Response of Quality Protein Maize (Zea mays L.) to Nitrogen Rates and Plant Population in Ambo, Central Ethiopia

Aims: Quality protein maize (QPM) is one of the major food crops in Ethiopia. However, agronomic management practices were not properly developed for QPM production in the highland areas of Ambo, central Ethiopia.

Methodology: A field experiment was conducted at Ambo Crop Protection Research Center Farm to investigate the effects of nitrogen and plant population using hybrid QPM variety, AMH-760Q.

Study Design: The treatments consist of four nitrogen rates (0, 46, 92 and 138 kg N ha-1) and four plant populations (44,444, 53,333, 66,666 and 88,888 plants ha-1) arranged in split plot design with three replications.

Results: The nitrogen rates and plant population were significantly (P = .05) influenced most of QPM parameters. Increase in both nitrogen rates and plant population delayed days to tasseling, silking and physiological maturity, and also increased plant height, stem diameter and leaf area index. The application of nitrogen increased ear diameter, ear length, number of ears per plant, number of seeds per ear, thousand seed weight, straw and grain yields. Similarly, plant population at 66,666 plants ha-1 improved most yield components, straw and grain yields of QPM. The straw, grain and total N uptake were also increased in response to N application. The interaction of nitrogen and plant population also significantly (P = .05) affected straw and grain yields.

Conclusion: The results demonstrate that the application of 92 and 138 kg N ha-1 to 66,666 plants ha-1 resulted in higher straw and grain yields. Also if there is a need for high straw production for livestock feed, 88,888 plants ha-1 with 92 kg N ha-1 could be recommended. This implies that QPM straw and grain yields could be maximized through proper matching plant population and N fertilizer rates.