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Introduction
A good management of nutrients in agriculture is crucial for adequate plant growth and development, but a major problem is low nutritional efficiency. A large amount of the nutrients, especially nitrogen, is lost into the atmosphere or enters ground- and surface waters unused causing major harm to ecosystems. Many farms in Germany and generally in Europe raise live-stock or produce biogas - which are both a source of fertilizer as a byproduct. Mineral fertilizers, animal manures, legumes and biogas slurries are the most common sources of nitrogen addition to soils. In agricultural practice, fertilizers are commonly used in combination, including both organic and mineral types, because most of the total nitrogen in organic fertilizers is in the organic form and it is not directly plant available.
The aim of this study was to evaluate the effect of different organic-mineral fertilizing strategies on nitrogen use efficiency and yields at a sandy soil.
Material and methods
The fertilizers were evaluated in pot experiment (completely randomized system) as a nutrient source for silage maize plants. The trial consisted of five treatments (four organic and one mineral): unseparated biogas digestate (UBD), separated solid extracted from the digestate using screw-press separators (SSBD), separated liquid biogas digestate (SLBD), Farmyard Manure (FYM) and mineral fertilizer – calcium ammonium nitrate (CAN) i.e., control without any fertilization (CTRL). Each Mitscherlich pot (diameter 20 cm, height 21 cm, capacity 6,2 l) is filled with 6 kg of sieved, sandy soil. There were four repetitions per treatment with the same total amount of nitrogen applied (expect the CTRL). After sowing and in the initial phases of plant growth, the irrigation ratio was set at 50 % of the maximum water holding capacity. The ratio was later increased to 80 %. The SPAD - 502 meter is used for measuring the chlorophyll content in the leaves, as it is related to the nitrogen status of the plant. Thirty random measurements are taken per pot in total - three times in August 2022.
At the end of the season, 97 days after sowing, the plants from each pot were harvested and weighed for their fresh mass. The samples of harvested material were grinded and collected in bags with small air holes. After weighing the fresh mass, the samples for analysis were dried for 48 hours at 60 °C and then analysed for the nitrogen content by Dumas method.
Results and Discussion
The more nitrogen absorbed by the plants, the higher the chlorophyll concentration was. The results indicate a significant increase in chlorophyll content early in the month of August 2022 for CAN, which remained sustained at an elevated level. This resulted in prolonged vegetation and a lengthened period of greenery. Further, the application of SLBD and SSBD treatment resulted in a higher starting level of chlorophyll content when compared to FYM and UBD treatment, implying that the type of fertilizer utilized has a notable impact on plant growth and chlorophyll content. The Tukey Test is utilized in the significant analysis of variance (ANOVA) for assessing whether differences exist between the means of groups with regard to the yields obtained in the pots. According to the results obtained, statistically significant differences were found among the control, manure, and mineral treatments. In conclusion, a high nutrient efficiency is a result of synchronizing nitrogen supply according to the demand. This can be reached with mineral and organic fertilizers but might further be influenced by factors not considered in the experiment – like timing and weather.
References
Fageria N.K., Baligar V.C. (2005) Enhancing Nitrogen Use Efficiency in Crop. Plants Advances in Agronomy, Academic Press, Vol. 88, pp. 97-185, ISSN 0065-2113, ISBN 9780120007868, https://doi.org/10.1016/S0065-2113(05)88004-6.
Nielsen, K., Roß, C. L., Hoffmann, M., Muskolus, A., Ellmer, F., & Kautz, T. (2020). The chemical composition of biogas digestates determines their effect on soil microbial activity. Agriculture, 10(6), 244.
Stevens C.J. (2019) Nitrogen in the environment. Science 08, Vol. 363, Issue 6427, pp. 578-580 DOI: 10.1126/science.aav8215.
| Keywords | nitrogen use efficiency (NUE); nutrient management; organic-mineral fertilizing strategies |
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