Water use of kabuli chickpea (Cicer arietinum L.) cultivars in Canterbury

A research program to study the growth, development and water use of Kabuli chickpeas was initiated in 1998 and continued to 2001. The response of early and late sown Kabuli chickpeas (cultivars - Sanford, Dwelley and B-90) to irrigation applied during the vegetative, flowering and pod-filling to physiological maturity phases was investigated in two growing seasons. Irrigation was applied weekly in amounts equal to the difference between the estimated potential evapotranspiration and rainfall plus irrigation in the previous week. Physiological and environmental parameters were measured to identify the causes of yield variability in relation to irrigation, sowing date and season. Seed yield depended on the interaction between irrigation and sowing date and cultivar and irrigation from emergence to physiological maturity. The later treatment gave the highest seed yield at > 4.7 t ha⁻¹. Averaged over years, irrigation increased seed yield by 74- 124 % and trends were similar for total dry matter (TDM) yield. The increase in seed yield due to irrigation was a function of greater TDM production, harvest index, pods plant ⁻¹ and mean seed weight. Further, seed yield was doubled in the November sown chickpeas (4.6 t ha⁻¹) compared to December sowing and cv. Sanford produced 14 and 16 % more seed than cv. Dwelley and cv. B-90 respectively. Green area index, green area duration (GAD), intercepted radiation, utilization coefficient and total intercepted PAR were significantly (P < 0.001) increased with irrigation. There was a highly significant linear relationship between TDM, seed yield and cumulative intercepted PAR for all sowing dates. In the range of 736 to 1128 MJ m⁻² intercepted PAR, yield increased linearly, producing 1.23 to 2.53 g dry matter MJ⁻¹ PAR and 0.77 to 0.91 g seed MJ⁻¹ PAR respectively. The TDM was more strongly correlated (r² = 0.69 - 0.83) with GAD than seed yield (r²= 0.60 - 0.69) and accumulation of TDM was highly dependent on intercepted PAR. Water use was about 426 mm for the fully irrigated treatment and at least 175 mm for the non-irrigated plants. There was a significant correlation (p < 0.001) between water use and biomass yield (r² ≥ 0.80) and water use and seed yield (r² ≥ 0.75). These cultivars are capable of drawing water from depths greater than 60 cm. However, most of the water use (0.49 to 0.93 mm 10⁻¹ cm soil layer day⁻¹) came from the top 0 - 30 cm, where most of the active roots were concentrated. There were also highly significant (p < 0.001) interactive effects of irrigation, sowing date and cultivar on water use efficiency (WUE) and the trend was similar to that for seed yield. The estimated WUE ranged from 22 - 29 kg dry matter ha⁻¹mm⁻¹ and 10 - 13 kg seed yield ha⁻¹ mm⁻¹. These cultivars have the potential to produce seed yields greater than 4 t ha⁻¹ in Canterbury providing they are early sown and are irrigated. Drought responses of yield, phenology, radiation use efficiency and yield components were determined, and were highly correlated with maximum potential soil moisture deficit (Dpmax). In the irrigated plots, Dpmax was above 62 mm and increased to about 358 mm in the rainfed plots. Chickpea yield, intercepted radiation and number of pods plant⁻¹ decreased linearly as the Dpmax increased. Both TDM and seed yield strongly depended upon total water received (rain plus irrigation) and the crop produced about 2.81 g m⁻² TDM and 1.65 g m⁻² seed per mm of water. Penman's model accurately described the response of yield to drought and the limiting deficit for this type of soil was approximately 150 and 90 mm for the November and December sowings respectively. There was little evidence supporting the idea of moisture sensitive period in these Kabuli chickpea cultivars. Irrigating at any stage of crop development increased yield, provided that the water is needed as determined by the potential soil moisture deficit and sowing early in the season (October - November). Over the range of Dpmax values experienced (62 - 358 mm), photothermal duration from sowing to harvest maturity decreased from above 1968 °Cdays (full irrigation) to about 1800 °Cdays (rainfed plots). Two years field data of chickpea cultivar Sanford were used to develop empirical relationships between water use, total intercepted radiation, GAI, total dry matter, pods m⁻² and seed yield. The empirical model derived was successful in predicting total intercepted PAR accurately. Seed yield of all the cultivars both rainfed and irrigated was predicted reasonably well. However, the model needs further validation in areas beyond Canterbury