Agriculture Reference
In-Depth Information
Table 18.1 Productivity, yield and nutrient dynamics of large cardamom agroforestry under alder
and mixed tree species (After Sharma et al. 1994)
Parameters
Alder-cardamom
Forest-cardamom
Biomass (kg ha −1 )
28,422
22,237
Net primary production (kg ha −1 year −1 )
10,843
7,501
Agronomic yield (kg ha −1 year −1 )
454
205
Nitrogen
Standing state in biomass (kg ha −1 )
395.15
205.26
N 2 -fixation (kg ha −1 year −1 )
65.34
-
Uptake from soil (kg ha −1 year −1 )
78.49
80.56
Retention (kg ha −1 year −1 )
56.12
49.55
Return to soil (kg ha −1 year −1 )
83.67
29.23
Exit through agronomic yield (kg ha −1 year −1 )
4.04
1.78
Use efficiency*
73
93
Back-translocation from senescent tree leaf (%)
3.85
17.49
Phosphorus
Standing state in biomass (kg ha −1 ) 32.357 17.900
Uptake from soil (kg ha −1 year −1 ) 13.178 6.517
Retention (kg ha −1 year −1 ) 6.328 3.840
Return to soil (kg ha −1 year −1 ) 6.146 2.347
Exit through agronomic yield (kg ha −1 year −1 ) 0.704 0.330
Use efficiency a 823 1151
Back-translocation from senescent tree leaf (%) 22.62 31.37
a Nutrient use efficiency is the ratio between annual production and nutrient uptake.
net annual fixation was 1.57 times greater in alder-cardamom (221 × 10 6 kJ ha −1
year −1 ). As for the net energy allocation in the under-storey, large cardamom crop
was much higher (45 percent) in the alder-cardamom system than in the forest-car-
damom system (31 percent) (Sharma R et al. 2002). Such figures clearly show that
N 2 -fixing alder is a better associate-shade-tree than mixed tree species, and creates
the conditions for a higher energy allocation in the cash-crop system. In absolute
terms, net energy allocation in cardamom crops was 2.3 times greater under the
alder-cardamom system, as opposed to the forest-cardamom system. In capsule
terms the increase was 2.2. Floor-litter energy build-up was conspicuous due to
more litter production and accumulation in the alder-cardamom system with 1.6
times more than in the forest-cardamom system.
The Energy Conversion Efficiency (ECE) at the autotrophic level is expressed as
a percentage and is defined as the ratio between the energy captured by vegetation
and the photo-synthetically active radiation that reaches an area over a certain period
of time (Sharma and Ambasht 1991). The ECE of the alder-cardamom system (1.87
percent) was higher than for the forest-cardamom system (1.19 percent). The range
of 1.8 to 3.5 percent ECE in the age series of Himalayan alder (Sharma and Ambasht
1991) and 1.8 to 4.2 percent in red alder stands in Canada (Smith 1977) indicate that
the 1.87 percent obtained in the alder-cardamom system is within the expected range.
Rawat and Singh (1988) reported an ECE of 1.1 percent in oak forests of the central
 
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