Micronutrient Knowledge Base

Soybean ( Glycine max) is one of the most important legume crops which fix atmospheric nitrogen in symbiotic association with bacteria through nodules. A study was conducted to investigate the effect of molybdenum and pre-inoculation of Rhizobium on biological nitrogen fixation and yield of soybean under drip irrigation system. A total of six treatments were used in this experiment which included control, 1 kg of Mo/ha, 1.5 kg of Mo/ha, 10 kg of Mo/ha, Rhizobium isolate UPMR020, UPMR020 + 1 kg of Mo/ha, UPMR020 + 1.5 kg of Mo/ha, UPMR020 + 10 kg of Mo/ha. Application of 1kg of Mo/ha along with bacterial inoculum produced the highest (51) nodules per plant. This treatment also produced the highest nodule's weight (199 mg/plant) and plant dry weight (72 g/ plant). Application of 1 kg of Mo/ha in association of UPMR020, produced significantly high yield (29.46 g/plant) compared to control which produced only 9.15 g/plant, thus indicating the potential of this treatment to be used for soybean with drip irrigation system. Key words: Glycine max, Growth, Molybdenum, Nodulation, Rhizobium, Yields

Micronutrients are essential plant nutrients that are found in trace amounts in tissue but play an imperative role in plant growth and development. Without these nutrients, plant nutrition would be compromised leading to potential declines in plant productivity. Of the 17 elements essential for plant growth, eight are micronutrients: boron (B), chlorine (CI), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn) and nickel (Ni). There is increasing interest from the agricultural community in micronutrient fertilization for a variety of reasons, including: soil erosion and long-term cropping have resulted in the removal of micronutrients from soils; increasing crop yields generally leads to greater micronutrient removal rates in grain and other harvested products; and the widespread replacement of micronutrient-rich manures with mineral fertilizers has reduced micronutrient addition from fertilizer sources. Collectively, these factors have led farmers to question whether micronutrient fertilization may now be required to meet the changing demands of crop nutrition. The Tri-State Fertilizer Recommendations state that, in general, soils in Michigan, Indiana, and Ohio have adequate amounts of micronutrients to support crop growth. The only reported micronutrient deficiencies in this region have been with B, Cu, Mn, and Zn. These deficiencies can cause plant abnormalities, reduced growth, and sometimes yield losses. The conditions under which micronutrient deficiencies are most likely to occur have been identified for the Tri-State region.

Boron is an essential micronutrient for plants, but too much boron is toxic to plants. Both boron deficiency and toxicity in soil significantly affect agricultural productivity worldwide. Boron plays crucial roles in developmental processes that influence yield traits in crops, partly because it is essential for maintaining cell wall integrity (Matthes et al. 2020). Although the mechanisms of boron uptake, transport, and utilization are well-characterized (Yoshinari and Takano 2017), the regulation of boron homeostasis in plants remains poorly understood. Unraveling how plants manage cellular boron levels and adapt to both deficiency and toxicity is essential for improving crop productivity and resilience under suboptimal boron conditions.