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Fluid Journal : Fluid Journal 1996-1998
1 Fluid Journal Winter 1997 Summary: Using an intermediate degree of mixing, accomplished via strip treatments, has proven the more efficient placement. This method of placement is definitely worth considering in the pursuit of attaining greater yield responses from fluid fertilizers. Timing of fertilizer application is very important for the nitrogen part of the fluid fertilizer Timing is not as important for phosphate and potassium, whereas placement is more important. Placement is not nearly as important for nitrogen because it can move through the soil and be available to the plant as long as it is in moist soil and not on the dry surface. The efficient use of fluid fertilizers to produce high yields depends upon proper time of application and proper placement in the soil. Fluid fertilizers, which are generally known for their nitrogen, phosphate, and potassium formulations, need to be applied so they are available in the soil at the root surface when plants need them. Since operations must be timed so they don't interfere with planting, etc., estimates must be established on how far in advance the fertilizer can be applied without losing its effectiveness. Move differently Timing and placement factors for nitrogen are different from those for phosphate and potassium. Thus, when using a fluid fertilizer containing all three nutrients, account must be made of what will happen to all three after application. Biggest difference is movement. Nitrogen. Nitrate will move with water in the soil. Hence, when applying nitrogen, leaching and denitrification are concerns. This usually means nitrogen must be applied near the time of use or else applied in the ammonium form if applied earlier. Ammonium doesn't move far in the soil but it will nitrify to nitrate if conditions are favorable. Nitrate can be lost by leaching or denitrification. Denitrification occurs under waterlogged conditions. Phosphate/potassium. Phosphate usually moves in soil less than one- tenth of an inch and potassium less than two- to three-tenths of an inch. Hence, these nutrients have to be applied where the roots are. Applying fertilizer on the surface after planting will not be effective. Approximately 30 to 60 percent of corn roots and 40 to 70 percent of soybean roots may be in the plow layer. Fertilizer should be banded into the moist soil of this layer. Feed from soil Corn roots are usually about one- quarter to one-third of an inch apart in the plow layer. On the average, corn roots are farther apart because soybean roots are less than half the length of corn roots. Since the soybean roots are separated by twice the distance phosphate can move, little of the phosphate will reach the roots. Most will remain in the soil for uptake by future crops. This is why with phosphate, and to some extent potassium, the primary function of a fertilization program should be to maintain a satisfactory level of these nutrients in the soil. Plants are not being fed with applied phosphate and potassium as much as a level of these nutrients is being maintained in the soil. Thus, corn and soybeans feed from by Dr. Stanley A. Barber Timing And Placement One Key to High Yields Purdue scientist shows how strip placement of fluids is superior to broadcasting. the soil. Unlike nitrogen, phosphorus and potassium are not directly used or uptaken by the crop. Absorb what is near Plant roots have a finite capability for absorbing nutrients. The rate at which a root segment absorbs nutrients increases as the level of nutrient around it increases, until it reaches a maximum. An example of this for phosphate uptake by corn roots is shown in Figure 1. The maximum uptake is at a lower concentration than is usually found near a fertilizer band. Hence, phosphate needs to be present throughout the soil around most of the roots. From the standpoint of the plant root, it is better to distribute fertilizer uniformly throughout the part of the soil where most of the roots are growing. Plant roots usually absorb at two- thirds to three-fourths of the maximum rate in order to get nutrients needed for maximum yields. Hence, if the soil is low in phosphate, it should be mixed Figure 1. Relationship between phosphate in solution at the root surface and the rate phosphate is taken up by corn roots, Barber, Purdue University. P Concentration - ppm 0 0.2 0.4 0.6 0.8 1.0 P Uptake Rate
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