Water‐Use Efficiency and Its Relation to Crop Canopy Area, Stomatal Regulation, and Root Distribution
            1

Although water-saving measures are increasingly being adopted in orchards, little is known about how different irrigation methods enhance water use efficiency at the root system level. To study the allocation of water sources of water absorption by cherry roots under two irrigation methods, surface irrigation and drip irrigation, oxygen isotope tracing and root excavation were used in this study. We found that different irrigation methods have different effects on the average δ18O content of soil water in the soil profile. The IsoSource model was applied to calculate the contribution rate of water absorption by cherry roots under these irrigation methods. During the drought period in spring (also a key period of water consumption for cherry trees), irrigation water was the main source of water absorbed by cherry roots. In summer, cherry roots exhibited a wide range of water absorption sources. In this case, relative to the surface irrigation mode, the drip irrigation mode demonstrated higher irrigation water use efficiency. After two years of the above experiment, root excavation was used to analyze the effects of these irrigation methods on the distribution pattern of roots. We found that root distribution is mainly affected by soil depth. The root system indexes in 10–30 cm soil layer differ significantly from those in other soil layers. Drip irrigation increased the root length density (RLD) and root surface area (RSA) in the shallow soil. There was no significant difference in root biomass density (RBD) and root volume ratio (RVR) between the two irrigation treatments. The effects of these irrigation methods on the 2D distribution of cherry RBD, RLD, RSA and RVR, which indicated that the cherry roots were mainly concentrated in the horizontal depths of 20 to 100 cm, which was related to the irrigation wet zone. In the current experiment, more than 85% of cherry roots were distributed in the space with horizontal radius of 0 to 100 cm and vertical depth of 0 to 80 cm; above 95% of cherry roots were distributed in the space with the horizontal radius of 0 to 150 cm and the vertical depth of 0 to 80 cm. Compared with surface irrigation, drip irrigation makes RLD and RSA more concentrated in the horizontal range of 30–100 cm and vertical range of 0–70 cm.

Download Full-text

Row spacing fails to modify soil evaporation and grain yield in spring wheat in a dry Mediterranean environment

Australian Journal of Agricultural Research ◽

10.1071/ar9930661 ◽

1993 ◽

Vol 44 (4) ◽

pp. 661 ◽

Cited By ~ 21

Author(s):

IAM Yunusa ◽

RK Belford ◽

D Tennant ◽

RH Sedgley

Keyword(s):

Solar Radiation ◽

Grain Yield ◽

Water Use Efficiency ◽

Water Use ◽

Ground Cover ◽

Soil Types ◽

Row Spacing ◽

Crop Canopy ◽

Mediterranean Environment ◽

Use Efficiency

The loss of moisture by evaporation from soil under crop canopies (Esc) has been recognized as a major cause of poor water use efficiency (WUE), and hence poor grain yield, in crops grown in environments with limited rainfall. Agronomic approaches to restrain Esc aim to reduce the transmission of solar radiation to the soil beneath the crop by improving ground cover by the crop canopy. However, the sparse canopies produced in these environments have a limited effect on evaporation during the energy dependent first stage (Es1); much of the evaporation is independent of energy at the soilsurface (Es2), and therefore less sensitive to the influence of the crop canopy. Manipulating plant arrangement, primarily by changing row spacing, may provide a simple approach for improving ground cover and restraining E,, without changing GAI, and thus improving WUE and grain yield. To explore the potential benefit of variable row spacing on Esc and grain yield in the dry (300 mm) Mediterranean environment of the eastern wheatbelt of Western Australia, spring wheat was grown in 0.09, 0.18, 0.27 and 0.36 m row spacings on coarse textured and fine textured soil types at Merredin in 1989. Esc was determined with an empirical model and measured with microlysimeters. Row spacing had no significant effect on the development of green area index (GAI), dry matter (DM) accumulation and evapotranspiration (ET) throughout the season. However, in mid-season, the proportion of ground covered by the canopy was higher and transmission of solar radiation was reduced in the 0.09 m row spacing compared with the 0.36 m row spacing. These effects did not restrain E,,, which was similar in all treatments. Esc was not restrained even when the plant density was doubled in the 0.09 m row spacing treatment. Esc during the season averaged 88 mm across all row spacings on both soils; this accounted for 56% and 48% of the mean seasonal ET on the coarse textured and fine textured soils respectively. Consequently, neither water use efficiency nor grain yield were affected by variation in row spacing; water use efficiency averaged 25 kg DM ha-1 mm-1 on both soil types. For dry Mediterranean environments of Western Australia, it was concluded on the basis of these results, and yield data from other row spacing trials in the same districts, that there are no significant yield benefits to be obtained by reducing the row spacing from the current spacing of 0.18 m.

Download Full-text

Improving Water Use Efficiency by Optimizing the Root Distribution Patterns under Varying Drip Emitter Density and Drought Stress for Cherry Tomato

Agronomy ◽

10.3390/agronomy11010003 ◽

2020 ◽

Vol 11 (1) ◽

pp. 3

Author(s):

Abdul Shabbir ◽

Hanping Mao ◽

Ikram Ullah ◽

Noman Ali Buttar ◽

Muhammad Ajmal ◽

...

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Root Distribution ◽

Deficit Irrigation ◽

Distribution Patterns ◽

Root Weight ◽

Cherry Tomato ◽

Cropping Season ◽

Use Efficiency ◽

Cropping Seasons

The spatial distribution of root systems in the soil has major impacts on soil water and nutrient uptake and ultimately crop yield. This research aimed to optimize the root distribution patterns, growth, and yield of cherry tomato by using a number of emitters per plant. A randomized complete block design technique was adopted by selecting eight treatments with two irrigation regimes and four levels of emitters under greenhouse conditions. The experiment results showed that the root distribution extended over the entire pot horizontally and shifted vertically upwards with increased emitter density. The deficit irrigation resulted in reduced horizontal root extension and shifted the root concentrations deeper. Notably, tomato plants with two emitters per plant and deficit irrigation treatment showed an optimal root distribution compared to the other treatments, showing wider and deeper dispersion measurements and higher root length density and root weight density through the soil with the highest benefit–cost ratio (1.3 and 1.1 cm cm−3, 89.8 and 77.7 µg cm−3, and 4.20 and 4.24 during spring–summer and fall-winter cropping seasons, respectively). The increases in yield and water use efficiency (due to increased yield) were 19% and 18.8%, respectively, for spring–summer cropping season and 11.5% and 11.8%, respectively, for fall–winter cropping season, with two emitters per plant over a single emitter. The decrease in yield was 5.3% and 4%, and increase in water use efficiency (due to deficit irrigation) was 26.2% and 27.9% for spring-summer and fall-winter cropping seasons, respectively, by deficit irrigation over full irrigation. Moreover, it was observed that two, three, and four emitters per plant had no significant effects on yield and water use efficiency. Thus, it was concluded that two emitters per plant with deficit irrigation is optimum under greenhouse conditions for the cultivation of potted cherry tomatoes, considering the root morphology, root distribution, dry matter production, yield, water use efficiency, and economic analysis.

Download Full-text