Browsing by Subject "Mineralization"

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Rahmenbedingungen für eine vereinfachte „gabenreduzierte“ N-Düngung zu Winterweizen (Triticum aestivum L.)
(2018) Makary, Thomas; Müller, Torsten
The split N-fertilization with CAN in three or four doses was considered a measure to improve the nitrogen supply of winter wheat in the past and still is considered a guarantor for good yield and quality. The split N-fertilization with CAN is also recommended to synchronize and harmonize N-demand of the plants as well as soil N-content. The aim of the current study was to analyze simplified (reduced number of N-servings) CAN strategies to winter wheat and the necessity of split nitrogen servings in order to achieve yield and quality aims. This interest was occasioned by impressive results of experiments on farmers’ fields using simplified N- strategies with CAN. Simplified CAN fertilization strategies are able to produce high grain yield and protein contents with winter wheat when the N-supply is ensured. Therefore, the common split N-servings with CAN are not necessary. Simplified strategies with UAN seem to be possible, but this requires further research on application techniques to reduce NH3 losses. Simplified CAN fertilization strategies were tested based on modern wheat varieties and the high plasticity in the development of the yield compounds. Modern wheat varieties show low harvest-indices which is important to reduce the risk of lodging. Furthermore, these varieties are able to overcome omitted N-servings through remobilization of N in the plants. Suboptimal conditions during the development within one important growing stage can be compensated during later growing stages when the growing conditions are better. These properties in combination with a late first application (BBCH 29/31) of N turned out to be the “gold standard” in our experiments. Reduction processes during the tillering (BBCH 25/27) period when N is applied confirm these findings. In addition, the application date for the heading stages (BBCH 49/51) when temperatures are high and conditions very dry have to be considered. Simplified N-fertilization systems can also be applied on Luvisols if the soils are not long-term fertilized by liquid manure. The positive soil characteristics of these soils and the high soil-borne fertility support the approach with simplified CAN strategies. In this situation, N-leaching into deeper soil layers is not likely as high precipitation rates in a short time would be necessary to cause this. In fact, a long term liquid manure application with high rates is not necessary when simplified CAN treatments are applied. Moreover, high N amounts in soils caused by long term liquid manure applications are a risk for N-losses and environmental pollution. Notwithstanding the above, organic fertilizers like liquid manure show positive effects on the soil chemistry and the physical properties of the soil. It is important to apply a system to better include the N fertilization effect of liquid manure during the vegetation period. Additionally, simplified CAN fertilization reduces the work effort on the farms. Currently, especially for livestock farms, which rely on N-fertilization, simplified CAN treatments are a good alternative to the common practice. Whereupon on shallow or sandy soils the approach with simplified CAN treatments should be restricted since these soils mostly show low water holding capacities and high percolate water rates. Under suboptimal growing conditions with high precipitation rates simplified CAN treatments can be a risk for the environment and the groundwater. Apart from that, the volatile weather conditions are the most important factor for yield and quality outcome. Mild conditions during the early winter lead to prolonged growing of the plants. In spring the number of tillers per m-2 is already determinated. Therefore, a combination of N doses at the beginning of the growing season in order to promote the number of tillers doesn´t yield the aimed results. The properties of modern wheat cultivars, tested soils, weather conditions and constraints of simplified CAN treatments show the complexity of N fertilization of winter wheat. Standard measures like the common split CAN fertilization are neither wrong nor ideal to create high yield and protein contents with a minimum of input. The most important items for a successful wheat production are high knowledge and attention levels for the plants and growing conditions. Combining the fertilizer requirement calculation and the knowledge on the field yield potential, the yield and quality of winter wheat can be optimized with a minimum of input.