Effects of reduced tillage and prolonged cover cropping in maize on soil quality and yield

Maize (Zea mays L.) is the most common arable crop on sandy soils in the Netherlands, and it is often grown for several consecutive years after temporary grassland. For the maize-growing years, reduced tillage intensity and prolonged growing period of cover crops could limit declines in soil organic matter (SOM) and soil biota while maintaining soil structure and maize yield. We measured soil parameters and maize yield in an eight-years field experiment on sandy Gleyic Podzol. Treatments included four cropping systems differing in tillage intensity but with conventional sowing dates (conventional inversion tillage (CT), non-inversion tillage (NIT), strip tillage (ST) and no-till (NT)), and two cropping systems (CT-prolonged and ST-prolonged) with prolonged growing period of a winter rye-winter pea cover crop combined with a late sown short-season maize (18 weeks growth). After eight years, we found no evidence for differences in SOM or total carbon content between the treatments. However, in the reduced-tillage treatments, SOM content was higher in the top (0-15 cm) than in the bottom (15-30 cm) of the plough layer, while in CT and CT-prolonged, this stratification was inverted. We observed differences in earthworm abundance, biomass and functional group distribution. In comparison to CT (100 %), the earthworm abundance was 153 % in NIT, 235 % in ST and 206 % in NT whereas earthworm biomass was 269 % in NIT, 325 % in ST and 475 % in NT. Epigeic earthworms were more affected by tillage than endogeic earthworms. Compared to CT, earthworm biomass was higher in CT-prolonged. The initially low earthworm population recovered during the course of the experiment independent of tillage intensity. Higher soil penetration resistance was observed in the reduced tillage systems compared to CT, independent of prolonging the cover crop. Despite the increased penetration resistance, the maize yields in NIT and ST were similar to CT. The maize yields were lower in NT, CT-prolonged and ST-prolonged compared to CT, but no differences were observed between CT-prolonged and ST-prolonged. The biomass of the harvested prolonged cover crop closed the yield gap in relation to CT in four out of six years in which cover crop biomass in CTprolonged and ST-prolonged was quantified. Based on our results, we recommend strip tillage for continuous maize-cropping systems on Dutch sandy soils. In the case of severe compacting of compaction prone soils, we recommend conventional tillage with a prolonged cover crop and short-season maize variety.