| Abstract: | Abstract Boron applied in 2 soybean field experiments at rates up to 2.12 kg/ha was not detectable in Ap or B2 horizon soil extracts approximately 6 weeks after B addition, although leaf B contents reflected added B. There was a measurable difference between the 2 fields in extractable B. Where the Ap horizon averaged 0.05 ppm B, soybean leaf content ranged 14 to 40 ppm B and no yield response was obtained with 0.56 to 2.24 kg/ha of added B. Where the Ap horizon averaged 0.11 ppm B, and leaf content reached 63 ppm B, soybean yield was reduced approximately two‐thirds by 2.24 kg/ha of added B. Data from these 2 field experiments and previous micronutrient field studies, where yield response to B fertilization was obtained when leaf B was 9 to 10 ppm in soybean leaves, suggest that plant tissue analyses for B can be used to evaluate B fertilization needs. Soil tests may not be useful for detecting B deficiency in coarse‐textured soils, but may aid in detection of areas where B levels are high. |
