Effect of N fertilizers on yield, N-uptake, and N-utilization in wheat, barley, potatoes, and maize.

The effect of six N fertilizer forms (calcium ammonium nitrate, urea, calcium cyanamide, ammonium nitrate sulfate, urea ammonium nitrate, and ammonium sulfate + nitrification inhibitor including at two fertilization levels and including a zero N control treatment) on N uptake and N-use efficiency of barley, wheat, and potato (maize) has been investigated in the Dürnast long-term trial since 1979. Yield (grain, tuber, cereal straw) and N-content were determined at the end of the season, whereas biomass and N content and soil parameters were occasionally determined during the growing season. Since 2015 the soil water content was further assessed in nine plots (control and calcium ammonium nitrate treatments). The study area is approximately 0.31 ha in size (6 replicates and 8 replicates until 2006), located 30 km north of Munich, Germany (4477221.13 E, 5362908.78N) in the Tertiary landscape. The average annual temperature is 7.8◦C, and the average annual precipitation is 810 mm (1971–2000). The dominant soil material is Tertiary sediments with deposits of Pleistocene loess. The composition of the soil is a consequence of loess deposition and subsequent erosion. According to the German Soil Survey (Arbeitsgruppe Bodenkunde, 1994), fine loamy Typic Udifluvent and fine-silty Dystric Eutrochrept are the dominant soil types.