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Fluid Journal : Fluid Journal 2002-2004
PAND K BALANCE During the 2002 summer we noticed a severe stand decline in plots where P had been applied without K. This was on the poorest fertility soils located at the study site. To our surprise, these stand losses were even greater than what we observed in plots where no P and K had been applied. To understand this stand decline we set up a group of plots where we provided P without K, so we could consider them as a single treatment. We compared them with plots that had been provided with 200 lbs/A/yr of K2O, this time combined with the same P rates of 50, 100, and 150 lbs/A of P2O5/yr. .TheKratewasse- lected for comparison because it pro- vided good yields (Figure 1) without being excessive, and because several of the 200 lbs/A of K2O plots were immedi- ately adjacent to the no-K plus P plots that had suffered extensive stand loss. Although extensive stand loss oc- curred in all plots between May and December of 2002, losses were espe- cially acute in the no-K plus P plots. Clearly, then, nutrient imbalance (add- ing P without K) has much graver con- sequences for alfalfa survival than we had anticipated. From an alfalfa persis- tence point of view, producers are bet- ter off not fertilizing than applying P alone if they suspect soil K levels are inadequate. Obviously, the best choice istosoiltestandapplyPandKasre- quired to meet yield goals of the alfalfa stand. Berg is graduate research assistant, and Drs. Joern, Johnson, Brouder and Volenec are professors in the Department of Agronomy at Purdue University. 3 Fluid Journal Fall 2003 Figure 4. Changes in plants/area. Data are averaged over all fertility treatments, 1997-2002. Plants/ft2
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