| dc.description.abstract | Poor rainfall, increasing temperatures, increasing population and poor soils pose threats and
concerns over survival of the human population. Conservation agriculture (CA), a potential
mitigation solution to these threats, is a sustainable agriculture system based on three principles:
minimum soil disturbance, permanent soil organic cover and diverse use of crop rotations.
However, little information is available on the performance of most maize genotypes in relation
to emergence, establishment, reproduction, senescence and grain yield under CA since they are
mainly developed under conventional practices. Hence, an experiment was set up at Harare (red
clay), Domboshava (DTC) (sandy loamy), Madziva (sandy), Hereford (red clay) and Zimuto
(sandy) where CA plots were laid adjacently to Conventional Tillage Practices (CP) plots. The
main objective of the study was to determine genotypic performance of 16 Zimbabwean
produced and grown maize genotypes and determine yield gains of combining CA and drought
tolerant maize varieties (DTs) at contrasting sites over two seasons. Results showed that CA and
CP tillage systems had a significant effect on emergence percentage, number of leaves per plant
at 6 weeks after sowing, anthesissilking interval (ASI) and grain yield (P < 0.05). Overall
emergence percentage, number of leaves per plant and grain yield were higher under CP as
compared to CA. ASI was shorter under CA as compared to CP. Medium season drought tolerant
maize varieties outperformed short season DT varieties with regards to early vigor, chlorophyll
content at grain filling stage and grain yield. The medium season DT maize varieties included
PGS 63, ZS 265 and Pannar 53. Short season varieties such as Pannar 413, ZM 309, SC 301 and
ZM 401 showed more grey leaf spot (GLS) incidences under CA as compared to CP. A
significant tillage system × genotype interaction was observed at all sites and most of the maize
genotypes had shorter ASI under CA as compared to CP. Sites showed significant effect on
emergence %, days to 50 % emergence, all the early vigor parameters, anthesis date
(AD),anthesissilking interval (ASI), leaf diseases, Area Under the Curve (AUC) and grain yield.
Hereford had the highest yield, shortest AD and high early vigor. Domboshava had the higher
grain yield, emergence and AUC gains under CA than CP as compared to other sites. Soil
moisture was higher under CA than CP at days during grain filling at DTC. Seasons had
significant effect on maize genotypes and most had higher yield in 2012-13 as compared to
2012-13. It is not all DT maize genotypes that have cumulative benefits under CA and varieties
with high susceptibility to fungi are not recommended under CA systems since conditions that
favor development of fungi are more prevalent under CA as compared to CP and these include
overwintering material (residues) and high moisture conditions. It is not all sites that have more
grain benefit under CA: From this research the sandy loamy site had more grain yield gains
under CA than CP as compared to clay and sandy sites which favored CP. | en_US |
