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Fluid Journal : Fluid Journal 1999-2001
2 Fluid Journal Winter 1999 used as a starter and may contain nutrients such as N, P, K, S, Mg, B, Zn, Cu. Managing tips Soil test. If P or K levels are high in the soil, response of starter applications may be low. If you don't soil test, you may needlessly waste valuable dollars fertilizing when you could put them elsewhere. Table 1 shows the importance of soil testing before applying starters. Source of fertilizer used for starter does not appear to make much difference. All NP sources reduced plant and ear height as compared to control. However, ammonium polyphosphate appeared to reduce ear height slightly more than other NP sources. Micronutrients are often yield limiting factors in the Coastal Plain. Growers might include them in starters when soil tests show a shortage of two or more pounds of these secondary elements. The results, however, are often a mixed bag. For example, if ammonium polyphosphate is used, sulfate forms of micronutrients cannot be used unless a separate tank and pumping unit are used. This is because they'll react and clog nozzles. To compensate, chelates are often used in the same tank at a rate of a half pound or less of actual nutrient. Figure 4 shows some yield advantage in using micronutrients. Hybrids. Studies have shown that a hybrid failing to respond to NP starters under field conditions produces a larger root system than one that consistently responds. If response under field conditions is due to only one element (N or P) because the other is supplied in adequate amount from the soil, then it is not known whether each hybrid responds in the same manner to the other element. Best practice is to be careful when selecting hybrids if using starters. Cautions. When applying starters, several cautionary rules should be observed: 1.DonotusehighratesofNorK directly over the seed since they may be leached around the seed and reduce germination 2. Avoid fertilizer in contact with the seed as it may reduce stand 3. Applying either 2 by 2 or surface banding is safer. Dr. Wright is professor of agronomy, University of Florida. Yield---bu/A 190 180 170 160 150 140 130 120 Check 10-34-0 10-34-0 Chelate Together 10-34-0 Chelate Seperate S S = Surface D = 2"-3" under seed D S S Figure 4. Effect of using micronutrients in starters on no-till corn yield. Table 1. Probability of a profitable response to row-applied phosphorus or potassium, Minnesota. Soil test % response to level--P or K PorK Low 95-100 Medium 65-95 High 30-65 Very High 10-30 Yield---bu/A 190 180 170 160 150 140 130 120 Check NP 15-30 NK 15-30 PK 30-30 NPK 15-30-30 Figure 3. Effect of adding K to an NP starter on corn yield.
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