Effect of shading and light recovery on the growth, leaf structure, and photosynthetic performance of soybean in a maize-soybean relay-strip intercropping system

Abstract

Intercropping is an important agronomic practice adopted to increase crop production and resource efficiency in areas with intensive agricultural production. Two sequential field trials were conducted in 2015–2016 to investigate the effect of shading on the morphological features, leaf structure, and photosynthetic characteristics of soybean in a maize-soybean relay-strip intercropping system. Three treatments were designed on the basis of different row configurations A1 (“50 cm + 50 cm” one row of maize and one row of soybean with a 50 cm spacing between the rows), A2 (“160 cm + 40 cm” two rows of maize by wide-narrow row planting, where two rows of soybean were planted in the wide rows with a width of 40 cm, and with 60 cm row spacing was used between the maize and soybean rows), and CK (sole cropping of soybean, with 70 cm rows spacing). Results showed that the photosynthetically active radiation transmittances of soybean canopy at V5 stage under A2 treatment (31.1%) were considerably higher than those under A1 (8.7%) treatment, and the red-to-far-red ratio was reduced significantly under A1 (0.7) and A2 (1.0) treatments compared with those under CK (1.2). By contrast with CK, stem diameter, total aboveground biomass, chlorophyll content and net photosynthetic rate decreased significantly except plant height under A1 and A2. The thickness of palisade tissue and spongy tissue of soybean leaf under A1 and A2 were significantly reduced at V5 stage compared with CK. The leaf thicknesses under A1 and A2 were lower than those in CK by 39.5% and 18.2%, respectively. At the R1 stage of soybean (after maize harvest), the soybean plant height, stem biomass, leaf biomass and petiole biomass under A1 and A2 treatments were still significantly lower than those under CK, but no significant differences were observed in Chl a/b, Pn, epidermis thickness and spongy tissue thickness of soybean leaves in A2 compared with CK. In addition, the soybean yields (g plant-1) under A1 and A2 were 54.69% and 16.83% lower than those in CK, respectively. These findings suggested that soybean plants can regulate its morphological characteristics and leaf anatomical structures under different light environments.

Optimum leaf excision increases the biomass accumulation and seed yield of maize plants under different planting patterns

“…This increase might be due to the improved light conditions, reduced shade and optimum thermal conditions at the remaining leaves of the maize that probably increased the chlorophyll contents of maize plants (Figure ). Similarly, other researchers have argued that improved light conditions increase the chlorophyll content of soybean plants (Fan et al, ; Feng et al, ). Photosynthetic characteristics are responsive to variation in LAI caused by various leaf excision treatments (T. Liu et al, ; Yang et al, ).…”

Water and radiation use in maize–pea intercropping is enhanced with increased plant density

“…Leaves of crops are sensitive to the light environment and photosynthetic capacity is generally decreased by shading (Fan et al., ). As a cereal and a C 4 crop, maize is highly efficient at light interception and utilization (Omoto, Taniguchi, & Miyake, ).…”

Optimum strip width increases dry matter, nutrient accumulation, and seed yield of intercrops under the relay intercropping system

“…Moreover, past studies have confirmed the adverse impacts of shading conditions on soybean morphology (Khalid et al, 2019;Raza, Feng, Iqbal, Ahmed, et al, 2019), physiology (Feng et al, 2018), and dry-matter accumulation (Ahmed et al, 2018;Yang et al, 2014). However, after maize harvesting in MSR, soybean exhibit strong recovery growth (Wu et al, 2016), and the competition for available resources with maize is compensated from the vegetative stage to the flowering stage (Fan et al, 2018). At the reproductive stage, soybean in MSR has better access to available resources compared to sole soybean plants, especially for light and nutrients .…”

“…In MSR, maize produces higher seed yield due to optimum growth and an edge row-effect, and in some studies, relay-cropped maize produced higher seed yield as compared to maize yield in sole cropping systems (Chen et al, 2017;Raza, Feng, Khalid, Iqbal, Meraj, et al, 2019;Yang et al, 2017). However, soybean in MSR produced lower crop yield than sole soybean because it is planted two months after maize sowing, and the severe competition for available resources with maize plants reduces the initial growth of soybean plants (Fan et al, 2018). Moreover, past studies have confirmed the adverse impacts of shading conditions on soybean morphology (Khalid et al, 2019;Raza, Feng, Iqbal, Ahmed, et al, 2019), physiology (Feng et al, 2018), and dry-matter accumulation (Ahmed et al, 2018;Yang et al, 2014).…”