**3. Major weed species in association with maize**

Infesting weed species in crop field generally depend on crop species, cropping systems and their management practices, environmental conditions, seasonal variation, soil properties, nutrients and moisture status as well as soil types. The Eastern Gangetic Plain (EGP) as known for high weed seed bank in soils especially lower EGP (Bangladesh and West Bengal) due to flash and steady floods bring weed seeds from distance in their catchment areas. The weed species also highly depend on seasons as maize is grown round the year in three seasons i.e. Kharif (Monsoon; June– September), Rabi (Winter; November–May) and Kharif 1 (Spring; February–June). The high weed seed pressure and diversity make more difficult to manage weeds manually in conservation agriculture as well as also in conventional agriculture. Grasses weed species during Kharif season in the maize field in EGP are *Echinochloa colona* (L.), *Digitaria ciliaris* (L.), *Leptochloa chinensis* (L.), *Dactyloctenium aegyptium, Cynodon dactylon, Echinochloa crus-galli, Eleusine indica, Setaria viridis, Panicum javanicum, Paspalum commersonii* etc. The broadleaf weeds are *Marsilea minuta, Polygonum hydropiper, Galinsoga ciliata, Physalis heterophylla, Heliotropium indicum, Phyllanthus niruri, Euphorbia hirta, Jussiaea repens, Amaranthus spinosus, Amaranthus viridis, Spilanthes paniculata, Lindernia anagallis, Paspalum distichum* etc. and the major sedges weeds are *Cyperus rotundus, Cyperus difformis, Cyperus iria, Eclipta prostrata, Ludwigia octovalvis, Portulaca oleracea, Fimbristylis miliacea, Scirpus* spp. etc. [29–31]. The perennial weeds species dominant round the years but the seasonal weeds are different when maize grown in dry season (winter maize) and the major dominant weeds are *Polygonum persicaria, Polygonum pensylvanicum, Polygonum orientale, Oldenlandia diffusa, Oldenlandia aquatic, Oxalis corniculate, Chenopodium arvensis, Physalis minima, Solanum nigrum, Hydrocotyle ranunculoides, Ageratum conyzoides, Medicago denticulate, Avena ludoviciana* etc. [32, 33].

A field experiment found that the most dominant weeds in maize field were sedge *C. rotundus* and dicot weeds *T. portulacastrum*, *D. arvensis*, *P. niruri* and grass *C. dactylon* [34]. In USA, it observed the most common broadleaves weed species

*Maize - Production and Use*

provides feed for animals [3].

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

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

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

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

provide high yield and profit margin in a more sustainable way.

provided cost-effective, faster and better weed control [14–16].

**2. Importance of tillage options on weed infestation in the crop field**

Weed management strategies are the key to success of the conservation agriculture based crop production especially at the beginning of 2 years. With the shift from conventional agriculture to conservation agriculture there will be a shift dynamic change in weed species, population and diversity. Therefore, initial weed management is an important phenomenon through integrated weed management approaches like stale seed-bed, mulch, and adjustment in planting dates, biological and mechanical control and effective combination use of herbicides. The many

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gases.

in a maize crop were *Chenopodium album, Asclepias syriaca, Ambrosia artemisiifolia, Physalis heterophylla* and *Polygonum rensylvanicum* and the most common grasses were *Elymus repens and Setaria pumila* [35]*.* In another studies conducted on sandy loam soils at Hyderabad, India [26, 36], revealed that among the major weeds in maize field *E. colona* (grasses), *E. crus-galli, Paspalum distichum, C. rotundus* (sedges)*, Ageratum conyzoides* and *T. portulacastrum, Sonchus oleraceus, Acalypha indica, Eclipta alba and Parthenium hysterophorus* (broad-leaved) were the predominant weeds. A 3 years field survey in Andhra Pradesh of India also confirmed that most dominant weed species in maize field were *E. colona*, followed by *P. repens*, *T. portulacastrum*, and *D. arvensis* [37].
