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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Fall 1994 Great Northern variety is quite tolerant. Similarly, Russet Burbank potatoes develop zinc deficiency under certain field conditions where White Rose show no symptoms. Researchers have demonstrated differential zinc uptake of inbred corn lines grown in nutrient solution, indicating genetic control of translocation, use, and requirements of zinc. Thus, the sensitivity of crops to zinc deficiency in the table should be taken as generally representative. Soil testing Soil tests for zinc are most often performed using an acid extract such as 0.1 N HCl or a chelating agent such as a DTPA extract. The DTPA with ammonium bicarbonate test is preferred for soils containing free CaCO3 and can be requested. Advantages of the DTPA extraction are that several micronutrients can be analyzed simultaneously and greater control can be exerted on sample longevity. Studies have shown that soils that may be high in total zinc may not be necessarily high in plant-available zinc, as indicated by the extract. Comparisons of five different extracts on Ontario soils, using corn as an indicator crop, showed that no single extract adequately represents all field conditions. This suggests that growers should use tests indigenous to their areas. Deficiency symptoms There are a number of visual symptoms in crops that will alert you to zinc deficiencies: Corn. Yellow streaks between veins. Dead areas in older leaves. Shortening of the internodes. Stunting of the plant. Silking and tasseling delayed. Chalky kernels. Reddish-brown coloration on portions of plant. Sorghum. Deficiency symptoms in grain sorghum are similar to corn, but 0 0.1 0.3 1.0 140 130 120 110 100 90 80 70 60 Figure 3. Effect on cor n yield when banding zinc near seed, University of Nebraska. Yield (bu/A) Zn - lbs/A Figure 2. Effect of rate of applied Zn on yield of corn grown on irrigated sandy soils having pH greater than 7, University of Nebr aska. 0 0.1 0.3 1.0 3.0 150 140 130 120 110 100 90 80 70 60 Yield (bu/A) Zn - lbs/A
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