Nitrogen fertilization coupled with foliar application of iron and molybdenum improves shade tolerance of soybean under maize-soybean intercropping

Abstract

Maize-soybean intercropping is practiced worldwide because of some of the anticipated advantages such as high crop yield and better utilization of resources (i.e., water, light, nutrients and land). However, the shade of the maize crop has a detrimental effect on the growth and yield of soybean under the maize-soybean intercropping system. Hence, this experiment was conducted to improve the shade tolerance of such soybean crops with optimal nitrogen (N) fertilization combined with foliar application of iron (Fe) and molybdenum (Mo). The treatments comprised five (5) maize-soybean intercropping practices: without fertilizer application (F0), with N fertilizer application (F1), with N fertilizer combined with foliar application of Fe (F2), with N fertilizer coupled with foliar application of Mo (F3) and with N fertilizer combined with foliar application of Fe and Mo (F4). The findings of this study showed that maize-soybean intercropping under F4 treatment had significantly (p< 0.05) increased growth indices such as leaf area (cm2), plant height (cm), stem diameter (mm), stem strength (g pot-1), and internode length (cm) and yield indices (i.e., No of pods plant-1, grain yield (g plant-1), 100-grain weight (g), and biomass dry matter (g plant-1)) of the soybean crop. Moreover, intercropping under F4 treatment enhanced the chlorophyll SPAD values by 26% and photosynthetic activities such as Pn by 30%, gs by 28%, and Tr by 28% of the soybean crops, but reduced its CO2 by 11%. Furthermore, maize-soybean intercropping under F4 treatment showed improved efficiency of leaf chlorophyll florescence parameters of soybean crops such as Fv/Fm (26%), qp (17%), ϕPSII (20%), and ETR (17%), but reduced NPQ (12%). In addition, the rubisco activity and soluble protein content of the soybean crop increased by 18% in maize-soybean intercropping under F4 treatment. Thus, this suggested that intercropping under optimal N fertilization combined with foliar application of Fe and Mo can improve the shade tolerance of soybean crops by regulating their chlorophyll content, photosynthetic activities, and the associated enzymes, thereby enhancing their yield and yield traits.

Maize-soybean intercropping at optimal N fertilization increases the N uptake, N yield and N use efficiency of maize crop by regulating the N assimilatory enzymes

“…Such improved N status and N use efficiency in the cereal-legume intercropping are directly linked to nitrogen assimilatory enzymes such as NR, NiR and GOGAT activities, which are the key enzymes involve in plant nitrogen metabolism ( Nasar et al., 2022b ). This study showed that maize-soybean intercropping significantly improved the NR, NiR and GOGAT activity of maize crop as compared with mono-cropping.…”

“…Possibly, this might be attributed to the nitrogen fixation ability of soybean, which helps improve the nitrogen content of maize plant, thereby enhancing the N metabolism and N-related enzymes of maize crop ( Nasar et al., 2022a ). It might also be due to the underlying rhizosphere alteration, changes in the soil enzymes and the root releasing chemicals, which ultimately triggers the plant nitrogen metabolisms system ( Nasar et al., 2022b ). Moreover, nitrogen fertilization is also known to improve the nitrogen metabolism of the plant by improving the nitrogen assimilatory enzymes ( Ben, 2016 ).…”

“…Additionally, the improved nitrogen assimilatory enzymes (i.e., NR, NiR and GOGAT activity) in the intercropping system equally contributes to the plant N content and its uptake ( Nasar et al., 2022a ). Previously, many studies have shown that cereal-legume cropping systems can significantly increase the plant N status due to the underlying rhizosphere modification ( Sun et al., 2018 ; Nasar et al., 2020b ; Raza et al., 2021 ), facilitative nutrient sharing through interspecific root interaction between intercrops ( Shao et al., 2020 ) and improved N assimilatory enzymes (i.e., NR, NiR and GOGAT) ( Nasar et al., 2022b ).…”

“…Thus, intercropping maize with soybean not only secures the regional food demand and nutritional quality of the forage industry but also improves the nutrient status of the maize crop besides providing an environmentally friendly and promising agricultural system for the future development. It is worth noting that, maize-soybean intercropping has been widely practiced to improve crop and forage yield, utilization of the natural resources, nutrient improvement of the cereal crop and soil health ( Du et al., 2020 ; Raza et al., 2020 ; Nasar et al., 2022b ). Nonetheless, relatively less data is available on the N yield, N use and utilization efficiency via regulation of N assimilatory enzymes in the maize-soybean intercropping.…”

Smallholder farmers' knowledge on the use of bioslurry as a soil fertility amendment input for potato production in Kenya

“…However, to obtain higher yields and quality crop production, farmers rush to use inorganic fertilizers (Mugo et al, 2021; Nasar et al, 2022). With the increase in environmental concerns, there is an urgent need to relook at the research priorities to focus on developing alternative sustainable crop production systems to be achieved through the providence of non‐pollutant, non‐conventional and cultural techniques.…”