PIAGRAN® 46 - Principle of action

PIAGRAN® 46 is readily soluble in water, is free of ballast materials and does not leave any residues in the soil.

From the plant cultivation point of view, urea is said to have a slow N effect. However, conversion into the ammonium N form that can be immediately assimulated by plants is very fast. According to AMBERGER and VILSMEIER (1980), this process takes 4 days at a soil temperature of 2 °C and only 2 days at a soil temperature of 10 °C. The ammonium-biased plant nutrition that commences immediately after dressing (FUCHS, 2000) means that crops fertilised with urea do not react with an immediate colour change as is the case for a nitrate-biased fertiliser.

On the one hand, they only take up the amount of nitrogen required for plant nutrition via an exchange process (sorption of the ammonia on clay minerals). On the other hand, ammonia is directly assimulated into protein compounds in the plant.

In contrast, after application of the fertiliser, nitrate is often taken up in excess to that required (luxury consumption) and it can then only be assimulated into protein compounds after an energy-intensive nitrate reduction. This high energy demand triggers increased formation of chlorophyll and the associated colour change.

The stepwise conversion of the ammonia nitrogen to nitrate, which also takes place subsequently with urea fertilisers, not only gives rise to a very well-balanced fertilising effect but, at the same time, it also decreases the risk of loss. If applied in early spring, urea has a doubly reliable effect because the conversion rate to nitrate is retarded at lower temperatures (according to AMBERGER and VILSMEIER, 50% in 6 weeks at 5°C, in 1 week at 20°C), so that the plants can obtain sufficient ammonium N and the nitrogen cannot be leached out as nitrate.

High N efficiency

The same fertilising effect of urea compared to calcium carbonate/ammonium nitrate mixtures, as determined by a number of agricultural research stations, is due to adequate provision of N to the plants. N losses under outdoor field conditions are also approximately the same. The latest studies by the Technical University of Munich (WEBER et al., 2000) using the most modern measuring methods over a 3-year period show only slight and almost equal ammonia losses of N under practical conditions. Only under extremely high temperatures and drought (mean daily temp. >15° C/, little or no precipitation) were the NH3 losses from urea-based fertilisers (winter wheat, 80 kg/ha N) were 3 kg/ha higher than those from calcium carbonate/ammonium nitrate mixtures. If the approx. two-fold increase in the N2O-N losses from ammonium nitrate compared to urea (MOSIER et al. 1993, EICHNER 1990) and the larger nitrate migration potential of a nitrate fertiliser are taken into consideration, the total N losses from the mineral fertiliser are comparatively low and are approximately the same for the various N forms.

Application recommendations

Optimum conditions for fertilisation with urea are not an exception, but are generally the rule. PIAGRAN® 46 exhibits a very good effect on the yield for almost all soils, temperatures and moisture conditions. Only in very light soils (soil quality index of less than 30), in soils with pH values greater than 7.5 and in the case of extreme drought should PIAGRAN® 46 be used preferentially as a topsoil fertiliser, whereby it should be lightly worked into the soil before sowing. On grassland, urea should be used in preference for the first dose owing to the extremely high biological activity and the lack of contact to the absorbing particles in the soil or in the case of damp conditions (overhead irrigation or subsequent precipitation).