There was a time in my life where I did most of the planting for my Dad and I. He did most of the spraying for the two of us. At the time we were each financially responsible for about half of the acres. Combined we could make fairly large herbicide orders and get some bulk discounts. But it all got ran through one sprayer.

So he'd go and take herbicide that he had mostly purchased and then he would spray some of it on his fields and some of it on my fields. He would make a hand written record for each field but his notes usually said how many ounces or pounds per acre of each product he was applying rather than how many gallons or pounds he was applying.

I had a spreadsheet for each field. I would take his hand written records and I would make entries into each field showing the total number of gallons or ounces of each product that he applied. Then I had a different spreadsheet that showed the amount of herbicide I had purchased from him for every product. Then I would make entries in that inventory spreadsheet representing how much herbicide I had used. I would often let the inventory get way into the red (costing him "interest" value on the product and I would also make up for it later by putting a lot of money towards herbicide I had not used yet so that he'd be gaining "interest" money on herbicide in an attempt to keep that aspect somewhat even. Finally, I was farming for multiple share rent landlords and had to bill them for their share of the herbicide. I had separate "billing" spreadsheets for them and I would take the calculations from my field spreadsheets and enter them into the billing spreadsheets to create bills for my landlords.

This was very time consuming.

I tried to get a tech college to create a PostgreSQL database for me. I hoped that whoever was running the sprayer would be able to use their smartphone or tablet to access the front end of the database over the internet. They would enter the field name and the rates they were running per acre and the number of acres they were running and I wanted the database to take that information and:

1. Update the inventory of what I had purchased from my Dad
2. Update the bill for my landlords

In this way all of the "office" work would be done at the same time as the sprayer operator was entering his record keeping data into the database with his smartphone.

A group of college students and their instructor actually did spend almost 2 hours driving out to meet me and go over the design of the database. They left and we communicated over the phone or email a few times as they worked on the project and then I never really heard anything again. Not sure what happened but I suspect it was too big of a project for a group of new students learning about databases to dive into.

What you built sounds like it would do most if not all of what I wanted except for the part about being able to install it on a server that I would manage and being able to access it from the field with a smartphone or tablet.