Estimated crop nutrient requirements and removal Nitrogen timing

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Estimated crop nutrient requirements and removal Nitrogen timing Powered By Docstoc
					OCTOBER 2004




IN THE KNOW
                                               Dear Agronomist,                                                                                             The advantages of water
                                               The dramatic increases in the yield potential of                                                             run Big N
                                               cotton, particularly with the advent of gene modified
                                               (GM) varieties, are putting a greater focus on post-
                                                                                                                                                            Water running Big N is
                                               emergent methods of nutrition application.
                                                                                                                                                            convenient and easy to use
                                                                                                                                                            because:
                                               These changes in yield potential are largely because
                                               GM varieties have a higher harvest index. As cotton
                                                                                                                                                            • There is very little
                                               yields increase, so too does the amount of nutrient
                                                                                                                                                              preparation or handling
Chris Dowling                                                                                                                                                 required to water run Big N.
                                               removed.
                                                                                                                                                              Nurse tanks are
Estimated crop nutrient requirements and removal                                                                                                              delivered to the paddock.
Nutrient 7.5 - 10 bales/ha                                                                 12.5 - 15 bales/ha
                                                                                                                                                              Big N is bubbled directly
                                                                                                                                                              into the irrigation
         Total required                                          Removal                   Total required                      Removal
                                                                                                                                                              ditch, requiring only
N        180                                                     120                       255                                 180
                                                                                                                                                              minimal supervision.
P        45                                                      20                        60                                  35
K        170                                                     35                        225                                 60                           • The application equipment
                                                                                                                                                              required to water run Big N
As we gain a better understanding of the complexity of nutrient
                                                                                                                                                              is simple, reliable and
uptake resulting from the higher peak demand, the rates, methods of
                                                                                                                                                              inexpensive.
placement and timing of cotton nutrition are being reconsidered.
                                                                                                                                                            • The flo-meter releases
Nitrogen timing                                                                                                                                               Big N accurately into the
While it may still be appropriate for most of the crop’s nitrogen                                                                                             irrigation ditch and it is easy
requirement to be applied pre-plant, a greater proportion of the                                                                                              to set.
increased nitrogen requirement may need to be applied during the                                                                                            • Application does not require
growing season.                                                                                                                                               any moving parts, ensuring
Water run application guidelines                                                                                                                              reliability of application.
Use these guidelines to help your grower clients to achieve an even,                                                                                        • Consistent product quality
effective application when water running Big N in cotton.                                                                                                     is assured, because
                                                                                                                                                              Big N is stored as a liquid
• Field trials conducted by Incitec in 1968 and 1991 showed that
                                                                                                                                                              under pressure.
  ammonia concentrations can vary between the head ditch and the
  tail drain. This decrease was thought to be as a result of fixation                                                                                       • Big N is a cost-effective
  of ammonia in the soil near the head ditch and subsequent                                                                                                   source of nitrogen, per tonne
  volatilisation as water moved down the furrows. See Figure 1.                                                                                               and per hectare applied.
Actions: Run irrigation water for some time before releasing Big N. Add
Big N during the first quarter of the anticipated watering period. Do not
run in fields longer than 600 metres, to prevent striping out.
                                                   WATER RUN BIG N - St GEORGE - 1991
                          18
                               HEAD DITCH                                             IN-FIELD                                TAIL DRAIN

                          16


                          14


                          12
   Concentration (mg/L)




                                                                                                                                                            Figure 1: Concentration of
                                                                                                                                                            ammonia in water at different
                          10


                           8                                                                                                                                distances from the injection
                           6                                                                                Total N
                                                                                                                                                            point in furrow irrigation,
                                                                                                            Ammonium N
                                                                                                                                                            St George, 1992.
                           4


                           2


            0
       Head ditch before             Head ditch 100m after   At siphon (600m after)     600m from siphon   900m from siphon      Tail drain (2100m after)

                                                                                 Sample Site                                                                New calculator available
• Ammonia is adsorbed in the top 5 – 6 cm of soil which is essentially a                                                                                    Recommending water run
  surface placement. Strategies are needed to ensure the right nitrogen                                                                                     Big N is now even easier with a
  timing.                                                                                                                                                   new calculator that determines
Action: Water run Big N in the irrigation prior to the anticipated nitrogen                                                                                 the orifice required for specific
demand. Between irrigations, most of the ammonia is converted to                                                                                            applications.
nitrate, which then moves into the root zone with the next irrigation.                                                                                      The ‘Big N water run orifice
• The stability of ammonia dissolved in water depends on both physical                                                                                      selector’ CD is part of a 2 page
  and chemical factors and these need to be considered to prevent                                                                                           guide to water running Big N.
  excess volatilisation.                                                                                                                                    The guide and CD are currently
Actions: Do not apply more than 100kg of Big N per ML. Ensure rapid                                                                                         being distributed to cotton
water movement. Place the injection point at least 100 metres from the                                                                                      advisers.
first syphon.                                                                                                                                               Please contact your Area Sales
For more information on successfully water running Big N or other                                                                                           Manager for more information.
cotton issues, call me on 0407 692 251.




Chris Dowling
                                                                                                                                                                              CR NR NSW/QLD B
Agronomist

				
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Description: Estimated crop nutrient requirements and removal Nitrogen timing