Jatropha - Bioenergy Crop Plants - page 319

14.3.3 p lantation
Field preparation for plantations mainly consists of land clearing and preparation of the planting
pits for the seedlings. Although planting can be done without any clearing, for oil production pur-
poses it is advisable to clear the land at least partially (Gour 2006). Tall trees can be left, but shrubs
and bushes that cover the soil should be cut. After clearing, planting pits of 30-45 cm × 30-45
cm × 30-45 cm should be dug before the rainy season (Gour 2006; Singh et al. 2006). For good
establishment, the pits are refilled with a mixture of the local soil/sand/organic matter (compost
and/or artificial fertilizer) in the ratio of 1:1:1, respectively. Seeds or cuttings can be directly planted
in the pits. Transplanting of prerooted cuttings (grown in poly bags) in the pits gives better results.
The best time for planting is the warm season—if watering can be provided, otherwise it has to be
carried out during the onset of the monsoon or monsoon season (Openshaw 2000). Gour (2006)
reported that seedlings require irrigation, especially during the first 2-3 months after planting. Of
course, the water demand depends on local soil and climatic conditions.
Actual plant spacing depends on the end use of the plant, seed quality, humidity, rainfall, inter-
cropping, etc. Narrow spacing is preferred if the plant is grown as a hedgerow, live fence, or for soil
conservation purposes. Plant spacing of 2 × 2 m (2500 plants/ha), 2.5 × 2.5 m (1600 plants/ha) or
3 × 3 m (1111 plants/ha) are common practice (Heller 1996). Kaushik and Kumar (2006) proposed
wider spacing (4 × 2 and 4 × 3 m) and spacing of 5 × 2 and 6 × 6 m as the optimum for an agro-
forestry system to obtain high yield from individual jatropha plants. In 2.5-year-old plantations, it
was observed that with the increase in spacing, seed yield per tree increased significantly, whereas
the seed yield per hectare decreased (Chikara et al. 2007). Openshaw (2000) recommended spacing
in hedgerows for soil conservation as 15-25 cm within and between rows (in case of double fence),
resulting in 4000-6700 plants/km. Wider spacing is reported to give larger yields of fruit, at least
in early years.

14.3.4 c arE and m aintEnancE

14.3.4.1 trimming and Pruning
Pruning and canopy management are important because they help in the growth of more branches
and the stimulation of abundant and healthy inflorescence, eventually enhancing good fruit setting
and seed yield (Gour 2006). Trimming of branches during the period from February to March for
the first 5 years is necessary to give bushy shape to the plant. Pruning at the age of 6 months is use-
ful to pinch off the terminal shoots to induce lateral branching (Gour 2006; Kaushik and Kumar
2006). Pruning the main branch at 30- to 45-cm height depending on the growth rate is ideal (Gour
2006). At the end of the first year, the secondary and tertiary branches should be pruned to induce
more branches. During the second year, each side branch should be pruned up to two-thirds of the
top portion, retaining one-third of the branches on the plant. Pruning should be done in the dry or
winter period after the trees have shed their leaves. This results in a lower and wider tree shape,
helps in earlier seed production, and facilitates manual harvesting. Once in every 10 years, the
entire plant has to be cut low, leaving a stump of 45 cm. The regrowth is quick, and the trees start
yielding again within approximately 1 year. This intervention induces new growth and helps to
stabilize the yield (Gour 2006; Kaushik and Kumar 2006). In addition to trimming hedgerows and
pruning plantations annually, periodic thinning of plantations is also recommended. Starting from
1600 seedlings/ha, stand density should be thinned to 400-500 trees/ha in the final mature stand
(Openshaw 2000).

14.3.4.2 Fertilizer application
Optimal application of fertilizer and irrigation water can increase the seed and oil yield. Permanent
humid situations and/or situations with high irrigation and fertilizer application can induce high
biomass but low seed production. The optimal levels of input to achieve high harvest index in a