may wish to do this to earn vouchers, money, or unique decorations.
You MAY open red toolboxes you find, and you MAY spend diamonds to unlock them.
You MAY continue to fill crates for friends and neighbors, participate in Derby tasks, complete boat and truck orders, and sell items and crops in your roadside stand, or to visitors in your town - though doing so could potentially lengthen the challenge for you.
You MAY flag your trees and bushes and boat crates for help.
You MAY spend money to plant as many fruit trees/bushes as you like.
You MAY spend diamonds to call in a boat more quickly.
You MAY spend diamonds to add a slot to the production queue of a machine or to your roadside stand during the challenge.
You MAY expand your barn, silo, land parcels, or Town buildings during the challenge.
In Hay Day there are:
5 Animal feeds (Chicken, Cow, Pig, Sheep, Goat)
9 raw animal goods (Eggs, Milk, Bacon, Wool, Goat's Milk, Honey, Lobster Tails, Fillets, Feathers)
116 produced items (not including Candy and Metal items)
5 Candy Items
14 Metal items
At 10 each, that's a total of 1300 items to produce, so you will need a barn capacity of at LEAST 1300 to complete the challenge and hold all pieces at once. BUT remember that if you choose to keep any of your expansion supplies, mining tools, etc, you will need even more space for them!
Candy Crush Mode - The same rules as above, but you must also produce 10 of each candy item. That's 50 additional items to make from scratch! Candy takes a really long time to produce, so be prepared to run your sugar and jam machines even longer!
Metal Illness Mode - The same rules as above, but you must also produce 10 of each jewelry item, bar of metal, and raw ore, that's 140 additional items! Be aware that if you are going for Metal Illness, a few of the conditions above are slightly different. Metal Illness can take a particularly long time because you cannot buy the equipment needed to progress, only earn it through working on your farm. For this reason, many people who attempt this challenge find that it requires a LOT of Wheating! Not for the faint of heart.
Utterly Ridiculous Mode - EVERYTHING at QTY 10 from scratch! You must produce 10 of each regular item, candy item AND 10 of each jewelry item, bar of metal, and raw ore, increasing the total required to a whopping 1,490 items! That's every available item in the game, and will take at LEAST 24 DAYS of constant production (but probably longer)! As an additional incredibly difficult challenge, you can only buy fruit trees and bushes with money earned from selling items created DURING the challenge. This will take a little bit of book keeping on your part unless you want to spend all of your cash before starting (not recommended, seriously, that's just crazy talk).
When you are ready to start, make note of the date and time you started by posting in this thread. Post again once you've completed the challenge (or given up like a quitter! 
) and revel in the glory of your own success!
Good luck!
A Few Clarifications:
Only the contents of your barn are being measured. The amount of crops/fruit you have in your silo at the end of the challenge doesn't really matter for the "final score". The amount of fruit you have is directly related to how much money you can spend on buying trees, and is not really representative of success.
If you should accidentally spend diamonds to speed up the production of an item, unfortunately the only fair thing to do is to immediately sell it. If you speed up a crop or tree, then do not harvest it until other trees or crops planted at the same time are also ripe (or if that's too complicated, remove the tree or bush to a remote corner of your farm and ignore it for the rest of the challenge).
Previous versions of the game allowed you to keep your mining materials at the start if you were not completing Metal Illness Mode. However, remember that the Top Hat requires refined coal to produce. So you'll have to get rid of any mining materials before you start, or find a way to keep track of the ones you had when you started and only use those you earned during the challenge.