Iron and manganese are essential trace minerals for plant resilience. The plant uses these minerals for many of the compounds it creates to defend itself against marauding microbes and insects. The iron to manganese ratio is the last of our six soil secrets. The goal here is to always ensure that your soil contains more parts per million (ppm) of iron than manganese. However, this ratio should never exceed 2 parts of iron to one part of manganese, or you may induce a manganese deficiency. Iron and manganese are antagonistic to each other when oversupplied, so a manganese excess can also induce an iron deficiency. The key is to achieve the desirable balance, where there is more iron than manganese, but never more than 2:1. If we were to be less specific, the most important thing here is to just make sure that iron is higher than manganese at all times.

Note: It is not always certain that a poor balance of these minerals in the soil will negatively impact the uptake of either, because various factors including soil type, environmental conditions and organic matter levels can also be involved. This caution is actually applicable to all of the six ratios and that is why we always suggest the use of leaf analyses to confirm a potential problem. 

If you can work toward improving these ratios and monitor your success with regular soil testing, the benefits will flow. Your soil will breathe better, biology will work better and resilience, nutrient uptake, production and profitability will increase. If you can not tick off improvements in at least three of these ratios each year, then you might need to seek a new consultant or improve your own knowledge of mineral balance requirements.