Wide Row Spacing: Is it Really Possible with No-Till - The Canadian Prairie Experience...

Guy Lafond1, Byron Irvine2, George Clayton3, Douglas Derksen4,
Eric Johnson5, Adrian Johnston6, Brian McConkey7, Perry Miller8 and David Rourke9.

1 Indian Head Research Farm, Indian Head, SK; 2 Brandon Research Centre, Brandon, MB; Saskatchewan Irrigation Development Center, Outlook, SK; 3 Lacombe Research Station, Lacombe, AB; 4 Brandon Research Center, Brandon, MB; 5 Saskatchewan Agriculture and Food, Scott Research Farm, Scott, SK; 6 Melfort Research Farm, Melfort, SK; 7 Swift Current Research Centre, Box 1030, Swift Current, SK; 8 Montana State University, Bozeman, Mt; 9 AG-Quest, Minto, MB.

Executive Summary

The objective of this review is to summarize all known studies dealing with row spacing effects on various crops conducted in western Canada during the past 30 years. An attempt was made to present as much data as possible in order to provide arguments in favor of both wide and narrow spacing. The crops discussed are lentil, field pea, canary seed, oat, flax, durum, winter wheat, barley, spring wheat and canola with the most information available for spring wheat and canola.

Although one could argue that for certain crops the risk of reduced yields with row spacings in the range of 10-12" is frequent enough to cause concern, one has to keep in mind what the absolute differences are and what the overall benefits are when considered on a whole farm basis. There are some implied economic and agronomic benefits with the use of wider row spacing under no-till that are never considered in the field studies. Some of the agronomic benefits are reduced soil disturbance and the ability to take advantage of the stubble height for trapping snow and the micro-climatic benefits. Some of the economic benefits are reduced draft, reduced costs due to fewer openers, and reduced energy costs. In deciding which way to go, a producer has to appreciate the risks. Based on the results presented, it appears that there were enough positive studies to show that in absolute terms, high yields can be obtained with 12" spacings without compromising the yield potential. When the yield potential was compromised, it could be explained on the basis of confounding effects due to seeding rates, experimental design and methodology. In some cases fertilizer placement and availability resulted in biases against the wide row spacing.

In order to establish the full potential of wide row spacings, it has to be evaluated in the context of a zero tillage production system because it can utilize the benefits of standing stubble and the mulch effect of crop residues.

 

1.0 Introduction

When we use the word issue, we usually associate it with a problem. In the context of this paper, we want to discuss how changes in row spacing can be a solution to the problem of dealing with crop residues at the soil surface.

In order to understand the discussion about row spacing, you have to go back to the early eighties and remember all the excitement about European intensive cereal production techniques which promoted concepts such as narrow row spacings, high seeding rates, high rates of fertilizer, split applications of nitrogen, plant growth regulators to control lodging and fungicides to control plant diseases. However, from the mid-eighties to the early nineties, severe problems with heat and drought led to low yields and/or crop failures on the prairies. This resulted in an urgency to develop crop production systems that would protect the soil from further degradation and conserve more water. This culminated with the adoption of zero tillage, sometimes called low disturbance direct seeding systems and its adoption on a wide scale.

In the process of developing and promoting these new production systems, producers faced an important dilemma. Tall stubble for trapping snow can create problems for the seeding operation because the rule of thumb is that the height of stubble should generally not exceed the spacing between the rows. However, the widely accepted view has been that narrow row spacings produce higher yields than wide row spacings. The producer was therefore left with the responsibility of seeking a balance between stubble height for conserving moisture and the need to maintain a narrow row spacing for maximizing grain yield.

This dilemma resulted in the need to evaluate the performance of wide spacings under zero tillage or low disturbance direct seeding systems. The question asked was whether or not the yield penalty suffered from using 12" row spacings could be offset given the benefits in terms of tall stubble for trapping snow, low soil disturbance, draft power requirements and cost of purchasing new equipment, ease of seeding and whether changes could be made to avoid the yield penalty when using a 12" spacing.

The objective of this paper is to summarize all the research work that was done on row spacing and on all crops with this type of information in Western Canada and to discuss the results in the context of a zero-tillage or low disturbance direct seeding system.

2.0 Discussion of Results

2.1 Lentil

Two studies were found for lentil. In one study (Table 1), the research was done under conventional tillage using two varieties while the second study (Table 2) was direct seeded into stubble using one variety. In the first study, no difference in two of the three years for Laird with lower yields recorded in the third year but the yield levels were very low indicating other more serious problems than row spacing limiting yield. Overall, no yield difference occurred in the 1500-2100 lbs/acre range. With Eston, yields on 12" spacing were clearly superior in one year and inferior in the two other years. In the second study, no difference in yield between row spacing even when using row spacings as wide as 16". In the second study, plant populations were monitored and populations tended to drop when the row spacings become wider. The drop in plant populations could be due to damage from seed-placed fertilizer which could also affect the inoculation of the plants.

Based on the results presented, when good crop management is practised, it is possible to produce high yields of lentil, even when going to row spacing greater than 8 inches, in this case 12" and 16".

Table 1: The effects of row spacing on grain yield (lbs/acre) in lentil at Morden, MB using two different varieties.

Row Spacing

inches

1980 1981 1983 Average
Laird
6 2089 1565 878 1510
9 1994 1668 681 1448
12 2103 1631 577 1436
Eston
6 2739 2103 1578 2140
9 2715 2280 1335 2110
12 2318 2434 1240 1997
Taken from Ali-Khan and Kiehn, 1989. Can. J. Plant Sci. 69:377-381.

 

Table 2. The effects of row spacing on plant populations (#/m2) and grain yield (lbs/ac) in Lentil at Unity and Swift Current, SK.

1994 1995

Row Spacing

inches

Plants/m2 Grain Yield Plants/m2 Grain Yield
6 120 1476 175 600
8 108 1060 135 625
12 107 1263 125 590
16 86 1422 135 725
Taken from annual reports prepared by Eric Johnson for projects funded by the Farm Based Canada Saskatchewan Green Plan Agreement
Row Spacing (") Seeding rate (lbs/acre) Plants/m2 Grain Yield (lbs/acre)
8 95 70a 1361
64 59b 1298ab
12 95 70a 1235bc
64 51b 1181c

Means followed by the same letter are not significantly different at p=0.05.

From McConkey and Miller, unpublished data for the period 1995 - 1998.

2.2 Field Pea

Only one study was found for row spacing effects on field pea using direct seeding (Table 3). With one variety, there was no difference in yield among row spacings in the range of 6-16 inches. With the other variety, there was a decrease in yield going from 6-16" with a corresponding decrease in plant populations. It could be argued that the decrease in yield as row spacing increased could be due to the reduction in plant population. It should be noted that producers have obtained very high field pea yields on 12" spacings without having to use narrow spacings. The increase in concentration of seed-placed fertilizer at wide row spacings may be affecting not only plant populations but the vigour of the plants as a result of sub-lethal damage to the root system and nitrogen fixation.

Further research is required under a wide range of conditions to determine the effect of row spacing on field pea.

Table 3. The effects of row spacing on plant populations (#/m2) and grain yield (bus/ac) in field pea at Unity, SK in 1994 and Swift Current, SK from 1995-1998.

Unity, SK Green Pea (var. Radley) Yellow Pea (var Express)

Row Spacing

inches

Plants/m2 Grain Yield Plants/m2 Grain Yield
6 64 21.3 71 52.9
8 74 23.8 83 51.0
12 70 19.4 64 46.1
16 50 24.8 52 35.8
Taken from annual reports prepared by Eric Johnson for projects funded by the Farm Based Canada Saskatchewan Green Plan Agreement for the Unity site.
Swift Current, SK Normal Leaved (1995-1998) Semi-leafless (1005-1998)

Row Spacing

(")

Seeding Rate (lbs/ac) Plants/m2

Grain Yield

(lbs/ac)

Plants/m2

Grain Yield

(lbs/ac)

8 155 41a 2258 42a 2095a
104 32b 2153 32b 1976a
12 155 37a 2297 38a 2065a
104 31b 2077 31b 1823b

Means followed by the same letter are not significantly different at p=0.05.

Taken from McConkey and Miller, unpublished data..

2.3 Canary Seed

Only one study was found for this crop and there was no difference in yield between a 9 and 12" spacing (Table 4). The study was done using a conventional tillage system.

Table 4. The effects of row spacing on grain yield of canaryseed at Indian Head, Sk. The results are based on three years of research.

Row Spacing (inches) Grain Yield (lbs/ac)
9 1433
12 1424
Taken from Holt, 1989. Can. J. Plant Sci.:69:1193-1198.

2.4 Oat

Only one study with oat was found and there was no difference in yield between the 6 and 12" spacing (Table 5). The study was conducted under a conventional tillage system.

Table 5. The effects of row spacing on grain yield in oat in Saskatoon.

Row Spacing (inches) 1966 1967
6 99.5 56.6
12 101.4 55.8
Taken from Austenson and Larter, 1969. Can. J. Plant Sci. 49:417-420.

2.5 Flax

A number of row spacing studies were reported over the period 1988-1995 (Table 6). Only one of eight studies showed a lower yield with 12" spacings with no differences between the other studies. The important point to note is that high yields of flax can be obtained with 12" row spacings and providing that adequate attention is given to fertilizer placement, maximum economic yields in flax are possible with 12 inch row spacings. It should be noted that flax is very susceptible to fertilizer damage and fertilizer should be placed away from the seed to minimize seedling damage. Flax is not a competitive crop and as such careful attention to weed control is necessary at all times, and possibly more so if wide row spacing is combined with high soil disturbance.

Table 6. The effects of row spacing on grain yields (bus/ac) of flax at five locations in Western Canada.

Indian Head Ituna Lethbridge Melfort
Row Spacing (inches) 1989 1990 1991 1990 1993 1994 1995

Row Spacing

(inches)

1988-1990
4 12 33 28 17 - - - 3.5 21
8 13 33 28 18 17 6 17 7.0 20
12 12 32 29 16 16 6 15 10.5 19

From Lafond, 1993. Can. J. Plant Sci.73: 375-382.

Zero-tillage.

R. Blackshaw, pers. communication.

Zero tillage

Stevenson and Wright, 1996. Can J. Plant Sci.76:537-544. Conventional tillage

Swift Current (1995-1998)
Row Spacing (inches) Plants/m-2 Grain Yield (lbs/acre)
8 151a 21a
12 108b 19b

Means followed by the same letter are not significantly different at p=0.05.

Taken from McConkey and Miller, unpublished data..

 

2.6 Durum

Results from 3 separate studies conducted at three different locations and over a wide range of yields (12 to 76 bus/acre) showed that yields of durum were not affected by row spacing ranging from solid seeding to 12 inches. All studies were done under zero tillage.

Table 7. The effects of row spacing on grain yield (bus/ac) in durum at three locations.

Indian Head Brandon Outlook (irrigation)
Row Spacing (inches) 1989 1990 1991 1992 19931 19941 19931 19941

Row Spacing

(inches)

Average

(5 station years)

4 12 24 49 60 58 40 34 49 3 76.3
8 13 24 51 61 61 41 35 49 6 76.2
12 14 26 52 62 61 42 35 47 8 76.4
From Lafond, 1994. Can. J. Plant Sci.74: 703-711 and 1 Lafond (unpublished results). Solid Seeding 76.0
B. Irvine, pers. communication

Swift Current 1995-1998

Row Spacing

(")

Seeding Rate (lbs/ac) Plants/m2 Grain Yield (bus/ac)
8 90 129a 34a
60 97b 31a
12 90 97b 28b
60 86b 27b

Means followed by the same letter are not significantly different at p=0.05.

Taken from McConkey and Miller, unpublished data..

 

2.7 Winter Wheat

Research trials looking at row spacing in winter wheat span the years 1985 to 1994. During those years, conclusions of no row spacing effects on grain yield all the way to a linear decrease in grain yield with row spacing have been reported (Table 8, 9, 10 and 11). It is very difficult to conclude what is the best approach given that producers want to use practises that will give them the greatest probability of success for attaining the highest yield possible. In Table 9, a difference was observed between 7" and 10" but then no difference between 10" and 11". It is important to note, that high yields of winter wheat were reported with wide row spacings and that at those high yield levels, using a narrow row spacing did not improve grain yields. Although a definitive conclusion cannot be made about the best row spacing to use, it is important to make sure that adequate plant populations are established and that damage as a result of seed-placed fertilizer be minimized. In the brown soil zone at Swift Current, no difference in row spacing between 11" and 14", were reported, regardless of stubble and year except for one year but the yield was higher at 14" than 12" (Table 11).

Table 8. The effects of row spacing on grain yield (bus/ac) of winter wheat at Indian Head, SK.

Row Spacing

(inches)

1990 1991 1992 1993 1994 Average
4 48.5 43.1 77.9 35.2 42.0 49.3
8 48.2 44.3 77.3 38.4 45.2 50.7
12 48.1 41.5 78.1 41.1 43.4 50.5
Lafond, unpublished results, Indian Head, SK.

 

Table 9. The effects of row spacing on grain yield (bus/ac) of winter wheat at selected sites in Northeast , SK.

Row Spacing (")

Melfort1

(1986)

Aylsham1 (1986)
3.5 54.9 51.6
7.0 52.5 53.4
10.6 46.8 46.9
14.2 45.6 46.8
Taken from Brandt et al. 1987. Proceedings of the 1987 Soils and Crops Workshop, University of Saskatchewan, S'toon, SK.

 

Table 10. The effects of row spacing on grain yield (bus/ac) in winter wheat at selected locations in SK.

1985/861 1986/871
Row Spacing (") Watrous Carlyle Clair P.Plain Watrous Carlyle Clair S'toon
6 10.3 43.4 32.3 34.3 8.9 30.5 33.8 17.9
12 8.3 46.2 32.6 29.3 8.6 30.6 30.1 15.8
1Averaged over 6 seeding rates ranging from 0.3-1.8 bus/ac.
1985/862 1986/872
Row Spacing (") Watrous Carlyle Clair P.Plain Watrous Carlyle Clair S'toon
6 16.3 50.7 38.5 32.4 20.0 35.4 38.1 24.7
8 15.4 49.7 32.9 32.6 16.9 29.2 37.1 22.1
12 11.8 47.0 31.0 28.3 17.9 28.5 31.6 18.3
18 13.2 42.0 26.8 25.6 16.6 26.3 30.0 26.5
24 10.9 39.7 22.5 21.6 13.2 21.3 27.5 14.1

2 Seeding rate of 1.3 bus/ac.

Taken from Hultgreen et al. 1988. Proceedings of the Soils and Crops Workshop, Universisty of Saskatchewan, S'toon, Sk.

 

Table 11. The effects of row spacing on grain yields (bus/acre) of winter wheat in the brown soil zone at Swift Current when grown on spring wheat, winter wheat and chemical fallow stubble in different years.

Row Spacing

(inches)

Winter wheat

Spring wheat

(silt loam)

Chemical fallow

Spring wheat

(fine sandy loam)

86 88 86 87 88 86 87 88 86 87 88
11 28 8 23 21 13 25 40 12 18 18 4
14 28 8 25 20 12 27 38 13 18 16 5
Level of sign. ns ns * ns ns ns ns ns ns ns ns
Taken from: McCleod et al. 1996. Can. J. Plant Sci. 76:207-214.

 

2.8 Barley

A large number of row spacing studies in barley were found and unlike winter wheat, the evidence was such that the greater majority most of the studies showed no effect on grain yield due to row spacing (Table 12, 13, 14). In this case, it is easy to conclude that with barley, high yields can be obtained even when using row spacings as wide as 12". The range in yields reported are 16 to 124 bus/acre. A combined analysis of barley yields across years and locations resulted in no significant difference between row spacings ranging from 6-12". A drop in yield was only observed at 16" (Table 14). However, in situations where no herbicides are used, as would be the case for in organic production, barley yields were higher with higher seeding rates and narrow spacings (Kirkland. 1993. J. Sust. Agric. 3:95-104).

 

Table 12. The effects of row spacing on grain yield (bus/ac) of barley at Indian Head, SK and Brandon, MB.

Row Spacing

(inches)

Indian Head1

(zero-till)

Indian Head2 (summerfallow) Brandon3 (zero-till)
1989 1990 1991 1992 19933 19943 1993 1994 1995 1993 1994
4 16.4 91.8 61.9 124.2 88.0 64.8 115 85.5 73.4 57.4 74.9
8 18.3 90.3 61.2 124.3 90.4 65.3 120 86.9 71.3 60.1 80.0
12 20.6 95.5 60.7 124.4 90.9 62.4 115 86.3 73.1 60.2 77.4

1 Lafond, 1994. Can. J. Plant Sci: 74:703-711

2 Lafond and Derksen, 1996. Can. J. Plant Sci. 76:791-793.

3 Lafond et al., 1996. Better Crops 4:20-22.

 

Table 13. The effects of row spacing on grain yield in barley at Saskatoon.

Row Spacing (inches) 1966 1967
6 80.6 46.4
12 77.0 43.3
Taken from Austenson and Larter, 1969. Can. J. Plant Sci. 49:417-420.

Table 14. The effects of row spacing on plant populations and grain yield in barley at Unity, Foam Lake and Naicam, in SK.

1994

Row Spacing

(inches)

Plants/m2

Grain Yield

(bus./acre)

Plants/m2

Grain Yield

(bus./acre)

Plants/m2

Grain Yield

(bus./acre)

6 66 54.3 70 69.1 133 53.1
8 72 52.8 89 65.9 96 48.7
12 76 54.7 77 69.8 71 48.6
16 66 53.0 89 58.3 71 46.2
1995
6 245 34.0 155 29.0 145 33
8 160 33.0 100 24.0 137 36
12 170 30.0 90 23.0 80 27
16 130 30.0 90 18.0 90 35
Taken from annual reports prepared by Eric Johnson for projects funded by the Farm Based Canada Saskatchewan Green Plan Agreement.

2.9 Spring wheat

By far the largest data set with respect to effects of row spacings on grain yield is with spring wheat. Some studies like those summarized in Table 15 show no difference due to row spacing among 4, 8 and 12" over a yield range of 7 to 82 bus/acre involving many years and locations.

 

Table 15. The effects of row spacing on grain yield (bus/ac) of spring wheat at Indian Head, SK and Brandon, MB.

Indian Head1

(zero-till)

Indian Head2

(conventional-till) (summerfallow)

Brandon3 (zero-till)

Row Spacing

(inches)

1989 1990 1991 1992 19933 19943 1993 1994 1995 1993 1994
4 6.8 42.0 49.3 52.1 47.3 39.7 78.5 70.7 51.2 22.5 38.9
8 7.5 41.9 49.4 52.1 49.9 41.4 82.2 66.3 51.5 23.3 41.6
12 7.4 42.2 49.1 51.2 51.2 41.9 82.2 65.1 50.4 24.1 38.1

1 Lafond, 1994. Can. J. Plant Sci: 74:703-711

2 Lafond and Derksen, 1996. Can. J. Plant Sci. 76:791-793.

3 Lafond et al. 1996. Better Crops 4:20-22.

Some studies showed a yield reduction from 6-9" but no differences between 6 and 12" (Table 17). In some, yield differences are observed in certain years favouring narrow row spacing but not in others, even though the yield levels are the same no difference (Table 16).

 

Table 16. The effects of row spacing on grain yield (bus/ac) for spring wheat at different locations in Saskatchewan.

Scott (1985-86)1 Melfort1
Row Spacing (inches) Plants/m2

Grain Yield

(bus/ac)

Grain Yield

(bus/ac)

4.5 171 60.2 74.8
9.0 136 54.4 61.5
18.0 107 45.8 -
1Averaged over the varieties Neepawa and HY320.
Row Spacing (inches) Melfort (1986)1 Carrot River1 (1986) Saskatoon1 (1986)
3.5 35.3 35.0 40.1
7.0 35.1 31.1 43.2
10.6 34.7 30.4 40.5
14.2 33.2 27.8 38.3

1Averaged over the varieties Neepawa and HY320.

Taken from Brandt et al. 1987. Proceedings of the 1987 Soils and Crops Workshop, University of Saskatchewan, S'toon, SK.

Swift Current (1995-1998)
Row Spacing (inches) Seeding Rate (lbs/ac) Plant/m2 Grain Yield (bus/ac)
8 60 183a 29a
40 86bc 28ab
12 60 97b 26bc
40 75c 26c

Means followed by the same letter are not significantly different at p=0.05.

Taken from McConkey and Miller, unpublished data.

 

In one study, a shank spacing of 10 and 15" was used onto which different openers were bolted (Table 18). The openers consisted of a narrow side-banding opener type, which placed the fertilizer to the side and below the seed. The paired-row opener puts the fertilizer in between and below two seed row spaced about 5" apart while the sweep opener spreads the seed and fertilizer together over a 6-8" area at the same level. Under conventional tillage, no difference between the narrow and paired row with 10" and 15" shank spacing but a slight reduction for the sweep opener with the 15" shank spacing. Under zero tillage, no difference between the narrow and the sweep opener even though they tended to be lower than the paired row opener. The authors claim that problems with seed and fertilizer separation occurred with the narrow opener which would explain the yield reduction. The loose soil condition under conventional tillage probably allowed for better separation.

Although a very clear and precise statement to the effect that row spacing in the range of 4-12" has no effect on grain yield in spring wheat is not possible, we can nonetheless state that providing proper crop production practises are used with wide row spacings, a yield reduction should not occur. The practises to be careful with will be discussed in the last section of this paper.

 

Table 18. The effects of shank spacing and opener type on the yield of spring wheat (bus/acre) at Minto, MB using two different tillage systems over two years (1994-1995).

Conventional Tillage
Opener Type 10" 15"
Narrow Side-Band Opener 38 37
Paired Row 38 37
Sweep 37 34
Zero Tillage
Narrow Side-Band Opener 34 33
Paired Row 37 36
Sweep 34 32
Xie, H. S., D.. R.. S.. Rourke and A. P. Hargrave. 1998. Effect of row spacing and seed/fertilizer placement on agronomic performance of wheat and canola in zero tillage systems. Can. J. Plant Sci. 78:389-394

Table 19. The effects of row spacing on the yield of spring wheat (bus/acre) at Melfort, Brandon and Beaverlodge for the period 1995-1998.

Row Spacing Melfort Brandon Beaverlodge
9" 50.6 51.3 25.2
12" 48.3 50.3 28.9
Source Johnston, Melfort Exp. Farm Derksen, Brandon Res. Ctr. Clayton, Lacombe Research Stn

2.10 Canola

There are a significant number of papers dealing with the effect of row spacing on canola but for this discussion we restricted ourselves to discussing information developed in Western Canada. It is generally accepted that higher seeding rates and narrow row spacings result in greater weed competition. However, these conditions can result in greater lodging potential and higher incidences of crop diseases. Since direct seeding openers are expensive and wider spaced openers clear trash better, it would be a great advantage if row spacings of at least 12" could be used without having to experience decreases in yield.

Higher seeding rates and narrower row spacings have generally not improved Western Canadian canola yields greatly (Table 1). When the same amount of seed is planted in narrow rows a greater number of plants establish and survive. This results in the more rapid development of the crop canopy. The development of a large canopy will improve the crop's competitive ability with weeds. It is my opinion that a uniform stand which emerges quickly is more important than row spacing in the normal 6-12" range of row spacings. While a narrow row spacing (more openers) will place seed in contact with a greater volume of soil and may improve the uniformity of plant emergence this is also possible using superior openers capable of placing seed shallow on a moist and firm seed-bed even on wider rows. When good seed to soil contact allows rapid and uniform plant emergence, the value of narrow row spacings is reduced providing weeds are adequately controlled.

Under direct seeding conditions, the residue from the previous crop will slow evaporation from the soil surface and thus may mitigate the effect of wider row spacings. Under centre pivot irrigation, where this work was done, evaporation from the soil surface is of limited importance since water is applied at 3-4 day intervals.

Early work was done by hand seeding and since no mention is made of weed control, we assume hand weeding was done. Hand weeding would tend to favour narrow row spacings since hand weeding can not be done until the crop is well established, by which time significant competition may have occurred. Hand seeding may result in differential packing due to the differing number of times the operator walked over the field. While some studies report yield reductions using current management practices on fallow these results differ from those obtained by the Canola Council under direct seeding conditions and under irrigated cropping conditions (moisture not limiting).

 

Table 20. The effect of row spacing on Brassica napus yields in Western Canada.



Site



# of

years



previous

crop/tillage

% of 6" spacing

3-4"
8-9" 12" 16-18"
Scott1 4 fallow

118
92
Winnipeg 3 fallow 81
Unity 3 stubble direct 107 98 100
Foam Lake 3 stubble direct 93 92 85
Naicam 3 stubble direct 97 95 84
Outlook small plot 3 irrigation 89 97 97
Outlook Large plot 6 irrigation 101 104
Beaverlodge 2 fallow 144 93
Edmonton2 4 fallow 82 72 57
1 % of 8"; 2 Variable plot width and therefore questionable data in my opinion.

2.10.1 Studies Showing Reduced Yields at Wider Row Spacings.

Effect of row spacing and rates of seeding on response of canola to rates and placement of phosphate fertilizer.

Site Dark Brown Scott Loam and Dark Brown Sutherland Clay conventional tillage and weed control using herbicides.

Plot Size 6 x 19 ft Seeding Equipment Double disc press

Fertilization Phosphorous was seed placed at 0 and 22 lbs P2O5 /ac

Seeding rates 2.7, 5.3, 8 lb/ac Previous Crop Fallow

 

Seed placed phosphorous fertilizer reduced plant numbers to a greater extent at the wide row spacings. In this study 12" spacings produced 8% less seed with or without fertilizer. The difference between the 8 and 12 inch spacings was less than between the 4 and 8 inch spacings. There was no effect of seeding rate on yield
although higher seeding rates increased plant population (Table 21).

 

Table 21. Influence of row spacing on canola plant populations, grain yields and seed quality at Scott and Saskatoon 1985-1989

Row spacing inches

Plants/m2

2 year mean

Grain yield bu/ac

4 year mean

Protein % 3 year mean

P %

3 year mean

Oil %

2 year mean

4 112 46.8 27.0 .57 41.8
8 67 39.6 27.1 .57 41.9
12 45 36.5 26.9 .57 42.2
LSD (0.05) 11 1.7 .19 ns .24
Ukrainetz, H. 1990. 1985-89. Final Report to the Canola Council of Canada Agronomic Research Program Grow with Canola.

Row spacing and seeding rates on canola in southern Manitoba.

 

Site Riverdale silty loam and Red River clay (Winnipeg, Manitoba)

Plot Size 16 rows 18' long Seeding Equipment Double disc press

Fertilization 34 lb/ac N as ammonium nitrate and 13 lb/ac elemental sulfur broadcast and incorporated in the fall prior to planting. Seeding rates 1.3, 2.7, 5.3 and 10.7 lb/ac

Previous Crop (not specified in report)

Yields were measured on a 16.4 long section of 2 rows with one guard row on each side of the yield test being removed just prior to harvest. In this trial, 12" rows gave 19% lower yields than rows spaced 6" apart. All seeding rates greater than 1.3 lb/ac had similar yields. The narrower row spacings had greater leaf area throughout the season and the higher seeding rates gave greater leaf area early in the season. The greater weed competition from narrow rows and high seeding rates is due in large part to the more rate development of canopy. It has been reported that some of the hybrid canola cultivars have the genetic potential to rapidly develop a large crop canopy (Table 22).

 

Table 22. Effect of row spacing on plant numbers and yield of rapeseed in Manitoba 1985-86.

row

spacing (inches)

plant numbers/m2 yield (bu/ac)
loam 1985 loam 1986 clay 1986 loam 1985 loam 1986 clay 1986
6 102(75) 193(75) 63(34) 62.6 53.9 42.2
12 91(55) 166(69) 57(32) 53.0 44.2 33.5
ns ns ns 7.1 6.8 6.1

1 numbers in brackets are % of seeds planted

Morrison M.J. McVetty, P.B.E, and Scarth, R. 1990. Can. J. Plant Sci. 70:127-37.

 

Effect of row spacing and seeding rate on canola yield in north west Alberta.

Site Beaverlodge

Plot Size 3' x 10' with varying number of rows Seeding Equipment Double disc hand seeder. The centre 1.5' x 8' area was harvested.

Fertilization 100 lb/ac N as ammonium nitrate and 45 lb/ac P2O5 broadcast and incorporated prior to planting. Seeding rates 6.2 and 12.4 lb/ac Previous Crop (not mentioned in report)

The extremely high yields resulting from the 3 inch row spacing are difficult to explain unless weed competition was high early in the season. Wider row spacings were not tested but it is interesting to note that yield differences between 6" and 9" spacings were very small relative to the difference between 3 and 6 inch row spacings (Table 23).

 

Table 23. Effect of row spacing on plant numbers and yield of rapeseed in NorthWest Alberta 1982-83.

Row spacing

Inches

Plant numbers/m2 Yield (bu/ac)
1982 1983 1982 1983
3 121 140 29.3 61.3
6 151 83 18.3 48.1
9 110 75 15.8 48.0
Christensen J.V. and Drabble J.C. 1984. Can. J. Plant Sci. 64:1011-13.

 

Effects of row spacing and seeding rate on canola yields in Central Alberta.

The varying plot width may have contributed to the high yields at the 6" spacing relative to wider row spacings. It is interesting to note that the largest differences are between 6" and 9" with fewer differences between 9 " and 12" (Table 24).

 

Table 24. Effect of row spacing on the yield of rapeseed near Edmonton 1971-72.



Row spacing

Inches

Yield (bu/ac)
Brassica rapa Brassica napus
Parkland Ellerslie Parkland Ellerslie
1971 1972 1971 1972 1971 1972 1971 1972
6 48.8 47.9 37.1 45.6 55.9 61.4 42.4 53.2
9 42.4 42.5 28.5 40.1 35.4 55.1 35.4 47.9
12 41.5 41.1 30.2 36.8 32.1 47.7 35.8 38.6
24 31.7 25.8 26.4 33.8 24.6 37.4 24.8 34.8
Kondra, Z.P. 1975.Can. J. Plant. Sci. 58:549-550.

 

2.10.2 Studies Showing no Yield Differences at Wider Row Spacings.

PAMI, 1995. Row Spacing trials 1993-95, Canola Production Centre Annual Reports

 

Site Unity, Naicam and Foam Lake

Plot Size 30' x 400' with 20 harvested from centre. Seeding Equipment Direct seed

with hoe openers Fertilization P, K and S seed placed as per soil test Nitrogen broadcast as urea 70 lb/ac of N as urea Seeding rates 6 lb/ac Previous Crop cereal grain

The effect of row spacing was limited up to 12" but the 16" spacings were lower yielding in all but 2 of the 9 site years (Table 25). When this work was conducted, only grass weed control was possible with post emergence products and weed control was a problem in some tests with higher infestations at wider row spacings. In 1994 both the Unity and Naicam sites had volunteer barley which reduced plant stands at wider row spacings and weeds were a more serious problem at wider row spacings in Unity.

 

Table 25. Effect of row spacing on canola under direct seeded conditions 1993-95.



Row spacing inches
Yield (bu/ac)
Foam Lake Naicam Unity
1993 1994 1995 1993 1994 1995 1993 1994 1995
6 24.0 28.1 28.6 15.4 28.4 28.0 41.0 33.5 14.1
8 21.6 25.7 28.1 15.1 27.0 27.2 41.1 34.3 16.5
12 24.0 23.0 27.3 14.7 26.2 27.4 40.7 33.1 13.5
16 22.0 21.8 24.9 11.4 24.4 25.8 40.9 30.7 15.3
PAMI, 1995. Row Spacing trials 1993-95, Canola Production Centre Annual reports.

Canola production under irrigation (row spacing, seeding rates and fungicide application).

 

Site Outlook under centre pivot irrigation Plot Size 16' x 65', centre 8.5' harvested Seeding Equipment Amazone drill with 1.5" shoe for 3' and 6", Conserva-Pak for 8", Conserva-Pak with shovels and diffuser for solid seed, broadcast and shallow cultivate for broadcast. Fertilization 100 lb/ac nitrogen was broadcast and incorporated or banded and 40 lb/ac P2O5 deep banded prior to seeding

Seeding rates 80, 150 and 220 seeds/m2 (approx 3,6 and 9 lb/ac) Previous Crop Wheat

With the exception of 1990 when plant stands were slow to establish due to an extra packing operation done on the broadcast seeded plots, yields were not affected by the method of seeding. Narrow rows and higher plant numbers had more plants but this did not influence final grain yield Table 26). When sclerotinia infections occured they were higher where the crop had lodged more; generally this was with narrow rows and high seeding rates.

 

Table 26. Effect of seeding method on canola yields under irrigation 1990-92



Row Spacing inches
Yield (bu/ac)

Outlook

1989

Outlook

1990

Riverhurst

1991

Outlook

1991

Outlook

1992

Riverhurst

1992

3 46.8 43.9 42.0 29.1 48.2 33.3
6.5 43.9 46.6 41.5 29.1 49.2 30.8
8 53.6 43.7 43.5 23.3 54.9 33.5
Solid seed with sweeps 48.3 45.0 44.1 29.2 50.4 30.4
broadcast 39.6 42.8 42.3 29.2 52.3 32.0
Irvine, B. 1992. Saskatchewan Irrigation Development Centre Annual Report.

 

Effect of row spacing and seeding rate on canola grain yields and Sclerotinia infections.

Site Outlook under centre pivot irrigation

Plot Size 10' x 30' with varying number of row depending on row spacing. Approximately the outside 2' on each side of the plot was removed prior to swathing

Seeding Equipment Amazone narrow row drill was used for all plots

Fertilization 100 lb/ac nitrogen was broadcast and incorporated or banded and 40 lb/ac P2O5 deep banded prior to seeding

Seeding rates 2.7 lb/ac Previous Crop wheat

Higher seeding rates increased lodging and sclerotinia infection levels but row spacings had very little impact (Table 27). Thus while high plant populations may suppress weeds, the increase in lodging under high moisture conditions results in harvest problems and potential yield reductions due to increased lodging and sclerotinia levels. With the exception of the 25 inch spacing, grain yields were not affected by row spacing.

 

Table 27. Effect of row spacing on lodging sclerotina and yield under centre pivot irrigation.

Row

Spacing

(inches)

Lodging cm from Soil Sclerotinia % infection Yield (bus/ac)
1992 1993 1991 1992 1993 1991 1992 1993
3.2 75 115 1.5 13.3 6.0 26.2 52.7 36.0
6.3 69 112 5.0 11.5 4.7 30.5 56.2 41.7
12.5 77 117 2.7 15.3 11.7 28.8 56.3 39.7
18.8 73 121 3.8 13.5 7.0 27.6 54.5 43.6
25.2 80 126 2.0 12.8 11 20.4 59.4 34.9

9" band

19" space

72 109 2.2 10.3 3.0 25.1 57.2 41.7
LSD 12 11 ns ns ns 5.5 7.8 4.6
Irvine, B. and D. Duncan. 1993. Saskatchewan Irrigation Development Centre Annual Report.

 

Effect of row spacing on the yield of canola at selected sites in the Parkland soil zone.

Site Melfort, Sk, Brandon, MB, Beaverlodge,AB.

Plot Size 24' x 60' with varying number of row dependeing on row spacing.

Seeding Equipment: Conserva-Pak plot seeder on 9" and 12" spacing

Fertilization 70 lbs/ac nitrogen was side-banded with phosphorus and sulfur.

Seeding rates ~6 lbs/ac Previous Crop wheat

When the fertilizer is placed in such a manner as not to bias against any row spacings, and providing that no damage from side-banding will be incurred, then no yield differences should be expected as shown in Table 28. At both locations, the canola yields were not different between 9 and 12 inches.

 

Table 28. The effects of row spacing on the yield of canola (bus/acre) at Melfort, Brandon and Beaverlodge in 1996.

Row Spacing Melfort Brandon Beaverlodge
9" 40.0 31.6 7.8
12" 43.1 31.3 8.9
Source Johnston, Melfort Exp. Farm Derksen, Brandon Res. Ctr. Clayton, Lacombe Res. Stn.

Effect of shank spacing and opener type on the yield of canola at Minto, MB.

 

Site Minto, MB.

Plot Size 10' x 23' with varying number of row dependeing on row spacing.

Previous Crop wheat

It is very obvious from the data presented in Table 29, that going from of a shank spacing of 10" to 15" did not have a negative effect on grain yield in canola regardless of the tillage system or opener type used. In fact, there was a slight improvement with the 15" shank spacing

under zero tillage with all the opener types used. The paired row system tended to do better than the narrow or the sweep opener. However some problems of poor seed and fertilizer separation was encountered with the narrow opener which would have biased the results downward emphasizing the importance of proper fertilizer separation to minimize damage to the emerging and growing crop.

 

Table 29. The effects of shank spacing and opener type on the yield of canola (bus/acre) at Minto, MB using two different tillage systems over two years (1994-1995).

Conventional Tillage
Opener Type 10" 15"
Narrow Side-Band Opener 27 27
Paired Row 30 30
Sweep 28 29
Zero Tillage
Narrow Side-Band Opener 33 35
Paired Row 36 39
Sweep 32 35
Xie, H. S., D.. R.. S.. Rourke and A. P. Hargrave. 1998. Effect of row spacing and seed/fertilizer placement on agronomic performance of wheat and canola in zero tillage systems. Can. J. Plant Sci. 78:389-394

2.11 Chick Pea.

It would appear that as long as plant populations are maintained, seeding chick pea on wide row spacings should not lead to important yield depressions.

 

Table 30. The effects of row spacing and seeding rate on plant population and grain yield at Swift Current, SK.

Desi (1995-1998) Kabuli (1996-1998)
Row Spacing (")

Seeding Rate

(lbs/ac)1

Plants/m2 Grain Yield (lbs/ac) Plants/m2 Grain Yield (lbs/ac)
8 1x 40a 1688a 22a 1090a
0.67x 36b 1643a 15bc 947b
12 1x 41a 1583a 20ab 1049a
0.67x 31c 1458b 13c 859b

1 The 1x rate for Desi chick pea is 96 lbs/acre and for Kabuli 230 lbs/ac.

Means followed by the same letter are not significantly different at p=0.05.

Taken from McConkey and Miller, unpublished data.

 

3.0 Implications of Results.

 

3.1 What are some of the advantages with the use of wide row spacings under zero-tillage?

Residue Management: The most important reason for using wide row spacings under zero-tillage has to do with the challenge of seeding through very heavy residue conditions, especially when combined with wet soil conditions ie. less soil and residue disturbance.

Water Conservation: The next most important reason is that in the drier parts of the prairies, producers are encouraged to maintain tall stubble to trap more snow and hence increase soil moisture levels. However, the rule of thumb is that stubble height should be similar to row spacing. This means that by going to wider row spacing, we can work with taller stubble and trap more snow. It is also well known that stubble cut at 10-16" can reduce wind speed at the soil surface by 60% relative to a tilled surface. This becomes very critical in the drier parts of the prairies.

Equipment Consideration: Adopting wider row spacings reduces the costs and the draft requirements because of the fewer number of openers present on the tool bar. However, the are far reaching. For example, a 33' seeder with 9" spacing has 44 openers. By going to 12" spacing, you have effectively increased the width of the machine to 44' for the same horsepower. This means that you have reduced your seeding time and tractor hours by roughly 33%. This is important because it allows for greater timeliness in the seeding operation, especially if the weather has not been cooperating. One could therefore argue that changes in row spacing can actually improve the timeliness of your seeding operation and lower your long term machinery costs at the same time.

3.2 Can wider rows be used successfully with a conventional tillage system?

Only a few studies have examined potential differences in row spacing as a function of tillage system (refer to Table 12, 15, 18, and 29) for barley, spring wheat and canola. In those studies, the response did not change with tillage system. This means that all the arguments used previously (refer to 3.1) with respect to equipment consideration also applies for the conventional tillage system. The only important consideration would be the implication for weed management.

3.3 Are weeds an important concern when using wide row spacings?

No studies in the past have tried to quantify the impact of row spacing on weeds, whether it pertains to weed communities, densities or control. One study is currently underway at Brandon in MB, at Melfort in SK and at Beaverlodge in AB where the effects of row spacing and fertilizer management on weed communities and densities are being quantified. It is too early at this time to make a recommendation. Problems with weeds on wide rows have been reported in the past. At this point, we can postulate that high levels of soil disturbance will encourage weed growth relative to low soil disturbance. This means that in a zero tillage systems, wide row spacings combined with narrow openers will reduce weed growth because of less soil disturbance. We can therefore speculate that weed problems will likely not change with the use of wider row spacings. There are numerous producers seeding on wide row spacings at the present time and if weeds were such a problem with wide row spacings, it would have been noted, but it is not the case.

3.4 Are adjustments in seeding rates required when changing row spacing?

Most of the studies reported in section 2.0 of this paper were done at different seeding rates and no statictical interactions between row spacing and seeding rate were reported. This is a clear indication that no changes in seeding rates are required when row spacing changes are made.

3.5. Are changes in harvest management required?

An important concern expressed by producers with regards to the use of wide row spacings has to do with harvest management If your operation is set-up with aeration bins and a grain dryer and straight combining is a normal part of your harvesting operation, no adjustments are required when changing to wide row spacings. However, if your harvest operation revolves around swathing, then switching to wide row spacings will require some adjustments. It will not be a problem for crops like field pea, lentil, canola or flax. It becomes an important concern with cereals, especially if the crop is thin. Some practical ways to minimize problems is to swath at a different angle to the direction of seeding. This can easily be done with a self-propelled swather. With a pull-type swather, you will have to seed at an angle. Producers who use wide row spacings and regularly swath their crops have made the observation that with moderate to heavy cereal crops, it is not a big concern, even if when swathing in the same direction as the seeding operation.

3.6 Does row spacing have an effect on plant diseases?

Work at the Saskatchewan Irrigation Development Centre in Outlook, SK on canola showed that row spacing had very little influence on sclerotinia infection levels. Other work on wheat and barley at Indian Head and Brandon showed that root diseases actually decreased at the wide row spacings. Work at Minto on wheat showed that at high levels, the increase in grain yield using narrow rows was only obtained when a foliar fungicide was used. Although very few studies examined the impact of row spacing on plant diseases, the few that have would indicate that there could be some potential benefits in terms of disease reduction with wide row spacings. For the sake of providing a recommendation, we can argue that using wide row spacings will not necessarily increase plant diseases.

3.7 Are adjustments in fertilizer management practises required when using wide row spacings?

One aspect of fertilizer management that requires special attention is placement. Going from 9" to 12" will increase the concentration of the fertilizer near or with the seed by 30%. Consequently, it is advised that care and attention be given to fertilizer placement. Even with crops like field pea, where phosphorus is sometimes the only fertilizer used, reductions on the order of 10-15% in plant stands can occur when the fertilizer is placed with the seed. It is therefore recommended that every effort be made to provide some separation between the seed and fertilizer to minimize the risk of crop damage.

3.8 What are some of the implications of row spacing in the wetter parts of the prairies?

One of the most important advantages of using wide row spacings has to do with ability to seed through heavy crop residues. In the wetter areas of prairies, this is critical because of the higher level of crop residues being produced. However when heavy crop residues are combined with heavy textured soils, using wide row spacings won't resolve all the problems because of the soil remaining wet for too long and delaying the seeding operation, not to mention making it very challenging. However, the other advantages of wide row spacing in terms of equipment, timeliness of operation, reduced field time and tractor hours still apply.. There may also be some advantages in terms of reduction in foliar and root diseases.

3.9 What are some of the implications of row spacing in the drier parts of the prairies?

The hypothesis proposed by McConkey and Miller (personal communication) for the dry areas is based on results from 1995 to 1998 with a number of crops. In a semiarid climate, the crop must fully exploit the soil moisture in the inter-row area to achieve highest grain yields; soil moisture not used by plant will be lost as evaporation from the soil surface. From about 4 weeks after planting, the effective lateral growth of normal leafed pea was greater than either canola or spring wheat. Based on the rapidity of reaching the 15 cm lateral growth (halfway between 12-inch row spacing), the crops ranked as pea, canola, and wheat. Considering all years individually, normal leafed pea rarely showed a significant yield decline due to widening row spacing from 8- to 12-inch spacing while wheat consistently exhibited a yield decline to such widening. Therefore, the pattern of yield declines from widening row spacing corresponded to the pattern of rates of observed lateral root growth. Spring wheat was the only crop for which inter-row soil moisture was occasionally significantly greater at the 12-inch row spacing than at the 8-inch row spacing, confirming that spring wheat does not as fully exploit soil water in the inter-row area at wider row spacings. Importantly, the canopy does not close as rapidly at 12-inch row spacing (data not shown), so higher solar radiation load on the inter-row area at 12-inch row spacing than 8-inch row spacing makes between-row soil moisture at 12-inch row spacing particularly vulnerable to loss by evaporation. This could be counteracted by seeding the crop into tall stubble. Stubble heights of 12-14 inches can reduce wind speed at the soil surface by 70%. Another strategy would be to seed with very little soil disturbance and keeping as much of the soil as possible covered with crop residues.

3.10. Why do recommendations about row spacing effects on grain yield vary among the various crops and studies done in Western Canada for the last 25-30 years?

All field experiments have some inherent biases built into them. In some cases, these biases can have a significant influence on the results. Examples of biases in the context of row spacing studies might involve: (1) confounding effects with seeding rates (2) error in the calculation of effective harvested area (3) border effects which become magnified when only a few rows are used per plot (4) problems with fertilizer placement favouring one spacing over another due to availability or damage. We therefore contend that the major reason why there are so many conflicting results with the effects of row spacing on grain yields has to do with unplanned biases introduced into the studies and having an effect on the results. The fact that high yields can be maintained with spacings as wide as 12" is a clear indication that the high yield potential of crops will not be compromised. As long as plant populations are maintained and fertilizer is managed properly, producers should not experience reduced yields because of the use of wide row spacings. However, it is possible that under certain circumstances, yields on wide row spacings may actually be lower and it is important through appropriate research to try and define what these conditions might be.

 

4.0 Yield Determination in Cereals.

4.1 Yield Components

Final grain yield in cereals is determined by three things; the number of heads per unit area, the number of kernels per head, and the weight of each grain. If the values for these three components are known, final gain yield can be accurately predicted.

Heads per unit area: The number of heads produced is determined by the number of seeds planted and the amount of tillering that the plants will undergo. As a rule, the main head and the first three primary tillers are the most productive. Also tillering can never fully compensate for grain yield in situations of thin stands. Tillering can also be affected by seeding depth, nitrogen availability and moisture stress. As the depth of planting increases, the ability of plants to produce tillers decreases. If nitrogen is too limiting, tillering will decrease and with periods of moisture stress, tillers will either abort or not develop.

Kernels per head: Kernels per head is determined by the number of spikelets formed and the number of florets in each spikelet producing seeds. The number of spikelets formed is determined very early in the growing season, usually by the four leaf stage. Lack of nitrogen availability and/or moisture stress prior to the four leaf stage can lead to fewer number of spikelets being formed. Some herbicides applied at that critical time can also reduce the number of spikelets being formed. The final number of kernels produced will be determined during the flowering period. Heat stress or frost can cause sterility in certain florets thereby reducing the final number of kernels produced.

Seed Weight: Seed weight will be affected by environmental conditions during seed filling and by plant diseases. Heavy disease pressure on the flag leaf will usually result in reduced kernel weight.

4.2 Effects of row spacing and seeding rate on yield components -Indian Head Studies.

Seeding Rate: Based on my research at the Indian Head Research Farm with cereals, as seeding rate changes from 0.5 to 3 bus/ac, plant numbers increase linearly and the number of heads produced increases in a more curvi-linear fashion, seed weight remains the same and the number of kernels per head decreases. Therefore compensation occurs between the number of heads produced and the number of kernels per head. It is important to realise that there is an optimum range for plant numbers in order to obtain the best yield possible because as mentioned before, tillering can never fully compensate for a thin stand (Table 31).

 

Table 31. Optimum plant population for different crops.

Crop Plants / m2 Plants / ft2
Barley 150-200 14-19
CPS wheat 200-250 19-23
HRS wheat 200-250 19-23
HRW wheat 200-250 19-23
Durum 200-250 19-23
Flax 300-400 28-37
Canola 80-180 7-17
Field Pea 75-85 7-8
Row Spacing: When going from 4" to 12" spacings, plant populations decreased, the number of heads produced decreased, seed weight remained more or less the same but the number of kernels per head increased. Our results showed that there were no yield differences when going from a four inch to a twelve inch row spacing, the compensation for a reduced number of heads was an increase in the number of kernels per head.

4.3 Effects of row spacing on plant development in wheat.

Another way of approaching this is to look more closely at how the development of an individual wheat plant is affected by row spacing. In this case, I am drawing from a study started in 1996 looking at the effects of nitrogen fertilizer management on wheat and canola production and their impact on weed communities. The N treatments were: Fall Banded - N, Spring Banded - N, Side-banded N on 12" spacing, Side-banded N on 9" spacing, Sweep with the fertilizer and seed spread over a 6" band at the same level. The second and third treatments allowed us to investigate the effects of row spacing. The plants were scored when the number of leaves on the main stem ranged from 5 to 6 leaves. The results presented in Table 32 show clearly that going from a row spacing of 9" to 12" or crowding the plants more tightly in a row is not affecting the way plants are developing in terms of the frequency of tillers as determined by the frequency of different tillers.

 

Table 32. The frequency (%) of different tillers as a function of row spacing.

Tiller 12" Row Spacing 9" Row Spacing
T0 22 21
T1 82 81
T2 62 63
T3 10 9
T4 0 0
T01 0 0
T11 6 5
T21 0 1
T31 0 0
T41 0 0

4.3 Strategies to consider when going to wider row spacings.

The discussion above has shown how cereal plants change their yield components with changes in row spacing and seeding rates.

When seeding rate is increased, the number of plants established increases linearly and the number of heads produced increases also but in a more curvilinear fashion. The fact that head number increases with increasing seeding rates explains why tillering never fully compensates in situations of a thin stand. When seeding rate increases we also observe a decrease in the number of kernels per head with little or no change in seed weight. The compensation for increased seeding rates is between more heads being produced and fewer kernels per head.

When row spacing increases, the number of plants established decreases and this in turn results in fewer heads being produced. However we observed an increase in the number of kernels being produced per head and no change in seed weight with increases in row spacing. It has also been shown that when tiller development is considered on an individual plant basis, there was no difference between the 9" and 12" row spacings in the frequency of the various tillers present.

Given the above information, the strategy is rather straight forward when it comes to avoiding potential yield loss when going to wider row spacings. It all comes down to plant populations and ensuring that we have optimum plant numbers. This may involve increasing the rate of seeding with wider row spacings or ensuring that no lethal or sub-lethal injury is incurred with fertilizer given the higher concentrations with increases in row spacings.


 

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