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Transcript
“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