## 3 Results  
### Greenhouse Experiment, Yield and N Uptake  
The results of the greenhouse experiment showed no significant effect of replacing CAN with AS on the dry matter yield of grass, except for in the 75% N dosage, where yield losses of 11.5% on sand and 13.7% on clay were observed compared to the 100% treatment (Figure 1 top). For the crop N uptake of the grass, the fertilizers showed a significant interaction effect with the soil, which can be seen in the 50% treatment on clay from the LSD groupings (Figure 2 top), though fertilizer alone was not significant. These results imply there may be a small effect on the dry matter yield of grass, but there is no evidence for reduced quality at the higher N dose.  
Figure 1: Total dry weight of the crop harvest of the ammonium sulfate (AS) (green) and calcium ammonium nitrate (CAN) treatments (orange) for two soils (clay and sand), two crops (grass and maize) and different levels of N dosages. The letters indicate groupings of the treatments determined by the least squares difference (LSD): two treatments with the same letter are not significantly different from each other. Grass and maize were analyzed separately and only 50% and 75% of the treatments were included in the statistical tests. LSD is 10.61 g pot\({}^{-1}\) for grass and 4.71 g pot\({}^{-1}\) for maize.  
The dry matter yield of maize showed no significant effect of fertilizer (Figure 1 bottom), but crop N uptake had a significant effect from fertilizer and the interaction of soil and fertilizer (Figure 2 bottom). This particularly affected the 75% dosage of maize on clay soil (Figure 2 left). This implies that the quality of maize might be slightly reduced by the use of AS, but there is no evidence for this affecting the dry yield.  
Figure 3 shows the NFRV results and significance test (a sign test of values combining the 75% and 50% treatments, but the crop-soil combinations were tested separately). The NFRV of AS was only significantly different from CAN for maize on clay, where it was 0.75 for the 50% dose and 0.84 for the 75% dose (standard deviations of 0.17 and 0.92, respectively). This is supported by similar results from the linear models, where the fertilizer showed an effect on maize N uptake, especially on clay soil.  
The remaining amounts of mineral N in the soil at the end of both the grass and maize greenhouse experiments were very low, near or below the detection limit of 0.9 mg of N kg\({}^{-1}\)). This leads to the conclusion that all available N was fully utilized for plant growth or lost via gaseous emissions after fertilization. The possibility of gaseous losses is further examined in Sections 3.2-3.4 on environmental monitoring campaigns.  
Figure 2: Total N uptake of the crop harvest of the ammonium sulfate (AS) (green) and calcium ammonium nitrate (CAN) treatments (orange) for two soils (clay and sand), two crops (grass and maize) and different levels of N dosages. The letters indicate groupings of the treatments determined by the LSD test: two treatments with the same letter are not significantly different from each other. Grass and maize were analyzed separately and only 50% and 75% of treatments were included in statistical tests. LSD is 0.02 g pot\({}^{-1}\) for grass and 0.31 g pot\({}^{-1}\) for maize.