Agricultural peatland conservation: how straw and wood chips application affect N & P dynamics and spinach and arugula yield?

Amending agricultural peatlands with straw and wood chips has recently shown promising potential in preserving soil carbon stock and restoring and maintaining porosity and drainage. However, reductions in crop yield and nitrogen (N) and phosphorus (P) availability was also observed with the application of such materials. The objective of this study was to simulate an autumn application of 15 t ha^‑1 of miscanthus straw and pressed pine chips under controlled conditions to assess its potential influence on N and P availability of peat soils and spinach and arugula development. The treatments were studied with and without cultivation to assess nutrient dynamics without the confounding effect of root nutrient uptake and fertilization. A succession of three baby leaf crops was performed and all the soils were sampled at seeding and harvest of each crop. N and P levels in the bare soils were reduced with the biomass application with the pressed pine consistently causing greater reduction than the miscanthus. The biomass application also reduced the crops yield and increased their C/N ratio with the pressed pine causing consistently greater reduction in yield and greater increase in crop C/N ratio than the miscanthus. However, the effect on crop yield and crop C/N ratio attenuated with time. Therefore, autumn application of 15 t ha^‑1 incorporated in 20 cm might reduce baby leaf greens yield through N deficiency in the following growing season when no adjustment is made to fertilization practices. In this case, delaying the seeding of the first crop or increasing N fertilization might attenuate adverse effect on crop yield. Field trials with different timing of seeding and different N and P fertilization rate are required to assess the influence on yield and N and P deficiency. Evaluating crops with slower development might also as it may allow a better synchronicity between the soil N supply and the crop N requirements.