This app developed by K-state allows a farmer to quickly tell hp necessary to pull a piece of equipment.
Potential Uses/ Testimonial:
The below description is from the Android Market Place.
No more standing at farm auctions wondering if your tractor could pull an implement for sale. The application has a built in list of many common implements. You can select ground and soil conditions, tractor type, pulling speed, working depth and size of the implement. Then hit calculate and the application will provide an estimate for the required drawbar and PTO horsepower.
Note: This app provides two horsepower measurements. Drawbar horsepower is the horsepower to pull the implement. PTO horsepower is the actual tractor horsepower you need based on tractor type and soil. Use PTO horsepower to match tractors to implements.