John Kempf

Cobalt to inhibit ethylene production, increase yields, and improve storability

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?

1. Lau, O. L. & Yang, S. F. Inhibition of ethylene production by cobaltous ion. Plant Physiol. 58, 114–117 (1976).

Using boron to speed up natural maturity and senescence

One of the characteristics boron is known for is to facilitate rapid nutrient transport to the sugar sinks. This effect can be very valuable to speed up crop maturity and senescence while also increasing harvest quality.

When an alfalfa crop is growing rapidly and still very vegetative in late fall as we approach winter dormancy it is possible to quickly trigger senescence and rapidly move the sugars contained in the plant down into the crown with a generous foliar application of boron. A treated section can turn brown within a few days to a week (depending on weather and time of year), as all the sugars move down into the crown and the plants begin to senesce. The following spring, the section treated with boron in the fall will emerge from winter dormancy much faster and with many more shoots than an untreated section, because the crowns have much more energy from the stored sugars. Any perennial crop with a similar growth pattern will show this effect.

This effect can also be used to speed up the natural maturity process of other crops. A generous foliar application of boron on fruit such as tomatoes or apples will speed up the natural sugar transport into the fruit. This can help the fruit color and mature quickly and evenly days to weeks earlier than plants without a generous supply of boron.

This effect of boron on speeding up maturity and natural ripening can also be used on small grains in place of a desiccant or harvesting aid. Wheat that receives a foliar application of boron can mature rapidly and dry down as much as five to ten days faster than plants without adequate boron. The upside is that there is often a gain in test wheat and protein content, since boron produces this effect by increasing photosynthate and protein transport into the grain rather than reducing transport to the grain as a desiccant might.

Boron does not produce these effects if the crop is not at the right stage of growth. It can only speed up the plant processes which are occurring naturally. Managed well, boron applications can speed up these natural processes dramatically, and produce a higher quality grain or fruit, with an improved nutritional content.

How much boron is required? It varies based on the existing boron content of the soil and the crop. Many crops and soils are deficient, which is why crops are not maturing well in the first place. Often, the upper end of label rates are required if this is the only application being applied in the season. It is better to supply the crops foundational boron requirements during the growing season, and then top off the requirements with a lighter application a few weeks before maturity to produce the optimal effects we are looking for.