International Journal of Horticulture, 2017,Vol.7, No. 23, 205-218
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deeper insight into the yam growth process, even when seed weight is recorded, thus enabling decision making on
the basis of above ground auxiliary variables, which are highly associated with yam yield.
3 Results
3.1 Regression analysis of yield on associated variables when yam detachment is made at second yield
recording
Analysis of variance in linear model on longitudinal data from 31 plants with interpolated values of variables at
interim time points are shown in Figure 3, Figure 4, Figure 5, Figure 6, Figure 7 with yield
y=y(t)
,
t
ɛ [0, 203]
days and seven auxiliary variables associated with interim weight
y
of yam. The variables in the Figure 3, Figure
4, Figure 5, Figure 6, Figure 7 are seed weight (
x
1
), time (
x
2
), maximum plant height (
x
3
), maximum girth at base
(
x
4
), maximum girth at middle (
x
5
), maximum girth at top (
x
6
), and canopy radius (
x
7
) and yield
y(t)
at time
t
. The
values of the variables are linearly interpolated at intermediate time points.
At time
t=
0
,
proliferation rate is taken to be 0. The data so constructed are used in R program with package
`persp' for three dimensional plots.
Data given in Figure 3, Figure 4, Figure 5, Figure 6, Figure 7 provide the following least squared regression line
with
R
2
=0.4638.
y
= - 0.5955137 + 1.3842935
x
1
+ 0.0025382
x
2
+ 0.0044606
x
3
- 0.0086307
x
4
+ 0.0278280
x
5
-0.0505629
x
6
+
0.0030111
x
7
Of these, the variables seed weight
x
1
and time
x
2
are highly significant with respective
p
values 7
e
-15 and 1.07
e
-09, in
t
test.
3.2 Proliferation rates of yield versus seed weight
Proliferation rate is related to yield by the relation
y (t)
=
exp
(
), higher the value of rate over a
considerable time region, higher is the yield. We compute the proliferation rate curve by a modified technique
proposed in Dasgupta (2017c), in Figure8, Figure 9,and Figure 10, for seed weight 800 g, 650 g, and 500 g,
respectively. Figure 8 has a hump like structure indicating high rate over a considerable region of time, indicating
massive accumulation of yam underground in that time zone. The performance is slightly poor for seed weight
650 g in Figure 9, as the peak value is not maintained for long. Proliferation rate of yield for seed weight 500 g
rises steep onto the top of Figure 10, indicating a good potential of yam growth if the rate could be maintained in
an extended lifetime by nourishing the plants.
Figure 8 Proliferation rate of yam (800 g): 2nd interim cut, wt. exp (-.01 x); spline
Proliferation rate is a scaled version of velocity . This measure is independent of the
choice of unit used in measuring
y
. Consider
(x, y)
coordinates of mean growth curve in Figure 2 for 800 g of
seed weight with yam detachment at the time of second growth recording. Time points
x
when at least one data
