How critical is plant to plant spacing for corn? Past research has shown variable results, with some results showing that for every 1 inch in variation from the targeted spacing, yields were reduced 2.5 bushels per acre. Other researchers report even higher losses, while others report less. National yield contest winners often state that slow planter speeds improve plant spacing uniformity and are part of their formula for success.
Fifteen producers in Nebraska, were part of a 2001 research project intended to compare grain yields across different planter speeds. How would planter speed affect plant spacing uniformity? Each location had three to four replications of three planter speeds: 2, 4, and 6 mph.
How was the experiment conducted?
The cooperators calibrated and used their own planters and equipment and managed the plots as they normally would. They also chose their own hybrid, tillage practices, etc, and harvested the grain. Yield data were obtained from on-combine yield monitors or weigh wagons. Plant to plant spacing was measured after emergence at all locations.
Four measures based on theoretical spacing do a good job of summarizing distributions of plant spacing for single seed planters. (See "Accurate tools for measuring plant uniformity" for more information on these measures). Briefly these measures are as follows:
- Multiples index (D) doubles, triples, etc. Smaller values of D indicate better performance than larger values.
- Miss index (M) skips. Smaller values of M indicate better performance than larger values.
- Quality of feed index (A). Larger values of A indicate better performance than smaller values.
- Precision (C) is a measure of the variability in spacing of the plants after removing the variability due to skips and multiples. A practical upper limit is 29%. Smaller values of C indicate better performance than larger values.
Cooperator planter systems
Thirteen producers used John Deere planters (10 with JD 7300, 2 with JD 7100, and 1 with a JD 1700). One cooperator used a Case IH 900 and the other producer used a composite of the Case IH 800, 900, and 955 planters. Target planting rates ranged from about 29,000 to slightly over 30,000 seeds per acre. All but two used 30-inch rows; the others were 34- and 36-inch rows.
Frequencies of plant spaces for the 13 sites with 30-inch rows are shown in Figure 1. Spacings between the two dotted vertical lines represent spacings in the target zone (see "Accurate tools for measuring plant uniformity" for a description of target zone). Spacings to the left of the first dotted line are considered multiples and spacings to the right of the second dotted line are considered skips.
Figure 1. Frequencies of plant spacing.
What did we learn from this planter speed research?
Planter speed did not affect corn grain yield but it did affect plant spacing accuracy (see Table 1). This is reflected in all four measurements (D, M, A, and C %). The 6 mph planter speed resulted in more 'doubles' and more skips or missing plants than the 2 and 4 mph speeds. Fewer plants were in the target spacing with 6 mph than with either the 2 or the 4 mph speeds. Precision did improve with slower planter speeds. Plants in Division II were closer to the target spacing at 2 mph than with either 4 or 6 mph speeds. In Table 1 are listed the yield averages and ranges for the 15 sites.
| Table 1. Measures of plant spacing accuracy for different planter speeds averaged over 15 locations and the 15 locations' averages (and range) over planter speeds. Univ. of Nebraska, 2001. | |||||
|---|---|---|---|---|---|
| Planter speed(mph) | % D | % M | % A | % C | % Yield (bu/acre) |
| 2 | 4.9 a* | 10.7 a | 84.42 a | 18.73 a | 207.1 a |
| 4 | 5.0 a | 10.5 a | 84.49 a | 20.08 b | 205.6 a |
| 6 | 7.6 b | 12.6 b | 79.85 b | 23.13 c | 205.5 a |
| 15 site average | 5.8 | 11.3 | 82.9 | 20.6 | 206 |
| (range) | (1.5 -10.6) | (4.9 - 18.4) | (71.0 - 88.1) | (16.4 - 26.1) | (187 -235) |
| * numbers within a column followed by the same letter are not different (P< 0.05). D = multiples index M = miss or skip index C = precision A = quality of feed index |
Grain yields were excellent at all locations. Although actual stands were near the target at most locations, plant spacing accuracy varied among locations:
- Planter speed effects for both 'M' and yield were consistent across locations.
- The multiples index was not affected by planter speed at 8 of the 15 locations. At 6 locations, increasing planter speed increased the number of doubles or multiples. Increasing planter speed reduced the "D" index at one location by nearly 50%.
- Quality of feed index was not affected by planter speed at 8 of the 15 locations. Speeds of 2 and 4 mph had similar values for quality of feed (resulted in greater plants in Division II) and thus better values than the 6 mph planter speed at six locations. Quality of feed, however, was increased 14% at the 6 mph speed compared to the 2 and 4 mph treatments at one location.
- Precision was affected by planter speed at 12 locations. Values of precision for all these locations either were similar for 2 and 4 mph and were larger (worse) for 6 mph, or small at 2 mph and greater (worse) at 4 and 6 mph. Thus, at 12 locations, faster planting speeds resulted in less precision.
Overall Conclusions
- Grain yields were excellent at the 15 on-farm sites in 2001. Perhaps the 2001 cooperators were more conscientious about planter maintenance and repair than those not involved in the study; we have no previous data with which to compare.
- Plant spacing accuracy was affected by planter speed. Generally the 6 mph speed resulted in less accuracy than the slower speeds. A reduction in accuracy can be easily observed in Figure 1; as an increased percentage of plants are further from the targeted plant spacing).
- Grain yield was not affected by inaccuracies in plant spacing or planter speed.
- There was an opportunity for improved plant spacing at some locations; however, this may not improve yields.
Text is taken from a Crop Watch article (University of Nebraska extension newsletter) written 17 May 2002 by Roger Elmore.