Speakers
Description
Understanding agricultural processes and their interaction with the environment is essential to improve agricultural practices in regards to climatic changes. In particular the management of soil water needs to be optimized to improve the crop resilience against extreme weather events and to obtain stable yield levels (Gaona et al., 2022). The most fertile soils in Germany occur in areas with Chernozem soils, which provide high availability of essential nutrients like nitrogen and optimal hydraulic conditions. This is to achieve high yields for the cultivation of cereal crops (Altermann et al., 2005). However, these areas tend to get dryer, which is why this study aims to identify phenological phases crucial for the yields of winter wheat and winter barley in their dependency to the available soil water.
The experiment was conducted at the test site in Bad Lauchstädt (51°24’N, 11°53’ E; 118 m.a.s.l.) with a mean temperature of 10.66°C and annual mean precipitation of 425 mm from 2013 until 2022 (difference of -58 mm to mean precipitation for the period 1896 - 2019) on loess soils enriched with carbonates. The plots of 20x22 m were set up with a three annual crop rotation of rape seed, winter wheat and winter barley as a typical regional crop rotation with crop residues returned. As part of the experiment, this study compares the dependency of cereal yields to the soil water available for the four management systems set up:
(i) conventional tillage with plow (P1) with a standard rate of N-fertilizer according to professional practices (N1),
(ii) conventional tillage with plow (P1) with half of the standard rate of N-fertilizer (N0),
(iii) conservational tillage practice (P0) with a standard rate of N-fertilizer according to professional practices (N1),
(iiii) conservational tillage practice (P0) with half of the standard rate of N-fertilizer (N0).
To understand the complex dynamics of yield development for agricultural crops and the interaction of environmental factors such as soil and weather with agronomic practices, agricultural models are useful tools to model these interactions. Modelling the soil water dynamics helps to reduce the error of the soil water observations as well as to generate complete datasets for specific depths without gaps. Therefore, the agricultural soil model CANDY (Carbon and Nitrogen Dynamics) was used to model the soil water and nitrogen dynamics in depth of 0-30, 0-60, 0-100 and 0-180 cm. To improve the model performances, adjustments to the soil physical conditions (field capacity and saturated water conductivity) done with observations of the soil water dynamics at depths of 10 cm, 45 cm, 100 cm and 180cm during the period of 2013 to 2022. To evaluate the impacts of soil water on grain yield of cereal crops, the amount of water for every phenological phase were accumulated based on plant specific BBCH values and has been set in relation to the yield observations with simple linear models.
The results show that the water availability during the flowering and fruit development have the strongest impact on the yield development of the cereals (Figure 1). Positive correlations were observed within all treatments except the P0N0 treatment. Low fertilization and conservational tillage show the lowest relationship for water availability during the phenological sensitive phase.
Moreover, the soil water availability during phenological phases until the fruit development had an increased impact on the yield. In our case, the greatest effect is observed for the phases heading, fruit development as well as fruit development. Furthermore, both N1 plots showed the highest correlation (R2) during the flowering phase with values up to 0.57. As a consequence, the soil water available during this phase plays an important role for the nitrogen uptake of crops.
The results also, revealed a low influence between soil water and crop yield with in the first phenological phases. However, soil water showed a positive correlation with increased influences in progressed phenological phases.
Figure 1 Caption: (A) Grain yield dependency (correlation coefficient, R) to the available soil water during phenological phases (Leaf development, tillering, stem elongation, heading, flowering, fruit development, ripening) for different nitrogen and tillage treatments for layers of various depths. (B) Strength (coefficient of determination, R²) of the grain yield dependency to the available soil water during phenological phases
| Keywords | soil water; cereal yields; modeling |
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