PIAGRAN® 46 is highly water soluble, fibre free and does not leave any soil residue.
Agronomically, urea is said to have a relatively slow nitrogen effect. However, conversion into readily available ammonium nitrogen occurs very quickly. According to AMBERGER & VILSMEIER (1980), this process takes up to four days at a soil temperature of 2 °C and just two days at a soil temperature of 10 °C. Applying ammonium-containing plant nutrients immediately following fertilisation (FUCHS, 2000) means that crops fertilised with urea do not immediately change colour, in contrast to crops fertilised with nitrate.
Plants only absorb as much nitrogen as required through the conversion process (sorption of nitrogen on clay minerals). Furthermore, plants directly use ammonium in the production of proteins.
On the other hand, following fertilisation, nitrate is absorbed in large, often excessive quantities (luxury consumption) and can only be used for protein production after the energy-intensive nitrate reduction process is complete. This high energy requirement results in increased chlorophyll production and a colour change.
Following urea fertilisation, the conversion process of ammonium nitrogen into nitrate results not only in a very balanced fertilisation effect, but also in a reduced risk of nutrient loss. When used in early spring, urea provides a double layer of protection since the speed of conversion to nitrate (according to AMBERGER & VILSMEIER 50% in 6 weeks at 5 °C and in 1 week at 20 °C) is slowed at lower temperatures, crops are supplied with optimal rates of ammonium nitrogen and the nitrogen cannot be washed out as nitrate.
In a number of tests, it has been shown that urea has the same fertilising effect as CAN. This results from an adequate nitrogen supply for the plants. Nitrogen loss in open fields is almost the same. The latest trials of the Technical University of Munich (WEBER et al., 2000) with modern measuring techniques over a three-year period show only limited and almost the same rate of ammonia loss in nitrogen forms under practice-oriented conditions. Urea fertilisation (winter wheat, 80 kg/ha N) only showed a higher loss of ammonia (3kg/ha more) than CAN in extremely high temperatures and during dry periods (Daily average temperature. >15 °C, little to no precipitation). Taking into account that the rate of N²O nitrogen loss from ammonium nitrate is twice the loss from urea (MOSIER et al. 1993, EICHNER 1990) and considering the larger nitrate shift potential of nitrate fertiliser, the total nitrogen loss rate of mineral fertiliser is comparatively low and relatively similar among the various forms of nitrogen.
Optimal conditions for urea fertilisation are more of an everyday occurrence than an exceptional event. In almost every soil, temperature and humidity conditions, PIAGRAN® is highly effective. Only in very light soil (soil value below 30), in soil with a pH value above 7.5 and in extremely dry conditions should PIAGRAN® 46 granule fertiliser be used on the top soil. A little working in before sowing is recommended. Due to an extremely high level of bioactivity and a lack of contact with sorbent particles of the soil, urea should be used on grasslands preferably in the first instance or under humid conditions (with watering or precipitation following).