Potato Grower

November 2014

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40 Potato Grower | NOVEMBER 2014 diggin' in NUTRIENT MANAGEMENT Timing is Everything Potatoes need phosphorus, and it matters when TIMING IS A CRITICALLY important aspect of nutrient management. It impacts everything from crop health to return on investment to the environment. It's no wonder "Right Time" is one of the four pillars of 4R Nutrient Stewardship, in addition to Right Rate, Right Source and Right Place. For any nutrient, one of the main goals is to have the nutrient release and availability match with plant uptake as closely as possible. There needs to be sufficient nutrient availability for crop demand over the growing season while minimizing soil nutrient loss. Consider the timing aspect of phosphorus management for potato production. Phosphorus (P) is an important nutrient for both potato yield and tuber quality. Potatoes can remove a considerable amount of phosphorus compared to other crops; for example, a 400 to 500 cwt. per acre yield could remove 60 to 80 pounds of P2O5 per acre. The majority of this phosphorus uptake occurs during the bulking growth stages more than 40 days after emergence, and continuing into the late bulking. The peak daily phosphorus uptake also occurs in this latter part of the season, meaning that the daily phosphorus uptake requirements are highest during bulking. But how does phosphorus fertilizer timing match up with this nutrient uptake? We know recommended phosphorus application timing is generally at planting or early in the season, which seems ironic given that peak uptake occurs much later in the season. We also know that traditional phosphorus fertilizers are highly water soluble, dissolving quickly into the soil solution where they can undergo chemical reactions in the soil that can later limit the phosphorus availability to plants (calcium, aluminum and iron are the most common elements that "tie up" soil phosphorus). If done in a timely manner before tissue levels have dropped below critical levels, in-season phosphorus applications can be of some help, but with phosphorus having limited mobility in the soil this is not as Reduced Rate 20% reduction in culls & undersized 13% increase total marketable yield Your witness. A grower trial of Crystal Green in Hermiston, Ore., produced positive results. By Trudy Naugler Klassen, Agronomy Research Analyst, Ostara Nutrient Recovery Technologies, Inc.

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