This SDSU Extension article describes soybean leaf tissue analysis, including micronutrient interpretation, as a quality-control check on soil fertility and fertilizer programs. Sampling protocol: collect leaf tissue at growth stage R1-R2 (beginning to full bloom), before R3 (beginning pod), when nutrient redistribution to seed begins. Collect only the uppermost fully-developed trifoliolate leaf (commonly the third leaf from the top), excluding the petiole; gather 30 trifoliolates from different plants in the area of interest and ship in a paper bag. Lab analysis costs about $34 per sample for all 13 nutrients, or about $26 if chloride and molybdenum are excluded. Reported micronutrient sufficiency ranges (ppm), with interpretive categories of likely responsive, small probability of response, sufficiency range, and excessive/toxic: iron <50 likely responsive, 50-54 small probability, 55-300 sufficient, >500 excessive (note: requires proper leaf washing for accurate results); manganese <20 responsive, 20-29 small probability, 30-100 sufficient, >200 excessive; zinc <20 responsive, 20-24 small probability, 25-60 sufficient, >75 excessive; copper <4 responsive, 4-5 small probability, 6-20 sufficient, >50 excessive; boron <20 responsive, 20-24 small probability, 25-60 sufficient, >80 excessive; molybdenum <0.2 responsive, 0.2-0.9 small probability, 1.0-5.0 sufficient (no excessive threshold given). The article cautions that plant analysis results are most useful for adjusting future fertility programs rather than in-season correction, should be interpreted cautiously if plants were sampled under drought, flooding, or herbicide damage, and that soil testing (not tissue testing) is still required to generate actual fertilizer rate recommendations.