How delaying post-silking senescence in lower leaves of maize plants increases carbon and nitrogen accumulation and grain yield

Planting maize at high densities leads to early leaf senescence,and the resulting reduction in the number of lower leaves affects the plant’s root function and lowers its grain yield.However,the nature of the process by which lower leaf senescence affects biomass accumulation and grain yield formation in maize is not clear.This study aimed to shed light on how these factors are related by investigating the effects of the plant growth regulator 6-benzyladenine(6-BA)on the senescence of lower leaves of maize plants.In two maize cultivars planted at densities of 67,500(low density,LD)and 90,000(high density,HD)plants ha^(-1),plants treated with 6-BA maintained a high green leaf area index(LAI)longer than control(CK)plants,enabling them to maintain a higher photosynthetic rate for a longer period of time and produce more biomass before reaching physiological maturity.Spraying the lower leaves of maize plants with a 6-BA solution increased the distribution of;C-photosynthates to their roots,lower leaves and bracts,a result that can be ascribed to a decreased retention of;C-photosynthates in the stem and grain.In both seasons of the experiment,maize plants treated with 6-BA accumulated more N in grain and maintained a higher N content in roots and leaves,especially in lower leaves,than CK.Increased C assimilation in the lower leaves may explain why N uptake in plants subjected to the 6-BA treatment exceeded that in CK plants and why both photosynthesis rate and dry matter accumulation were maintained throughout grain filling.Our results suggest that a suitable distribution of C and N in leaves post-silking may maintain plant root function,increase N use efficiency,maximize the duration of high LAI,and increase grain yield.

Effects of reducing and postponing controlled-release urea application on soil nitrogen regulation and maize grain yield

Controlled-release urea(CRU-N)fertilizer application is a solution to improve the utilization rate of nitrogen(N),reduces economic costs and improves crop yields.It is significant to study the effects of release CRU-N reduction and the combined application of conventional urea on soil N control and the large-scale maize planting system.In this study,the effects of controlled-release nitrogen fertilizer reduction and postponement on soil nitrogen components,enzyme activities,and yields were investigated.Seven treatments were set up in this study,including no N fertilizer(CK),100%conventional urea(U),100%controlled-release urea(S),30%controlled-release urea(SU_(3/7)),50%controlled-release urea(SU_(5/5)),70%controlled-release urea(SU_(7/3))and Sodium Salt of Polyaspartic Acid(PASP)-N.The results showed that mixed CRU-N and urea increased yields and net benefits compared with conventional urea at the same application rate of N,and reduced N loss.The application of CRU-N at 70%for maize represented the best overall effects.Compared with U treatment,soil ammonium nitrogen(NH_(4)-N),soil nitrate-nitrogen(NO_(3)-N),and microbial biomass nitrogen(SMB-N)of CRU-N at 70%(SU_(7/3))increased by 35.00%,15.53%,and 25.04%.However,soil nitrate reductase(S-NR)and urease(S-UA)were the best in SU_(5/5) and significantly higher than other treatments.The applications of CRU-N would effectively increase soil N;CRU-N in 50%proportion can promote the maize root growth and improve the efficient utilization of N by soil microorganisms.Like the yields(9186.61 kg/hm^(2)),expertly in the proportion of 70%CRU-N(SU_(7/3))plays a vital role in a wheat-maize rotation system,which can potentially be used to improve the yields,nitrogen use efficiency,and net benefit with low N losses.In conclusion,using CRU-N fertilize effectively improves soil nitrogen,and various ratios of CRU-N can ensure the continuous release the nutrients during the growing period.And among the different proportions of CRU-N,it is optimal in SU_(7/3).

Increased grain yield with improved photosynthetic characters in modern maize parental lines

The grain yield of maize has increased continuously in past decades, largely through hybrid innovation, cultivation tech-nology, and in particular, recent genetic improvements in photosynthesis. Elite inbred lines are crucial for innovating new germplasm. Here, we analyzed variations in grain yield and a series of eco-physiological photosynthetic traits after anthesis in sixteen parental lines of maize (Zea mays L.) released during three different eras (1960s, 1980s, 2000s). We found that grain yield and biomass signiifcantly increased in the 2000s than those in the 1980s and 1960s. Leaf area, chlorophyl , and soluble protein content slowly decreased, and maintained a higher net photosynthesis rate (Pn) and improved stomatal conductance (Gs) after anthesis in the 2000s. In addition, the parental lines in the 2000s obtained higher actual photo-chemistry efifciency (ФPSI ) and the maximum PSII photochemistry efifciency (Fv/Fm), which largely improved light partition-ing and chlorophyl lfuorescence characteristic, including higher photochemical and photosystem II (PSII) reaction center activity, lower thermal energy dissipation in antenna proteins. Meanwhile, more lamel ae per granum within chloroplasts were observed in the parental lines of the 2000s, with a clear and complete chloroplast membrane, which wil greatly help to improve photosynthetic capacity and energy efifciency of ear leaf in maize parental lines. It is concluded that grain yield increase in modern maize parental lines is mainly attributed to the improved chloroplast structure and more light energy catched for the photochemical reaction, thus having a better stay-green characteristic and stronger photosynthetic capac-ity after anthesis. Our direct physiological evaluation of these inbred lines provides important information for the further development of promising maize cultivars.

Net energy yield and carbon footprint of summer corn under different N fertilizer rates in the North China Plain

Excessive use of N fertilizer in intensive agriculture can increase crop yield and at the same time cause high carbon（C） emissions.This study was conducted to determine optimized N fertilizer application for high grain yield and lower C emissions in summer corn（Zea mays L.）.A field experiment, including 0（N0）, 75（N75）, 150（N150）, 225（N225）, and 300（N300） kg N ha–1 treatments, was carried out during 2010–2012 in the North China Plain（NCP）.The results showed that grain yield, input energy, greenhouse gas（GHG） emissions, and carbon footprint（CF） were all increased with the increase of N rate, except net energy yield（NEY）.The treatment of N225 had the highest grain yield（10 364.7 kg ha–1） and NEY（6.8%）, but the CF（0.25） was lower than that of N300, which indicates that a rate of 225 kg N ha–1 can be optimal for summer corn in NCP.Comparing GHG emision compontents, N fertilizer（0–51.1%） was the highest and followed by electricity for irrigation（19.73–49.35%）.We conclude that optimazing N fertilizer application rate and reducing electricity for irrigation are the two key measures to increase crop yield, improve energy efficiency and decrease GHG emissions in corn production.

Nutrient uptake,maximum yield production,and economic return of maize under deficit irrigation with biochar and inorganic fertiliser amendments

The individual and combined effects of biochar(B)and inorganic fertiliser(F)have all been widely proofed to improve soil fertility and enhance crop growth and yield under irrigation(I)and rain fed conditions.However,the strength of their individual and combined effects on crop productivity has been scarcely reported.In addition,few studies have assessed their individual and co-application effects on economic returns.Therefore,a 2-year field experiment which consisted of factorial combination of irrigation(I)[100%full irrigation(FI),80%FI and 60%FI],biochar(0 and 20 t/ha)and fertiliser(0 and 300 kg/ha)was conducted.According to the results,irrigation was the dominant factor that influences maize grain yield,followed by inorganic fertiliser and biochar,and they were all significant in their main effects.The strength of interaction effects among,I,F and B on maize grain yield follow the sequence F×I>B×F>B×I.The economic analysis showed that the ternary combination of B,F and I was more economical than the binary combination of B plus I,and F plus I(in that order),when compared with the standalone application of I at maximum production in the field experiment.In addition,combined applications of biochar and fertiliser improved soil nutrients,nutrient uptake in all irrigation treatments,compared to the standalone applications of biochar or fertiliser.Further research is,therefore,recommended for long-term evaluation of the economic viability of integrating biochar with fertiliser under irrigation.

Role of alternate and fixed partial root-zone drying on water use efficiency and growth of maize(Zea mays L.)in gypsiferous soils

Alternate partial root-zone drying(APRD)is a water-saving method but can regulate crop physiological responses.A pot experiment has been conducted to study the efficiency of partial and fixed root-zone drying on the growth and production of maize(Zea mays L)in addition to the water use efficiency in soils with different gypsum content.The experimental treatments include three irrigation treatments,i.e.Conventional Irrigation(CI),Alternate Partial Root-zone Drying(APRD)and Fixed Partial Root-zone Drying(FPRD),and three soils with different gypsum content"(60.0[G1],153.7[G2],and 314.2[G3]g kg^(-1))".The vegetative growth,root dry mass and physiological indices(leaf relative water content,carotenoid concentration,proline)have been studied during three stages of maize plant growth(jointing,tasselling,and maturing).The Results showed that compared to CI,APRD and FPRD increased water use efficiency by 38.93 and 14.94%based on dry seed yield.In addition,compared to CI,APRD increased maize seed yield by 4.62-20.71%,while FPRD decreased yield by 19.24-5.28%for the gypsiferous soils G2 and G3,respectively.APRD has a slight effect on leaf water potential,leaf relative water content,carotenoid and proline activities from jointing to maturing stages at the three gypsiferous soils.Results suggest that APRD could make maize plants use water even more productively with better adaptation to water shortages in the gypsiferous soils.