de Bie, Kees 
  
Figure 6° shows how the soil-WHC affects yields (ANOVA P of 5.3%). Soils with a 
poor WHC had higher yields. This can be explained by the fact that soils with 
adequate water contents throughout the year promoted luxuriant growth, no 
flowering, and poor fruit production (Purseglove 1977). If step-wise forward 
regression, with all classes of terrain, texture and WHC as co-variables was done, 
only WHC would significantly explain 6.3% of the variability of Ln(Yields+1). 
Slope angles within orchards varied from 0-20% (median of 4%); the data were 
poorly correlated with yield (Pearson coefficient of 11%). The pH of the topsoil 
(measured with a field kit; range of 4.0-8.0; median of 6.0) and yield had a 
correlation of 17%. The farmer's assessment of the fertility status of the orchard 
soil is positively though not significantly correlated with yield (Figure 6°). 
6 T T T 
  
T T T T T T T 
o 
T 
| 
T 
1 
> 
T 
1 
T 
r 
T 
  
14x 
- 13x | E | 
16x | 
= | 
gr 11x Ar nn F conn 
d i i iis | 15x 
Ln (Yield+1) 
o 
T 
N 
T 
- 
T 
L 
T 
L 
T 
  
  
  
  
  
  
  
  
  
  
  
CSC SCL  LSSL Hill Footslope Terrace other poor Other Good 
a. Top-soil Texture b. Terrain form C. Water holding capacity d. Soil fertility 
Figure 6. Mango yields plotted against land and soil characteristics. 
4.5 Operations and Observations 
PLANTING 
Mango is planted during the rainy season that lasts from May to September. 
Generally, purchased seedlings are planted without applying any inputs (30x) or 
with application of farmyard manure, NPK, and/or the insecticide ‘Furadan’ (9x). 
Ten farmers planted mango seeds without use of any soil amendments or 
pesticides. 
PRUNING 
Annual pruning takes place during July and August. Half of the farmers pruned 
their trees; the impact of pruning on yields was clear (Figure 7^). Linear regression 
showed that pruning explains significantly 12.696 of the total variability in yields: 
Ln(Yield+1) = 0.81 + 1.31 (if pruning is done). 
WEEDING 
Only 2 out of 45 farmers did not weed their orchards. Normally, weeding started 
during the first months of the rainy season (May to July) and ended in the period 
Aug.-Oct. (Figure 7^). Weeding was done manually (23x), by 2-wheel tractor (18x) 
or by 4-wheel tractor (4x). Figure 7^ shows the clear impact of mechanical 
weeding on mango yields. It explained 596 of the overall yield variability with a P of 
the coefficient of 7%. The relation between yield and weeding is: Ln(Yield*1) 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 
329