The impact of broiler litter and copper fertility on soybean yield components in Western Kentucky

Broiler litter has been used increasingly as a means of fertilizer because of the rising costs of commercial fertilizer. Recently, limited research has been completed analyzing the effects of broiler litter applications on soybean yields. Several studies have been conducted at Murray State over the last several years in this area. This research study was an extension of the previous studies, but with a new emphasis on copper fertility and copper's effect on soybean yield. Therefore, the overall purpose of this study was to continue to examine the residual effects of broiler litter fertilization on soybean yield in Calloway County, Kentucky. A related experiment was to examine the effect of copper fertility on soybean yield. The effect of drought on soybean yield was analyzed as a minor objective. Randomized block designs were used in setting up both experiments and the data was collected and analyzed through analysis of variance. The broiler litter experiment had eight different treatments with four replications of each treatment. The historical treatments were 0, 1, 2, 3, 4, 5, 6, and 7 tons of broiler litter applied per acre. The broiler litter treatments were last applied in May of 2008. The copper fertility experiment had three different treatments with four replications of each treatment. The treatments were 0, 10, and 20 lbs. Cu per acre respectively and were applied the previous year on May 28, 2009. Both of the experiments were planted on the same day and were planted on May 28, 2010 with a 30 inch row width. Only one soybean variety was used with both experiments, and both experiments were planted using no-tillage practices. The soybean variety used was Caverndale CF 470. This was a commercial variety at 4.7 maturity and was glyphosate resistant. For each experiment, yield component analysis was used to examine the prior objectives, and the following measurements were made: overall plant numbers/4.1ft2, pods/plant, seeds per plant, and seed weight across treatments. No significant differences were found in both experiments across treatments. Following the conclusion of the yield component analysis a comparison was made comparing the yield component results to the average total yield results for both experiments. No significant differences were found in the average total yield in both experiments, but an interesting note was that the copper experiment yielded better on average than the broiler litter experiment. This difference in yield between the two experiments was around 10 bu/A. The yield component analysis method was precise enough to support and confirm the overall yield results. Although these two experiments were in adjacent fields and managed the same, the reasons for this difference in yields require further study. The effect of drought during the 2010 growing season was evident. This really affected the results for the study and was another reason why future studies should be conducted.