FarmTalk – Crop disease impacts

THE ADOPTION OF CONSERVATION farming practices in the Mallee has given benefits through increased moisture conservation, increased surface cover and reduced erosion. Stubble retention and reduced tillage practices can have a positive impact on the soil physical characteristics by creating an environment that enhances soil structure and water infiltration. Stubble retention also improves the chemical characteristics e.g. organic carbon, and improves nutrient supply and biological activity of the soil which, can lead to improved plant nutrition. Improved biological activity can also lower inoculum persistence and disease severity. However, stubble and crop residue borne diseases such as crown rot (Fusarium pseudograminearum), take-all (Gaeumannomyces graminis var. tritici), rhizoctonia root rot (Rhizoctonia solani AG8), common root rot (Bipolaris sorokiniana) eyespot (Oculimacula yallundae), yellow leaf spot (Pyrenophora tritici-repentis), SFNB (barley spot form of net blotch) and NFNB (barley net form of net blotch) can increase with stubble retention in particular in continuous cereal cropping systems. Environmental conditions in the preceding summer and during the growing season are also important in determining how much impact soil-borne diseases have on yield. For example, low summer rainfall reduces the potential for the breakdown of pathogen inoculum, reduces potential to store moisture within the soil profile, reduces breakdown of herbicide residues and limits N mineralization. These all limit the ability of the crop to tolerate soil-borne pathogens. This Farm Talk explains the disease and stubble interactions in low rainfall farming systems and the effect of stubble management on stubble and soilborne diseases.