de Bie, Kees 
  
1.06 + 0.921 (if weeded by tractor). The canopy cover of all trees in the orchard 
(96) is significantly correlated with the use of tractors (Figure 7°); the two-sample t- 
test showed that the distributions shown are significantly different (P=0.4%). 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
6 T T 6 T T 1 NETT TIU 
sr ] Sr | Eco i 
ger 
24 M 48 Ji PT | 
T T = eor | i | abe / i 
63 4 ET *:s« 3, | i 22x | 48 [i id 
= = i i 3 Li \ off 
5 5 A ó 40: uh 
1 21x Va bed 1 jmd | 1 8 2 €t pu | 
0" LH {1 1 1 1 EL 0 i i i i 0 1 L 1 i 1 1 
a NR upb M, oto MU on dono ue fios de 
Figure 7. a: Effect of pruning on mango yields. 
b: Months of weeding. 
c: Effect of weeding method on mango yields. 
d: Relation between canopy cover and weeding by tractor 
(counts, normal curves and box-plots). 
FERTILIZATION 
Farmers used compound fertilizers (NPKs) anly (21x), NPKs with Farm Yard 
Manure (FYM; 6x), FYM only (5x) or none (13x). These amendments did not have 
a significant impact on yields, although NPKs appear to improve yields (Figure 8 
left). Half of the farmers that did not achieve yields did apply NPKs. Most farmers 
that applied NPKs (27x) applied it during the period March-July (Figure 8 right). 
Two farmers applied NPKs during two separate periods. NPK application was 
mainly by surface broadcasting under the tree canopy (23x); four farmers 
practiced various forms of incorporation in the soil. Quantities applied were 
expressed in various units, e.g. handfuls/tree, and could not be converted to 
standard units. The main NPK-type used was 15-15-15. 
  
  
  
  
  
  
  
  
  
6 T T 
5+ | E 1 
ce 5 
+ | 
S | 
S3Ssr = 
= 7 27x DT] 
AL | 4 Start 
End 
0 i LL 1 1-1 1 4 5 1 1 1 1 
None Applied Jan. May Sep. Dec. 
NPKs applied NPK application 
Figure 8. Impact of mineral fertilizer application on mango yields. 
  
330 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.