Conventional urea loses a large proportion of its nitrogen before rubber trees can use it. Here is what controlled-release urea can change.

Conventional urea loses a large proportion of its nitrogen before rubber trees can use it. Here is what controlled-release urea can change.

Nitrogen is the most applied and most frequently wasted nutrient in Hevea brasiliensis plantations. In Malaysian conditions, a substantial share of the nitrogen in urea spread on the soil surface can be lost as ammonia in the first days after application, before significant root uptake has occurred. Leaching losses add to this under high rainfall. The result is a large gap between the nitrogen that appears on the fertiliser bag and the nitrogen that reaches the cambium layer where latex yield is built.

Why nitrogen loss in rubber plantations is high

Rubber is typically grown on acidic, highly weathered soils that are low in organic matter. In these conditions urea hydrolyses to ammonium within days of application in warm, moist soil, and the soil's cation exchange capacity is low, meaning ammonium ions formed by hydrolysis are poorly retained and prone to further loss. Surface application, which is standard practice in rubber due to the difficulty of incorporation under a mature canopy, maximises exposure to volatilisation.

The problem compounds over time. Rubber planted on exhausted soils from earlier cycles shows progressively lower nitrogen use efficiency as organic matter continues to decline. Without active soil organic matter management, each kilogram of nitrogen applied delivers diminishing agronomic returns.

What controlled-release urea is designed to do

Controlled-release and coated urea formulations release nitrogen gradually instead of all at once, so less of each application sits exposed to volatilisation and leaching in the days after spreading. Most of the published field research on controlled-release urea in rubber comes from China, and results depend on the coating, soil, rainfall and rate applied. Before switching a whole estate, compare the two products side by side on your own blocks over at least one full season, and judge them on yield and on the cost per kilogram of dry rubber, not on the price per bag.

How nitrogen demand changes with age

Immature rubber (years 1 to 7) has a high nitrogen demand for trunk girth development. Tapping-phase rubber (years 7 to 25) prioritises nitrogen for latex regeneration. The two phases have different optimal nitrogen rates and timing. A single standardised programme applied across both phases misses the opportunity to optimise at each stage. Using Mucuna bracteata or Pueraria javanica as interrow cover in immature rubber provides biological nitrogen fixation that partially substitutes for fertiliser nitrogen during the establishment phase, while SoilBoost EA, a humic acid soil conditioner, is used to support root-zone cation exchange capacity, which helps the soil hold more of the applied nitrogen against leaching.

Sulphur in rubber nutrition

Sulphur is a secondary nutrient in rubber that is often overlooked. It is required for amino acid synthesis and plays a direct role in the latex coagulation chemistry that determines processing quality. Sulphur deficiency is increasingly common in areas where atmospheric sulphur deposition has declined due to reduced industrial emissions. Where ammonium sulphate is used as a nitrogen source rather than urea, the sulphur requirement is simultaneously addressed. Seed Activator supports establishment-phase cover crop germination for interrow management during replanting cycles.