CHAPTER ONE

INTRODUCTION

1. BACKGROUND OF THE STUDY

Maize is one of the most widely planted crops in the world. Its plant area and production ranks the second in China. Around 30% of maize is planted in North China Plain (NCP) and the production in NCP is up to 50% of the whole country (Li, 2010). NCP is characterized by a double cropping system of winter wheat and summer maize. Weed control in maize fields in NCP largely depends on chemical methods. High input of herbicides results in environmental pollution and the development of weed resistance. In addition, the cost for weed control is also too high. An effective way to reduce the side effect of the herbicide was to apply the lowest dose needed for biologically effective weed control (Kudsk and Streibig, 2003). It is important to provide information about the minimum effective dose of herbicides to be applied in the field situation. Although such studies have been carried out worldwide for more than 30 years (Kir and Dogan, 2009).

Maize (Zea mays L.) occupies third rank among the cereal crops after Wheat and Rice, extensively sown under irrigated and somewhat in rainfed areas of almost all the provinces of Pakistan but Punjab and NWFP are the major producers (GOP, 2008). In Pakistan, maize is grown on an area of 1,026 thousand hectares with the production of 3.313 million tones and average grain yield of 3264 kg ha-1 (GOP, 2008). But the average national yield per hectare is still far below as compare to the other maize growing countries of the world like Italy (9530 kg ha-1 ), USA (8600 kg ha-1), Canada (6630 kg ha-1), Argentina (5650 kg ha-1) and China (4570 Kg ha-1) (Anonymous, 2005). Despite suitable production environment and high yielding varieties of maize, the yield per hectare in Pakistan is still very low. Considering factors responsible for low yield, weed infestation is of prime importance. Excessive growth of weeds in maize field leads to 66 % to 80 % reduction in crop yield (Adigun, 2001 and Ford and Pleasant, 1994). Weeds compete with the crop plants for space, light, moisture, nutrients and carbon dioxide, which reduced not only the yield, grain quality and hinder harvest operations but also increase the cost of production (Rutta et al. 1991).

The commonly used chemicals for weed control in summer maize include pre-emergence herbicides, such as atrazine or metribuzin mixed with acetochlor or metolachlor, and post-emergence herbicides, such as nicosulfuron, rimsulfuron, mesotrione (China Pesticide Information Network, 2012). In NCP, the performance of pre-emergence herbicides is not good due to the adoption of non-tillage techniques in maize production. So the use of post-emergence herbicides is increasing. In post-emergence programs, the use of herbicides at reduced doses is one of the most important tools to limit herbicide input into the environment according to the integrated weed management system (Swanton and Weise, 1991). In nowadays, nicosulfuron and mesotrione are the two most commonly used post-emergence herbicides in summer maize field in NCP. Nicosulfuron is registered to control dicotyledonous and monocotyledonous weeds and mesotrione is registered to control annual broadleaved and some grass weeds in maize (China Pesticide Information Network, 2012). However, some varieties of maize are sensitive to these two herbicides and crop injury often occurs after their application (O'Sullivan et al., 1995; Williams et al., 2005; Zhang et al., 2010). It is urgent to provide information about the minimum effective doses of these two herbicides.

Topramezone belongs to the new chemical class of pyrazolones or benzoylpyrazoles and was commercially introduced in 2006 (Grossmann and Ehrhardt, 2007; Zollinger and Ries, 2006). It was newly registered as a post-emergence herbicide applied in maize to control annual grass and broadleaved weeds in China in 2010. The combination of nicosulfuron/mesotrione is a new product under registering in China. Schuster et al., 2007, Schuster et al., 2008 reported there was antagonism on Setaria viridis L. and Sorghum bicolor L. when nicosulfuron was tank-mixed with mesotrione. But Skrzypczak et al. (2011) reported that the tank-mixture of these two herbicides and adjuvant gave no antagonistic effect. So, the efficacy of this combination needs to be studied.

1. STATEMENT OF THE PROBLEM

Herbicides are truely essential to good yield of maize crop by suppressing different types of weeds. Weeds highly affect maize yield throughout, competing with crops for light, moisture, space and plant nutrients and thus constantly interfering with the normal growth of crops (Patel et al., 2013). About two hundred and eighty different types of weeds have been recorded in Khyber Pakhtunkhwa with varying infestation status (Marwat, 1984). Herbicides controlled 65-90% of weed flora and gave 100-150% more maize yield than weedy check (Nadeem et al., 2006).

Proper control of weeds is a key factor to sustain crop yield. Literature revealed that intensity of weeds and their competition time with crop plant are very important factors to determine the yield losses. High weeds intensity and more competition time with crop plants causes more reduction in crop yield (Chaudhary et al., 2008; Dalley et al., 2006). Weed competition at early growth stages of crop cause more reduction in growth and yield (Reddy et al., 2004). Altering emergence time of weeds and their timely control are essential components to shift weed-crop completion in favor of crop (Akhtar et al., 2000). If the proper weed control methods are not operated during the critical period of competition then effective weed management and profit are not be attained (Tanveer et al., 1999).

High yielding hybrids and varieties play an important role in high maize production. The Khyber Pakhtunkhwa has a unique agricultural environment, where raising of two maize crops a year are possible, by adopting appropriate cultivars and hybrids. Many hybrids and cultivars classified on the basis of the crop’s maturity as early and late maturing are available in the market (Begna et al., 2001). Maize cultivars and hybrids taking a long time to mature may not suit the situation for the field will not be vacated in due course of time to be normally planted with wheat, i.e. disturbing the cropping pattern (Ahmad et al., 2012). Therefore, quick and early maturing hybrids/varieties with high yield are intensely needed.

In the light of the above and the existing gaps in literature, the study will investigate the effectiveness of different post emergency herbicide on the performance of maize.

1. AIM AND OBJECTIVES OF THE STUDY

The aim of the study is to investigate the relationship effect of post emergency herbicide and maize performance.

Specifically, the study seeks to:

1. Investigate the relationship between post emergency herbicide and maize performance
2. Examine the positive effect of post emergency herbicide on maize performance
3. Examine the negative effect of post emergency herbicide on maize performance
4. Ascertain the challenges of post emergency herbicide on the performance of maize

1. RESEARCH QUESTIONS

Arising from the research objectives, the following research questions will be addressed in the study as presented below:

1. What is the relationship between post emergency herbicide and maize performance?
2. What is the positive effect of post emergency herbicide on maize performance?
3. What is the negative effect of post emergency herbicide on maize performance?
4. What are the challenges of post emergency herbicide on the performance of maize?

1. STATEMENT OF THE HYPOTHESIS

H0 there is no relationship effect of post emergency herbicide and maize performance.

H1 there is relationship effect of post emergency herbicide and maize performance.

1. SIGNIFICANCE OF THE STUDY

Maize (Zea mays L.) occupies third rank among the cereal crops after Wheat and Rice, extensively sown under irrigated and somewhat in rainfed areas; it cannot grow yield in an uncontrolled weed environment.

The study is on the investigation of effectiveness of different post emergency herbicide on the performance of maize. The findings of the study therefore will be use to the farmers on the effectiveness of herbicide on maize growth.

It will also reveal that no maize can survive its growth in an uncontrolled weed environment, and as such weed should be properly and timely control through the use of herbicide to ensure the survival growth of maize.

1. SCOPE OF THE STUDY

This study focuses mainly on the investigation of the effectiveness of different post emergency herbicide on the performance of maize. Specifically, the interest of the study will be restricted to farmers.

The focus of the study will on the investigation of the positive and negative effect of post emergency herbicide on maize growth; challenges of post emergency herbicide on the performance of maize; and the relationship between post emergency herbicide and maize performance.

1. LIMITATION OF THE STUDY

TIME CONSTRAINTS: One the challenges experienced by the researcher is the issue of time; the research will simultaneously engage in departmental activities like seminars and attendance to lectures. But the researcher was able to meet up with the deadline for the submission of the project.

FINANCIAL CONSTRAINTS: Every research work needs funding; however lack of adequate funds might affect the speed of the researcher in getting materials for completion of the project.

1.9 DEFINITION OF TERMS

Maize

A Central American cereal plant that yields large grains (corn or sweetcorn) set in rows on a cob. The many varieties include some used for stockfeed and corn oil.

Post-emergent Herbicides

Are used to kill weeds after they have germinated. These specialized herbicides must be used as the plant is actively growing and not simply green.

Weeds control

Weed control is the prevention or control of unwanted and invasive plants. By effectively controlling unwanted plants, there is less competition for water, nutrients and light for beneficial and desirable vegetation.

Grain yield

The amount of plant crop (such as cereal, grain or legume) harvested per unit area for a given time. Supplement. In agriculture, the crop yield is a measure of the grains or dry matter quantity in a particular area. It is usually expressed in kilograms per hectare (or metric ton per hectare).

Grain quality

Defined by several factors such as physical (moisture content, bulk density, kernel size, kernel hardness, vitreousness, kernel density and damaged kernels), safety (fungal infection, mycotoxins, insects and mites and their fragments, foreign material odour and dust) and compositional factors.