Yield and yield development of chickpea (Cicer arietinum L.)

Preliminary research has shown that chickpea has the potential to be a high yielding crop. However, like most grain legumes, the problem of harvest index variability in chickpeas hinders the realisation of their full potential seed yield. The overall objective of this work was to study the effect of agronomic factors on the development of seed yield in chickpeas. Experiments in 1992-93 and 1993-94 studied the effects of sowing date, nitrogen and inoculation. The high rate of abortion of reproductive structures observed in the 1992-93 and 1993-94 seasons led to the 1994-95 experiment. This experiment was designed to study the effect of reduced light intensity and water availability on the abortion of reproductive structures in chickpeas. The optimum time of sowing of chickpeas in Canterbury was found to be from October to early November. This gave a seed yield over 3 t/ha. Application of 90 kg of N/ha increased seed yield by 18 % in soils that were low in available nitrogen. Irrigating chickpeas in an unusually dry year (1994-95) gave a seed yield of 3.9 t/ha in full light. Inoculation with Rhizobium had no effect on seed yield. In 1993-94 more than 60 % of seed yield was produced on secondary branches and only about 10 % on main stems. In 1994-95 irrigated plants produced about 50 % of their seed yield on secondary branches. However, unirrigated plants had more than 40 % of their seed yield on primary branches with about 35 % on secondary branches. In both 1993-94 and 1994-95, secondary branches accounted for 60-79 % of the total number of branches per plant. The heaviest seeds (average 317 mg) in early sown plants were located on the middle third of the branches, while in later sowings, the heaviest seeds (average 325 mg) were located on the bottom third of the branches. The differences in total dry matter (TDM) production due to sowing date in 1993-94 were mainly a function of plant population. However, maximum dry matter production was not affected by plant population. Maximum crop growth rates increased from 12 g/m² per day in the July sowing to 21 g/m² per day in the November sowing. In 1993-94 nitrogen at 90 kg/ha increased TDM production from 693 to 783 g/m² (P<0.01). There was a highly significant linear relationship (r² = 0.991) between dry matter accumulation and cumulative intercepted photosynthetically active radiation (PAR) in 1994-95, which showed the plants produced 2.6 g dry matter for each MJ of intercepted PAR. Irrigated plants reached canopy closure (LAI = 3) about 12 days faster than unirrigated plants (71 DAE). Irrigation significantly increased PAR interception by 38 % from 355 to 490 MJ/m² (P<0.001). Crop growth rate (CGR) of unshaded plants (27 g/m² per day) was 93 % higher than the CGR of shaded plants. Harvest index (HI) ranged from approximately 0.23 in winter to 0.40 in the spring sown plants. Irrigation and reduced light intensity both reduced HI from approximately 0.52 to 0.37 (P<0.001). A combination of the two factors together decreased HI from 0.56 to 0.25 (P