Agriculture Reference
In-Depth Information
chemical fertilizers. In the twenty-first century, the importance of chemical fertilizers in improving
crop yields will continue and is expected to be still higher due to the necessity of increase in yields
per unit land area rather than increasing land areas. Further, judicious use of chemical fertilizers
along with other complementary methods, such as the use of organic manures, and exploiting the
genetic potential of crop species and cultivars within species in nutrient utilization will be extremely
useful and necessary (Fageria, 2005).
The main objectives of controlled condition experiments are to understand the basic prin-
ciples. In the case of soil fertility and plant nutrition, such experiments are mainly conducted to
understand nutrient movements, absorption, and utilization processes in soil plant systems. In
addition, nutrient/elemental deficiency/toxicity symptoms and adequate and toxic concentrations
in plant tissue are also determined under controlled conditions. Further, for example, pot experi-
ments with different types of soils can show the degree of response that may be anticipated at
different soil test levels and serve as excellent checks on the ratings being used. Since such tests
provide no measure of the cumulative effects of treatments on yield or soil buildup or depletion,
they have limited value in determining the rates of fertilizer that should be recommended for sus-
tained productivity. Greenhouse pot studies, in which plants are used for estimating the relative
availability of nutrients, can also provide useful indices of the relative availability of a standard
fertilizer source in different soils and indices of different fertilizer sources. A detailed discussion
regarding the basic principles and methodology in conducting controlled condition experiments
is given by Fageria (2005).
3.7.1.1 Observation and Data Transformation in Greenhouse Experiments
In greenhouse experiments, important observations that should be recorded and that will be helpful
in the analysis and interpretation of experimental results are growth, yield, and yield components.
For example, in cereals, important measurements or observations are plant height, dry weight of
straw, grain yield, panicle number, grain sterility, and thousand grain weight. Similarly, in legumes,
the straw yield, grain yield number of pods, seeds per pod, and hundred grain weight are gener-
ally recorded. In addition, GHI is also calculated based on the straw and grain yield data to know
how photosynthetic products were translocated to economic parts (grain or seeds) of the plant.
Greenhouse experimental data should be transformed per plant basis (generally 3-4 plants per
pot are used for annual crops) for statistical analysis. The following equations are used for data
transformation for statistical analysis in the greenhouse experiments:
strawyield ingpot
numberofplants pot
−
1
Strawyield gplant
(
−
1
)
=
−
1
grainyield ingpot
numberofplants pot
−
1
Grainyield gplant
(
−
1
)
=
−
1
numberofpanicles pot
numberofpla
−
1
Number of panicles plant
(
−
1
)
=
nts pot
−1
unfilledspikelets
unfilledand filledspi
Spikelet sterility
(%) =
kelets
× 100
grainweight pot in g
numberofgrainspo
−1
Thousandgrain weight g
()=
×
1000
t
−1
