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Fluid Journal : Fluid Journal 2005-2007
F all 2005 Fluid Journal 2 using KTS was imposed on subplots that had the broadcast with tillage treatment in 2002 to determine if early- season K stress observed in many reduced-till fields might be mitigated with this material. Soil test analyses, averaged for the depth increments (0 to 2-, 2 to 4- and 4 to 8-inch depths) showed a statistically significant (but not functionally significant) difference in pH for the long-term till (ridge-till) and slot-plant (no-till) treatments (6.4 vs. 6.6), but bulk density, organic matter, Bray P, and exchangeable K, Ca, and Mg showed no significant differences. The fall-applied 14-40-40 lbs N-P2O5-K2O/A deep-band strips had significantly higher Bray P and exchangeable K than the broadcast or broadcast with tillage strips, probably because the soil samples were collected from within the corn rows and therefore there was a high probability that one or more of the concentrated fertilizer bands was hit during the sampling process. The most notable soil test differences, however, were the stratification for bulk density, organic matter, pH, Bray P, and exchangeable K as shown in Table 1. This stratification was not unexpected since it had been evident within the first few years at this site and documented for the Clarion- Nicollet-Webster soil association in an on-farm study just a few miles away. The "rescue" KTS treatment applied to the broadcast with tillage strips in 2003 provided an additional 35 lbs/A K2Oand24lbs/ASattheV10toV12 growth stages. Analysis of leaf tissue from opposite and below the primary ear at anthesis showed no significant differences for K, Ca, Mg concentrations due to tillage or supplemental fertilizer treatments. Corn yields showed a small difference, averaging 176, 179, and 180 bu/A for the broadcast 14-40-40, broadcast + KTS, and deep-band 14-40-40 treatments, respectively. Grain moisture averaged 16.2, 16.1 and 16.0 percent, respectively. 2004 Subsequently, a more detailed study comparing a high-volume (20- to 30-gal/ A) surface dribble application of K fertilizer at planting with broadcast and deep-band treatments was proposed, funded, and implemented starting in 2004. Soil samples collected from both tillage treatments in Block 70 (continuous corn) and 71 (corn/ soybean rotation) prior to applying fertilizer treatments in 2004 again showed stratification of P and K (Table 2), but perhaps most revealing were the soil test results expressed as a percentage of base saturation. At this research site and in a nearby on-farm study on the same soil association, K saturation was below 2 percent for both long-term tillage treatments. Whole plant analyses showed slightly higher K concentrations for all three placement methods but the differences were not statistically different. Leaf samples at anthesis were significantly different with the control being lower than all of the K treatments. Soybean leaf samples at full bloom (R4) also had numerically but not significantly different K concentrations. The Ca and Mg concentrations in whole plant and leaf samples were very high for both control and treated plots. Concentrations of Ca and Mg in soybeans were decreased by additional K applications. Grain yield for both crops also showed a significant positive response Figure 1. Grain yield response in 2004 to K treatments on slot- and till- plant plots near Ames, Iowa. Figure 2. Profile distribution of bio-available K three weeks after broadcasting dry material (top right), subsurface banding dry material (bottom left), or surface dribble application (bottom right) approximately two inches to side of corn row in 2004. Control is shown top left.
Fluid Journal 2002-2004
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