Differential regulation of belowground rhizospheric ecosystem by biological and chemical nitrogen supplies: implications for maize yield enhancement mechanisms.

Nitrogen (N) content affects aboveground maize growth and nutrient absorption by altering the belowground rhizospheric ecosystem, impacting both yield and quality. However, the mechanisms through which different N supply methods (chemical and biological N supplies) regulate the belowground rhizospheric ecosystem to enhance maize yield remain unclear. To address this issue, we conducted a field experiment in northeast China, comprising three treatments: maize monocropping without N fertilizer application (MM), maize/alfalfa intercropping without N fertilizer application (BNF), and maize monocropping with N fertilizer application (CNS). The MM treatment represents the control, while the BNF treatment represents the biological N supply form, and CNS treatment represents the chemical N supply form. In the autumn of 2019, samples of maize and rhizospheric soil were collected to assess parameters including yield, rhizospheric soil characteristics, and microbial indicators. Both BNF and MM significantly increased maize yield and different yield components compared with MM, with no statistically significant difference in total yield between BNF and CNS. Furthermore, BNF significantly improved N by 12.61% and available N (AN) by 13.20% compared with MM. Furthermore, BNF treatment also significantly increased the Shannon index by 1.90%, while the CNS treatment significantly increased the Chao1 index by 28.1% and ACE index by 29.49%, with no significant difference between CNS and BNF. However, CNS had a more pronounced impact on structure of the rhizosphere soil bacterial community compared to BNF, inducing more significant fluctuations within the microbial network (modularity index and negative cohesion index). Regarding N transformation pathways predicted by bacterial functions, BNF significantly increased the N fixation pathway, while CNS significantly increased assimilatory nitrate reduction. In CNS, AN, NO3-N, NH4-N, assimilatory nitrate reduction, and community structure contributed significantly to maize yield, whereas in BNF, N fixation, community structure, community stability, NO3-N, and NH4-N played significant roles in enhancing maize yield. While CNS and BNF can achieve comparable maize yields in practical agricultural production, they have significantly different impacts on the belowground rhizosphere ecosystem, leading to different mechanisms of yield enhancement.

The effect of maize-alfalfa intercropping on the physiological characteristics, nitrogen uptake and yield of maize.

In Northeastern China, the intensive cropping system and increased use of chemical fertilizer has caused severe problems in terms of sustainable agricultural development. Therefore, to improve agricultural sustainability and crop productivity the farming system needs to be modified in the region. A pot experiment was conducted to evaluate the effect of maize-alfalfa intercropping on the physiological characteristics, nitrogen (N) uptake and yield of the maize crops in northeast China in 2017-2018. The study findings showed that intercropping under N fertilization progressively improved the physio-agronomic indices of the maize crop as compared to mono-cropping. The grain yield, 100 seed weight and biomass dry matter of maize crop improved in intercropping when it was practiced with N fertilizer. Furthermore, intercropping with N fertilization increased the chlorophyll content of the maize crop at bell-mouthed, silking, filing and mature stages by 19%, 44%, 12%, and 9% in 2017 and by 23%, 43%, 15%, and 11% in 2018, respectively, as compared with the monocropping system. Unlike monocropping, intercropping with N fertilization increased the photosynthesis rate (14% and 15%), stomatal conductance (74% and 98%) and transpiration rate (74% and 75%) in 2017 and 2018, respectively. However, intercropping reduced intercellular CO2 (Ci ). Moreover, intercropping with N fertilization increased the maize N content of grain and leaves as well as total N uptake by 49%, 31% and 93% in 2017 and 53%, 34% and 132%, respectively, in 2018 as compared to monocropping. In conclusion, our results suggest that maize-alfalfa intercropping with optimal N fertilization provides a practical method for improving growth, yield and N accumulation in the maize crop.

Home environment and psychosocial predictors of obesity status among community-residing men and women.

BACKGROUND/OBJECTIVES: Prior research indicates that features of the home environment (for example, televisions, exercise equipment) may be associated with obesity, but no prior study has examined objective features of the home food environment (for example, location of food) in combination with behavioral (for example, food purchasing), psychological (for example, self-efficacy) and social factors among obese adults. This study identified factors associated with obesity status from measures of home environment, food purchasing behavior, eating behavior and psychosocial functioning. SUBJECTS/METHODS: One hundred community-residing obese (mean body mass index (BMI)=36.8, s.e.=0.60) and nonobese (mean BMI=23.7, s.e.=0.57) adults (mean age=42.7, s.e.=1.50; range=20-78 years) completed an observational study with 2-h home interview/assessment and 2-week follow-up evaluation of food purchases and physical activity. Data were analyzed with analysis of variance and logistic regression, controlling for sex. RESULTS: Univariate analyses revealed that homes of obese individuals had less healthy food available than homes of nonobese (F(1,97)=6.49, P=0.012), with food distributed across a greater number of highly visible locations (F(1,96)=6.20, P=0.01). Although there was no group difference in household income or size, obese individuals reported greater food insecurity (F(1,97)=9.70, P<0.001), more reliance on fast food (F(1,97)=7.63, P=0.01) and more long-term food storage capacity in number of refrigerators (F(1,97)=3.79, P=0.05) and freezers (F(1,97)=5.11, P=0.03). Obese individuals also reported greater depressive symptoms (F(1,97)=10.41, P=0.002) and lower ability to control eating in various situations (F(1,97)=20.62, P<0.001). Multiple logistic regression revealed that obesity status was associated with lower self-esteem (odds ratio (OR) 0.58, P=0.011), less healthy food consumption (OR 0.94, P=0.048) and more food available in the home (OR 1.04, P=0.036). CONCLUSIONS: The overall pattern of results reflected that home food environment and psychosocial functioning of obese individuals differed in meaningful ways from that of nonobese individuals. In particular, lower self-esteem may be an important psychosocial aspect of obesity, especially in the context of greater food consumption and food storage/availability.