5A soil scientist measures soil organic matter content in four experimental fields. Field A has 3.2% organic matter, Field B has 4.5%, Field C has 2.8%, and Field D has 5.1%. If she mixes equal samples from each field to create a composite sample, what is the organic matter percentage in the composite?

["Title: Understanding Soil Organic Matter: Calculating Composite Percentages from Four Experimental Fields", "Soil organic matter (SOM) is a critical component of soil health, influencing fertility, structure, water retention, and microbial activity. For soil scientists, accurately measuring organic matter content is essential to evaluate soil quality and guide sustainable land management. In a recent observational study, five scientists measured SOM across four distinct experimental fields, obtaining the following values:", "- Field A: 3.2%\n- Field B: 4.5%\n- Field C: 2.8%\n- Field D: 5.1%", "But what happens when samples are mixed to create a representative composite? This article explores the calculation and significance of blending equal samples from these four fields.", "### The Science Behind Composite Soil Sampling", "Mixing soil from multiple fields—known as composite sampling—ensures a more representative analysis of overall soil conditions rather than relying on a single point sample. This method minimizes variability and gives a holistic view of soil properties across treated or varied plots.", "In this case, the scientists take equal volumes from each field, meaning each contributes equally to the final sample. The organic matter percentage of the composite sample is calculated by averaging the individual percentages.", "### Calculating the Average Organic Matter Content", "To determine the organic matter content in the composite sample:", "1. Add the percentages from all four fields:\n ( 3.2 + 4.5 + 2.8 + 5.1 = 15.6 )\n2. Divide the total by the number of samples (4):\n ( \frac{15.6}{4} = 3.9 )", "Thus, the composite soil sample has 3.9% organic matter.", "### Why This Matters in Soil Science Research", "Achieving precision in soil analysis is critical for interpreting data accurately. Organic matter directly affects crop productivity and carbon sequestration potential, making even small differences significant in long-term studies. By combining samples from distinct fields, researchers obtain a balanced estimate that better reflects real-world conditions across a landscape mosaic—important for precision agriculture, environmental monitoring, and climate change mitigation.", "### Conclusion", "Composite soil sampling is a fundamental technique for obtaining reliable and representative data. The calculated 3.9% organic matter in the blended sample from Fields A, B, C, and D highlights how averaging individual measurements provides sound insight into overall soil health. For soil scientists and land managers, such methods ensure informed, data-driven decisions that enhance productivity and sustainability.", "---", "Keywords: soil organic matter, SOM measurement, composite soil sample, soil scientist, organic content analysis, experimental fields, 3.9% organic matter, soil health, soil science methodology."]