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Chemical and Biological Technologies in Agriculture
Fig. 2 | Chemical and Biological Technologies in Agriculture

Fig. 2

From: The impact of the long-term application of mineral nitrogen and sewage sludge fertilizers on the quality of soil organic matter

Fig. 2

Trends in maize monoculture silage dry mass yields during the experiment. The red trend line is an average of all treatments. The horizontal axis represents 3-year periods starting with 1997–1999 (1) and ending with 2018–2020 (8). Con Unfertilized control; N120 Mineral fertilization (120 kg N ha−1); N240 Mineral fertilization (240 kg N ha−1); S120 Sewage sludge (120 kg N ha−1); S240 Sewage sludge (240 kg N ha−1) *only the unfertilized control treatment showed significantly low yields (Tukey HSD test; p < 0.05) during all periods, and differences among the fertilization treatments were not significant

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