Study on dry matter accumulation and leaf response to light and CO2 of maize under irrigation quota

Efective irrigation can maintain the vigorous photosynthetic metabolism of leaves and lay a physiological foundation for their material production. Dry matter accumulation and leaf response to light and carbon dioxide of maize under irrigation quotas of 50 mm (Q0), 90 mm (Q1), 170 mm (Q2) and 250 mm (Q3) were studied. The results showed that the dry matter accumulation were signifcantly increased in Q2 and Q3 treatment compared with CK at R3, R4 and R6 stages. With the increase of light intensity, the photosynthesis-light response curves of Q2 and Q3 treatments were increased the most. The apparent quantum efciency, maximum net photosynthetic rate, light saturation point and dark respiration rate of Q2 and Q3 treatments were signifcantly higher than those of Q0 and Q1 treatments at V12, R1 and R3 stages. The light compensation point was apparently lower than that of Q0 and Q1 treatments. The maize photosynthesis-CO2 response curves of Q2 and Q3 treatments demonstrated the largest increase with the increase of CO2 concentration. The CO2 saturation point, maximum net photosynthetic rate and carboxylation efciency of Q2 and Q3 treatments were signifcantly higher than those of Q0 and Q1 treatments. The CO2 compensation point was obviously lower than that of Q0 and Q1 treatments. The study provides an efective irrigation and management method for maize in semi-arid area of west Jilin Province, China. When the irrigation quota reached 170 mm, the dry matter accumulation of maize and the response of maize leaves to light and CO2 were both better. 170 mm could be used as the reference value of maize irrigation quota in western Jilin Province

Effects of straw returning on soil moisture and maize yield in semi-humid area

The purpose of this study was to control the effects of different tillage and straw returning methods on the temporal and spatial changes of soil moisture, photosynthetic characteristics of maize leaves, maize yield and water use efficiency, and to provide the basis for the cultivation mode of maize yield increase, water efficiency and soil sustainable utilization in semi-humid area. The spatial and temporal changes of soil moisture, leaf photosynthetic characteristics, maize yield and water use efficiency (WUE) were studied under four treatments, rotary cultivation and ridging of straws (CK), full amount and deep turning of straw back to the field (SP), no till straw smashed in full amount, covering and returning to the field (SC) and straw mulching and mechanical deep loosening (SS). The spatial and temporal dynamics of soil water storage showed a single peak curve in 2018 and a double peak curve in 2019. Soil water storage increased with the increase of soil depth. The soil water storage of SC and SS treatments were significantly higher than that of SP and CK treatments in the range of 0–60 cm. The net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci) and transpiration rate (Tr) of maize leaves of SP, SC and SS treatments were significantly increased compared with CK treatment in 2018 and 2019, the Pn, Gs, Ci and Tr of SP and SC treatments were significantly lower than those of SS treatment. The stomatal limitation percentage (Ls) of SS treatment was significantly decreased compared with CK, SP and SC treatments. The yield of SS treatment increased by 13.88% and 14.82% in 2018 and 2019, SP treatment increased by 7.59% and 9.12%, SC treatment increased by 7.42% and 8.5%, respectively, compared with CK treatment. The water use efficiency (WUE) of SS treatment increased by 13.89% and 9.80% in 2018 and 2019, SP treatment increased by 6.36% and 6.02%, SC treatment increased by 5.77% and 3.92%, respectively. Straw returning reduced soil water evaporation, increased soil water storage, promoted maize photosynthesis and dry matter accumulation, and significantly increased maize yield and water use efficiency. Straw mulching subsoiling is more suitable for drought resistance, yield increase and water efficient cultivation technology mode of maize in rain fed agricultural area

The Effect of Drip Irrigation Quota on Biochemical Activities and Yield-Related Traits in Different Drought-Tolerant Maize Varieties

Drip irrigation has a close relationship with the growth and development of maize grains and yield formation in semiarid areas. To explore the response mechanism of grain yield formation to drip irrigation quotas, a 2-year pond planting experiment was conducted under controlled conditions, by using two maize varieties with differences in drought resistance as experimental materials. Six treatments were set up, including CK1 (drought-resistant variety, 500 mm), T1 (drought-resistant variety, 350 mm), T2 (drought-resistant variety, 200 mm), CK2 (drought-sensitive variety, 500 mm), T3 (drought-sensitive variety, 350 mm), and T4 (drought-sensitive variety, 200 mm). The changes in maize grain filling characteristics, related hormones, enzyme activity related to starch synthesis, sugars and amino acids contents, and yield were analysed. The results showed that 100-grain weight at different filling times, filling rate, average filling rate, auxin, cytokinin, acid sucrose invertase, sucrose synthase, starch synthase, and adenosine diphosphate glucose pyro phosphorylase activities in maize grains decreased and the abscisic acid content and content of various amino acids and sugars in grains increased with the decrease in drip irrigation quota. The percentage of changes in drought-sensitive maize varieties was relatively high. The maize yield decreased with the decrease in drip irrigation quota. In summary, there was no significant difference in grain filling characteristics, hormone content, starch synthesis enzyme activity, and yield between maize treated with T1 (drought-resistant variety, 350 mm) and the control treatment. This effectively maintained grain growth and yield formation, achieving the goal of water saving and stable yields

Are medical record front page data suitable for risk adjustment in hospital performance measurement? Development and validation of a risk model of in-hospital mortality after acute myocardial infarction

Objectives To develop a model of in-hospital mortality using medical record front page (MRFP) data and assess its validity in case-mix standardisation by comparison with a model developed using the complete medical record data.Design A nationally representative retrospective study.Setting Representative hospitals in China, covering 161 hospitals in modelling cohort and 156 hospitals in validation cohort.Participants Representative patients admitted for acute myocardial infarction. 8370 patients in modelling cohort and 9704 patients in validation cohort.Primary outcome measures In-hospital mortality, which was defined explicitly as death that occurred during hospitalisation, and the hospital-level risk standardised mortality rate (RSMR).Results A total of 14 variables were included in the model predicting in-hospital mortality based on MRFP data, with the area under receiver operating characteristic curve of 0.78 among modelling cohort and 0.79 among validation cohort. The median of absolute difference between the hospital RSMR predicted by hierarchical generalised linear models established based on MRFP data and complete medical record data, which was built as ‘reference model’, was 0.08% (10th and 90th percentiles: −1.8% and 1.6%). In the regression model comparing the RSMR between two models, the slope and intercept of the regression equation is 0.90 and 0.007 in modelling cohort, while 0.85 and 0.010 in validation cohort, which indicated that the evaluation capability from two models were very similar.Conclusions The models based on MRFP data showed good discrimination and calibration capability, as well as similar risk prediction effect in comparison with the model based on complete medical record data, which proved that MRFP data could be suitable for risk adjustment in hospital performance measurement