Poly-γ-glutamic acid enhanced the yield and photosynthesis of soybeans by adjusting soil aggregates and water distribution

BACKGROUND

Poly-γ-glutamic acid (γ-PGA) is employed extensively in agriculture to enhance soil water retention; however, the underlying mechanism by which γ-PGA improves soil structure and soybean productivity in arid regions remains poorly understood. A micro-scale field experiment was conducted in the arid region of northwest China, employing five concentrations of γ-PGA to investigate its impacts on soybean yield, photosynthesis, and water-use efficiency, as well as soil aggregates and water distribution. The five levels of γ-PGA were 0 (CK), 10 (P1), 20 (P2), 40 (P3), and 80 kg ha-1 (P4).

RESULTS

The results demonstrated that the application of γ-PGA significantly improved soybean yield, photosynthesis, and chlorophyll content. It resulted in a decrease in soil aggregate content with a maximum diameter of less than 0.053 mm and an increase in the stability of soil aggregates in the uppermost layer of the soil (0-30 cm). The application of γ-PGA significantly increased soil water content, particularly in the uppermost layer of the soil, and effectively reduced water consumption and improving water use efficiency in soybeans. Overall, the P3 treatment exhibited the most pronounced improvement of soybean yield, photosynthesis, water-use efficiency, as well as distribution of soil aggregates and water. The correlation matrix heatmap also revealed a strong correlation between improvement of soybean yield or photosynthesis at various γ-PGA application levels and the enhancement of soil stability or soil water content.

CONCLUSION

The multivariate regression analysis revealed that an optimal application level of 46 kg ha-1 γ-PGA could enhance effectively both yield and water use efficiency of soybean in the arid region of northwest China. © 2024 Society of Chemical Industry.

[Effects of micro-sprinkling hose irrigation with different hose lengths on soil water distribution, dry matter accumulation, and grain yield of wheat fields]

To explore the optimal hose length of micro-sprinkling hose irrigation in wheat fields, a field trial taking JiMai 22 as test material was carried out in two growing seasons (2015-2016 and 2016-2017). Three lengths of micro-sprinkling hoses with 80-mm width were used, including 60 m (T₁), 80 m (T₂) and 100 m (T₃). The length of trial plot was equal to the hose length. The trial plots were divided to different sample sections every 20-m length along the irrigation direction, which were named as A, B, C, D and E sections, respectively, to examine the effects of micro-sprinkling hose irrigations with different hose lengths on soil water distribution, dry matter accumulation and grain yield of wheat fields. The results showed that: 1) After irrigation at the jointing and anthesis stages in the two growing seasons, the relative soil water content in the 0-40 cm soil layer showed T₁<T₂<T₃ in the A section, T₁, T₂<T₃ in the B section, T₁>T₂, T₃ in the C section and T₂>T₃ in the D section. The CV of relative soil water content in different sections in the same treatment showed T₁<T₂<T₃. 2) Leaf area index and the rate of canopy photosynthesis active radiation interception at 20 d and 30 d after anthesis, and dry matter accumulation amount after anthesis and at the maturity stage had no significant differences in the A or B section among different treatments. Those indices showed T₁>T₂, T₃ in the C section and T₂>T₃ in the D section. Leaf area index and rate of canopy photosynthesis active radiation interception at 20 d and 30 d after anthesis and dry matter accumulation amount after anthesis showed T₁, T₂>T₃, and dry matter accumulation amount at the maturity stage showed T₁> T₂>T₃. 3) In the two growing seasons, grain yield in the A and B sections had no significant differences among different treatments, and that showed T₁>T₂, T₃ in the C section and T₂>T₃ in the D section. Grain yield of each treatment showed T₁, T₂>T₃. 4) The grain yield and water use efficiency showed T₁> T₂>T₃, and the irrigation water use efficiency showed T₁>T₂>T₃ among different treatments in the two growing seasons. Considering grain yield and water use efficiency, hose irrigation with micro-sprinkling hose at 80-mm width and 60-m length was optimal treatment for water-saving and high-yield irrigation, and the suboptimal length was 80 m under this condition. The results could provide theoretical basis for water-saving and high-yield irrigation with micro-sprinkling hose in wheat fields in Shandong Province.

A multi-imaging approach to study the root-soil interface

BACKGROUND AND AIMS

Dynamic processes occurring at the soil-root interface crucially influence soil physical, chemical and biological properties at a local scale around the roots, and are technically challenging to capture in situ. This study presents a novel multi-imaging approach combining fluorescence and neutron radiography that is able to simultaneously monitor root growth, water content distribution, root respiration and root exudation.

METHODS

Germinated seeds of white lupins (Lupinus albus) were planted in boron-free glass rhizotrons. After 11 d, the rhizotrons were wetted from the bottom and time series of fluorescence and neutron images were taken during the subsequent day and night cycles for 13 d. The following day (i.e. 25 d after planting) the rhizotrons were again wetted from the bottom and the measurements were repeated. Fluorescence sensor foils were attached to the inner sides of the glass and measurements of oxygen and pH were made on the basis of fluorescence intensity. The experimental set-up allowed for simultaneous fluorescence imaging and neutron radiography.

KEY RESULTS

The interrelated patterns of root growth and distribution in the soil, root respiration, exudation and water uptake could all be studied non-destructively and at high temporal and spatial resolution. The older parts of the root system with greater root-length density were associated with fast decreases of water content and rapid changes in oxygen concentration. pH values around the roots located in areas with low soil water content were significantly lower than the rest of the root system.

CONCLUSIONS

The results suggest that the combined imaging set-up developed here, incorporating fluorescence intensity measurements, is able to map important biogeochemical parameters in the soil around living plants with a spatial resolution that is sufficiently high enough to relate the patterns observed to the root system.