It has been proved that irrigation with high saline water and leaching fraction (LF) affect crop yield, but the effects of irrigation water salinity (ECiw) and LF on fruit quality remain largely elusive. We therefore investigated the effects of ECiw and LF on the yield, fruit quality, and ion content of hot peppers. An experiment using irrigation water with five levels of salinity (ECiw of 0.9, 1.6, 2.7, 4.7, and 7.0 dS·m−1) and two LFs (0.17 and 0.29) was conducted in a rain shelter. The experiment took the form of a completely randomized block design, and each treatment was replicated four times. We increased the salinity of the irrigation water by adding 1:1 milliequivalent concentrations of NaCl and CaCl2 to a half-strength Hoagland solution. The plants were irrigated for 120% and 140% evapotranspiration, corresponding to an LF of 0.17 and 0.29. Results showed that the total fruit yield decreased significantly with an increase in the ECiw as a result of reduction both in the fresh weight of fruit and the number of fruit per plant. An increase in the ECiw also led to a decrease in the total dry biomass of fruit and plant, as well as decreasing water use efficiency (WUEF). Salinity reduced the appearance of the fruit by both decreasing the length (FL) and maximum width (FMW) of the fruit. However, increased ECiw also improved the taste of the hot peppers by increasing the total soluble solid (TSS) content, as well as adding to their nutritional quality with a higher content of Vitamin C (VC). Their storage quality was also improved because of an improvement in the firmness of the fruit (Fn) as well as a reduction in the fruit water content (FWC). An increase in the LF led to an increase in the total fruit yield, total dry biomass of fruit and plant, and WUEF; it also increased the FWC and VC content, and decreased the FMW and fruit shape index (FSI). The threshold-slope linear response and sigmoidal-sharp models were both a good fit for the measured total fruit yield, and the LF had no significant effect on the model parameters. The relative TSS and Fn increased linearly as the electrical conductivity (EC) of soil-saturated paste extract (ECe) increased, whereas they decreased linearly as the relative seasonal evapotranspiration (ETr) increased regardless of the LFs. The relative FW, FL, and FMW decreased linearly with the increased ECe, and increased linearly with the increased ETr regardless of the LFs. The relative fruit Na+ concentration increased linearly as the ECe increased. The regression correlations between the total fruit yield, fruit quality parameters, ion contents, and ECe or ETr could provide important information for salinity and irrigation water management with a compromise between the hot pepper yield and fruit quality.
Rangjian Qiu, Yuanshu Jing, Chunwei Liu, Zaiqiang Yang, and Zhenchang Wang
Rangjian Qiu, Zaiqiang Yang, Yuanshu Jing, Chunwei Liu, Xiaosan Luo, and Zhenchang Wang
In this experiment, the responses of plant growth, gas exchange parameters, and ion concentration to different levels of irrigation water salinity (ECiw of 0.9, 1.6, 2.7, 4.7 and 7.0 dS·m−1) and leaching fractions (LFs of 0.17, 0.29) were investigated in hot pepper plants. The pot experiment was conducted using a completely randomized block design with four replications in a rain shelter. Results showed that the height of the hot pepper plants decreased as the ECiw was increased from 25 d after transplanting (DAT) and increased when the LF was increased from 55 DAT. Neither the ECiw nor the LF influenced the root length. An increase in the ECiw caused the suppression of the stem diameter (SD); leaf length; leaf area; leaf chlorophyll content (CCI); dry biomass of roots, stems, and leaves; net photosynthesis (P n); stomatal conductance (g S); transpiration rate (T r); and intercellular CO2 concentration (C i). An increase in the LF caused the SD, leaf length, leaf area, and dry biomass of stems and leaves to increase. However, the dry biomass of roots and the P n, g S, T r, and C i were not significantly affected by the LF, except for the C i measured on 23 DAT and the T r on 76 DAT. The Na+ concentrations in the roots and stems increased, whereas the K+/Na+ ratios decreased as the ECiw increased. An increase in the LF led to a decrease in the Na+ concentration of the roots and stems, whereas there was an increase in the K+ concentration in the stems and the K+/Na+ ratios in the roots and stems. Collectively, an increase in the ECiw had an adverse effect on plant growth and gas exchange and led to the accumulation of the Na+ concentration in the roots and stems, whereas an increase in the LF enhanced plant growth, leaf transpiration, and K+ concentration and reduced the accumulation of the Na+ concentration in the roots and stems. We suggest that higher quantity of water should be applied in higher saline irrigation for satisfactory performance for hot pepper growth.