The effect of reduced branching on yield and water use of chickpea (Cicer arietinum L.) in a Mediterranean type environment

Abstract

An earlier study indicated that seed yield in chickpea was limited by the low harvest index of later-formed basal branches and that eliminating these by restricting branching to no more than two per plant, each with a high harvest index, should result in higher seed yields. This was tested in a dry Mediterranean type environment at Merredin in the south western Australian cereal belt by debranching high density stands of chickpea (70 plants m−2), leaving only the main stem and first basal branch, and comparing them with freely branching controls. Eliminating less productive, later basal branches had virtually no effect on above-ground biological yield (approx. 650 g m−2) but increased the harvest index by 31% and seed yield from 1.35 to 1.87 t ha− (P < 0.01). Dry matter ot tops, produced after flowering in the debranched crop, exceeded the control by 39 g m−2 and this was associated with an increased in apical (fruiting) branches of 110% in the main stem and 183% in the first basal branch. The debranched crop produced 73% more pods than the control, due to more flowers (2800 v. 2263 m−2) and increased pod set (61 v. 44%). Increased efficiency of podding in the debranched crop was compensated, to a small extent, by decreases in seeds per pod and mean seed weight relative to the control. Maximum leaf area index of 2.6 was similar for both treatments but took 14 days longer to attain in the debranched treatment, thus increasing leaf area duration (LAD) during seed filling. In the debranched crop, slower canopy development was associated with lower water use (122 mm v. 137 mm) orior to flowering, and with greater LAD and increased water use (76 mm v. 61 mm) after flowering. Total water-use was about the same at 198 mm. Leaf water potentials were consistently higher in the debranched plants throughout the season, reaching −2.6 MPa (0.6 MPa higher than controls) at 119 days, 30 days after 50% flowering. The debranched crop produced 9.5 v. 6.8 kg seed ha−1 mm−1 of total water used. Results are discussed in relation to application of the ideotype approach to yield improvement, noting that selection from stands at conventional low plant densities may fail to detect higher yielding, less competitive (communal) plant types.