A:   I am unaware of any solid information to answer your question. One factor to consider is the level of success establishing the turnips. If it is very low, compensation obviously would not be needed. Because you are concerned about water usage, this suggests the field is dryland so success will be very dependent on rainfall after seeding. Assuming good success, the vast majority of N and other nutrients used by the turnips will be recycled via animal waste although distribution will be less even due to concentration in urine patches and cow pies. There probably would be some impact on next year's crop due to water usage but how much is very much unknown. Maybe it would be possible to leave an area or two free of turnips and compare crop yields from turnip and turnip-free areas next year in order to determine compensation -- obviously a troublesome nuisance but the best way to measure actual impacts. Left over bulbs can be a small problem, especially in no-till fields but are unlikely to be any problem if any tillage is used. Broken bulbs will quickly rot in the spring (making some unpleasant odors) and healthy bulbs will develop seed stalks as the bulbs nearly wither away. Use of a brassica without a bulb would avoid such problems but also would reduce much of the feed potential provided by bulbs. One form of compensation would be to split the benefits gained from the turnips. For example, if local stalk rental is 20 cents per cow-day of grazing, determine how many extra cow-days resulted from use of the turnips and compensate the tenant with 5 to 10 cents per day.