The effect of conservation and conventional agricultural practices on the population of plant pathogenic nematodes in the wheat-sugerbeet rotation system

Extended Abstract
Introduction:
In recent years, conservation agriculture-based cropping systems have been widely adopted by many farmers in different regions of the world (Hobbs et al., 2008). Many benefits are associated with conservation agriculture which include improvement of soil productivity, reduction of soil erosion, improvement of water-use efficiency, increasing soil biodiversity and soil biological activity and reduction in labour requirement. However, the three main principles of conservation agriculture- e.g., minimal soil disturbance (no-tillage), crop residue management and crop rotation may have direct and indirect effect on the population of soil-borne plant pathogens, including plant parasitic nematodes. Therefore, depending on the local agro-ecological environment, it is necessary to investigate the effect of conservation agriculture practices on plant diseases and pests. The main objective of this research was to compare the possible differential impacts of conservation agriculture practices and the conventional agriculture practices on the population of plant parasitic nematodes in wheat-suger beet rotation system.
Materials and Methods: The effects of tillage systems and residue management of the wheat - sugar beet rotation systems on the density population of plant parasitic nematodes were determined during 5 consecutive cropping seasons (2012-2017) at Jolge Rokh Agricultural Research Station, Khorasan Razavi, Iran. The experimental design was a split-plot arrangement in a randomized complete block with three replications. Three tillage systems (conventional tillage, minimum tillage and no-tillage) were assigned to the main plots and three levels of residue management (0, 30, and 60%) were assigned to the sub plots. To determine the population of plant parasitic nematodes in soil, samples were taken from each plot. The nematodes were extracted using sieving and centrifugal-flotation technique and identified based on the relevant diagnostic keys (Hunt, 1993).
Results and Discussion:
Plant parasitic nematodes including root lesion nematode (Pratylenchus neglectus), pin nematode (Paratylenchus spp.), Geocenamus spp., stem and bulb nematode (Ditylenchus spp.), Boleodorus spp. Tylenchus spp. and Filenchus spp. were identified and their populations were measured in different treatments. The results of analysis of variance of the plant parasitic nematodes showed that the effect of tillage on the population of Filenchus spp. and the interaction between tillage × residue retention on the population of pin nematode (Paratylenchus spp.) and stem and bulb nematode (Ditylenchus spp.) was significant at α=5%. The results of analysis of variance also indicated that the effect of tillage methods, residue retention and the interaction between tillage × residue retention on the population of other identified plant parasitic nematodes and the total number of plant parasitic nematodes were not statistically significant in the wheat-sugerbeet rotation system at the Jolge Rokh conditions. In general, the results showed that the conservation agriculture practices have no significant influence on the population of major plant parasitic nematodes in the wheat-suger beet cropping system at the Jolge Rokh conditions. However, since the population dynamics of plant parasitic nematodes are highly influenced by many factors including environmental conditions, physical, chemical and biological properties of soil as well as the crop plants used in rotation system, any technical advice for using conservation agriculture cropping systems should be based on the results of local reseach and agroechological condions.
Acknowledgement:
This study was supported by the Agricultural Research, Education and Extension Organization (AREEO) and the Seed and Plant Improvement Institute (SPII) of the Iranian Ministry of Agriculture Jihad (project number 01-43-03-9153-91002).The authors would like to thank AREEO and SPII for their financial and administrative support. The authors would like also to thank Mr. Amir Ahmadian Yazdi and A. Rastegar Pymani from the Plant Protection Department, Khorasan Razavi Agricultural and Natural Resources Research and Education Center for their technical assistance.

Key words: Crop rotation, plant disease, plant residue, tillage

References:
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Hunt, D.J. 1993. Aphelenchida, Longidoridae and Trichodoridae: their systematics and bionomics. CAB International , Hertfordshire, UK, pp 352