**5. Weed control in zero-till maize by chemical measures**

In maize production, weed management is considered as an important agronomic measure for attaining the potential yield. To minimize the maize yield loss due to weed competition, farmers are practicing several methods for controlling the weeds are available such as mechanical, cultural, biological and chemical control methods. The cultural methods are very expensive and time consuming so, farmers have to move towards other alternative methods of weed control [10]. Furthermore, due to the increasing cost and non-availability of labour for manual weeding during peak and critical maize growth stages significantly influence the maize yield. The role of herbicides is not only control the weeds timely and effectively, but also offer a great scope for minimizing the cost of production [10]. The chemical control method is quick, more effective, time and labour saving method than others [13]. However, it is important to use a broad-spectrum herbicide program including preand post-emergence herbicides for season-long effective weed control and to avoid shifts towards problematic weed species [32] or evolution of herbicide-resistant weed biotypes. On the other hand, it is decisive to select the appropriate weedicide depending upon the weed flora exist in a given field. In addition, the precise dose, methods, weed growth stage, timings, soil moisture and application techniques should be followed. A number of herbicides have been evaluated in sequential

**121**

maize yield.

*Chemical Weed Management in Maize (*Zea mays *L.) under Conservation Agricultural Systems…*

combination and suggested pre- and post-emergence herbicide application for effective weed control in dry direct drill-seeded rice systems, including under zerotillage conditions [17]. Use of pre-sowing, pre- and post-emergence application of herbicides would make herbicidal weed control more acceptable to farmers which will not change the existing agronomic practices but will allow for complete control of weeds under CA based management practices. Pre-emergence herbicides spray will control the weeds up to 25 days after seeding and followed that post-emergence application depending on weed flora will take care to keep weeds below crop injury level. Pre-planting, pre and post-emergence herbicides either in sequential or tank mixture will be taken care of all types of weed flora an ideal means in view of

**6. Effect of pre-sowing herbicides on weed control of maize**

Generally, pre-sowing/planting herbicides are non-selective which are applied to control prevailing complex annual and perennial weeds flora erstwhile to planting, particularly under the CA-based cropping system. Among them, herbicide

cides [52, 53]. Where Glyphosate and Paraquat herbicides are available and popular as these are systemic non-selective and contact herbicides, respectively, and kill both annual and perennial weeds. To be effective, the systemic (Glyphosate) should be applied when weeds are growing actively so that the herbicide is absorbed and translocated into the entire plant system [17], but contact herbicide (Paraquat) can

Currently, the present rates of many herbicides do not work properly against many weeds, due to their resistance against the target weeds. Therefore, it is important to apply a new product to be available earlier than normal in order to maximize the contribution of residual weed control after crop emergence. The earlier study found that if the pre-sowing herbicide is applied before planting and is incorporated in the soil with light tillage, the efficacy of the applied herbicides was found the maximum [54].

When herbicides apply immediately or 1–4 days after maize seeds sowing, and it can be also mixed with soil during sowing, but it must be applied before weed seed emergence, are known as pre-emergence herbicides. Earlier findings [55] showed that pendimethalin can be applied as pre-emergence to get maximum weed control efficiency and crop selectivity by decreasing the weed population and increased the maize grain yield over the weedy check field [56]. Thus, Mekky et al. [57] reported that when pre-emergence herbicides were applied immediately after seed sowing or pre-emergence, weed control efficiency was the maximum and also increased the

A field experiment in the clay loam soils of Guntur, Andhra Pradesh (India),

lowed by (*fb*) manual hand weeding (HW) at 30 DAS recorded the tallest plant and the maximum dry-weight over un-weeded check at all stages of crop growth [30]. Scientist [26] reported that when maize was grown under zero till condition with

in combination of two hand weeding at 20 and 40 DAS was produced significantly

applied at pre-emergence fol-

and topramezone 0.030 kg ha<sup>−</sup><sup>1</sup>

with zero tillage maize found that atrazine 1.5 kg ha<sup>−</sup><sup>1</sup>

pre-emergence herbicides atrazine at 1.0 kg ha<sup>−</sup><sup>1</sup>

higher plant height, dry matter production of maize.

**7. Effect of pre-emergence herbicides on weed control in maize**

or 0.5–1.5% by volume), Glucofosinate, or dicamba and

or 0.5% by volume) are the most widely applicable herbi-

*DOI: http://dx.doi.org/10.5772/intechopen.89030*

economics and usefulness in maize [17, 31, 32].

Glyphosate (1 kg ai ha<sup>−</sup><sup>1</sup>

Paraquat (0.5 kg ai ha<sup>−</sup><sup>1</sup>

be applied just before the sowing.

*Chemical Weed Management in Maize (*Zea mays *L.) under Conservation Agricultural Systems… DOI: http://dx.doi.org/10.5772/intechopen.89030*

combination and suggested pre- and post-emergence herbicide application for effective weed control in dry direct drill-seeded rice systems, including under zerotillage conditions [17]. Use of pre-sowing, pre- and post-emergence application of herbicides would make herbicidal weed control more acceptable to farmers which will not change the existing agronomic practices but will allow for complete control of weeds under CA based management practices. Pre-emergence herbicides spray will control the weeds up to 25 days after seeding and followed that post-emergence application depending on weed flora will take care to keep weeds below crop injury level. Pre-planting, pre and post-emergence herbicides either in sequential or tank mixture will be taken care of all types of weed flora an ideal means in view of economics and usefulness in maize [17, 31, 32].
