اثر روش‌های خاک‌ورزی و مدیریت بقایای گیاهی برجمعیّت نماتدهای بیمارگر گیاهی در تناوب گندم ((triticum aestivum l.، جو (hordeum vulgare l.)و پنبه (gossypium hirsutum l.)

این تحقیق به‌منظور بررسی اثر شیوه‌های خاک‌ورزی و سطوح مختلف نگهداری بقایای گیاهی بر جمعیّت نماتدهای بیمارگر گیاهی در سیستم تناوبی گندم ((triticum aestivum l.، جو  (hordeum vulgare l.)و پنبه  (gossypium hirsutum l.)به‌مدت پنج سال زراعی (1395-1390) در ایستگاه تحقیقات کشاورزی گناباد اجرا شد. آزمایش بر پایه کرت‌های خرد شده در قالب طرح بلوک‌های کامل تصادفی و با سه تکرار انجام شد. روش‌های خاک‌ورزی شامل، خاک‌ورزی متداول (شخم + دیسک + تسطیح + کاشت با بذرکار)، کم خاک‌ورزی (چیزل پیلر یا دیسک + کاشت با بذرکار) و بی خاک‌ورزی (کاشت مستقیم با بذرکار no till) در کرت‌های اصلی و مدیریت بقایای گیاهی شامل تیمار بدون بقایای گیاهی، حفظ 30 درصد و حفظ 60 درصد بقایای محصول سال قبل در کرت‌های فرعی قرار گرفتند. جمعیّت نماتدهای پارازیت گیاهی در هر کرت به‌روش الک و سانتریفیوژ استخراج و با استفاده از کلیدهای معتبر تا سطح جنس یا گونه تشخیص داده شدند و جمعیّت آن‌ها مورد مقایسه قرار گرفت. بر اساس نتایج، نماتد‌های پارازیت شامل نماتد مولد زخم ریشه (pratylenchus thornei)، نماتد سنجاقی (paratylenchus spp.)، نماتد مارپیچی (helicotylenchus spp.)، geocenamus spp.، نماتد ساقه و پیاز، (ditylenchus spp.)،boleodorus spp. ، tylenchus spp. و filenchus spp. تشخیص داده شدند. نتایج تجزیه واریانس نشان داد اثر تیمارهای خاک‌ورزی، نگهداری بقایا و برهم‌کنش خاک‌ورزی و نگهداری بقایا بر جمعیّت اغلب نماتدها و تعداد کل نماتدهای پارازیت گیاهی معنی‌دار نبوده است. اثر خاک‌ورزی بر جمعیّت boleodorus spp. و برهم‌کنش خاک‌ورزی و نگهداری بقایا بر جمعیّت .tylenchus spp در سطح پنج درصد معنی‌دار بوده است. بر پایه نتایج این تحقیق، تغییر در عملیات خاک‌ورزی از متداول به کم و بی خاک‌ورزی و حفظ بقایای گیاهی روی سطح خاک در سیستم تناوب زراعی گندم، گندم، جو، پنبه و گندم خطر افزایش جمعیّت نماتدهای مهم بیمارگر گیاهی را افزایش نمی‌دهد و با توجه به مزایای کشاورزی حفاظتی، این سیستم زراعی برای این اقلیم و مناطق مشابه قابل توصیه می باشد.

The Effect of Different Tillage Methods and Crop Residue Management on the Population of Plant Parasitic Nematodes in the Wheat (Triticum aestivum L.), Barley (Hordeum vulgare L.) and Cotton (Gossypium hirsutum L.)Rotation System

IntroductionConventional tillagebased farming systems had negative effects on the quality of essential natural resources including soil, water, and plant biodiversity. In the recent decades, Conservation Agriculture (CA) farming systems based on the three interlinked principles, namely: no or minimum mechanical soil disturbance, crop residue retention and crop rotation introduced and adopted as an alternative to conventional agriculture. However, the influence of conservation agriculture practices on the population of soilborne plant pathogens including plant parasitic nematodes is not well studied. This study was performed to determine the effect of different tillage methods and different levels of residue management on the population of plant parasitic nematodes in the wheatbarleycottonwheat rotation system during five consecutive cropping seasons (20122017) at the Gonabad Agricultural Research and Education Organization.Materials and MethodsThe experimental design was splitplot layout based on a randomized complete block design with three replications. Three tillage methods (such as conventional tillage, minimum tillage, and notillage) were assigned to main plots and three levels of residue retention (no residue retention, 30% of residue retention, and 60% of residue retention) were assigned to sub plots. The planting area of each subplot was 450 m2 (30 m length and 15 m width) and the total are of each main plot was 4050 m2 (9×450 m). To compare the population density of plant pathogenic nematodes in different crops, a combined soil sample from each experimental plot was collected. The nematodes were extracted from soil samples using sieving and centrifugalflotation technique and were identified to genus or species level using relevant systematic references. The data were analyzed using MSTATC statistical software package. The Duncan multiple range tests were applied to separate the differences between means.Results and DiscussionPlant pathogenic nematodes including root lesion nematode (Pratylenchus thornei), pin nematode (Paratylenchus spp.), spiral nematode (Helicotylenchus spp.), Geocenamus spp., stem and bulb nematode (Ditylenchus spp.), Boleodorus spp., Tylenchus spp. and Filenchus spp. were identified in different treatments. Based on the results of analysis of variance, the effect of tillage methods, residue retention and the interaction between tillage × residue retention was not statistically significant on the population of most plant parasitic nematodes but the interaction between tillage × residue retention was significant on the total number of plant parasitic nematodes and the population of Tylenchus spp. and Geocenamus spp. In average the highest density of plant pathogenic nematodes was related to the notillage system with 30% of residue retention and the lowest density was related to the minimum tillage system with 30% of residue retention. The results of this study indicated that different tillage systems and different levels of residue retention under the wheatbarleycottonwheat rotation system do not affect dramatically the population density of important species of plant pathogenic nematodes including the root lesion nematode (Pratylenchus thornei). Some other studies reported that reducing tillage intensity was associated with reducing population densities of plant pathogenic nematodes, which was contrary to the results of this study.ConclusionThe results of this study indicated that conservation agriculture under the wheatbarleycottonwheat rotation system in temperate climatic zone of Khorasan Razavi (Gonabad) does not significantly affect the population of plant pathogenic nematodes and increases the risk of crop damage by this group of plan pathogens.AcknowledgementsThis study has been financially supported by the Agricultural Research, Education and Extension Organization (AREEO) and the Seed and Plant Improvement Institute (SPII) (project number 174303915491002).The authors would like to thank AREEO and SPII for their financial and administrative supports.The excellent technical and laboratory assistance of A. Rastegar Paymani and A. Ahmadian Yazdi from the department of plant protection is acknowledged.