Impact of different pre-crops on soil nitrogen and growth of following winter wheat

Winter wheat yields are varying by preceding crop as shown for certain preceding crops like wheat itself, winter oilseed rape or different legumes. However, there is hardly any published data on the pre-crop effect of other economically important crops such as sugar beet and silage maize. Further, the mechanisms of the pre-crop effect are partially unknown.

In this study, winter wheat was grown after wheat, winter oilseed rape, sugar beet and silage maize over two winter wheat growing periods (harvest years 2024 and 2025) in a long-term crop rotation trial in Central Germany. Soil mineral nitrogen (SMN) in 0-90 cm soil depth was analyzed at sowing in October, in December, January and February. After the last SMN sampling, plots were split into no (N0) and regular nitrogen fertilization (Nopt). At harvest, grain yield and straw biomass were recorded as well as nitrogen uptake.

Levels of SMN at sowing in October were clearly affected by pre-crop type with higher values after oilseed rape and lowest values after silage maize and sugar beet. In December, SMN levels were similar to October, while in January differences between the pre-crops became smaller and were mostly levelled by February. At N0, in both years, wheat grain yield as well as straw biomass was clearly highest after oilseed rape with up to 100 % more total biomass than after the other pre-crops. Other pre-crops had similar effects on total biomass. At Nopt, differences between the pre-crops were overall much lower, yet highest yields were found after oilseed rape.

December SMN levels correlated with grain yields at N0 over both years, while a similar correlation was even found under Nopt conditions in one of the study years. Thus, it appears nitrogen supply originating from pre-crops affects winter wheat growth. This might be one way pre-crops affect wheat growth beyond regulation of disease pressure.