Influence of rates and time of Npk fertilizer application on cassava (Manihot esculenta Crantz)

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The influence of rate and time of NPK fertilizer application on cassava were studied at the research field of CSIR-Crops Research Institutes (CRI) at Fumesua, Kumasi. The experimental design employed was a 4 x 3 factorial experiment with 3 replications. The two factors studied were rate of NPK (15 – 15 – 15) fertilizer and the levels were 0, 200, 400 and 800kg/ha. The second factor was time of fertilizer application which were: 8, 16 and 24 WAP. The treatments were arranged in Randomised Complete Block Design (RCBD). The variety studied was Ampong, an improved cassava variety from the Crops Research Institute. The results shown that, all the fertilizer treatments resulted in greater growth, measured on plant height and canopy spread. Again, fertilizer treatments resulted in greater number of roots/plant ranging from 4.33 to 6.50 with the 400kg/ha recording the greatest which was significant (P<0.05) to the control only. Similarly, fertilizer application improved yield ranging from 23.0 to 36.0 t/ha and the highest yield obtained by the 400kg/ha treatment which was significantly (P<0.05) higher than the control. In addition, fertilizer application did not affect (P>0.05) root quality factors including tuber shelf life at 7 days after harvesting. Finally, time of fertilizer application did not affect (P>0.05) cassava growth, yield and other parameters studied. Among the fertilizer rates, the 400kg/ha gave the best growth and root yield. Indeed, there appeared to be negative effects of fertilizer beyond this rate. The most profitable treatment was the 400kg/ha and that, if farmers would apply fertilizer, it will enhance growth, root yield and income levels of farmers.  
A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, in partial fulfillment of the requirements for the award of Master of Philosophy Degree in Agronomy.