Row spacing in a no-till system

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					                  Row spacing in a
                   no-till system
                                                          A rule of thumb is to allow a travel speed
            30cm (12 inch) row spacing in                 of 1km/hr for every inch of row spacing
            no-till will work:                            when using a knife point operating at
Farming     − If weed control does not rely on crop
              competition alone.
                                                          7-8cm depth and press wheels. The
                                                          optimum speed will vary with machine and

                                                          sowing conditions. If possible, get someone
            − If it allows you to change the way you      else to drive and walk behind the seeder
              sow (e.g faster, earlier, fewer seeder      to see what is happening to the soil at
              fills, wider machine with                   difference speeds.
              same tractor).                              Timing of operations is also a consideration.
                                                          If an individual farm has a large area to sow,
            − If it allows you to change your seed        30cm row spacing or wider allows are larger
              bed preparation which then increases        area to be sown in a shorter space of time
              efficiency or capacity.                     in a no-till system.
            − If the impact of wider row spacing on       Is yield affected by row spacing?
              crop nutrition is taken into account.       Research in WA showed that cereal yields
            − If it allows you to use other               are slightly reduced at wide row spacing
              advantageous technology.                    (30cm) if the spread of seed within the row
                                                          is confined to 2.5cm (Amjad and Anderson
                                                          2006). This equates to a 1% reduction
           What is the optimum                            in yield for every 2.5cm over 17.5cm row
           row spacing?                                   spacing. Yield loss is minimised if the spread
                                                          of seed within the row is increased (i.e
           Most no-till systems range between 22.5cm      an increase in seed bed utilisation, SBU).
           and 30cm row spacing. Many farmers have        Increased SBU can lead to a reduction
           opted for 30cm row spacing. Row spacing        in efficacy of the IBS trifluralin and the
           is generally a compromise between ease         competitiveness of the crop row, but the
           of stubble handling, optimal seed bed          latter can be compensated for by increasing
           utilisation, weed competition, optimum         sowing rate.
           travel speed and soil throw and hence
           effective use of pre-emergent herbicides.      Try to spread seed across the disturbed
           For example 30cm spacing allows greater        width of soils where practical, and ensure
           travel speed and therefore more soil throw     that the sowing technology (eg. a proven
           as well as good trash clearance and the        spreader boot) you use for this is reliable
           ability to inter-row sow with ease. Narrower   and does not reduce germination.
           spacings such as 22.5cm provide better         What about weed competition?
           weed competition but restrict travel speed
                                                          Research data suggests that ryegrass
           and trash clearance and are more difficult
                                                          populations can be higher under wide row
           for inter-row sowing.                          spacing (Figure 1). However, wider row
                                                          spacing allows greater travel speed which
           How does row spacing affect
                                                          causes greater soil throw, so robust rates
           sowing speed?                                  of pre-emergent herbicides can be used
           Optimum travel speed depends on row            effectively. In a 4 year trial in WA, the effect
           spacing, soil type and soil moisture.          of wider rows on ryegrass numbers was
           Optimum travel speed allows enough soil        minimal by the fourth year. Less weed seeds
           throw to allow incorporation of                emerge in the undisturbed inter-row. It was
           pre-emergent herbicides without landing        found that sowing rate was much more
           herbicide treated soil in the adjacent drill   important than row spacing in reducing
           row (which may cause crop damage).             weed numbers (Minkey et al. 2001).
                                                                     Should I vary row spacing for
                                                                     various crops?
                800                                                  Many no-till farming operations are sowing cereals and
   Ryegrass     600
                                                                     canola at 30cm spacing.
   Heads /m2    400                                                  Oaten hay: Optimum row spacing for oaten hay
                                                                     production is around 17.5cm to reduce stem diameter,
                  0                            180
                                                       Row Spacing   avoid lodging and to keep the hay windrow off the
                       50   100   200                     mm         ground during curing. Cross sowing if using wider row
                                                                     spacing may achieve the same result.
                 Seeding rate kg/ha
                                                                     Pulses: Lentils can be grown on 30cm spacing but may
                                                                     lodge, causing harvest problems if there is no stubble
                                                                     present to support them. Sowing between the rows of
Figure 1. Row spacing and seeding rate                               standing stubbles has increased harvestability of lentils.
interaction with ryegrass competition in
wheat. Source: Minkey et al. (2001)                                  Lupins, faba beans and chickpeas have been sown on
                                                                     wider rows (35.5cm – 61cm). Reasons for this include:
BCG trials from 1997-1999 underlined the importance of               water harvesting in low rainfall environments, reducing
using effective herbicides where crops are sown on wide              disease risk by improved airflow and reduced spray costs
row spacings. In paddocks where herbicides were not                  by using banded spraying.
available for weed control due to resistance, cereal crops
on 17.5cm row spacing out yielded crops on 35.5cm row                How does row spacing affect my
spacing due to the increased competition.
                                                                     ability to inter-row sow?
What are the crop nutrition implications                             The ability to sow back between the row of a previous
of different row spacings?                                           crop is proving beneficial in reducing the impact of cereal
                                                                     root and foliar disease and for improved harvestability
P and Zn nutrition: Initially when shifting into no till             of lentils. A minimum of 30cm row spacing is suggested
and wider rows, there could be less soil mixing and                  for inter-row sowing using 2cm guidance systems.
mineralisation (Rainbow 2004). Adequate P and Zn                     Narrower row spacing can be used in conjunction with
nutrition in no-till systems is particularly important due           inter-row sowing, however it is more difficult to achieve
to the increased risk of rhizoctonia, especially in the early        (McCallum 2005).
years of no-till.
Fertiliser toxicity: Germination and establishment can               Should I modify existing machinery
be affected where too much fertiliser is placed near the             or buy new?
seed. For a given band width of seed, the safe rate of               Both options can be viable depending on machinery
fertiliser that can be applied in the drill row with the             modification skills and/or financial situation.
seed decreases as row spacing increases (Table 1). Canola
is particularly sensitive to fertiliser toxicity, especially,        If intending to modify an existing machine, be aware that
when sowing in light textured dry soils. Fertiliser toxicity         the value of your existing machinery to a dealer may be
can be avoided by placing some fertiliser below the seed             significantly decreased, particularly if the frame is altered.
or by increasing seed spread within the row (greater seed            Do your sums on the real cost of modification, including
bed utilisation) (Rainbow 2003).                                     extra hose kits if double shooting. Work out the cost of
                                                                     upgrading an existing machine compared to a purpose
Table 1. Approximate safe rates of N kg/ha                           built no-till seeder.
with the seed of cereal grains if seed bed has
good soil moisture (at or near field capacity)                       References
for 7 and 12 inch row spacing. Use half these                        Amjad M and Anderson K.W (2006) Managing yield reductions
rates on dry soil.                                                   from wide row spacing in wheat. Australian Journal of
                                                                     Experimental Agriculture, 46, 1313-1321
                                   Soil Texture                      Minkey, Reithmuller & Hashem (2001), Effect of row spacing
   Seed               Light Sandy             Medium- Heavy          and seeding rate of wheat on the emergence and competitive
  Spread                 Loam                  (loam to clay)        ability of annual ryegrass in a no-tillage seeding system.
                                                                     Agriculture Western Australia, Merredin Dryland Research
                17.5cm            30cm        17.5cm        30cm     Institute, Crop Updates.

   25mm               20           11           25            15     McCallum, M (2005), Inter row sowing. Yorke Peninsula
                                                                     Alkaline Soils Group Annual Results Book
   50mm               40           22           50            30     Rainbow R (2003) Seed Bed Utilisation: A better concept for
                                                                     calculating maximum fertiliser rates in the seed row. SANTFA.
  100mm               80           44          100            60
                                                                     Rainbow RW and Slee DV (2004) The Essential Guide to No-till
Source: Rainbow (2003)                                               Farming (South Australian No-Till Farmers Association).

         T h i s w o r k w a s s u p p o r t e d b y G R D C , B i rc h i p C ro p p i n g G ro u p a n d V N T FA

Birchip Cropping Group t 03 54922787 f 03 54922753 PO Box 85, Birchip, 3483
                VNTFA t 03 53820422 f 03 53820477 P.O Box 1397, Horsham, 3402

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