Compost Application Compensates Yield Loss in a Successive Winter Wheat Rotation: Evidence From a Multiple Isotope Labelling Study

Introduction

Successive winter wheat (WW) rotations lead to yield decline due to a less favourable microbial community and changes in soil nutrient availability. Research on mitigation options is limited and has great potential to improve farming profitability.

Materials and Methods

Using a quadruple isotope labelling study (¹³C, ¹⁵N, ²H and ¹⁸O) and a novel mesocosm experimental setup enabling the growth of wheat in outdoor conditions, we investigated the effects of the rotational position and compost application on the productivity of WW, grown either after oilseed rape or in self-succession, during the flowering (T1) and grain ripening stage (T2).

Results

The initial high soil nutrient content after oilseed rape created a long-lasting soil legacy that gave an advantage to the first WW after oilseed rape (W1) compared to the growth of the second WW after oilseed rape (W2), with significantly higher soil nitrate, ammonium, dissolved organic carbon, and microbial biomass than in W2. Compost significantly compensated for the disadvantage of W2, and by T2, these effects were reflected in enhanced root growth and nutrient uptake in the compost-amended W2. Allocation of freshly assimilated carbon was 46.2% higher in the compost-amended compared to the unamended W2. A similar trend was observed for plant ¹⁵N from the ¹⁵N-labelled fertiliser. Compost increased the contribution of the topsoil and decreased the contribution of the subsoil to total plant water uptake, which resulted in a 30% higher plant growth and yield gain in the compost-amended W2.

Conclusion

Our findings highlight the capacity of compost to buffer negative plant-soil feedbacks in monotonous crop rotations by influencing key rhizosphere processes, while simultaneously improving wheat growth and yield.