The environment,especially the minimum temperature,affects summer maize grain yield by regulating ear differentiation and grain development

Ear differentiation,grain development and their interaction with factors in the growing environment,such as temperature,solar radiation and precipitation,greatly influence grain number and grain weight,and ultimately affect summer maize production.In this study,field experiments involving different sowing dates were conducted over three years to evaluate the effects of temperature factors,average solar radiation and total precipitation on the growth process,ear differentiation,fertilization characteristics,grain filling and yield of summer maize varieties with different growth durations.Four hybrids were evaluated in Huang-Huai-Hai Plain(HHHP),China from 2018 to 2020 with five different sowing dates.The results showed that the grain yield formation of summer maize was strongly impacted by the environment from the silking(R1)to milking(R3)stage.Average minimum temperature(AT_(min))was the key environmental factor that determined yield.Reductions in the length of the growing season(r=–0.556,P<0.01)and the total floret number on ear(R^(2)=0.200,P<0.001)were found when AT_(min) was elevated from the emerging(VE)to R1 stage.Both grain-filling rate(R^(2)=0.520,P<0.001)and the floret abortion rate on ear(R^(2)=0.437,P<0.001)showed quadratic relationships with AT_(min) from the R1 to physiological maturity(R6)stage,while the number of days after the R1 stage(r=–0.756,P<0.01)was negatively correlated with AT_(min).An increase in AT_(min) was beneficial for the promotion of yield when it did not exceeded a certain level(above 23°C during the R1–R3 stage and 20–21°C during the R1-R6 stage).Enhanced solar radiation and precipitation during R1–R6 increased the grain-filling rate(R^(2)=0.562,P<0.001 and R^(2)=0.229,P<0.05,respectively).Compared with short-season hybrids,full-season hybrids showed much greater suitability for a critical environment.The coordinated regulation of AT_(min),ear differentiation and grain development at the pre-and post-silking stages improved maize yield by increasing total floret number and grain-filling rate,and by reducing the floret abortion rate on ear.

Water and nitrogen footprint assessment of integrated agronomic practice management in a summer maize cropping system

The footprints of water and nitrogen(WF and NF)provide a comprehensive overview of the type and quantity of water consumption and reactive nitrogen(Nr)loss in crop production.In this study,a field experiment over two years(2019 and 2020)compared three integrated agronomic practice management(IAPM)systems:An improved management system(T2),a high-yield production system(T3),and an integrated soil-crop management system(ISCM)using a local smallholder farmer’s practice system(T1)as control,to investigate the responses of WF,Nr losses,water use efficiency(WUE),and nitrogen use efficiency(NUE)to IAPM.The results showed that IAPM optimized water distribution and promoted water use by summer maize.The evapotranspiration over the whole maize growth period of IAPM increased,but yield increased more,leading to a significant increase in WUE.The WUE of the T2,T3,and ISCM treatments was significantly greater than in the T1 treatment,in 2019 and 2020respectively,by 19.8-21.5,31.8-40.6,and 34.4-44.6%.The lowest WF was found in the ISCM treatment,which was 31.0%lower than that of the T1 treatment.In addition,the ISCM treatment optimized soil total nitrogen(TN)distribution and significantly increased TN in the cultivated layer.Excessive nitrogen fertilizer was applied in treatment T3,producing the highest maize yield,and resulting in the highest Nr losses.In contrast,the ISCM treatment used a reduced nitrogen fertilizer rate,sacrificing grain yield partly,which reduced Nr losses and eventually led to a significant increase in nitrogen use efficiency and nitrogen recovery.The Nr level in the ISCM treatment was34.8%lower than in the T1 treatment while NUE was significantly higher than in the T1 treatment by 56.8-63.1%in2019 and 2020,respectively.Considering yield,WUE,NUE,WF,and NF together,ISCM should be used as a more sustainable and clean system for sustainable production of summer maize.

Soil physical properties and maize root growth under different tillage systems in the North China Plain

The standard cultivation system in the North China Plain is double cropping of winter wheat and summer maize. The main effects of this cultivation system on root development and yield are decreases in soil nutrient content and depth of the plow layer under either long-term no-tillage or rotary tillage before winter wheat sowing and no tillage before summer maize sowing. In this study, we investigated the combined effects of tillage practices before winter wheat and summer maize sowing on soil properties and root growth and distribution in summer maize. Zhengdan 958(ZD958) was used as experimental material, with three tillage treatments: rotary tillage before winter wheat sowing and no tillage before summer maize sowing(RTW + NTM), moldboard plowing before winter wheat sowing and no tillage before summer maize sowing(MPW + NTM), and moldboard plowing before winter wheat sowing and rotary tillage before summer maize sowing(MPW + RTM).Tillage practice showed a significant(P < 0.05) effect on grain yield of summer maize. Grain yields under MPW + RTM and MPW + NTM were 30.6% and 24.0% higher, respectively, than that under RTW + NTM. Soil bulk density and soil penetration resistance decreased among tillage systems in the order RTW + NTM > MPW + NTM > MPW + RTM. Soil bulk densities were 3.3% and 515% lower in MPW + NTM and MPW + RTM, respectively, than that in RTW + NTM, and soil penetration resistances were respectively 17.8% and 20.4% lower,across growth stages and soil depths. Root dry matter and root length density were highest under MPW + RTM, with the resulting increased root activity leading to a yield increase of summer maize. Thus the marked effects of moldboard plowing before winter-wheat sowing on root length density, soil penetration resistance, and soil bulk density may contribute to higher yield.

Poor development of spike differentiation triggered by lower photosynthesis and carbon partitioning reduces summer maize yield after waterlogging

Stable yield of staple grains must be ensured to satisfy food demands for daily dietary energy requirements against the backdrop of global climate change. Summer maize, a staple crop, suffers severe yield losses due to extreme rainfall events, threatening food security. A randomized block experiment with four treatments: control, no water stress(CK);waterlogging for 6 days at the third leaf, sixth leaf stage,and 10 th day after tasseling, was conducted to investigate the mechanism of waterlogging-induced yield losses of summer maize. Waterlogging delayed plant growth and impaired tassel and ear differentiation,leading to high grain yield losses of Denghai 605(DH605). Waterlogging at third leaf(V3) stage reduced the photosynthesis of DH605, reducing total dry matter weight. Waterlogging at V3 stage reduced sucrose-cleaving enzymes activities in spike nodes and ears, reducing the carbon partitioned to ears(–53.1%), shanks(–46.5%), and ear nodes(–71.5%) but increasing the carbon partitioned to ear leaves(9.6%) and tassels(43.9%) in comparison with CK. The reductions in total carbon assimilate together with the reduced carbon partitioning to ears resulted in poor development of spikes(with respectively 15.2%and 20.6% reductions in total florets and fertilized florets) and lengthened the anthesis–silking interval by around 1 day, leading to high yield losses.

Exogenous SA or 6-BA maintains photosynthetic activity in maize leaves under high temperature stress

With global warming, high-temperature(HT) stress has become a major abiotic stress for crops, in particular summer maize in China. Photosynthesis is sensitive to HT. Salicylic acid(SA) and 6-benzyladenine(6-BA) can improve the adaptation of plants to various biotic and abiotic stresses. However, their contribution to maintaining photosynthetic activity and alleviating photoinhibition in maize leaves under HT stress is still unclear. The effects of exogenous SA or 6-BA on growth, photosynthesis capacity, photosystem Ⅱ(PSII) activity, subcellular ultrastructure, antioxidant system, and plant hormones in maize leaves under HT stress were investigated. Under HT conditions, application of SA or 6-BA up-regulated gibberellin and zeatin content in leaves, increasing leaf area index(LAI). It also expanded the stomata by reducing abscisic acid and jasmonic acid content in leaves, cooling them and increasing CO2supply to photosynthesis. A higher net photosynthetic rate, combined with increased activity of the antioxidant system, alleviated oxidative stress in maize plants sprayed with SA or 6-BA, allowing them to maintain their chloroplast ultrastructure and PSII activity, in particular electron transfer from QAto QB. The increased LAI and net photosynthetic rate per unit leaf area also resulted in the accumulation of more biomass.

Responses of photosynthetic characteristics and leaf senescence in summer maize to simultaneous stresses of waterlogging and shading

A field experiment was performed to investigate the physiological mechanism of the simultaneous stresses of waterlogging and shading on leaf photosynthetic and senescence during three growth stages of summer maize.The responses of leaf gas exchange parameters and antioxidant enzyme activities of the summer maize hybrids Denghai 605(DH605)to waterlogging(W),shading(S),and their combination(W+S)for 6 days at the third leaf stage(V3),the sixth leaf stage(V6),and the tasseling stage(VT)were recorded.Shading,waterlogging,and their combination disturbed the activities of protective enzymes and increased the contents of H2O2and O-2,accelerating leaf senescence and disordering photosynthetic characteristics.Under waterlogging,shading and their combination,leaf Pn,the photo-assimilates and grain yield was decreased.The greatest reduction for waterlogging and the combined stresses occurred at V3 and that for shading stress occurred at VT.The individual and combined stresses reduced the activities of protective enzymes and inhibited photosynthesis,reducing the accumulation of photosynthetic compounds and thereby yield.Waterlogging and the combined stresses at the V3 stage showed the greatest effect on leaf photosynthetic and senescence,followed by the V6 and VT stages.The greatest effect for shading stress occurred at VT,followed by the V6 and V3 stages,and the combined influence of shading and waterlogging was greater than that of either single stress.

Combined effects of high temperature and waterlogging on yield and stem development of summer maize

The purpose of this study was to identify the physiological mechanism underlying the effects of high temperature and waterlogging on summer maize.The stem development and yield of the maize hybrid Denghai 605 in response to high-temperature stress,waterlogging stress,and their combination applied for six days at the third-leaf,sixth-leaf,and tasseling stages were recorded.The combined stresses reduced lignin biosynthetic enzyme activity and lignin accumulation,leading to abnormal stem development.Reduction of the area and number of vascular bundles in stems led to reduced dry matter accumulation and allocation.Decreased grain dry weight at all three stages reduced grain yield relative to a control.In summary,high temperature,waterlogging,and their combined stress impaired stem development and grain yield of summer maize.The combined stresses were more damaging than either stress alone.

Integrated agronomic practice management decreases soil carbon emission and increases environmental ecological benefits of summer maize

Integrated agronomic practice management(IAPM)is an effective strategy for increasing nitrogen(N)use efficiency(NUE)and yield during crop production.Although various studies have evaluated the mechanism of a single agronomic management practice to increase yield and production efficiency and decrease environmental costs,few have investigated the effects of IAPM systems.A field experiment was conducted using four IAPM systems,a local smallholder farmers’practice system(T1),an improved management system(T2),a high-yield production system(T3),and an optimized management system(OMS),to study the annual yield,greenhouse gas(GHG)emissions,carbon(C)footprint(CF),and net environmental ecological benefit(NEEB)of summer maize.The results revealed that OMS was the most advantageous choice of IAPM,which increased yield and NUE and reduced GHG emissions and CF.Under OMS,yield and NUE were 42.6%and 88.1%higher,and N_(2)O,CO_(2),and CH4 emissions were on average 35.4%,5.8%,and 156.5%lower,respectively,than those under T1.Of the four IAPM systems,OMS resulted in the best soil quality,the lowest soil bulk density,the highest soil C/N ratio,and the highest soil total organic C content,which contributed to reduced GHG emissions.Carbon footprint and cost were the lowest under OMS,which decreased fertilizer input and GHG emissions.Optimized management system reduced CF and C cost by 5.9%and 33.9%,respectively,and increased NEEB by 111.4%compared to T1.Although T3 had the highest yield,it also had the highest GHG emissions and CF.In conclusion,OMS delivered a high yield and NUE while mitigating negative environmental impacts and increasing NEEB.Therefore,OMS is a suitable management system to increase the productivity and sustainability of summer maize.