Maize Topdressing: Comparative Advantage Of Urea vs Calcium Ammonium Nitrate (CAN)
In recent years there has been a trend among maize growers to top dress with Calcium Ammonium Nitrate (CAN) fertilizer in preference to Urea. The lower volatilization risk in dry soils and the perceived neutral effect on soil acidity has encouraged the trend, along with the subsidized price through NCPB.
Urea vs Calcium Ammonium Nitrate (CAN)
But how accurate are these claims, and what is the best value approach for your crop?
Calcium Ammonium Nitrate (CAN) contains 28% nitrogen typically, and is rapidly and efficiently taken up by plants. The Nitrogen content is far lower than Urea however which contains 46% nitrogen, so the actual cost per Kg of Nitrogen is more expensive:
- CAN – Sh 1,900 per bag (14kg of N in a bag) = Sh 135 per Kg of Nitrogen
- Urea – Sh 1,900 per bag (23kg of N in a bag) = Sh 82 per Kg of Nitrogen
We can see here that the Nitrogen in Calcium Ammonium Nitrate (CAN) costs 65% more than Urea because it is less concentrated. So even if some N is lost after applying Urea, it is still far less expensive than CAN. Applied in the right conditions to moist soils, losses are very small. In most soils the acidifying effect of Urea is minimal, and the Calcium in CAN is not in a form that is particularly available.
Maize can easily achieve 9 t/ha (40 bags per acre) with the right agronomy and adequate moisture, but it does require adequate nutrition to achieve this. The amount of fertilizer required is best calculated by multiplying the target yield in tons per hectare, by 20-25 Kg. For a 30 bag per acre crop this is 160 Kg of Nitrogen.
Timing is final part of getting fertilizer right; DAP or a compound fertilizer at planting forms a good base for crop emergence, with the balance applied as Urea as a top dressing. Soil Mineral Nitrogen testing can help too, by accounting for residual nitrogen in the soil profile.
And finally, top yields require accurate application. This can be discussed in detail with your CropNuts agronomy contact for independent agronomic advice.