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Fluid Journal : Fluid Journal 2002-2004
2 Fluid Journal Winter 2002 Erwinia carotovora. For example, Erwinia bacteria infect many vegetable crops and are also responsible for stor- age rot in potato tubers. Increasing bean tissue calcium content from l.6 to 3.4 percent greatly reduced Erwinia cartovora infection (Table 1). Plants containing 1.6 percent calcium were completely destroyed within six days. Plants containing 3.4 percent calcium were healthy and possessed no symp- toms of infection. Fungal pathogenic infection is also reduced with increased calcium uptake by plants. A steady supply of available calcium delivered during fertigation by calcium nitrate reduces Fusarium oxysporum activity, the fungal pathogen that causes wilt and crown rot in toma- toes. Research indicates that tomato plants receiving low rates of calcium fertilization were severely infected with Fusarium oxysporum, compared to healthy plants receiving higher calcium rates. Calcium fertilization also reduces Pythium blight and root rot of turf grass and citrus. How effective is calcium fertilization in comparison to other nutrients? Re- search indicates that calcium uptake in plant tissue is superior to potassium in reducing the infection of the fungal pathogen Botrytis in lettuce (Table 2). Increasing potassium concentration in lettuce from 1.44 to 4.89 percent did not deter Botrytis infection. However, de- creasing tissue calcium concentration by half from 1.06 to 0.54 percent in- creased infection from a slight to moder- ate rating. A further decrease in calcium by one-half in the tissue (0.54 to 0.22%) resulted in severe Botrytis infection. Lesson to be learned: enhanced cell wall structural integrity supplied by calcium fertilization is important for plant health. Increasing N efficiency Surface application of urea with soluble calcium fertilizer solutions re- duces ammonia volatilization. The soluble calcium fertilizer source, either calcium nitrate or calcium chloride, for example, precipitates the carbonate com- ponent from the solutions as calcium carbonate. As a result, the concentrated fertilizer solution pH is decreased. Sub- sequently, less ammonia is lost. Water soluble calcium fertilizer sources are key in this reaction. Calcium sources such as lime, gypsum and soil exchangeable calcium cannot reduce ammonia volatil- ization loss. A recent field experiment with urea calcium ammonium nitrate ("UCAN" 21- 0-0-4Ca with a calcium/urea ratio of 0.4), UAN, and UAN + Agrotain® (urease inhibitor) was conducted at Kansas State University to determine nitrogen fertilizer efficiency of each source. The test crop was corn. Results as shown in Figure 1 indicate that within each fertil- izer rate, UCAN produced the highest yields and the highest nitrogen fertilizer efficiency. A three-fold increase in yield per pound of nitrogen applied was ob- served for UCAN-21 in comparison to surface-applied UAN or UAN plus Agrotain® at the 50- and 100-lb/A rates of N. UAN and UAN plus Yield-bu/A 120LRUAN N effifiency-bu/lb of N applied UAN + NBPT UCAN - 21 100 80 60 40 20 0 50 Control (No N)= 41 bu/A Figure 1. Corn grain yield and N fertilizer efficiency by N source and rate. 100 150 50 100 150 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 N-lbs/ Table 2. Bean tissue calcium content effect on bacterial pathogen infection. Percent K Percent Ca Percent Mg Botrytis infection rating * 1.44 1.06 0.32 4 2.38 0.54 0.41 7 3.42 0.22 0.47 13 4.89 0.18 0.42 15 * 0-5 = slight; 6-10 = moderate; 11-15 = severe
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