As a farmer or grower, you apply fertiliser because you can’t afford not to. So, finding ways of getting that fertiliser to work more efficiently makes economic sense.
Recent field trials in Southland NZ (2014 - 2018) found that adding humates to urea applications increased pasture production by 9.8% more than adding urea alone. And since it’s not a complicated or costly process to add the humates, this would seem to be a worthwhile strategy if nutrient efficiency is a goal.
What are humates?
Humates are a type of organic matter formed from the dead tissues of plants and animals. They are natural, organic compounds. Their main elements are carbon, hydrogen, nitrogen, and oxygen, although they are complex and vary greatly in their chemical structure.
Humates and humic substances are widespread, the best sources being soil, compost, manure, peat and coal deposits like lignite. Apart from their use in agriculture, humates are also important to the pharmaceutical and biomedical industries.
According to MPI’s criteria, humates are fertiliser additives rather than actual fertiliser since they don’t directly provide plants with specific nutrients like nitrogen, phosphorus, and potassium.
However, humate compounds are generally categorised into 3 groups: fulvic acid, humic acid, and humin. There is now a large body of research describing how humates benefit soil health, soil structure, and plant growth.
Adding humates to nitrogen fertiliser can increase nutrient efficiency and reduce nutrient wastage.
Benefits to soil structure
As far back as 1965, scientists were claiming that humates were “nature’s soil conditioners par excellence”. More recent studies show that improvements in water holding capacity, soil pororsity, and aeration do indeed occur, especially where humates are added to less fertile soils or soils tired from constant cropping.
High CEC
Humic substances and humates typically have a high CEC (cation exchange capacity) value. In other words, they have the ability to store or retain plant nutrients.
Having a high CEC apparently allows humates to bind with toxic metals like aluminium, which can be a troublesome element in NZ soils. And some scientists state that humates are capable of binding with pesticides and herbicides too.
Increased microbes
In earlier studies, microbial populations were believed to increase with the addition of humates, both in size and diversity. New DNA technology is enabling scientists to verify that this is so. For example, the recent trials in Southland NZ mentioned above found that a wider variety of fungi were present after the application of humates. The researchers also found that this diversity correlated to an increase in pasture production.
Increased nutrient uptake
Many other studies have found that humic acid increases plant growth and in particular, plant root formation where most nutrient uptake occurs.
The Southland study suggested that nutrient uptake increased when humate was added to urea because plant root hairs were more developed and able to absorb more nutrients.
There was also the idea that due to the humic acid, the plants increased their root secretions to stimulate their rhizobial fungi. The fungi in turn increased the availability of plant nutrients, allowing the plants to take them up in greater quantities.
Humates are worthwhile
While we’ve known about humates for a long time, and known that these compounds are great for soil and plant health, the research hasn’t always been conclusive in regards to their benefits as a fertiliser additive. However, with milestone projects like the recent field trials in Southland, we can now be more confident that adding humates to fertiliser like urea is a worthwhile thing to do.
This article was published in the Coast & Country News.
