Agronomy Library > Soil Conservation

Row Spacing Comparison for Direct Seeded Field Peas - Direct Seeding Advantage 2004
Author: Rick Taillieu, Reduced Tillage LINKAGES
Date Created: November 23, 2004
Last Reviewed: March 02, 2007

Project Background 
Row spacing continues to be one of the most discussed, and often disputed, aspects of a direct seeding system. Producers continue to weigh the pros and cons of wide versus narrow row spacing while research continues to provide inconsistent results. Row spacing is often equated to stand density and canopy closure, but opener size and design also have to be factored in. The research results are most often measured in yield numbers and fail to consider the additional aspects of row spacing.

Reduced Tillage LINKAGES worked with Hillcrest Acres of Camrose on a row spacing comparison in 2004. Hillcrest Acres owns two Flexicoil 5000 air dills with paired row openers – one on 9" spacing and one on 12" spacing.

On April 30, a 65 acre field of Majorette field peas was direct seeded with the two drills, alternating between the 51 foot wide 9" spaced drill and the 57 foot wide 12" spaced drill across the entire field resulting in 24 total strips. The seeding rate for the peas was 180 pounds per acre and Jumpstart and liquid inoculant were used.

This project was a demonstration site for the Greenhouse Gas Mitigation Program for Canadian Agriculture and was part of the Alberta Pulse Growers On-Farm Agronomy program. It is important to not that this was a demonstration project for extension purposes and not scientific research. Plant counts conducted by the Battle River Research Group found that there was very little difference in the plants per square foot between the two drills. The counts were in the 4 plants per square foot range which was much lower than the target plant population of 7 plant stands per square foot. This may have resulted from using common seed (removed from certified by several generations) and the lack of a seed treatment.

Observations and Results 
 
Plant Stand 
Targeted plant stands were aattained using each drill.

Canopy Closure
As was expected, the wider row spacing was slower to form a canopy. The narrower row spacing closed the canopy approximately 7-10 days earlier. As a result of the thin plant stand, a thin canopy resulted regardless of spacing.

Weed Pressure
There was very little visual difference in the weed pressure when comparing the two systems prior to or after herbicide application. The field was sprayed on June 4th with Select and a ½ rate of Pursuit.

Disease Pressure 
There was very little disease present regardless of the row spacing. 
Yield
We had hoped to produce a yield map for the entire field but unfortunately yield mapping was not available at harvest time. The harvest was done on the evening of Tuesday, September 7th with the first harvest snow due to arrive the next morning. A weigh wagon was used to take weigh two 9" strips and a two 12" strips. Each strip was 0.48 acres in size.
  
Harvest yield – average of 2 strips
9" row spacing
12" row spacing
62.1 bu/acre
61.4 bu/acre
 Visual observations and yield monitor readings indicated that field variability was more closely related to soil conditions and weed pressure than to row spacing. 

Other Factors to Consider

Residue Clearance
An important factor to consider when comparing or considering row spacing is that seeding implements with wider row spacing have more room to allow crop residue to pass through the machine at seeding time. Increasing the number of ranks will also improve residue flow through the drill. In any case residue management should always begin at the combine.

Horsepower Requirements
This is a very simple equation, in that more openers require more horsepower. With wider row spacing, you can either pull a larger drill with the same tractor or the same drill with a smaller tractor
Number of openers (Flexicoil 5000 example)
Drill width
27’
33’
39’
45’
51’
57’
9" spacing
37
45
53
61
68
77
12"spacing
27
33
39
45
51
57

The actual horsepower required will depend on a number of factors including opener type, soil type and conditions, seeding depth and more. When PAMI (Prairie Agricultural Machinery Institute) tested double shoot openers in 1995, they found that the drawbar power required to operate each Flexicoil HS (Heavy Soil) paired row opener at 5 mph varied from 1.5 hp to 2.7 hp per opener. (PAMI evaluation report #721) 
Drawbar horsepower required for Flexicoil HS paired row opener on Flexicoil 5000 (2 hp per opener example)
Drill width
27’
33’
39’
45’
51’
57’
9" spacing
74
90
106
122
136
154
12"spacing
54
66
78
90
102
114

Given this example, 90 hp would be required for either a 33’ machine on 9" spacing or a 45’ machine on 12" spacing.

Opener Design & Row Spacing Interactions 
To visualize the emerging crop and resulting canopy you must consider both the opener design and the row spacing. With single shoot openers that spread the seed; a wider opener on wider row spacing can allow the same seedbed utilization as a narrower opener on narrower rows. 
Single Shoot Seedbed Utilization (SBU)
3" spread tip
4" spread tip
9" row spacing
33%
44%
12" row spacing
25%
33%

Similar comparisons can be made using double shoot openers, but it is important to consider the pattern that the seed is placed in. For example the distance between paired rows on the same opener will increase as the opener gets wider, but at the same time the distance between the two adjacent openers decreases.
The interaction the opener and row spacing will effect the percentage of soil disturbed, the amount of stubble left standing, moisture conservation, and amount of fertilizer that can be safely placed wit the seed. It will also effect how much residue you can seed through.

Costs 
Keep in mind that more openers increase purchase and replacement costs.

Conclusions
1. It is important to remember that direct seeding is a system, and the configuration of your drill is only one small part of the whole management system. 
2. A quick search of the Reduced Tillage LINKAGES Farmer to Farmer network revealed an equal number of producers seeding on 9" spacing and 12" spacing. 
3. It is my belief that your crop rotation, fertility program and integrated pest management programs will play a much larger role in helping you maximize yield and profitability, than row spacing will.