Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 17: 948 - 958. Published May 8, 2009.
Investigation of agronomic factors constraining productivity of grain maize (Zea mays L.) at Zanyokwe irrigation scheme, Eastern Cape, South Africa
Fanadzo, M., Chiduza, C*. and Mnkeni, P.N.S.
Department of Agronomy, Faculty of Science and Agriculture, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa.
*Corresponding author email: cchiduza@ufh.ac.za Tel: +2740-602-2226; Fax: +2786-628-2602
ABSTRACT
Objective: The underperformance of many smallholder irrigation schemes in South Africa is largely attributed to socio-economic constraints, but little attention has been paid to the relationship between farmer agronomic practices and crop productivity. Two on-farm trials were therefore carried out at Zanyokwe irrigation scheme (ZIS) to: (i) evaluate the relationship between cultivar, nitrogen (N) rate, plant population and planting time on maize grain yield (Experiment 1); and (ii) compare grain yields of new hybrids to cultivars commonly grown by farmers (Experiment 2).
Methodology and results: The treatments for experiment 1 were maize cultivars (PAN6777 and DKC61-25), N rate (60 and 250 kg N ha-1), plant population (40 000 and 90 000 plants ha-1) and planting time (early: within the first 28 days of beginning of season on 15 November or late: planting after 15 December). In Experiment 2, eight cultivars were compared; two popularly grown by farmers at ZIS and two each from the three maturity classes (early, medium and late), which were top performers in regional variety trials conducted by the ARC from 2002 to 2004. Regardless of cultivar, higher yields were obtained when maize was planted early and fertilised at 250 kg N ha-1. The short-season cultivar DKC61-25 yielded optimally when grown early at 90 000 plants ha-1 whilst the long-season cultivar PAN777 performed better at 40 000 plants ha-1. Generally, N rate and planting time had the most significant effects on yield. New hybrids yielded 50 to 65% more than the cultivars commonly grown by farmers.
Conclusion and application of findings: These preliminary results suggest that lack of viability of smallholder irrigation schemes in South Africa is partly a result of inappropriate agronomic practices for irrigated crop production by farmers. It is recommended that more focused research be designed to address the problems of planting time, fertility, and cultivar selection and population management in ZIS. Training programs on basic management practices such as cultivar selection for irrigated crop production by the Department of Agriculture are expected to benefit farmers as part of the ongoing revitalization of smallholder irrigation schemes in the province.
Key words: Maize, grain yield, agronomic constraints, research agenda
FULL PAPER [PDF AVAILABLE HERE]
