Einflüsse von Minimalbodenbearbeitung und Transfermulch auf den Initialbefall und die Populationsentwicklung des Kartoffelkäfers (Leptinotarsa decemlineata)

Nutrient supply and late blight, caused by Phytophtora infestans are the major challenges in organic potato production. Copper fungicides are harmful to the environment in high dosages and their ban in Europe is imminent. Some organic farmers reported to us that the use of green manure based fresh mulch would considerably reduce late blight while supplying nutrients to the potatoes. Experiments were conducted in 2014-2016 under organic conditions with natural inoculum using inversion and non-inversion tillage and various green manure mulch sources to verify these effects. No P. infestans occurred in 2015 and Data from one experiment in 2014 and two in 2016 are presented.
The experiment in 2014 combined reduced tillage with 10-12 cm fresh winter pea rye based mulch applied right at potato emergence compared to a regular plough based system. In the first experiment in 2016, triticale-vetch and grass clover mulches were compared ton o mulch in a regularly ploughed field. In the second experiment, triticale vetch was grown as pre-crop to potatoes and rototilled to a depth of 5cm prior to potato planting. Half the area was subsequently hilled and covered with a C-rich mulch of fresh triticale, the other half was left unmulched.
In all three experiments, the epidemic onset with P. infestans was delayed by a few days and plants died of late blight between 10 to 20 days later when mulched compared to non-mulched plants. Areas under the disease progress curve were reduced by 27 to 38% depending on mulch type and year. Microclimatic conditions in the fields were substantially drier due to the hygroscopic properties of the drying plant materials. However, depending on the weather conditions, mulching increased or reduced potato yields by affecting soil moisture and temperature pointing to a need for system optimization before recommending the technology in practice.