Water use of chickpea (Cicer arietinum L.): Response to genotype and phosphorus fertilizer rates in winter and summer sowings

In the rainfed cropping systems of the semi-arid tropics where water supply is often limited and erratic, management practices should always be geared towards efficient utilisation of the water available for crop growth. This study aimed at evaluating the effects of genotype and phosphorus fertilizer rates on water use and water use efficiency of chickpea in the dry environments of Limpopo Province, South Africa. Field experiments were conducted during winter 2009 (Experiment I) and summer 2009/2010 (Experiment II) using a factorial treatment combination of 3 phosphorus (P) fertilizer rates (0 kg P ha^-1 [low], 45 kg P ha^-1[medium] and 90 kg P ha^-1 [high]) and 4 chickpea genotypes (ICCV92944, ICCV3110, ICCV4306 and ICCV7307) arranged in a randomized complete block design with 3 replications. Crop evapotranspiration (ET) was determined by monitoring soil water content at 7-day intervals using a neutron probe, and water use efficiency was determined as a ratio of total crop biomass/grain yield to cumulative ET. Genotype and phosphorus application did not affect ET in both Experiment I and II. Genotype did not affect water use efficiency of biomass production (WUE_b) in both experiments. In contrast, WUE_b) increased with P rate in Experiment II. Similarly, water use efficiency of grain yield (WUE_g) was greater at high (4.7 kg ha^-1 mm^-1) compared with medium (4.2 kg ha^-1 mm^-1) and low (3.0 kg ha^-1 mm^-1) P rate in Experiment II. WUE_g varied from 1.33 kg ha^-1 mm^-1 (genotype ICCV4306) to 6.4 kg ha^-1mm^-1(ICCV92944) in Experiment I, and from 3.1 kg ha^-1 mm^-1 (ICCV92944) to 4.9 kg ha^-1 mm^-1 (ICCV4306) in Experiment II. Grain yield increased (P<0.001) with WUE_g in both Experiment I (R² = 0.94) and Experiment II (R² = 0.99). Therefore use of management practices that enhance water use efficiency such as genotype selection and P fertilizer application may be immensely important in improving chickpea productivity in dry environments.