تأثير انواع شخم و گياهان پوششي بر عملكرد و اجزاي عملكرد گندم

Effect of Different Tillage Methods and Cover Crop Types on Yield and Yield Components of Wheat

به‌منظور بررسی اثر كاربرد گیاهان پوششی در یك نظام زراعی مبتنی بر گندم و همچنین مطالعه اثر روش‌های شخم در این نظام، آزمایشی در سال زراعی 94-1393 در مزرعه دانشكده كشاورزی دانشگاه بیرجند به‌صورت كرت‌های خرد شده در قالب طرح پایه بلوك‌های كامل تصادفی در سه تكرار اجرا شد. سه نوع روش خاك‌ورزی (شامل عدم خاك‌ورزی، خاك‌ورزی كاهشی و خاك‌ورزی رایج) به‌عنوان عامل اصلی و گیاهان پوششی در 5 سطح (شامل خلر، منداب، جو ترش، تریتیكاله و عدم كشت گیاه پوششی به‌عنوان شاهد) به‌عنوان عامل فرعی در نظر گرفته شد. نتایج نشان داد كه اثر روش خاك‌ورزی بر تعداد سنبله در مترمربع، وزن سنبله در مترمربع، عملكرد بیولوژیك و عملكرد دانه معنی‌دار (P <0.05) بود به‌طوری‌كه سیستم عدم خاك‌ورزی و خاك‌ورزی كاهشی نسبت به خاك‌ورزی رایج، تعداد سنبله در مترمربع، عملكرد بیولوژیك و عملكرد دانه بیشتری تولید كردند. هم‌چنین نوع گیاه پوششی تأثیر معنی‌داری بر عملكرد دانه، وزن سنبله در متر مربع و وزن هزار دانه گندم (P <0.01)، تعداد سنبله در متر مربع، تعداد دانه در سنبله و عملكرد بیولوژیك (P <0.05) داشت، به‌طوری‌كه در تیمار گیاه پوششی خلر و منداب، بیشترین عملكرد دانه گندم (به‌ترتیب 1/6511 و 2/6422 كیلوگرم در هكتار) مشاهده شد. به‌طور كلی یافته‌های این پژوهش، موفقیت كشت گیاهان پوششی خلر و منداب و اعمال روش‌های خاك‌ورزی حفاظتی را در بهبود عملكرد گندم نشان داد.

Introduction Conservation agriculture is an appropriate strategy for maintaining and improving agricultural resources which increases crop production and stability and also provides environmental protection. This attitude contributes to the conservation of natural resources (soil, water, and air) and is one of the most effective ways to overcome the drought crisis, water management and compensation of soil organic matter in arid and semi-arid regions. The practice of zero-tillage decreases the mineralization of organic matter and contributes to the sequestration of organic carbon in the soil. Higher amounts of organic matter in the soil improve soil structure and root growth, water infiltration and retention, and cation exchange capacity. In addition, zero-tillage reduces soil compaction and crop production costs. Cover crops are cultivated to protect the soil from erosion and elements loss by leaching or runoff and also improve the soil moisture and temperature. Given that South Khorasan farmers still use traditional methods of cultivation of wheat, and cover crops have no place in their farming systems, the aim of this study was to investigate the effect of cover crops types and tillage systems on yield and yield components of wheat in Birjand region. Materials and Methods A split plot field experiment was conducted based on randomized complete block design with three replications at the Research Farm of the University of Birjand over the growing season of 2014-2015. The main factor was the type of tillage (no-till, reduced tillage and conventional tillage) and cover crop type (chickling pea (Lathyrus sativus), rocket salad (Eruca sativa), triticale (X Triticosecale witmack), barley (Hordeum vulgaris) and control (no cover crop)) was considered as sub plots. Cover crops were planted on July 2014. Before planting wheat, cover crops were dried through spraying paraquat herbicide using a backpack sprayer at a rate of 3 L ha-1. Then the three tillage treatments were applied, seedbed preparation was carried out and wheat Anfarm- 4 (Bam) was planted. At the end of the growing season, yield and yield components of wheat were measured. Results and Discussion The results indicated that the maximum grain yield, biological yield, and spike.m-2 of wheat were observed with the no-till and reduced tillage treatments. The wheat spike weight significantly increased in the treatment of no-tillage compared with conventional tillage treatment. It seems that increased crop yield under no-till and reduced till systems might be owing to the enhancement of the soil nutrient status, reduced weed populations, improved physical health of the soil improved soil water status and increased efficiency of nutrient usage in these systems comparing with the conventional tillage systems. The main effect of cover crop type showed that incorporating chickling pea and rocket salad resulted in the greatest grain yield, thousand-kernal weight, spike weight, and biological yield of wheat compared to the control (no cover crop) and also chickling pea, rocket salad and barley caused the greatest grain. Spike-1 of wheat compared to the control (no cover crop). Although the use of total cover crops improved yield and yield components in wheat. Chickling pea superiority in many traits was evident in comparison with other cover crops. This superiority could be due to the fact that this plant belongs to the legume family and legumes release higher amounts of nitrogen during decomposition compared to grass species. Grasses produce large amounts of carbon and are slowly decomposed. Although rocket salad does not belong to the legume family, due to having deep roots, it is able to absorb nutrients from the deep soil layers and provide the main plant with these nutrients after its decay. Conclusions The results of this study revealed that employment of conservation tillage systems remarkably affected the yield and yield components of wheat, and the greatest positive influence on crop yield and yield components were observed where chickling pea and rocket salad were sown before wheat cultivation. Thus, cover crops and conservation tillage systems can be used as a promising solution for the development of sustainable agriculture and protecting the health of ecosystems.