Impact of Soil Productivity on the Growth of Two Meyer Lemon Trees

(1) University High School, Irvine, California
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Home gardening is one of the most popular activities in the United States. As participation increases, more homeowners are turning to home testing to solve gardening problems. We aimed to apply home soil testing to one such problem: identifying the cause of the growth differences between two lemon trees in our backyard. Since the two lemon trees are of the same species, were planted at the same time side-by-side, and given similar amounts of water and fertilizer, we hypothesized that differences in physical and chemical soil characteristics were influencing differences in soil productivity and plant growth. We tested five factors that affect soil productivity: soil composition, permeability, water-holding capacity (WHC), pH and free ions, and ion exchange capacity. We analyzed five soil samples with three trials each from the root spread perimeter of each tree, then analyzed variance of the results. We found that the soil samples from the lemon tree with higher growth had significantly higher WHC and permeability due to higher humus content and better anion exchange capacity (AEC) due to higher clay content. High sand content and low humus content reduced WHC, permeability, and AEC in the poor soil. All samples had sufficient nutrients and ideal pH, so the two soils did not differ obviously in the tested chemical characteristics. A clay and humus mixture can be added to improve soil productivity for the lowerperforming tree. Overall, our study demonstrated the effectiveness of home soil testing to characterize soils and help homeowners solve common gardening problems.

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