Biochar Implications Under Limited Irrigation for Sweet Corn Production in a Semi-Arid Environment

Abstract

The integration of biochar and deficit irrigation is increasingly being evaluated as a water-saving strategy to minimize crop yield losses under reduced irrigation in arid and semi-arid regions such as West Texas. A 2-year (2019 and 2020) open-field study evaluated the effect of two types of biochar amendments (hardwood and softwood) and three irrigation rates [100, 70, and 40% crop evapotranspiration (ET _c ) replacement] on the physiology, plant growth, and yield of sweet corn in semi-arid West Texas. All experimental units were replicated four times in a split-plot design. The chlorophyll content (Chl _SPAD ) in 40% ET _c dropped significantly compared to 100% ET _c and 70% ET _c during the reproductive phase. Although water stress under 40% ET _c decreased photosynthesis (P _n ) to limit transpiration (E) by stomatal closure, it improved intrinsic water use efficiency (iWUE). The above-mentioned gas exchange parameters were comparable between 100% ET _c and 70% ET _c . Both biochar treatments increased Chl _SPAD content over non-amended plots, however, their effect on gas exchange parameters was non-significant. All growth and yield-related parameters were comparable between 100% ET _c and 70% ET _c , but significantly greater than 40% ET _c , except water productivity (WP). Both deficit irrigation treatments improved WP over full irrigation in 2019, but in 2020, the WP gains were observed only under 70% ET _c . Hardwood biochar decreased soil bulk density and increased soil porosity, but it had a marginal effect on the water retention characteristics. These results suggest that 70% ET _c can be used as an alternative to full irrigation to save water with a minimal yield penalty for sweet corn production in the West Texas region. The hardwood biochar application improved the vegetative biomass significantly but yield marginally during the first 2 years of application. A long-term study is required to test the effect of biochar under deficit irrigation beyond 2 years.

Keywords: drought stress; photosynthesis; physiology; plant available water; semi-arid; water holding capacity; water productivity.

FIGURE 1

Daily maximum (max) and minimum (min) relative humidity (RH), daily maximum and minimum air temperature (AT), daily average solar radiation (SR), rainfall (Rf), and cumulative rainfall plus irrigation (RF + I) during the 2019 and 2020 growing seasons.

FIGURE 2

Measured soil water retention curves at (A) 0–5 cm and (B) 5–10 cm soil depths for biochar treatments after harvest in 2020.

FIGURE 3

Effect of biochar on the volumetric water content of soil at (A) saturated water content (0 kPa), (B) field capacity (-33 kPa), (C) the permanent wilting point (-1,500 kPa), and (D) plant available water after harvest in 2020. The error bars represent ± standard error. Different letters indicate significant differences (p ≤ 0.05) among treatments.

FIGURE 4

Chlorophyll (Chl_SPAD) of sweet corn under deficit irrigation (A,B) and biochar application (C,D) during the 2019 and 2020 growing seasons. The error bars represent ± standard error. Different letters indicate significant differences (p ≤ 0.05) among treatments on a measurement day in Figures 4–8.

FIGURE 5

Stomatal conductance (g_s) of sweet corn under deficit irrigation (A,B) and biochar application (C,D) during the 2019 and 2020 growing seasons.

FIGURE 6

Transpiration (E) of sweet corn under deficit irrigation (A,B) and biochar application (C,D) during the 2019 and 2020 growing seasons.

FIGURE 7

Photosynthesis (P_n) of sweet corn under deficit irrigation (A,B) and biochar application (C,D) during the 2019 and 2020 growing seasons.

FIGURE 8

Intrinsic water use efficiency (iWUE) of sweet corn under deficit irrigation (A,B) and biochar application (C,D) during the 2019 and 2020 growing seasons.