ABSTRACT

The effects of five weed management techniques and a weed free control on weed infestation and on the growth and yield of a plantain landrace (Musa spp. AAB Agbagba) were evaluated during the two cropping seasons of 2005 and 2006 at Nsukka, Nigeria. The experiment was laid out in randomised complete block design (RCBD) with six treatments and replicated four times. The treatments comprised six weed management techniques, which consisted of slashing at 8-weekly intervals, mulching with sawdust alone, use of glyphosate + intermittent slashing, use of sawdust mulching + glyphosate, use of glyphosate alone and a weed-free (by hoeing) control. Results of the study showed that there was a significant (P<0.05) difference in the effectiveness of the various weed management techniques on weed control. Mulching + glyphosate treatment was the most effective weed control technique compared to other treatments. The result also showed a significant (P<0.05) difference in the suckering ability as a result of the mulching effect. This was such that mulched plots produced the highest number of suckers with a mean value of 4.2 and glyphosate alone treated plots produced the least number of suckers with a mean value of l.7 at 36 WAT. Plant heights, number of leaves, leaf area and fruit yield were also significantly (P <0.05) affected by the treatments. The result showed that mulching + glyphosate weed management strategy supported the best plant growth with mean values of 139.7 cm, 4.3 and 12348.8 cm2 for plant height, number of leaves and leaf area respectively without any lodging. The treatment also supported the best fruit yield of 12.1t/ha with the highest benefit/cost ratio of 3.87 and gross margin of 74.2 as compared to the rest of the other treatments.

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INTRODUCTION

Bananas and plantains belong to the genus Musa and the family Musaceae (Stover and Simmonds, 1987), and are fast growing herbaceous perennials arising from underground rhizomes or corms. They originated from South-East Asia (Onwueme, 1984) and Western Pacific regions where the inedible, seed-bearing diploid ancestors can still be found in the natural forest vegetations (Robinson, 1996). The flesh stalks or pseudo stems formed by upright concentric layers of leaf sheaths constitute the functional trunks (Simmonds, 1966). Suckers spring up around the main plant forming a mat, the oldest suckers replacing the main plant when it fruits and dies (Lee, 2000).

According to Robinson (1996), the root system in banana plants is fleshy and adventitious from the beginning. A banana adventitious root system spreads profusely. Horizontal extension of the primary roots can go as far as 5 metres; although commonly it can reach up to 2 metres. The vertical root zone is very shallow with about 40% of the root volume in the top 100 mm and 85% in the top 300 mm. Occasionally primary root penetrates up to 600 mm below the soil. Swennen et al (1986) reported that the proportion of secondary and tertiary roots in plantains are 53% and 46%, compared with 22% and 77% respectively for bananas. They proposed that the relative shortage of tertiary roots which produce most of the root hairs, was the contributing factor towards poor productivity and rapid yield decline in the plantain group.

Plantains require a hot humid environment. Ideally, the average air temperature should be about 30°C and rainfall of at least 100 mm per month. According to Robinson (1996), an average annual rainfall of 2000 to 2500 mm evenly distributed throughout the year is considered satisfactory. Plantain is a shallow rooting crop and like all herbaceous perennials, it is highly susceptible to weed competition (Ndubizu and Manufor, 1988).

Plantains are starchy bananas which make up one-quarter of the total world population of bananas (Musa spp). Unlike the sweet desert bananas, plantains are a staple food which is fried, baked, boiled (and then sometimes pounded) or roasted and consumed alone or together with other food (Swennen, 1990). They are a major food in developing countries and in Western and Central Africa, about 70 million people are estimated to depend on Musa fruits for a large proportion of their daily carbohydrates intake (Rowe, 1998). Bananas and plantains represent the world's second largest fruit crop with an annual production of 74 million tons (FAO, 1991). They rank as the fourth most important global food commodity after rice, wheat and maize in terms of the gross value of production (INIBAP, 1992). They are of great importance in tropical agriculture, where they have attracted a great deal of research (Simmonds and Weatherup,

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1990).

In the humid rain forest of lowland and upland Africa, the genus Musa provides one of the most important basic staple food for large populations (Vuylsteke and Swennen, 1992). African countries account for 35% of world's plantain and banana production (INIBAP, 1989). In Nigeria, plantain is an important traditional staple food for both rural and urban dwellers and serves as a source of revenue for small holders who produce them both at the compound farms, mixed crop farms and small-scale sole plantain farms (Baiyeri, 1998).

Over the years, there has been a compendium of problems that tend to impede crop production generally and plantain production in particular. Some of these problems are draught and organic matter status of the soil (Awodoyin, 2003), pests and diseases, labour shortage, poor agronomic practices and post harvest constraints (Robinson, 1996) and weed menace. Of these problems, weed menace happens to be the most detrimental and its control cost is highly prohibitive. Weed control is the single most important component accounting for 30 - 40 percent of the overall cost of plantain production in Nigeria (Ndubizu and Obiefuna, 1979). Bananas and plantains have become more difficult to produce and more expensive for consumers to buy in recent decades due to these problems (IITA Annual Report, 1994).

Although Nigeria produces about 1 million tonnes of plantain annually, the fruits are under supplied probably because most of the fruits are supplied from small scale plantation growers or home gardens (Awodoyin, 2003). According to him, this shortfall in supply indicates that there is a potential for increased production to supply the domestic and international market and to exploit this potential, plantain production must shift from small-scale production to medium — large scale production systems.

Plantains are the fourth most important global food commodity. They also play a role in feeding the ever rising world population in general and Africa in particular. Plantains serve as a source of revenue for small holders. Of all the problems militating against plantain production, weed menace serves as one of the most serious impediments or stumbling blocks to its production. The acquisition therefore, of a weed management technique, which will effectively suppress weed menace and enhance plantain productivity to meet the demand by the teeming world population becomes paramount. It is against this background that the initiative of the researcher to undertake this painstaking and cost intensive study stands justified.

OBJECTIVES OF THE STUDY

The objectives of the study therefore are:

(1)   To evaluate the efficiency of six weed management techniques for the control of weeds in plantain production (Musa sp. AAB) and,