de Bie, Kees
only 15% that the residuals are normally distributed (Figure 12). In spite of this
low probability, the results are considered sound; only 6 orchards (see the solid
line in the left graph of Figure 12) showed Ln(yield+1) residuals of 1.5 to 3.5 while
their actual reported yields were zero.
2 T T T T T 5 3 T T T T T 20 T T T T T
5 rv 7
$y 2 So o e a 157 |
Ok ET IS zz. @&e----- = a ; -
2 qu e e e £ !
3 Ce ? ° 5 :
3 A % iA 10r 1
© 5 | a
a "S !
2r | # |
S 5 t
-3r = 3
9 & o9 ee
4 | 1 | l ] 2 o Se © od ©
-1 0 1 2 3. 4 5 6 U 4 -3 -2 -1 0 1 2 E -3 -2 -1 0 1 2
Estimates Residuals Residuals
Figure 12. Normality of regression results.
The model can be written as an equation with two look-up tables:
Ln (Yield+1) in ‘000 Bath/ha = - 1.11 + 1.165*YEA + 1.32*AZO + 0.008*TRA*CCO + 0.78*IRR
+ 0.35*pH + values from look-up tables
Where:
YEA = 1 for a relatively good year and -1 for a relatively bad year
AZO = 1 if Azodrin is used as pesticide
TRA = 1 if weeding with a tractor (not manual)
CCO = Canopy cover of all trees in the orchard (%)
IRR = 1 if possible to apply supplementary irrigation water
pH = pH of the topsoil
Look-up tables:
1 Water holding capacity 2 pest control by motor sprayer
Terrain unit poor other Prunin Not done Done
Hill +0.87 0.00 Not done 0.00 no cases
Footslope . -1.37 -0.40 Done +0.52 +1.14
Terrace -0.98 0.00
The equation suggests that yields are higher if:
e Itis not an off-year (effect by biennial bearing behavior of mango)
e The top-soil has a relatively high pH
e The orchard is situated on hills and has soils with a relatively poor water
holding capacity
The ability exists to apply supplementary irrigation water
In fully grown orchards weeding is done by tractor
Pruning is practiced
Spraying of insecticides is done using a motor sprayer
Azodrin is used to control caterpillars
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 335
