Before the season starts, list every field operation on one sheet, one row per operation. In each row, write the earliest date the operation can acceptably start, the latest date it can acceptably finish, its place in the order, and the name of the person who decides when it starts. The span between that start and that finish is the operation’s window, and the sheet is your operations calendar. Many farmers already carry these dates in their heads. What is usually missing is having them on paper before the morning two operations need the same tractor.
On many farms each operation is decided on the day, going by the weather and by whether the field looks ready. That works until two operations come due at once, or the crew for one is busy on the other. Then the choice is made in a hurry, and the crop under the operation that waited loses yield or quality later in the season. Machinery economists call that loss the timeliness cost, the economic consequences of performing a field operation at non-optimal time. Writing the window down lets you make the choice ahead of time instead of under pressure.
Why does a late date cost money?
Because every field operation has a best date, and the crop loses value on either side of it. Schuler and Frank put it plainly in their University of Wisconsin-Extension guide to machinery costs: every field operation is best done at a certain time, and done at another time the crop loses quantity or quality. The window is the stretch on each side of the best date where that loss is still small enough to accept. Writing the window means deciding how many days late you can live with before the loss gets too big.
A late start hurts more the more ground is still waiting. Every acre the machine has not reached yet keeps losing until it gets there, so Carina Gunnarsson, in a doctoral thesis on grain and forage farms at the Swedish University of Agricultural Sciences, found that timeliness costs occur on the whole area before the operation starts and thereafter on a decreasing area depending on the capacity of the operation. A slow planter or a short crew makes the loss bigger, because more acres sit past their best date each day.
Why do two operations end up competing for the same day?
Because days fit for fieldwork are few, and the weather sets them, not the calendar. Williams and Llewelyn, at K-State Research and Extension, went through thirty-two years of Kansas records and found that the least-cost size of equipment is affected by the number of days available for field work, and that the actual number of field work-days available each week varies considerably from year to year. The counts are from Kansas, but good days are scarce on any farm, and they tend to come for several operations at once.
Rain is not the only cause. Kachala and colleagues, in a 2026 review of corn research in Africa published in the journal Frontiers in Agronomy, list labor shortages, land not ready, tight cash and late input delivery next to rainfall as causes of delay that narrow the feasible window for acting. Writing the order and the decider before the rush lets the scarce good day go to the operation that can least afford to lose it, instead of to whichever one the person standing in the yard thinks of first.
What goes in each row?
For each operation: the earliest date it may start, the date it must be finished by, and its place in the order, so that no operation starts ahead of one it depends on. Planning models for farm machinery, such as the one Bochtis and colleagues published in an agricultural engineering journal, use the same shape: a time window for each operation, built to allow early or late servicing but with some form of additional cost or penalty if the window is missed. The calendar keeps that structure without the math, posted where the people who run the operations can read it.
The calendar covers the season now under way, and you rewrite it each season because the weather and the crew change. Which crop goes in which field over the next several seasons belongs to the multi-year production plan, a separate sheet you fill in for several seasons at a time. What actually got done, on what day and with what, goes in the field log as the work happens. At the end of the season, laying the log beside the calendar is how you check each operation against its window.
How much does a late operation cost?
Nobody can hand you a figure that holds for your farm. Gunnarsson stresses in her thesis that timeliness costs are specific for regions and are subject to annual variations, so a number from one farm in one year does not carry over to another.
Schuler and Frank use as an example that yield may decrease 1 percent per day if the operation is not done on the optimum date, and note that the real size depends on crop value, yield, the machine, the weather and the hours a day available for fieldwork. Kachala and colleagues add that the rule that late work cuts yield is treated as settled, even though policy must still determine how much loss follows a specified delay.
So why write the window if the loss has no fixed size? Because knowing that late work costs yield is not the same as acting on it. They warn that without a local estimate, missed windows can remain rhetorically acknowledged but operationally under-prioritised. With the window on paper and a name beside it, what everyone already agrees on becomes a date someone answers for.
Who decides when an operation starts, and which one waits?
One named person for each operation, and a written rule for each pair that collides. A window with nobody’s name beside it is only an intention: when the day comes, nobody is sure whose call it is. The name here is the person who decides the start; who is on the schedule to do it on the day, and who covers if they are out, goes on the posted work schedule, a separate sheet.
The collision rule is a management choice, not an agronomic one. When two windows overlap and one machine or one crew has to serve both, you write down which operation takes the day and why, usually the one with the narrower window or the costlier delay.
At the end of the season you compare the calendar with what happened. A figure chosen in advance, such as how many operations finished inside their window, tells you whether the season went the way the calendar planned; choosing one operational number is a separate article on writing down where such a figure comes from and who reports it. Settling before the rush who decides what, and checking it afterwards, is part of everyday farm management.
Where to start
Two hours, with the list of fields and last season’s dates on the table, from a calendar if you kept one or from memory if you did not. One sheet, one row per operation, in the order they have to happen.
You find out whether the calendar was worth the two hours on the morning two operations want the same tractor: someone points at the row where it is already written which one goes first and who decides. That answer went on paper weeks earlier, before anyone was in a hurry.