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Fluid Journal : Fluid Journal 1996-1998
Winter 1997 by the root mass. The concentration in the soil must be maintained at a high level. As phosphorus is withdrawn from the soil solution, there must be an ample reserve to replace that phosphorus that is absorbed by the roots. As populations increase, the old "sufficiency" levels of phosphorus may be "insufficient" or too low. Therefore, so-called sufficiency levels of phosphorus should be increased far beyond what some agronomists suggest if plant populations are being increased to levels needed to produce high yields. It is interesting to note that corn will absorb no more nutrients per bushel from a 250-bu/A crop than from a lower- yielding crop. Yet, to reach 250 bu/A, the concentration of nutrients may have to be higher than sufficiency levels suggested. ANSWER: The solution to simplifying soil test interpretation is to soil sample using the ABC system described earlier. Recommendations based on placing sufficient fertilizer where the greatest uptake occurs can then be made. Ignoring the fertility levels in the B and C zones and making recommendations from shallow soil samples is like flying a plane in a fog without using instruments. Rainfall PROBLEM: Limited rain and snow is a major obstacle to high yields in the western Corn Belt. One obvious remedy is irrigation but irrigation water is expensive. Under dryland conditions, moisture conservation can mean the difference between a good crop and crop failure. ANSWER: There are many ways to improve water-use efficiency, including weed control, insect control, narrow rows, contour farming, conservation tillage, and so the list goes on. But one of the most effective ways to increase water-use efficiency is again through root zone banding or deep placement of fertilizer. Many times deeper root systems will carry the plant through periods of stress that occur at critical moments, thus increasing yields substantially. Use the ballpoint pen measure on the grower sometime. Ask whether he would like to grow a crop in six inches (the length of the pen) or in 12 inches of soil in a dry year. You'll get no argument from most growers. They'll say, "Give me the deep-rooted crop when the weather is dry." Absorption zone critical PROBLEM: Assuming we have the right climate, hybrid, pest control, population level, high nutrient levels, we still need a deep soil profile to allow plant roots to proliferate. If populations are to increase we need to increase the soil volume available to the root system. If corn is planted in 30-inch rows at 18,000 plants/A and fertility is six inches deep, roots have an absorption zone of only nine gallons. Increase population to 28,000 plants/A, the zone shrinks to six gallons! The roots become restricted, compacted, crowded, and nutrients are less available. ANSWER: Build a bigger box! The problem of restricted root volume can be solved by increasing the depth of fertility. Suppose we develop a soil with fertility and tilth 12 inches deep. Now the absorption zone available to each plant is 12 gallons! Under these conditions, 28,000 plants/A will produce a healthy plant with very little size reduction. Super high yields are possible. Production of 250-bu/A corn can be accomplished with 35,000 ears/A weighing a half pound each. Tilth PROBLEM: A common mistake is to underestimate the importance of tilth, viewing instead the importance of fertilization for high yield levels as primary. Fertility is easy to correct. Tilth, on the other hand, takes several years of skillful management to improve. Fertility is a small problem compared to tilth. Tilth is that magical combination of soil properties that distinguishes a soil by its physical and chemical characteristics. Tilth makes a soil crumbly, increases water-holding capacity, and improves aeration necessary for fertilizer uptake. Organic matter---a fragile group of organic compounds made up of carbon, nitrogen, phosphorus, and other essential nutrients---is the key to producing tilth. It's easy to destroy and difficult to maintain or produce. ANSWER: Tilth in modern farming can be achieved by a combination of residue management, deep tillage, and, finally, deep fertilizer placement. Residues can be incorporated into the soil with sufficient nutrients to provide a favorable environment for the production of organic matter. Deep tillage can incorporate some of this residue into the deeper profile. The payoff is profitable high yields for the grower who achieves high soil productivity! _________________________________ Lohry is chairman of Nutra-Flo Company in Sioux City, IA. !
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