| Abstrakt: |
Although crop rotation reduces the incidence of soil-borne diseases, reduced tillage practices create the risk of increased disease incidence. Monoculture maize (MM) under both conventional tillage (CT) and conservation agriculture (CA) crop systems were evaluated against two-and three-year rotation CA systems of maize with cowpea and sunflower, respectively. Pearl millet was the third crop in the three-year rotation systems. Plant mass, root and crown rot severity and frequencies of 15 soil-borne fungi on maize roots and crowns were investigated at three sampling dates, i.e. 21, 70 and 100 days after planting (DAP), together with yield. The trial was initiated during 2008/09 on a sandy loam soil in the Highveld climatic area of South Africa and the current study focused on the 2011/12, 2012/13 and 2013/14 seasons. Lower yields and plant mass at 100 DAP were obtained for the MM-CT treatment compared with MM-CA and rotated maize during the drought-stricken 2012/13 season. Yields obtained for this season correlated with crown rot severity at 100 DAP. Stenocarpella maydisand Macrophomina phaseolinacorrelated negatively with crown rot and plant mass at 100 DAP as well as yield (2012/13). Both fungi were most prominent in the MM-CT system. |
