Urea Stabilization

Urea is the most widely used nitrogen source in Australia, accounting for some 80% of all nitrogen sales. Costing less than one cent per percentage point of nitrogen (on a per kg basis), this 46% farmers' favourite is regarded as more cost-effective than all other competitors, with the exception of anhydrous knifing in broadacre. However, even in the cost-conscious broadacre arena, the granular / liquid versatility of urea is often preferred when factoring in the inconvenience of the anhydrous tank. There are of course other considerations in the urea / anhydrous comparison. Anhydrous ammonia is a harsh soil-life killer, which would never be used if the biological impact were fully understood by the landowner. However, from a plant health and environmental perspective, there are also concerns relating to the instability and overapplication of urea.

Urea cannot be retained in the soil by the soil's two storage systems - the clay colloid and the humus colloid. As a result, the high nitrogen content floods the soil solution and the plant takes up nitrates with its 'drinking water', whether or not they are actually required. Nitrate overload is a serious problem in modern horticulture, and the end product of this excess is a poor-quality plant, which is more susceptible to insect and disease attack. The consumer is the big loser in this scenario, as excess nitrates in food are a proven carcinogen. The environment is the other loser. Urea is notoriously unstable. It is generally accepted that only 28 of the 46 nitrogen units in urea ever reach their mark. The remaining 40% of the product is oxidised or ends up polluting our waterways. Humic acid is the key to the stabilisation of urea.

Humic acid is also a colloidal material, but unlike the clay or humus colloids in the soil, the humate colloid can actually store urea. In fact, with a CEC of 450, humic acid can stabilise urea to the extent that virtually all of the 46 units of N are retained for plant utilisation, and even several inches of rainfall cannot budge the nitrogen from the humate colloid. This stabilising effect is only possible if humic acid is combined with urea prior to application or, alternatively, if soluble humic acid granules are combined with granulated urea to bond as they dissolve. If urea and humic acid are not applied together, then other nutrients can crowd the humate storehouse and reduce the nitrogen storage potential.

This stabilisation is a valuable gain, but there is another benefit associated with the fusion of urea and humic acid. There is no longer the force-feeding aspect involved in urea fertilising, when the plant can feed from the humate storehouse when and if nitrogen is needed. Nitrate overload is avoided and a healthier, more resistant plant is the result.