Abstract:
Most of the farmers of irrigated areas cultivate their fields with simple cultivator which
creates a hard pan in the subsoil due to tilling the soil at same depth with same implement
which has adverse effect on crop growth and yield. In addition to tillage nitrogen
management is a key factor for better crop growth and yield. Two field experiments were
conducted to evaluate the “impact of different tillage systems, nitrogen rates and time of
application on growth, yield attributes, grain yield, quality and nitrogen uptake of hybrid
maize” at the Agronomic Research Area, University of Agriculture, Faisalabad during 2008
and 2009. Both the experiments were laid out on a randomized complete block design
(RCBD) with split plot arrangement using three replications, in a net plot size of 4.5m x 10m.
In first experiment three tillage systems (conventional tillage, tillage with mouldboard plough
+ 2-cultivation and tillage with chisel plough + 2-cultivation) were kept in main plots and
nitrogen levels (100, 150 and 200 kg N ha-1) in sub-plots. Different tillage systems
significantly influenced soil physical properties, growth and yield characteristics as well as
maize yield. Increasing tillage intensity resulted to improved soil porosity and reduced soil
bulk density which led to higher crop yield. Chisel ploughed plots produced higher leaf area
index (LAI), crop growth rate (CGR), leaf area duration (LAD), yield and yield components
in comparison with other tillage systems. Maize yield with chisel tilled plots was 18% and
9% higher than mould board ploughed and conventionally tilled plots, respectively.
Generally differences between different nitrogen application rates were more pronounced,
increasing nitrogen application rate had positive impact on growth, yield components, yield
and kernel quality. Increased LAI, CGR, grains weight per cob, 1000-grain weight and grain
yield was recorded with 200 kg ha-1 nitrogen application. Maize yield with 200 kg ha-1
nitrogen application was 17% and 8.50% higher than 100 and 150 kg ha-1 nitrogen
application respectively. The N uptake at 200 kg ha-1 nitrogen application was 240.88 kg ha-1
which was higher in comparison with other nitrogen treatments. Nitrogen application showed
positive association with protein contents but negative association with grain oil and starch
contents.
In the second experiment different systems and nitrogen application timings were allotted to
main plots and subplots respectively. Physiological, agronomic and qualitative traits in maize
varied with nitrogen application timings. Physiological attributes like LAI and CGR was
higher with nitrogen application in three splits i.e. 1/3 at sowing + 1/3 at knee height + 1/3 at
tasseling, while the lowest was recorded with nitrogen application in two splits i.e. 1⁄2 at knee
height + 1⁄2 at tasseling. The yield contributing parameters such as grains weight per cob and
1000-grain weight were found higher in plots fertilized with nitrogen in three splits. Similarly
the highest grain yield was recorded in plots fertilized with nitrogen in three splits in
comparison with other nitrogen treatments. The higher LAI, CGR and maize yield with
nitrogen application in three splits was probably due to more availability of nitrogen at
critical growth stages as compared to other nitrogen application timings. In addition to
physiological and agronomic traits, nitrogen application at different growth stages also
significantly affected the maize quality. Nitrogen application in three splits resulted to higher
grain protein contents (8.23%) and (8.16%) during 2008 and 2009, respectively while the
lowest grain protein contents recorded where all the nitrogen was applied at the sowing time.
The higher protein contents in 2008 were probably due to drier environments at grain
development as compared to 2009. Nitrogen uptake was also higher with nitrogen application
in three splits while the lowest N uptake was recorded in sole application. Nitrogen uptake
was higher during 2009, while lower during 2008 which might be attributed to nitrogen
losses through leaching due to high rainfall at seedling stage during 2008. On the basis of
economic analysis benefit-cost ratio (BCR) was calculated for both the experiments which
showed that maize grown with nitrogen application @ 200 kg ha-1 in three splits by
ploughing the soil with chisel plough was economical and gave more profit compared with
other treatments. However, it is concluded that for obtaining higher maize yield and net
income maize hybrid pioneer 31R88 should be grown with 200 kg ha-1 nitrogen application
in three splits by preparing the field with chisel plough.