ABSTRACT
A study was carried out at the Department of Crop Science, Faculty of Agriculture Experimental Farm, University of Nigeria, Nsukka to: (i) evaluate the growth and yield of four improved cassava varieties, (ii) determine optimum NPK fertilizer rate for increased productivity and (iii) determine the best mode of fertilizer application for increased productivity. The experiment was laid out in a randomized complete block design with three replications. Four varieties of cassava; TMS 01-1368 (yellow root), TME 419, TMS 98 05 05 and TMS 05 10, four levels of NPK fertilizer 0, 200, 400 and 600 and three modes of fertilizer application; single at 4 weeks after planting (WAP), split at 4 and 8 WAP and split-split at 4, 8 and 12 WAP were used for the study. Data were collected on the following agronomic and yield parameters: survival count, number of branches, number of leaves, plant height, stem girth, canopy diameter, tubers and garri yields (tonnes/ha). The variety TME 419 under the early establishment gave significantly (p<0.05) higher percentage survival count of 91 % although it was statistically similar to TMS 01 1368 (yellow root) with 90.8 %. The variety TMS 98 05 05 gave significantly (p<0.05) lower survival count and was statistically similar to variety TMS 05 10.The variety TMS 98 05 05 gave significantly (p< 0.05) higher number of leaves. TME 419 variety had significantly (p< 0.05) lower number of leaves in the second and fourth month after planting. Fertilizer application rate of 200 kg/ha gave significantly higher number of leaves at the second month after planting while 600 kg/ha gave significantly (p<0.05) higher number of leaves in the fourth month. The control gave the lowest number of leaves in both months and the single application of fertilizer gave significantly (p<0.05) higher number of leaves of 67 at the fourth month of crop growth. The variety TMS 98 05 05 at the early season planting gave significantly higher tuber and garri yields of 39.8 and 9.68 t/ha, respectively, at 12 months of crop growth although it was statistically similar to TMS 01 05. The rate of 200 kg/ha of NPK gave significantly (p < 0.05) higher tuber and garri yields of 24.69 t/ha and 5.15 t/ha, respectively at 6 months of growth. However, the rate of 400 kg/ha of NPK gave significantly (p < 0.05) higher tuber and garri yields of 39.4 and 10.12 t/ha at 12 months of growth. The 400 kg/ha rate of fertilizer gave similar growth and yield results when compared with 600 kg/ha rate and should be adopted because of lower production cost. Split application of fertilizer is statistically similar to split – split application and should be adopted for cassava production since it is more economical to farmers because it minimizes cost of labour for fertilizer application and reduction in total cost of cassava production. TMS 98 05 05 that showed significantly highest growth and yield measures could be adopted for production in Nsukka in order to boost cassava production.
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INTRODUCTION
Cassava (Manihot esculenta Crantz.) is a perennial shrub of the family Euphorbiaceae. It is a root crop that is propagated vegetatively from stem cuttings for commercial purposes but can also be propagated through seed. Cassava has been a crop of South America where the indigenous tribes learnt to extract the poisonous juice from the root for the preparation of meal (Leon, 1997). After the conquest of the Americans, the plant was taken to Africa and Asia where it became an important crop for human as well as animal consumption (Ross, 1975). The leaves and tender shoots are important source of vitamins, minerals and proteins (Balagopalan, 2002; Nweke et al., 2002). It was introduced into the southern part of Nigeria during the period of slave trade proliferated by Portuguese explorers and colonizers in the sixteenth century. Nigeria is the world’s largest producer of cassava. The Presidential Cassava Transformation Initiative in Nigeria in 2003 sought to position cassava as a commodity crop and foreign exchange earner, beyond its traditional role as a food crop. Due to its adaptability to marginal soils and erratic rainfall, high productivity per unit of land and labour and possibility of supply throughout the year has been obtained (Nweke et al., 2002). The adaptation to different edapho-climatic conditions (Adeniji et al., 2011) makes cassava a favorite dry season crop grown in inland valleys in west and central Africa (Lahai and Ekanayake, 2009) and it is highly susceptible to excessive water (Ande, 2011). It displays an exceptional ability to adapt to climate change (Albuquerque, 1978). Cassava can grow and yield reasonably well on soil of low fertility where production of most other crops would be uneconomical (Carter et al, 1992). Under favorable soil and climatic conditions, fresh tuber yields of 40-60 t/ha can be obtained (IITA, 2005) It has high resistance to drought, pest and diseases conditions. Also it is suitable to store its roots for long periods underground even after they have matured. Cassava is one of the efficient producers of carbohydrates among the higher plants (Rogers and Appan, 1971). Due to tolerance of cassava to water stress, cassava is used as a famine crop in North Africa where it is the main food source during prolonged periods of drought (Purseeglove, 1954). The root of cassava is made into flours. It has other products as dry extraction of starch, glue or adhesives and modified starch, in pharmaceutical as dextrines, as processing inputs, as industrial starch for drilling and processing food (Arene, 1978). It is extensively used as filler in the manufacture of paints (Godfrey et al., 2012). Interest has recently been developed in its large scale exploitation as an animal feed or as a raw material for the production of starch or power alcohol. On a worldwide basis, it is ranked as the sixth most important source of calories in
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the human diet (FAO, 1999). Cassava is the world’s sixth most important crop (Lebot, 2009) and constitutes a staple food for over 700 million people (Njoku et al., 2010)
Depending on the varietal and ecological factors of cassava, some of the varieties are early maturing while others have longer periods to mature. The long duration of 8-24 months of cassava in the soil requires steady supply of nutrient for optimum growth and yield of the crop. However, it has been suggested that commercial cassava be established in marginal soils (Evenson and Keating, 1978). Use of fertilizers and other organic manures are limited in cassava farms as farmers always grow the crop on fallow lands (Acosta and Perez, 1954). Fallow land is expected to supply the nutrient needs of cassava. It has been reported that cassava extracts large amounts of nutrients from the soil especially K and N and continuous cultivation without adequate fertilization would lead to soil depletion and reduced yield (Kurmarohita, 1978). Cassava removes about 55 kg/ha N, 132 kg/ha P and 112 kg/ha K (Howeler, 1991)
Based on the foregoing, it is important to determine NPK fertilizer requirement and best mode of application for increased cassava productivity in improved cassava varieties. Hence, the objectives of the study were to:
1. evaluate growth and yield of four improved cassava varieties
2. determine optimum NPK fertilizer rate for increased productivity, and
3. determine the best mode of fertilizer application for increased productivity.
