**1. Introduction**

Maize (*Zea mays* L*.*) is the third most important cereal after rice and wheat, which is widely grown in the world and used as a primary staple food in many developing countries. The area and production under maize in the world in 2013–2014 was 177 m ha with 967 Mt. production and contributed almost 5% of the world's dietary energy supply [1]. Recent projection indicates that by 2020 the demand of maize in all developing countries will overtake the demand of wheat and rice [2], with Asia accounting for nearly 60% of the global demand for maize. Half of the world maize is produced in the developing countries where maize grain is one of the major sources of food energy for the poor people and its plant biomass provides feed for animals [3].

Eastern Gangetic Plains (EGP) covering three neighboring countries (India, Bangladesh and Nepal) has a very high yield potential of maize production. In recent decades, maize an emerging as a cash crop for smallholder farmers because of its high yield potentiality due to favorable climatic conditions which allows maize production round the years in three seasons [4]. The EGP is mainly dominated by rice-based farming systems having maximum coverage of rice-rice cropping system which is associated with own problems of high water consumption, production costs and labour use, and further soil health deterioration. All these associated problems make rice-rice production is unsustainable and unprofitable. Farmers are looking for the alternative crop of dry season rice called boro rice (winter rice) to diversify their cropping systems and maize is one of the most suitable crops to provide high yield and profit margin in a more sustainable way.

Presently, more than 90% maize grows in EGP by manual dibbling after intensive tillage operations (4–6 dry tillage) which delayed the maize sowing by at least 1–2 weeks [5]. A number of repetitive tillage operations increase the cost of cultivation due to higher energy and labor use and delayed planting which further reduces the net margins of the farmers. Since, the conservation agricultural (CA) based management practices (minimum/zero tillage) are the new emerging technologies growing an attention worldwide due to higher economic benefits, improvement in soil health and also found more environmental friendly by reducing greenhouse gases.

Although CA-based maize cultivation has many benefits, however weed infestation is one of the serious constraints that limits maize production though weed management is also a major concern in conventional production system. The competition between weeds and maize at critical growth stages could be reduced both the quality and quantity of maize yield over 30% [6] as weeds compete with crop for essential resources [7–9]. For controlling weeds in crop field, farmers are generally adopting mechanical, cultural, biological and chemical control methods. Among them, exhausted by cultural methods, farmers are moving towards other alternative methods due to labour crisis during critical period of weed control [6, 10, 11]. While, the mechanical methods are still useful but are unable to effective control of weeds successfully due to the absence of right machinery [12]. The judicious and right use of a different combination of herbicides as pre-plant, pre-emergence and post-emergence can provide effective and efficient weed control under CA system as well as conventional system [13]. The chemical weed control may be provided cost-effective, faster and better weed control [14–16].
