If you have ever wondered what really goes on after you apply urea, you are not alone. We’ve put together a simple diagram to show the two main routes urea can take once it is out of the fertiliser shed either sprayed as a foliar application or spread as granular urea. The science is fascinating (and useful), but the end story is all about speed, waste, and looking after your soil.
Why Compare the Two Pathways?
Knowing how urea travels through your pasture matters if you want to get the best bang for your buck. Many have seen foliar-applied urea give crops a fast green-up and a kick into gear, while soil-applied urea is slower, sometimes feels “wasted”, and can drop your soil’s pH. There is solid science under these differences:
Granular Urea – Soil Applied The Long Way Round
Spreading solid urea kicks off a longer process. The urea is first broken down by soil microbes to ammonia, then quickly changes to ammonium. From there, different soil bacteria change it into nitrite, then nitrate. Plants mainly absorb ammonium and nitrate, but every stage offers chances for urea to be lost through leaching, runoff or conversion to gas. Rain can wash nitrate deep into the soil, while wet soils can turn it into nitrogen gas, either way, these are losses paid for but not utilised. Sometimes granular urea can be a more practical application method when conditions are too wet, or windy to spray, but the losses are still high.
Foliar Urea Application Direct and Fast
When dissolved urea is sprayed onto leaves, the plants quickly absorb it through small pores called stomata. Once inside, the plant’s enzymes break it down to ammonia, and this is almost immediately fixed into amino acids like glutamine and glutamate. Because the process barely involves the soil, there is little loss on the way, and plants can use the urea almost straight away for growth and repair.
Why do long term urea applications increase soil acidity?
The biggie for long-term soil health is acidification. The main problem appears when ammonium becomes nitrate. That stage pumps hydrogen ions into the soil, bit by bit tipping the balance toward more acidic ground. This is one reason why paddocks with regular high urea use often end up needing more lime/gypsum or dolomite.
Foliar urea gives you speed and less losses = more growth for less cost. It is efficient for a rapid result or mid-season boost. Granular urea is reliable for bulk feeding but brings more risk of wastage and can acidify your soil if used too heavily or too often. What ever method you use, apply them both wisely, converting your nutrient input programme to a foliar focused plan will allow you to better manage your pH, trace elements, can help get the most out of every tonne and keep your soils healthy for the long haul.
The Tow and Fert’s ability to suspend lime flour and micronised gypsum means you’re able to offset any pH shift caused by your urea applications at the same time as applying fertiliser, all in one pass so you don’t need a sprayer and a spreader.
The team here at Tow and Fert can help you start that journey and connect you with the right support to ensure you’re getting the right advice. Just reach out here.