Growth, yield and water use efficiency response of greenhouse-grown hot pepper under Time-Space deficit irrigation

Greenhouse-grown hot pepper was used to investigate the effect of Time-Space deficit irrigation (TSDI), a newly developing irrigation technique based on regulated deficit irrigation (RDI) and partial rootzone drying (PRD), by measuring plant growth, yield and irrigation water use efficiency. The treatments consisted of factorial combinations of three factors, organized following an orthogonal L9 (3)4 test design with four growing stages. Three irrigation strategies (conventional furrow irrigation with full-water when soil water content was lower by 80% of field capacity (F), conventional furrow irrigation with 50% of full-water (D) and alternate furrow irrigation with 50% of full-water (P)) as the main plot factor were applied to select the optimum irrigation parameter at different stages of crop development, the treatment in which irrigation water was applied to both sides of root system when soil water content was lower by 80% of field capacity during all stages was considered as control (FFFF). Water consumption showed some significant effect of irrigation treatment during the growing period of different drought stress patterns application, and therefore decreased in these treatments to a level around 54.68–70.33% of FFFF. Total dry mass was reduced by 1.17–38.66% in TSDI treatments compared to FFFF. However, the root–shoot ratio of FFFF was lower than other treatments and the differences from FFFF and other TSDI treatments were statistically significant. The highest total fresh fruit yield (19.57 T ha−1) was obtained in the FFFF treatment. All deficit irrigations increased the water use efficiency of hot pepper from a minimum of 1.33% to a maximum of 54.49%. At harvest, although there was difference recorded as single fruit weight and single fruit volume were reduced under the TSDI treatments, total soluble solids concentration of fruit harvested under the water-deficit treatments were higher compared to FFFF.

Research highlights▶ Time-Space deficit irrigation (TSDI) with varying degree and irrigation strategies at different growth stages reduced the fruit growth rate of hot pepper, but the re-watering had over compensatory effect to reduce the negative influence on fruit growth. Water deficit treatment at seeding stage obviously suppressed the vegetative growth of hot pepper and was advantageous to transfer more stored photosynthesis product and nutrition substances to the reproductive organ after the flowering stage. ▶ With regard to irrigation water use efficiency in the production of fresh fruit weight, a certain amount of deficit succeeds in improving it, the greatest efficiency is achieved by the treatment of DFDP. As a rule, the treatments with deficit at several stages prove to be more efficient, except for FDDD and PPDF. ▶ Further orthogonal analysis showed that appropriate degree of deficit irrigation at the first growth period, irrigation renewal in time at the second and third growth period, partial rootzone drying at the fourth growing period could result in high yield, total biomass and better yield components in hot pepper in a greenhouse environment. ▶ The optimum soil water deficit levels with highest yield, total biomass, water use efficiency, were proved to be 50%–60%, 80%–90%, 60%–70%, and 50%–60% of field capacity at the four growth stages above mentioned, with the corresponding optimum total irrigation water of 176 mm which was distributed as following: 30 mm during the seeding stage, 70 mm during the bloom and fruit setting stage, 53 mm during the vigorous fruit-bearing stage, and 23 mm during the later fruit-bearing stage. ▶ The results of this study suggest that the difficulty to generally apply TSDI for increasing shoot biomass production but the DFDP practices can be viable and advantageous option next to FFFF to prevent crop yield reduction when and if there is water shortage or to improve crop quality. The ultimate profitability of a given watering regime for plant growth in the greenhouse requires fine-tuning of the pattern and level of water supply to the responses of the plant during different stages.