Growth and Development of Horticultural Crops (1+1)

Tools for the canopy management

• Canopy architecture is a natural expression of the genetic make up of a tree. Genotypes vary in the canopy size and shape. However, the size and shape of the canopy may also be manipulated through various means.
  
Some details of a few of them are given here under.
Training

• Training of the perennial trees to the open vase centre is an age old practice to harvest the advantage of the light and ventilation. Basically, the training is a potential tool to manage the canopy architecture of a plant with weak stem like grape vine. Bower system of the training has been found to be the best in tropics throughout the world.
  
• Although, it is an expensive training system associated with the reduced light and temperature in vine canopy, increased humidity and disease incidence, it is inevitable for exploiting fully the productive potential of the grape cine in tropics, where the phenomenon of the apical dominance is more pronounced.
  
• It is possible to develop as many as 10 shoots/m2 by subdividing the apices growing in horizontal plain. Vertical canopies, which envisage the best utilization of the light and the minimization of building up of a high humidity in vine canopy, do not have provision to increase the number of fruiting units per unit area.
• The best way to manage the canopy in grape vines is to develop diageotropic canopies and increase the fruitfulness of the buds and consequently the cluster:cane ratio.
Pruning

• Pruning is a tool to regulate the tree size and shape to achieve a desired architecture of the canopy and also to reduce the foliage density by removing the unproductive branches of a tree.
  
• Shanmugavelu and Selvarajan, 1985 observed an increased fruiting in Himayunddin, Rumani and Kalepad varieties of mango. Pruning in mango was favourable for flowering by redistribution of endogenous harmones (Madhavarao and Shanmugavelu, 1975) and increasing the total phenolic contents in shoots (Chacko, 1968).
  
• The incidence of mango malformation was also reduced by reducing the foliage density by pruning. In mango annual topping or hedging or the combination of both, effectively controlled tree size but reduced the yields.
  
• On contrasts, topping plus biannual hedging although controlling vegetative growth to a lesser degree than annual pruning, produced yield similar to those of control trees.
  
• Topping at 15^° or 30^° produced better results than topping at 0° (Table 1).
  
• Hedging one side per year or all four sides every two years resulted in higher yields than hedging two sides per year (Table 2) (Victor and Nunez, 1997).
Table 1. Effect of topping angle on growth and yield of mature "Tommy Atkins" mango trees



Topping Angle	Growth				Yield (kg/tree)			Cumulative
	Height (m)		Canopy Vol(m3)
	1994	1995	1994	1995	1993	1994	1995
0o	6.22 b	6.30 b	147 c	122 b	139 b	240 ab	233 b	612
15o	6.83 b	7.10 b	299 b	158 b	187 b	283 a	248 b	718
30o	6.78 b	6.70 b	210 b	136 b	141 b	250 ab	242 b	633
Control	7.80 a	8.40 a	355 a	317 a	214 a	224 a	347 b	785

Table 2. Hedging intensity effect on growth and yield of mature "Tommy Atkins" mango trees



Topping Angle	Growth				Yield (kg/tree)			Cumulative
	Height (m)		Canopy Vol(m3)
	1994	1995	1994	1995	1993	1994	1995
One side (AN)	6.57 b	5.9 b	109 c	104 b	69 b	172	217 b	458
Two side (AN)	6.43 b	6.10 b	103 c	113 b	128 b	140	265 b	533
Four sides (AN)	6.57 b	6.10 b	215 b	136 b	85 b	235	245 b	565
Control	7.80 a	8.4 a	355 a	317 a	213 a	224	347 a	784

Means separation within columns by Tukey's multiple range test, 5% level.
• In Africa for mango size maintenance, pruning is performed shortly after harvest. The aim is to remove the growth which occurred after the previous harvest by heading all of the braches back. Size maintenance pruning is performed by hand or by mechanically hedging and may only be required every second or third year in cultivars or situations where yearly canopy expansion is not substantial.
• Yield in citrus could also be increased by removing the upright branches and encouraging the horizontal ones by pruning (Goswami et al., 1993). While, pruning of one-year-old shoots to their half length has been recommended to increase the yields in mandarin, skirt pruning at a length of 1 m could also increase the yield in Washington Navel sweet orange. Pruning and shoot topping are the regular practices to shape the canopy and to promote fruiting and ripening in grape.