Prospects for timely planting of the 2014 corn crop
It is generally acknowledged that the U.S. average corn yield is largely determined by weather conditions during the reproductive and grain filling stages during the summer months. Still, weather conditions during other times of the year, as well as the timeliness of planting, are known to influence the yield outcome. In the case of the timeliness of planting, it has been demonstrated that U.S. average yields are negatively correlated to the portion of the acreage planted after the optimum date for maximum yield potential regardless of subsequent weather. With the slow start to planting the 2014 corn crop, there is some concern that a larger than average percent of the crop may be planted after the optimum date and therefore reduce the average yield potential.
Here, we examine the prospects for timely planting of the 2014 corn crop in Illinois. That analysis is extended to the U.S. based on the assumption that planting conditions experienced in Illinois can be applied to the rest of the major corn producing states. Prospects for completing planting of the 2014 corn crop in a timely fashion depend on four factors:
1) The date of the end of the optimum planting window,
2) The percentage of the crop already planted
3) The number of days suitable for planting in the remaining portion of the optimum planting window, and
4) The rate of planting per suitable day for fieldwork.
There is not complete agreement on the optimum planting window for maximizing corn yields and that optimum window varies by geographic location. For analysis purposes, however, it is useful to identify one date for the end of the optimum window that can be applied to the entire production region. Acreage planted after that date would be considered to be planted late and yield potential would be expected to be reduced as the percentage of the acreage planted late increases. As indicated in last Monday's post we currently define the end of the optimum planting window for corn in the 18 major corn producing states to be May 20. The percentage of the crop planted after that date would be considered to be planted late.
click image to zoom The USDA's weekly Crop Progress report indicated that 32 percent of the corn acreage in Illinois and 19 percent of the corn acreage in the 18 major corn producing states was planted as of April 27. For none of the 2014 crop to be planted late, progress needs to reach 100 percent by May 20, or in about three weeks. The first factor that will determine the prospects for completing planting by May 20 is the number of days that will be available for corn planting in the next three weeks. Obviously, the answer is not known, but we estimate the likelihood of zero to 21 days of suitable days based on the historical distribution of suitable days as reported in the USDA weekly Illinois Weather and Crops report for the 44 years from 1970 through 2013. The frequency and cumulative percentage of the number of suitable field days during the three week period from roughly April 30 through May 20 are reported in Table 1. Over the 44 year period there were 11 or fewer suitable field days in that three week period 52.3 percent of the time. In other words, the median number of suitable field days during this three-week period was about 11 days, so that "normally" farmers were able plant about half the time. The range of suitable days is surprisingly wide, with a minimum of 4 days and a maximum of 19 days. Note that there was a 15.9 percent chance of a week or less of suitable field days during this three-week period.