The results show that the timing of nitrogen fertilization has a significant influence on the growth of the lateral shoots and thus on the cone yield. The later the N-fertilization, the further up the lateral shoot growth shifted. At a certain point in time, when N-fertilization was too late, an overall reduction in lateral shoot lengths was the result, which, in turn, can have a negative effect on come yield.
4.7
Investigation of uptake rate and distribution of nitrogen (15N) applied via fertigation
Team:
M. Waldinger (Master Thesis), J. Stampfl
Collaboration:
Prof. Dr. U. Schmidhalter, Lehrstuhl für Pflanzenernährung, Wissenschaftszentrum Weihenstephan, TU München (Chair of Plant Nutrition, Science Center, Weihenstephan, Munich Technical University)
Duration:
May 2019 to October 2019
Background and objectives of the project In many plants, including hops, nitrogen (N) is the most yield-limiting nutrient. Within the current, increasingly restrictive legal framework, it is particularly important that the right amount of nitrogen is available to the plant at the right time. In this context, nitrogen administered in excess, as well as nitrogen not taken up by the plant, can be equally problematic. In the research project "Improving the nutrient efficiency in hops through fertilization systems with fertigation," various fertilization systems were tested in extensive field trials between 2017 and 2019. To be able to draw conclusions about the uptake, distribution, and storage of nitrogen, field tests with the nitrogen isotope 15N and its corresponding 15N-Tracer-Method were conducted for this master thesis. Method The investigations were conducted in 2019 at two locations with sandy loam. The varieties were Perle and Herkules. Figure 4.19 shows the fertilization regimen for the Perle location; Figure 4.20, the one for the Herkules location. At both locations, controls without N-fertilization (A) served as references, as did a plot fertilized with three equal rounds of granulated fertilizer (B). For the fertigated plants (C to F), one-third of the fertilizer requirement was administered in the form of granulated fertilizer and two-thirds via irrigation. The fertigated plants had different start dates for their 6-week fertigation period.
44
