Cobalt is an under valued and under used nutrient. If you are not managing cobalt, it is costing you yield and storability. It is likely costing a lot of yield.
When plants contain adequate levels of cobalt ethylene production is inhibited(1). This is a really big deal. You may not know about the many effects of ethylene in influencing growth, node elongation, and speeding up senescence. Here is a story, and short list of some of the impacts cobalt has.
When we worked with an organic green bean grower, in the first season, yields increased from a prior four year average of 3.7 tons per acre, to over 10 tons per acre. Almost a 3x yield increase. While all the other nutrients also had to be managed well, (and were, using plant sap analysis) I attribute much of the yield increase to managing cobalt.
Green beans set flowers over an extended period, but are usually concentrated into different ‘sets’. It is common for processing green beans to only have the first and second set be in the optimal size range when harvested. The third set is still too small, but if harvest is delayed until the third set is large enough, the first set is too mature with the seeds beginning to swell.
Seeds mature faster in response to ethylene. When we supplied this crop with cobalt, it delayed seed maturity on the first set, and permitted the harvest of the first, second, and third set, all being in the appropriate size range at once.
Ethylene increases node length. When you have adequate cobalt, nodes will be much shorter. This means plants are short, stocky, and sturdy, have more nodes per inch of crop height, and can carry the heavy crop load.
Ethylene decreases the number of flowers/buds/fruit. When you have adequate cobalt, there are more flowers set per node, and higher fruit count. On soybeans, you can have as high as 10-12 pods per node (or higher) instead of only 2-3.
These are three significant contributing factor to increasing yields 3x.
When we store fruit for extended periods, such as apples, one of the challenges with degrading fruit quality while in storage is because of continued senescence and ethylene production. This can be inhibited with cobalt, which will improve storability. Any fruit or vegetable which gets stored or shipped will find its shelf life improved when it has adequate cobalt.
Cobalt is needed as an enzyme cofactor by rhizobium bacteria for nitrogen fixation. Many legumes fix only a fraction of the nitrogen they are capable of, because they lack adequate cobalt.
Cobalt is one of those elements that exist in the soil in different oxidation states. Plants use only the reduced form, and the reduced form is in very limited supply because of historical exposure to glyphosate and other management practices on most agricultural soils. Because of this, we often apply to the plant in the early stages of regenerating a soil system.
Cobalt is considered an essential plant nutrient. Why don’t we begin managing it as though it were as important as nitrogen?