Soil tillage in organic farming: impacts of conservation tillage on soil fertility, weeds and crops

Summary

Organic farmers are encouraged to adopt conservation tillage to preserve soil quality and fertility and prevent erosion. In the framework of a national study, we compared conservation (no tillage NT and reduced tillage RT) and conventional (mouldboard ploughing MP and shallow mouldboard ploughing SMP) tillage systems in 3 field experiments and 2 on-farm surveys. We measured the impacts of soil tillage on: (1) soil compaction: more compacted soil under NT and RT, (2) earthworm populations: more earthworms under NT, (3) weed infestation: weed level tends to be higher under NT, but it is not a general trend, and (4) crops: crop yields are lower under NT according to weed infestation. Then, independent of soil type and experimental year (2 to 5 years), it seems that soil physical fertility decreases under NT and RT. But, the first reason of a decline of crop yield under NT is the weed infestation.