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POTASSIUM NITRATE BENEFITS ON TOP DRESSING APPLICATION IN ONION Prilled potassium nitrate (12% N - 38.2% K) is a potassium source that provides rapidly absorbed nitrate-nitrogen, a plant’s preferred nitrogen source, with 2-4 mm prill size.
Prilled potassium nitrate contains exclusively nitrate nitrogen.
• Fast acting and readily soluble source of nitrogen, directly available for uptake by the roots, independent of the activity of nitrifying bacteria, resulting in faster uptake and greater efficiency for the plant. Prilled potassium nitrate (12% N - 38.2% K)
Potassium nitrate provides the ideal N:K ratio during bulb development stage
K and N demand reaches a peak during bulb development stage, when the application of prilled KNO3 will: • increase bulb size and weight • lower the impact on soil salinity (vs SOP or MOP), which affects yield and post-harvest weight losses Nutrient uptake in onions: high K & N uptake during bulb development stage
• Due its synergistic effect, promotes the uptake of cations: potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn). Prilled potassium nitrate is virtually chloride free.
• Yield and quality are negatively affected by chloride. The presence of nitrate nitrogen in potassium nitrate (NO3-), acts antagonistically to chloride (Cl-) uptake if present in soil or water. • No contribution to soil salinity: both elements, K & N, can be fully taken up by the plant. Proven benefits of prilled potassium nitrate in onions: • Increased yield, due to greater weight of bulbs.
• Decreased weight loss during storage and increased shelf life. • Greater tolerance to diseases such as basal rot and white rot.
mg/plant
• Improved resistance to drought and cold injuries. Recommendation of use:
Apply prilled potassium nitrate at 150-200 kg / ha, as top dressing, at the beginning or during bulb development stage: Days after sowing
Source: Vidigal et al. 2002.
Yield potential at different soil and irrigation water EC (= salinity) levels
Transplanting 4th leaf
Formation of leaf 5
Formation of leaf 6 & 7
Initiation of bulb formation
Bulb thickening
Formed bulb Fall or soft to maturity neck/harvest
150 to 200 kg/ha
Source: Water quality for Agriculture. R.S. Ayers and D.S. Wescot. 1994
Prilled potassium nitrate is sold by Yara Fertilizers (New Zealand) Ltd under the brand UNIKA® PLUS. For additional information, please visit: www.sqmnutrition.com NZGROWER : OCTOBER 2021 71
