Another example of a practice that has costs beyond the farm level is shifting from fall application of N to spring application. Dr. Dan Otto, ISU Extension Economist, estimated the annualized infrastructure cost (storage, handling and application equipment) to shift all fall fertilizer application from fall to spring at $397.34 million.
It is assumed 25% of the nitrogen is applied in the fall. Twenty-‐five percent of the estimated state average application of 171lbsN/acre means 43lbsN/acre is applied in the fall. However, the
recommended maximum return to nitrogen (MRTN) is 156lbsN/acre. Reducing N application rates to the MRTN level means it is not necessary to build the entire additional infrastructure Otto assumed would be needed, thus lowering the needed investment.
The industry currently applies an estimated 128lbsN/acre in the spring. The difference between the 156lbsN/acre capacity and the current 128lbsN/acre is 28lbsN/acre. This is 65% of the 43lbsN/acre capacity that Otto recommended building. Otto’s estimate was $397.34 million annually for the added capacity, but only 75% of that was for nitrogen, or $297.75 million. At 65% of that capacity is $194 million annually for infrastructure costs that would need to be added to move to spring-‐only application.
Moving application of liquid swine manure from fall to spring creates added costs for pork producers and commercial manure applicators. Most manure storage is built to hold a year’s supply or more of manure. Shifting from fall to spring will cause logistical problems in the transition year because there is typically not enough storage to forgo fall pump out and additional land will be required to empty storage in the spring after manure had been applied to the fields in the fall. The application time window is narrower in the spring than the fall. It will require additional equipment and labor to apply the same amount of manure in fewer days and thus increase the cost of manure application.
An additional consideration in changing from fall to spring fertilizer application is timeliness of farming operations. If fertilization is moved to a spring application without changing spring operations, there will be less time available for planting the crop. Conversely, if tillage operations change, there may be more time available. The two main factors to consider when evaluating the impact of changing field
operations are the number of days suitable for fieldwork and the time it takes for each operation performed. The time it takes per operation and to a lesser extent, the days available, will be influenced by the power unit and the size of the implement.
Corn and soybean yields have an optimum planting date. In the Iowa latitudes, May 10 is the critical planting date for corn. After that date, yields begin to decline. Field trials by Iowa State University have documented this pattern. Planting delayed two weeks results in a 10% reduction in yield and a delay of four weeks could lead to a 25% yield reduction.
The National Agricultural Statistics Service provides a weekly estimate of the days suitable for fieldwork. Iowa State University Extension compiled these estimates from 1958 through 2007. For Iowa from April 2 through May 13, there was a median of 20.6 days suitable for fieldwork. Obviously the days suitable for fieldwork and the first day when fieldwork is possible will vary by year and region of the state. However, having an estimate of the median number of days is necessary to estimate the timeliness cost of changing operations or the timing of the operations.
The second component for calculating potential timeliness yield loss is estimating the amount of time
for all of the operations performed. ISU Extension publication AgDM A3 -‐24, Estimating the Field
Capacity of Farm Machines, provides an estimate of the time for a variety of operations and sizes of
implement.
As an example, assume a 1,500-‐acre farm using 12 hours per day following a disk/cultivate tillage regime. A 33-‐foot tandem disk is estimated to cover 19.2 acres in an hour. That means a farmer could cover 230 acres in a day, so it would take 6.5 days to tandem disk (1500/230). A 50-‐foot field cultivator can cover 33.9 acres an hour or 407 acres per 12-‐hour day. With 1,500 acres it would take 3.7 days. A 24-‐row, 30-‐inch planter covers 21.8 acres an hour or 262 acres in a 12-‐hour day. Planting would add another 5.7 days for a 1,500-‐acre farm. Finally, a 17-‐knife anhydrous applicator would cover 16.2 acres an hour or 194 acres a day. This means for a 1,500-‐acre farm with large equipment and using a
disk/cultivator tillage system, it would take 6.5 + 3.7 + 7.7 + 5.7 = 23.6 days.
The number of days for fieldwork in this hypothetical example would exceed the median number of days available, assuming the goal was to be planted by May 10. A farmer would suffer yield loss if all the operations had to be performed in the spring.
The fieldwork estimate does not include maintenance or travel. Therefore, a 12-‐hour day is appropriate for the examples. The total number of days needed for fieldwork to avoid planting delays depends on the size of the equipment, the number and type of operation, and days available. The losses could be serious in some situations. With $5 corn and a 1.5-‐bushel per day yield loss, a farmer with 1,500 acres of corn would lose $11,250 for every day of delay. In the example above, planting would be at least three days beyond May 10. Therefore, this hypothetical farmer would have a $33,750 loss due to delayed
planting. Applying the yield loss to the 25% of the acres that would shift from fall to spring fertilizer application is predicted to reduce total corn production by approximately 16 million bushels, and the price would be expected to increase approximately $0.02/bushel.