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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Summer 1995 Fertilizers... The need for boron fertilization is increasing because of higher crop yields and reduced levels of organic matter (the primary soil source) and because of years of intensive crop removal. As shown in the diagram of the boron cycle (Figure 1), the soil-plant system is dynamic and strongly influenced by weather. The key to controlling boron- use efficiency in the system is sound fertilizer management... using available knowledge to assess fertilizer boron needs and implementing them for best efficiency in terms of farmer profits. Plant & Animal Residues Boron Weakly Held On Organic Matter & Clay Surfaces Strongly Complexed within Organic Matter & Clayys Plant Intake Boron in Soil Solution Leaching Boron Fertilizer Weathering of Soil Minerals Figure 1. The boron cycle...a dynamic system, changing daily as it is influenced by the soil-plant system, wether and fertilizer management. Table 2. Relative requirements of boron. High Medium Low Cotton Corn Barley Canola Flax Oats Sunflower Grain Sorghum Soybeans Cauliflower Brussel Sprouts Rye Beets Cabbage Rice Sugar Beets Onions Wheat Carrots Potaoes Beans Broccoli Sweet Corn Peas Apples Tomatoes Pecan Peanuts Tobacco Sugarcane related. Total boron need can be traced to differences among crops and produc-tion practices such as yield goal or variety selection needed for improving productivity and profitability. For example, total boron removed in Table 1 is six times higher for alfalfa yielding 10.8 tons/A than that yielding 6 tons/A. By comparison, boron content of high-yielding corn is about the same as that for alfalfa yielding 6 tons/A. The need for boron fertilization is increasing because of higher crop yields and reduced levels of organic matter (the primary soil source), and because of years of intensive boron removal by crops. As shown in the boron cycle dia-gram (Figure 1), the soil-plant system is dynamic and strongly influenced by weather. The key to controlling boron-use efficiency in this system is sound fertilizer management, using available knowledge to assess fertilizer boron needs and implementing them for best efficiency. Quantifying need As we have already seen, there are many soil-plant factors that point to the need for boron fertilization. But how do we quantify that need---both in terms of documenting the fact that fertilizer should be applied and the rate per acre to use? There are several places we can look for help. Management capability. Well- managed farms produce high yields. High yields require greater levels of production inputs (including boron) for sustainability. Depending on soil fertility levels and crops being grown, a part of the crop's boron requirement may need to be provided as fertilizer. Remember, as a farmer moves his yield goals up, his chances of needing boron fertilization increase. Field history. Once boron deficiency exists in a field, those soils will always---to varying degrees---be deficient. The highest boron- demanding crop grown in the rotation should be fertilized with boron. Crop needs. Table 2 shows which crops have high, medium, and low boron requirements. Keep in mind that some varieties and hybrids within a
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