Extra crop competition with weeds by reducing crop row spacingPeter Newman

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The AHRI Communication Team(Peter Newman, Brogan Micallef & Lisa Mayer)

50100

200400

0

200

400

600

800

1000

90

180

270

Seeding rate(kg/ha)

Ry

eg

ras

s h

ea

ds

/m2

Row spacing(mm)

David Minkey, Merredin

Near perfect data set from the 90’s

It’s possible to improve competition with weeds byReducing row spacingIncreasing seeding rateBoth!

30 kg/ha60 kg/ha

90 kg/ha120 kg/ha

0

50

100

150

200

250

300

Brome + ryegrass seed heads /m2

7" Rows

14" Rows

Seeding rate

Row spacing

1999 - Mingenew

• More practical seeding rates & row spacings

• Increasing competition reduces weed seed set

• Little benefit in increasing seeding rate above 60 kg/ha

Pan

icle

s /m

2

90 mm

180 mm

270 mm

360 mm

0 100 200 300 400 500 600 700 800 900

2004 - Ryegrass seeds/m2

Glen Riethmuller27 year trial – stubble retained

• 27 year long crop row spacing & residue trial (Merredin)

• Same row spacing is repeated on the same plots

• Compares stubble burning with full stubble retention

• Uses pre-emergent herbicides for ryegrass control

• Introducing a ryetec seed catching system (2004) saw big differences in ryegrass seed set between row spacings

Glen Riethmuller27 year trial – stubble retained

90 mm

180 mm

270 mm

360 mm

0 10 20 30 40 50 60 70 80 90

0.7

0.4

19

77.5

2013 - ryegrass seed set /m2

The holy grail of crop competition research!

• 27 years of narrow row spacing & normal herbicide use with full stubble retention has smashed the ryegrass

• Narrow crop row spacing is a great way to suppress weeds

1% / inch

And the best news of all?

Narrow row spacing of wheat yields more than wide row spacing!

• 1% yield decrease for every inch of row spacing wider than 7” (18cm)(CSU survey)

• The higher yielding the crop, the greater the benefit

• Narrow row spacing results in more crop, less weeds.

It’s better than being free, it makes money!

Seeding Efficiency(% of seeds that emerge)

15cm22cm

30cm

0102030405060708090

100

Ribbon sowing treatment

120

90

60Crop row spacing

(cm)

Se

ed

ing

eff

icie

nc

y

(%)

Seeding rate (kg/ha)

• Narrow row spacing is an efficient use of wheat seed

• Knowing seed size, germination % & seed rate the number of wheat seeds sown was calculated

• Narrow row spacings at lower seeding rates had higher seeding efficiency

• Almost 100% of the wheat seed sown at 15cm row spacing at 60 kg/ha emerged compared to only 70% of the seed emerging in the wide row spacing, high seeding rate

Benefit compared to 12”

10” (25cm)

7.5” (19cm)

Reduction in row spacing (cm) 5 11

Wheat yield benefit (kg/ha) 40 88

$/ha benefit $10.80 $23.76

Cost compared to 12”

10” (25cm)

7.5” (19cm)

Extra cost of bar (John Deere) $13,000 $24,000

Cost /ha/yr (8yr 2000ha) $0.81 $1.50

Extra fuel ($/ha) $1.20 $3.50

Delayed sowing cost ($/ha) 0 $5.56

Total extra cost /ha $2.01 $10.56

Net benefit $/ha

10”(25cm)

7.5”(19cm)

Cost $2.01 $10.56

Benefit $10.80 $23.76

Net Benefit $/ha $8.79 $13.20

Wheat – 2 t/haYield increase of 8 kg/ha/cm

Summary

• Very cost effective method of weed control

• Cereal crops sown at narrow row spacing yield more & compete better in most situations

• Higher percentage of seeds sown emerge at narrow row spacing

• Can achieve narrower row spacing with modern equipment

Not every grower can achieve 7.5” (19cm) row spacing but most growers can achieve narrower than their current row spacing.

Food for thought for the next machinery purchase.