The Effects of Saline Water Drip Irrigation on Tomato Yield, Quality, and Blossom-End Rot Incidence --- A 3a Case Study in the South of China

<div><p>Saline water resources are abundant in the coastal areas of south China. Most of these resources still have not been effectively utilized. A 3-year study on the effects of saline water irrigation on tomato yield, quality and blossom-end rot (BER) was conducted at different lower limits of soil matric potential (-10 kPa, -20 kPa, -30 kPa, -40 kPa and -50 kPa). Saline water differing in electrical conductivity (EC) (3 dS/m, 4 dS/m, 4.5 dS/m, 5 dS/m and 5.5 dS/m) was supplied to the plant after the seedling establishment. In all three years, irrigation water with 5.5 dS/m salinity reduced the maximum leaf area index (LAI_m) and chlorophyll content the most significantly when compared with other salinity treatments. However, compared with the control treatment (CK), a slight increase in LAI_m and chlorophyll content was observed with 3~4 dS/m salinity. Saline water improved tomato quality, including fruit density, soluble solid, total acid, vitamin C and the sugar-acid ratio. There was a positive relationship between the overall tomato quality and salinity of irrigation water, as analyzed by principal component analysis (PCA). The tomato yield decreased with increased salinity. The 5.5 dS/m treatment reduced the tomato yield (Y_t) by 22.4~31.1%, 12.6~28.0% and 11.7~27.3%, respectively in 2012, 2013 and 2014, compared with CK. Moreover, a significant (P≤0.01) coupling effect of salinity and soil matric potential on Y_t was detected. Saline water caused Y_t to increase more markedly when the lower limit of soil matric potential was controlled at a relatively lower level. The critical salinity level that produced significant increases in the BER_i was 3 dS/m~4 dS/m. Following the increase in BER_i under saline water irrigation, marketable tomato yield (Y_m) decreased by 8.9%~33.8% in 2012, 5.1%~30.4% in 2013 and 10.1%~32.3% in 2014 compared with CK. In terms of maintaining the Y_t and Y_m, the salinity of irrigation water should be controlled under 4 dS/m, and the lower limit of soil matric potential should be greater than -20 kPa.</p></div

Variations of soil salinity with different treatments.

<p>(SIM and SOM represent the sampling location inside and outside the mulch, respectively.). DAT represented days after transplanted, Seedlings were transplanted into the fields on June 10.</p

The date of irrigation, drainage and soil sampling.

<p>The date of irrigation, drainage and soil sampling.</p

The tomato yield with different treatments.

<p>(The values of tomato yield are the means of three replications. Means followed by the same letter (a, b, c) do not differ significantly at the 0.05 level, according to Duncan’s multiple range test. I and D represent quotas of irrigation and depths of drain ditch, respectively. **and ns represent indicate the experimental treatment has an extremely significant (at 0.01 level) effect and no significant effect on the tomato yield, respectively.)</p

The comprehensive quality index (CQI) of tomato fruits irrigated using saline waters with different EC across the 3 years (The CQI was calculated using the Principle Component Analysis).

<p>The comprehensive quality index (CQI) of tomato fruits irrigated using saline waters with different EC across the 3 years (The CQI was calculated using the Principle Component Analysis).</p

Plant height, stem diameter and leaf area index of tomato under different treatments.

<p>Plant height, stem diameter and leaf area index of tomato under different treatments.</p

The content of available N (a), P (b) and K (c) in soil at a 0-20-cm depth with different treatments.

<p>(SIM and SOM represent the sampling location inside and outside the mulch, respectively. Means followed by the same letter (a, b, c) do not differ significantly at the 0.05 level, according to Duncan’s multiple range test. I and D represent quotas of irrigation and depths of drain ditch, respectively. *, **and ns indicate that the experimental treatment has a significant (at 0.05 level) effect, an extremely significant (at 0.01 level) effect, and no significant effect on the available nutrient, respectively.)</p

Ionic composition of the saline water treatments.

<p>Ionic composition of the saline water treatments.</p

Tomato yield (Y_t) with different treatments across the 3 years (t/ha).

<p>Note: The values of Y_t in three years are means of 3 replications. In the same column and in the same year, means followed by the same letter (a, b) do not differ significantly at the 5% level according to a LSD test. Each value is the mean ± SD (n = 3). Figures prior to ** were the F values, and ** mean significance at P≤0.01.</p><p>Tomato yield (Y_t) with different treatments across the 3 years (t/ha).</p

Experimental design.

<p>Experimental design.</p