Download into potatoes” “ - Agroconsultas Online

“Putting the
into potatoes”
Hydro Potato Workshop
March/April 2003
USA Work - 1985
• Independent research has produced this
information but what is it showing us?
• Something is significantly affecting tuber
yield of potatoes, but what is it?
• P2O5tato crops which stay phosphate rich
longer produce higher yields
• Tuber yield is increased by 0.6 t/ha for every
extra day during which tissue phosphorus is
maintained above 0.22%
Petiole phosphorus levels decline
naturally as the season progresses
• What can be done to delay arrival at
the critical P=0.22% threshold?
Rate of Petiole P decline
(Phosyn Holland 1998/99)
70
Tuber yield (t/ha)
60
50
2
R = 0.88
40
30
20
10
0
Slower
Rate of P decline in petioles
Faster
• Confirmation of Westermann’s work. Slow rates of
P decline are associated with higher yields
Delaying the P decline?
• Apply a product solution
• Develop a pro-active analysis system to
identify the problems early
Apply more phosphorus fertilizer
• Potato soils are rarely deficient in
phosphorus, in fact the opposite is more
often the case.
• So will applying more phosphorus to the
soil make any difference?
• Probably not. Plants have difficulty taking
up phosphorus from the soil even when
soil levels are satisfactory
Phosphorus uptake from the soil requires a
well developed root system
• Plants only absorb phosphate from very close
(less than 1mm) to the root surface (plants must
“forage” for P)
Cold soils reduce phosphorus availability
Relative availability (%)
100
73
43
31
21
18
16
13
Soil temperature (oC)
• A drop in soil temperature from 21 to 13 oC
reduces phosphorus availability by almost 70%
Use foliar applications of phosphorus
• Although it is considered a macronutrient the annual requirements are
relatively small
• Phosphorus is readily taken up and
translocated by leaves
• Foliar application overcomes any soil or
environmental conditions which may limit
uptake from the soil
Foliar phosphorus applications
• Foliar sprays throughout tuber
bulking can help delay the natural
decline in petiole phosphate and
increase yield potential.
• Use Hydrophos (29% P2O5, 4%
Mg, 5%K2O) throughout tuber
bulking.
Delaying the P decline?
• Apply a product solution
• Develop a pro-active analysis system to
identify the problems early
Development of the Phosyn
guideline systems
0
20
40
60
80
100
120
140
160
180
Days after planting
• Green guidelines are the Idaho program
200
Phosyn guideline systems
0
20
40
60
80
100
120
140
160
180
Days after planting
• Red guideline becomes a more proactive
system allowing earlier, less frequent
sampling
200
Delaying the P decline will
increase yields
• Apply Hydrophos to supplement soil
applications
• Use MEGALAB.net analysis to identify
phosphorus problems pro-actively
Thanks for your attention