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Fluid Journal : Fluid Journal 1993-1995
3 Fluid Journal Spring 1993 tillage equaled or exceeded conven- tional tillage because a sufficient amount of potassium was applied in the starter fertilizer. The test showed an 18- bushel per acre increase from starter on a till-plant plot compared to only a 9- bushel per acre increase in a plowed control. Even when 160 pounds of K2O were applied broadcast, the starter fertil- izer increased the till plant yield by l8 bushels per acre! The broadcast po- tassium was "positionally unavailable" because of sufficient K already in the surface zone. Table 4. Effect of starter on corn grain yield. Method Broadcast Plus StarterDifference .... . . ..... (bu/A) . . ......... Plowed 117 126 8 Till Plant 118 136 18 In a 125-bushel per acre corn crop, above-ground residue contains about 100 pounds of potassium. If a field is not tilled, and the residue is allowed to accumulate and decompose, potassium will accumulate on the surface each crop year. After five years of no-till, 500 pounds of K2O will be piped up from the subsoil to the surface! This potassium is essentially "positionally unavailable" to the current crop because it is sitting on the surface and subject to the drying patterns during the summer months. It makes no sense at all to sur- face broadcast potassium on no-till when chances are that the surface al- ready contains enough K. Cooler temperatures. Liquid starter at planting time can overcome the effects of low soil temperatures inherent in con- servation tillage. A look at Figure l shows why. The "concentration effect" from the band of starter fertilizer offers a young root system a readily available source of complete plant food, including nitrogen, phosphorus, potassium, sulfur and zinc. The phosphorus concentration in a band is over 200 times higher than a broadcast and disk-in application. This higher concentration reduces soil fixa- tion and helps to increase root uptake. In conventional tillage, where the ex- posed soil is black, sunlight will warm the soil much quicker than in con- servation tillage where insulating resi- due blankets the soil. Resulting low soil temperature in con- servation tillage reduces plant growth and nutrition. The residue, which ben- eficially reduces erosion, increases wa- ter infiltration and contributes organic matter, is also our biggest enemy be- cause the insulating layer reduces soil temperature from early spring to corn planting time. Soil temperature difference can amount to as much as 7°F. This doesn't sound like much difference, does it? But, think of this. An extra 9 degrees can triple the phosphorus uptake in the warmer soil! Figure 2 shows that band- ing starter fertilizer could increase the uptake of phosphorus 233 percent in cold soils and prevent deficiencies. Denitrification losses. Addition of nitrification inhibitors to liquid starter can keep nitrogen in the ammonium form longer and reduce denitrification and leaching. Denitrification occurs when nitrogen converts to gaseous forms that are released to the atmos- phere. Denitrification losses occur fre- quently in compacted or water logged soils because they lack oxygen and in conservation fields because of ex- tremely active biological systems. Poor fertilizer efficiency. The most spectacular response from any plant food applied with starter is the tremen- dous increase in fertilizer efficiency gained by banding zinc in starter. In Ne- braska tests, one-tenth of a pound of zinc increased yields by 37 bushels per acre! Researchers said, "With placement below and to the side of the seed only small amounts of zinc were needed to produce maximum yields" (Table 5). Table 5. Effect of starter applied zinc on corn grain yield over two years. lb Zinc/A Yield bu/A Increase 0 82 0.1 119 37 0.3 127 45 1.0 135 53 Drastic changes in tillage practices, such as switching from conventional tillage to no-till, require drastic changes in fertilizer practices. For example, we have talked about tie-up of nutrients in residue, denitrification of nitrogen, lack of movement of phosphorus, potassium Band contains 200 times more nutrients per cubic inch than disk-in or plowed under! Figure 1. Starter fertilizer at planting counteracts low temperatures because concentration effect" helps roots absorb more. Table 3. Effect of at-planting fertilizer applications on no-till corn yield. Yield Treatment (bu/A) NoN 61 80 lb Broadcast 121 80 lb Injected 155 Figure 2. P2O5 uptake by young corn plants 14 days after emergence in 590 F soil. 4 3 2 1 0 Band Broadcast P Uptake (oz/A)
Fluid Journal 1996-1998