I - --ii

have a much lower critical concentration value for the available soil phosphorus
than the other grain legumes such as lentils and faba beans (Saxena 1979), their
growth and yield can be substantially restricted under field conditions due to a
deficient phosphorus supply. On a field at the ICARDA subsite in Kafrantoon,
where the available soil phosphorus was 2.5 ppm P in the top 15-cm soil layer and
1.5 ppm in the subsequent 15-cm soil layer, conspicuous growth and nodulation
response to phosphate application was obtained (Tab. 6) with winter-planted ILC
482 chickpeas in 1980-81 season. Because of the presence of a native population
of Cicer Rhizobium at this site, there was no difference in the number of nodules
per plant: however, the nodule dry weight was very much restricted by a shortage
of phosp'iorus. Thus phosphorus deficiency resulted, indirectly, in a nitrogen
deficienc.y by restricting symbiosis, which ultimately reflected in a poorer phytomass
yteld (Tab. 6). Application of 50kg P20 5/ha resulted in improved nodule dry
wei,,ht as well as total shoot phytomass. This experiment illustrates the importance
of an adequate phosphorus supply in permitting the development of a
suitable symbiotic system.
The data presented in Tab.s 5 and 6 emphasize the importance of the fertility
status in determining the need for fertilizer application. The fertilizer phosphorus
had no effect on the crop at an available phosphorus status in soil of 7.5 ppm
P, but improved the crop performance on a soil with an available phosphorus
content of 2.5 ppm P. In both experimental sites, the available soil potassium
Table 6
Effect of fertilizer application and inoculation with chickpea Rhizobium on the nodulation and
shoot dry matter per plant at the flowering stage of ILC 482 at ICARDA subsite
Kafrantoon, 1980-81 winter planting.
Nodules per plant Shoot dry weight
Treatments Number Dry weight (mg) (g/plant)
Control
50g P2,/ha (P)
60 kg K,0/ha (K)
Inoculation (1)
1 + P
1 + K
i + P + K
100 kg N/ha + P + K
LSD (5%)
90 DAE Flowering 90 DAE Flowering 90 DAE Flowering
20.5
25.6
24.0
25.6
27.7
27.4
29.1
26.0
N.S.
1. DAE = days after emergence.
NS = not significant.
22.7
25.8
24.0
22.7
23.5
28.9
26.6
22.0
N.S.
67.5
176.0
84.6
94.4
167.7
94.6
211.1
86.7
34.6
105.5
175.'
109.1
116.8
179.7
111.7
157.2
96.2
52.1
0.84
1.68
0.88
1.01
1.59
0.91
1.98
1.31
0.36
1.65
3.30
1.79
1.79
2.79
1.33
2.99
3.15
0.82
135