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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Late Spring 1993 Table 3. Effect of compaction on alfalfa forage K concentration. Arlington, WS, 1991-1992. Compaction Level 1991 1992 Cut1 Cut2 Cut1 Cut2 Cut3 5 tons 4.21 2.81 2.68 2.50 2.47 14 tons 2.96 2.73 2.42 2.39 2.36 Pr>F 0.01 0.42 0.07 0.19 0.03 Average over soil test K and annual K treatments. 2.0 1.5 1.0 0.5 0 Yield - tons/A 5T 14T 5T 14T 1991 Compaction Level 1992 Cut 1 Cut 2 Cut 3 1.75 1.50 1.25 1.00 117 ppm 142 ppm 179 ppm Yield - tons/A <5T Compaction Level 14T Figure 1. Effect of compaction and K fertilization on alfalfa yield, Arlington, WI, 1991-1992. Figure 2. Interaction between woil test K and alfalfa yield, Arlington, WI, first cut, 1992. seasons because of the increased waterholding capacity of a soil caused by a greater number of pores. Total yield was reduced to 58 and 81 percent of the noncompacted treatment in 1991 and 1992, respectively. A yield response to soil test K was observed for the first cutting in both years; however, these responses were relatively small (0.09 and 0.17 ton/A in 1991 and 1992, respectively). This response was not significant for the later cuttings in either year. The response to soil test K for total yield was significant at the 18 and 13 percent level for 1991 and 1992, respectively. There did not appear to he a benefit from banding (versus broadcasting) K treatments. Higher rates of annual K application tended to increase yield. These differences, however, were not significant (data not shown). Table 2 shows the effects of compaction treatments on soil bulk density. It's apparent that wheel traffic with the 14-ton payloader increased bulk density to a depth of 18 inches. Bulk density was especially high in the 6- to 12-inch depth increment where 1.59 g/cc bulk density measured in 1991 translated into a 10 percent reduction in soil porosity by compaction. Visible observation of several plants pulled from the compacted area showed kinked roots at depths of three to four inches. Measurements in 1992 show that bulk density increased somewhat in the uncompacted treatments at the 0 to 6- inch depth increment. This is most likely a result of harvest traffic, which, while maintained at a load of less than five tons, was not controlled. Alfalfa stand count was higher in the compacted treatments in both years of the study. Many of the crowns in the compacted plots were poorly developed and contained only a few stems. This effect may be a result of reduced growth on compacted plots and less competition for space between adjacent plants. Soil test K and annual K treatments did not affect stand. A significant interaction between soil test K level and total yield was observed for the first cut in 1992 (Figure 2). In this case, a small yield response to soil test K (0.04 ton/A)
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