Cover crops for sustainable maize production.

Conventional maize-after-maize in the UK is frequently associated with soil compaction, runoff and soil erosion, due to a late autumn harvest and a post-harvest management that leaves minimal soil protection. Consequently, maize cultivation leads to on-site soil degradation and off-site environmental pollution. Soil conservation practices such as cover cropping could improve the sustainability of maize. Two field experiments were established within commercially grown maize (Herefordshire) in two consecutive years to investigate the role of different species of cover crops in reducing runoff, preventing soil erosion and enhancing soil microbial community. Experiment 1 compared common non-cover crop post-harvest managements with Lolium multiflorum and Secale cereale. Experiment 2 compared Lolium multiflorum and the mixtures Lolium multiflorum & Vicia villosa and Lolium multiflorum & Trifolium alexandrinum with the traditional method of post-harvest wintered maize stubbles without cover crops. Runoff and soil loss were monitored using enclosed erosion plots periodically sampled. Soil was tested for chemical parameters such as organic matter, organic carbon, total nitrogen, available phosphorus, and biological parameters such as microbial and fungal biomass, phospholipid fatty acid analysis and multiple substrates induced respiration. Additionally, during Experiment 2 easily available glomalin related soil proteins and aggregate stability were measured. Results showed a trend in the reduction of runoff and soil erosion. However, no significant differences were recorded. Overall, the impact of cover crops on soil microbiology was limited. Cover crops had a priming effect during Experiment 1 that led to a reduction of organic matter and organic carbon due to microbial activity. In Experiment 2 the relative abundance of fungi increased in the cover crop treatments. This was possibly due to the decrease of easily available nutrients and the increase of plant root debris, which are more available to fungi rather than bacteria. Cover crops seemed a practical option to improve the sustainability of maize production due to lack of an adverse impact on maize yield and the encouraging results on runoff, soil erosion and soil fungi. However, the effects were limited and further investigation is needed to prove the impact of cover crops in the long-term.PhD in Environment and Agrifoo