Combining Ability and Heterotic Effects in Newly Developed Early Maturing and High-Yielding Maize Hybrids under Low and Recommended Nitrogen Conditions

Nitrogen (N) is a crucial nutrient vital for the growth and productivity of maize. However, excessive nitrogen application can result in numerous environmental and ecological problems, such as water pollution, biodiversity loss, and greenhouse gas emissions. Therefore, breeding maize hybrids resilient to low nitrogen conditions is crucial for sustainable agriculture, especially under low nitrogen conditions. Consequently, this study aimed to evaluate the combining ability and heterosis of maize lines, recognize promising hybrids, and study gene action controlling key traits under low and recommended N stress conditions. The half-diallel mating design hybridized seven maize inbreds, resulting in 21 F1 hybrids. These hybrids, along with two high-yielding commercial hybrids (SC10 and TWC310), were evaluated in field trials under recommended (290 kg/ha) and low N (166 kg N/ha) conditions. Significant variations were observed among assessed hybrids for all measured traits, with non-additive gene action being predominant for grain yield and its related characteristics under recommended and low N conditions. Inbred lines P105 and P106 were recognized as effective combiners for earliness, with P105 also excelling in shorter plant height and lower ear placement. In addition, P101, P102, and P104 were identified as good combiners for increasing grain yield and related attributes under low N conditions. The crosses P105 × P106 and P106 × P107 demonstrated outstanding heterotic effects for earliness, while hybrids P101 × P102 and P102 × P104 exhibited remarkable heterotic effects for grain yield low nitrogen stress conditions. These promising hybrids could be considered for commercial use after further evaluation. Strong positive correlations were found between grain yield and ear height, plant height, number of kernels per row, and 1000-grain weight, highlighting their importance for indirect selection to enhance the grain yield of maize under low N stress conditions.

The microbial community,nutrient supply and crop yields differ along a potassium fertilizer gradient under wheat-maize double-cropping systems

Soil microorganisms play critical roles in ecosystem function.However,the relative impact of the potassium(K)fertilizer gradient on the microbial community in wheat-maize double-cropping systems remains unclear.In this long-term field experiment(2008-2019),we researched bacterial and fungal diversity,composition,and community assemblage in the soil along a K fertilizer gradient in the wheat season(K0,no K fertilizer;K1,45 kg ha^(-1) K_(2)O;K_(2),90 kg ha^(-1)K_(2)O;K3,135 kg ha^(-1)K_(2)O)and in the maize season(K0,no K fertilizer;K_(1),150 kg ha^(-1) K_(2)O;K_(2),300 kg ha^(-1)K_(2)O;K_(3),450 kg ha^(-1)K_(2)O)using bacterial 16S rRNA and fungal internally transcribed spacer(ITS)data.We observed that environmental variables,such as mean annual soil temperature(MAT)and precipitation,available K,ammonium,nitrate,and organic matter,impacted the soil bacterial and fungal communities,and their impacts varied with fertilizer treatments and crop species.Furthermore,the relative abundance of bacteria involved in soil nutrient transformation(phylum Actinobacteria and class Alphaproteobacteria)in the wheat season was significantly increased compared to the maize season,and the optimal K fertilizer dosage(K2 treatment)boosted the relative bacterial abundance of soil nutrient transformation(genus Lactobacillus)and soil denitrification(phylum Proteobacteria)bacteria in the wheat season.The abundance of the soil bacterial community promoting root growth and nutrient absorption(genus Herbaspirillum)in the maize season was improved compared to the wheat season,and the K2 treatment enhanced the bacterial abundance of soil nutrient transformation(genus MND1)and soil nitrogen cycling(genus Nitrospira)genera in the maize season.The results indicated that the bacterial and fungal communities in the double-cropping system exhibited variable sensitivities and assembly mechanisms along a K fertilizer gradient,and microhabitats explained the largest amount of the variation in crop yields,and improved wheat?maize yields by 11.2-22.6 and 9.2-23.8%with K addition,respectively.These modes are shaped contemporaneously by the different meteorological factors and soil nutrient changes in the K fertilizer gradients.

Effects of Zinc on the Yield,Uptake and Distribution of Nitrogen/Phosphorus/Potassium/Zinc in Different Genotypes of Maize

[Objective] To study the effects of Zinc on the yield,nitrogen/phosphorus/potassium/Zinc uptake and distribution of different genotypes of maize.[Method] Using two different genotypes of maize as materials,the effects of Zn on the yield,N/P/K /Zn uptake and distribution of different genotypes of maize were studied by pot cultivation.[Result] Appropriate Zn supply could improve the grain number per kernel.The Zn content in different organs of maize showed little difference under low Zn treatment （Zn0,Zn1）.With the increase of Zn supply,Zn content in leaf,stem and sheath rapidly increased,but the increasing amplitude of Zn content in the kernel and bract were less.The excessive Zn in maize was mainly translocated in lower organs to reduce the damage of them to plants.Different Zn supply levels had less effects on the absorption and translocation of N,P and K in low-Zn insensitive variety Mudan 9.While the absorption and translation of N,P,K in low Zn sensitive variety （Sidan 19） was more easily influenced by the amount of Zn supplied.[Conclusion] Appropriate Zn supply could enhance the maize yield and utilization rate of N and K,and reduce the absorption and utilization of P.

Grain yield and N uptake of maize in response to increased plant density under reduced water and nitrogen supply conditions

The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs.Increasing the planting density can maintain higher yields,but also consumes more of these restrictive resources.However,whether an increased maize density can compensate for the negative effects of reduced water and N supply on grain yield and N uptake in the arid irrigated areas remains unknown.This study is part of a long-term positioning trial that started in 2016.A split-split plot field experiment of maize was implemented in the arid irrigated area of northwestern China in 2020 to 2021.The treatments included two irrigation levels:local conventional irrigation reduced by 20%(W1,3,240 m^(3)ha^(-1))and local conventional irrigation(W2,4,050 m^(3)ha^(-1));two N application rates:local conventional N reduced by 25%(N1,270 kg ha^(-1))and local conventional N(360 kg ha^(-1));and three planting densities:local conventional density(D1,75,000 plants ha^(-1)),density increased by 30%(D2,97,500 plants ha-1),and density increased by 60%(D3,120,000 plants ha^(-1)).Our results showed that the grain yield and aboveground N accumulation of maize were lower under the reduced water and N inputs,but increasing the maize density by 30% can compensate for the reductions of grain yield and aboveground N accumulation caused by the reduced water and N supply.When water was reduced while the N application rate remained unchanged,increasing the planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%.Under reduced water and N inputs,increasing the maize density by 30% enhanced N uptake efficiency and N partial factor productivity,and it also compensated for the N harvest index and N metabolic related enzyme activities.Compared with W2N2D1,the N uptake efficiency and N partial factor productivity increased by 28.6 and 17.6%under W1N1D2.W1N2D2 had 8.4% higher N uptake efficiency and 13.9% higher N partial factor productivity than W2N2D1.W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at the R2(blister)stage and 19.6% at the V6(6th leaf)stage,and increased net income and the benefit:cost ratio by 22.1 and 16.7%,respectively.W1N1D2 and W1N2D2 reduced the nitrate nitrogen and ammoniacal nitrogen contents at the R6 stage in the 40-100 cm soil layer,compared with W2N2D1.In summary,increasing the planting density by 30% can compensate for the loss of grain yield and aboveground N accumulation under reduced water and N inputs.Meanwhile,increasing the maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while the N application rate remained constant in arid irrigation areas.

Effects of potassium deficiency on photosynthesis,chloroplast ultrastructure,ROS,and antioxidant activities in maize(Zea mays L.)

Potassium(K)deficiency significantly decreases photosynthesis due to leaf chlorosis induced by accumulation of reactive oxygen species(ROS).But,the physiological mechanism for adjusting antioxidative defense system to protect leaf function in maize(Zea mays L.)is unknown.In the present study,four maize inbred lines(K-tolerant,90-21-3 and 099;K-sensitive,D937 and 835)were used to analyze leaf photosynthesis,anatomical structure,chloroplast ultrastructure,ROS,and antioxidant activities.The results showed that the chlorophyll content,net photosynthetic rate(P_n),stomatal conductance(G_s),photochemical quenching(q_P),and electron transport rate of PSII(ETR)in 90-21-3 and 099 were higher than those in D937 and 835 under K deficiency treatment.Parameters of leaf anatomical structure in D937 that were significantly changed under K deficiency treatment include smaller thickness of leaf,lower epidermis cells,and vascular bundle area,whereas the vascular bundle area,xylem vessel number,and area in 90-21-3 were significantly larger or higher.D937 also had seriously damaged chloroplasts and PSII reaction centers along with increased superoxide anion(O_2^-·)and hydrogen peroxide(H_2O_2).Activities of antioxidants,like superoxide dismutase(SOD),catalase(CAT),and ascorbate peroxidase(APX),were significantly stimulated in 90-21-3 resulting in lower levels of O_2^-·and H_2O_2.These results indicated that the K-tolerant maize promoted antioxidant enzyme activities to maintain ROS homeostasis and suffered less oxidative damage on the photosynthetic apparatus,thereby maintaining regular photosynthesis under K deficiency stress.

ZmbZIP27 regulates nitrogen-mediated leaf angle by modulating lignin deposition in maize

In grain crops such as maize(Zea mays),leaf angle(LA)is a key agronomic trait affecting light interception and thus planting density and yield.Nitrogen(N)affects LA in plants,but we lack a good understanding of how N regulates LA.Here,we report that N deficiency enhanced lignin deposition in the ligular region of maize seedlings.In situ hybridization showed that the bZIP transcription factor gene ZmbZIP27 is mainly expressed in the phloem of maize vascular bundles.Under N-sufficient conditions,transgenic maize overexpressing ZmbZIP27 showed significantly smaller LA compared with wild type(WT).By contrast,zmbzip27_(ems)mutant showed larger LA under both N-deficient and N-sufficient conditions compared with WT.Overexpression of ZmbZIP27 enhanced lignin deposition in the ligular region of maize in the field.We further demonstrated that ZmbZIP27 could directly bind the promoters of the microRNA genes ZmMIR528a and ZmMIR528b and negatively regulate the expression levels of ZmmiR528.ZmmiR528 knockdown transgenic maize displayed erect architecture in the field by increasing lignin content in the ligular region of maize.Taken together,these results indicate that ZmbZIP27 regulates N-mediated LA size by regulating the expression of ZmmiR528 and modulating lignin deposition in maize.

Response of root morphology, physiology and endogenous hormones in maize(Zea mays L.) to potassium deficiency

Potassium （K） deficiency is one of the major abiotic stresses which has drastically influenced maize growth and yield around the world. However, the physiological mechanism of K deficiency tolerance is not yet fully understood. To identify the differences of root morphology, physiology and endogenous hormones at different growing stages, two maize inbred lines 90-21-3 （tolerance to K deficiency） and D937 （sensitive to K deficiency） were cultivated in the long-term K fertilizer experimental pool under high potassium （＋K） and low potassium （-K） treatments. The results indicated that the root length, volume and surface area of 90-21-3 were significantly higher than those of D937 under -K treatment at different growing stages. It was noteworthy that the lateral roots of 90-21-3 were dramatically higher than those of D937 at tasselling and flowering stage under-K treatment. Meanwhile, the values of superoxide dismutase （SOD） and oxidizing force of 90-21-3 were apparently higher than those of D937, whereas malondialdehyde （MDA） content of D937 was obviously increased. Compared with ＋K treatment, the indole-3-acetic acid （IAA） content of 90-21-3 was largely increased under-K treatment, whereas it was sharply decreased in D937. On the contrary, abscisic acid （ABA） content of 90-21-3 was slightly increased, but that of D937 was significantly increased. The zeatin riboside （ZR） content of 90-21-3 was significantly decreased, while that of D937 was relatively increased. These results indicated that the endogenous hormones were stimulated in 90-21-3 to adjust lateral root development and to maintain the physiology function thereby alleviating K deficiency.

The transcription factor ZmNAC84 increases maize salt tolerance by regulating ZmCAT1 expression

Salt stress severely affects plant growth and yield.The transcription factor NAC plays a variety of important roles in plant abiotic stress,but we know relatively little about the specific molecular mechanisms of NAC in antioxidant defense.Here,our genetic studies reveal the positive regulation of salt tolerance in maize by the transcription factor ZmNAC84.Under salt stress,overexpression of ZmNAC84 in maize increased the expression of ZmCAT1,enhanced CAT activity,and consequently reduced H_(2)O_(2) accumulation,thereby improving salt stress tolerance in maize.Whereas RNA interference-mediated knockdown of ZmNAC84 produced the opposite effect.Subsequently,we found that ZmNAC84 directly binds to and regulates the expression of the ZmCAT1 promoter,and the hybridized material also demonstrated that ZmCAT1 is a downstream target gene of ZmNAC84.In addition,phenotypic and biochemical analyses indicated that ZmCAT1 positively regulated salt tolerance by regulating H_(2)O_(2) accumulation under salt stress.Taken together,these results reveal the function of ZmNAC84 in regulating ZmCAT1-mediated antioxidant defense in response to salt stress in plants.

Manure substitution improves maize yield by promoting soil fertility and mediating the microbial community in lime concretion black soil

Synthetic nitrogen(N)fertilizer has made a great contribution to the improvement of soil fertility and productivity,but excessive application of synthetic N fertilizer may cause agroecosystem risks,such as soil acidification,groundwater contamination and biodiversity reduction.Meanwhile,organic substitution has received increasing attention for its ecologically and environmentally friendly and productivity benefits.However,the linkages between manure substitution,crop yield and the underlying microbial mechanisms remain uncertain.To bridge this gap,a three-year field experiment was conducted with five fertilization regimes:i)Control,non-fertilization;CF,conventional synthetic fertilizer application;CF_(1/2)M_(1/2),1/2 N input via synthetic fertilizer and 1/2 N input via manure;CF_(1/4)M_(3/4),1/4 N input synthetic fertilizer and 3/4 N input via manure;M,manure application.All fertilization treatments were designed to have equal N input.Our results showed that all manure substituted treatments achieved high soil fertility indexes(SFI)and productivities by increasing the soil organic carbon(SOC),total N(TN)and available phosphorus(AP)concentrations,and by altering the bacterial community diversity and composition compared with CF.SOC,AP,and the soil C:N ratio were mainly responsible for microbial community variations.The co-occurrence network revealed that SOC and AP had strong positive associations with Rhodospirillales and Burkholderiales,while TN and C:N ratio had positive and negative associations with Micromonosporaceae,respectively.These specific taxa are implicated in soil macroelement turnover.Random Forest analysis predicted that both biotic(bacterial composition and Micromonosporaceae)and abiotic(AP,SOC,SFI,and TN)factors had significant effects on crop yield.The present work strengthens our understanding of the effects of manure substitution on crop yield and provides theoretical support for optimizing fertilization strategies.

Identification, pathogenicity, and fungicide sensitivity of Eutiarosporella dactylidis associated with leaf blight on maize in China

Maize(Zea mays L.) is an economically vital grain crop that is cultivated worldwide. In 2011, a maize foliar disease was detected in Lingtai and Lintao counties in Gansu Province, China. The characteristic signs and symptoms of this disease include irregular chlorotic lesions on the tips and edges of infected leaves and black punctate fruiting bodies in dead leaf tissues. Given favourable environmental conditions, this disease spread to areas surrounding Gansu. In this study, infected leaves were collected from Gansu and Ningxia Hui Autonomous Region between 2018and 2020 to identify the disease-causing pathogen. Based on morphological features, pathogenicity tests, and multilocus phylogenetic analysis involving internal transcribed spacer(ITS), 18S small subunit rDNA(SSU), 28S large subunit rDNA(LSU), translation elongation factor 1-alpha(TEF), and β-tubulin(TUB) sequences, Eutiarosporella dactylidis was identified as the causative pathogen of this newly discovered leaf blight. Furthermore, an in vitro bioassay was conducted on representative strains using six fungicides, and both fludioxonil and carbendazim were found to significantly inhibit the mycelial growth of E. dactylidis. The results of this study provide a reference for the detection and management of Eutiarosporella leaf blight.

Effect of Potassium on Ultrastructure of Maize Stalk Pith and Young Root and Their Relation to Stalk Rot Resistance

To study the mechanism of potassium （K） application on improvement of maize resistance to stalk rot at cellular level, scanning electron microscope and transmission electron microscope were used to observe the effect of K on the ultrastructure of maize stalk pith tissue and young root tip cell influenced by K and pathogen. In K deficient treatment, parenchyma cells of stalk pith had abnormal structure, and the cell wall between upper and lower adjacent cell was damaged, resulting in the loss of connections between vascular cells and insufficient supporting capacity. However, an improved K nutrition helped to keep a quite tight arrangement of root cell with thick cell wall, and prevent the invasion of pathogen effectively. Moreover, K treated root cell had abundant golgi apparatus, which could excrete large amount of secretions to degrade mycelium. Papillary and highly electronic intensity dot were accumulated at the invading point to prevent the deveJopment of the mycelium. Improved K nutrition could increase the resistant ability of maize plant to stalk rot, through keeping cell structure stability, preventing the expansion of intracellular space to reduce the chances of pathogen invasions, and through reinforcing cell wall and formation of intercellular and intracellular material to restrict further development of pathogen in host cell.

Engineering high amylose and resistant starch in maize by CRISPR/Cas9-mediated editing of starch branching enzymes

To improve the amylose content(AC)and resistant starch content(RSC)of maize kernel starch,we employed the CRISPR/Cas9 system to create mutants of starch branching enzyme I(SBEI)and starch branching enzyme IIb(SBEIIb).A frameshift mutation in SBEI(E1,a nucleotide insertion in exon 6)led to plants with higher RSC(1.07%),lower hundred-kernel weight(HKW,24.71±0.14 g),and lower plant height(PH,218.50±9.42 cm)compared to the wild type(WT).Like the WT,E1 kernel starch had irregular,polygonal shapes with sharp edges.A frameshift mutation in SBEIIb(E2,a four-nucleotide deletion in exon 8)led to higher AC(53.48%)and higher RSC(26.93%)than that for the WT.E2 kernel starch was significantly different from the WT regarding granule morphology,chain length distribution pattern,X-ray diffraction pattern,and thermal characteristics;the starch granules were more irregular in shape and comprised typical B-type crystals.Mutating SBEI and SBEIIb(E12)had a synergistic effect on RSC,HKW,PH,starch properties,and starch biosynthesis-associated gene expression.SBEIIa,SS1,SSIIa,SSIIIa,and SSIIIb were upregulated in E12 endosperm compared to WT endosperm.This study lays the foundation for rapidly improving the starch properties of elite maize lines.

Dynamics and genetic regulation of macronutrient concentrations during grain development in maize

Nitrogen(N), phosphorus(P), and potassium(K) are essential macronutrients that are crucial not only for maize growth and development, but also for crop yield and quality. The genetic basis of macronutrient dynamics and accumulation during grain filling in maize remains largely unknown. In this study, we evaluated grain N, P, and K concentrations in 206 recombinant inbred lines generated from a cross of DH1M and T877 at six time points after pollination. We then calculated conditional phenotypic values at different time intervals to explore the dynamic characteristics of the N, P, and K concentrations. Abundant phenotypic variations were observed in the concentrations and net changes of these nutrients. Unconditional quantitative trait locus(QTL) mapping revealed 41 non-redundant QTLs, including 17, 16, and 14 for the N, P, and K concentrations, respectively. Conditional QTL mapping uncovered 39 non-redundant QTLs related to net changes in the N, P, and K concentrations. By combining QTL, gene expression, co-expression analysis, and comparative genomic data, we identified 44, 36, and 44 candidate genes for the N, P, and K concentrations, respectively, including GRMZM2G371058 encoding a Doftype zinc finger DNA-binding family protein, which was associated with the N concentration, and GRMZM2G113967encoding a CBL-interacting protein kinase, which was related to the K concentration. The results deepen our understanding of the genetic factors controlling N, P, and K accumulation during maize grain development and provide valuable genes for the genetic improvement of nutrient concentrations in maize.

Effects of long-term full straw return on yield and potassium response in wheat-maize rotation

The effect of long-term straw return on crop yield, soil potassium（K） content, soil organic matter, and crop response to K from both straw and chemical K fertilizer（K_2SO_4） were investigated in a fixed site field experiment for winter wheat-summer maize rotation in 6 years for 12 seasons. The field experiment was located in northern part of North China Plain with a sandy soil in relatively low yield potential. Two factors, straw return and chemical K fertilizer, were studied with two levels in each factor. Field split design was employed, with two straw treatments, full straw return of previous crop（St） and no straw return, in main plots, and two chemical K fertilizer treatments, 0 and 60 kg K2 O ha^（–1）, as sub-plots. The results showed that straw return significantly increased yields of winter wheat and summer maize by 16.5 and 13.2% in average, respectively, and the positive effect of straw return to crop yield showed more effective in lower yield season. Straw return significantly increased K absorption by the crops, with significant increase in straw part. In treatment with straw return, the K content in crop straw increased by 15.9 and 21.8% in wheat and maize, respectively, compared with no straw return treatment. But, straw return had little effect on K content in grain of the crops. Straw return had significant influences on total K uptake by wheat and maize plants, with an increase of 32.7 and 30.9%, respectively. There was a significant correlation between crop yield and K uptake by the plant. To produce 100 kg grain, the wheat and maize plants absorbed 3.26 and 2.24 kg K2 O, respectively. The contents of soil available K and soil organic matter were significantly affected by the straw return with an increase of 6.07 and 23.0%, respectively, compared to no straw return treatment. K_2SO_4 application in rate of 60 kg K2 O ha^（–1） showed no significant effect on wheat and maize yield, K content in crop straw, total K uptake by the crops, soil available K content, and soil organic matter. The apparent K utilization rate（percentage of applied K absorbed by the crop in the season） showed difference for wheat and maize with different K sources. In wheat season, the K utilization rate from K_2SO_4 was higher than that from straw, while in maize season, the K utilization rate from straw was higher than that from chemical fertilizer. In the whole wheat-maize rotation system, the K absorption efficiency by the two crops from straw was higher than that from K_2SO_4.

Effects of drip and flood irrigation on carbon dioxide exchange and crop growth in the maize ecosystem in the Hetao Irrigation District,China

Drip irrigation and flood irrigation are major irrigation methods for maize crops in the Hetao Irrigation District,Inner Mongolia Autonomous Region,China.This research delves into the effects of these irrigation methods on carbon dioxide(CO_(2))exchange and crop growth in this region.The experimental site was divided into drip and flood irrigation zones.The irrigation schedules of this study aligned with the local commonly used irrigation schedule.We employed a developed chamber system to measure the diurnal CO_(2)exchange of maize plants during various growth stages under both drip and flood irrigation methods.From May to September in 2020 and 2021,two sets of repeated experiments were conducted.In each experiment,a total of nine measurements of CO_(2)exchange were performed to obtain carbon exchange data at different growth stages of maize crop.During each CO_(2)exchange measurement event,CO_(2)flux data were collected every two hours over a day-long period to capture the diurnal variations in CO_(2)exchange.During each CO_(2)exchange measurement event,the biological parameters(aboveground biomass and crop growth rate)of maize and environmental parameters(including air humidity,air temperature,precipitation,soil water content,and photosynthetically active radiation)were measured.The results indicated a V-shaped trend in net ecosystem CO_(2)exchange in daytime,reducing slowly at night,while the net assimilation rate(net primary productivity)exhibited a contrasting trend.Notably,compared with flood irrigation,drip irrigation demonstrated significantly higher average daily soil CO_(2)emission and greater average daily CO_(2)absorption by maize plants.Consequently,within the maize ecosystem,drip irrigation appeared more conducive to absorbing atmospheric CO_(2).Furthermore,drip irrigation demonstrated a faster crop growth rate and increased aboveground biomass compared with flood irrigation.A strong linear relationship existed between leaf area index and light utilization efficiency,irrespective of the irrigation method.Notably,drip irrigation displayed superior light use efficiency compared with flood irrigation.The final yield results corroborated these findings,indicating that drip irrigation yielded higher harvest index and overall yield than flood irrigation.The results of this study provide a basis for the selection of optimal irrigation methods commonly used in the Hetao Irrigation District.This research also serves as a reference for future irrigation studies that consider measurements of both carbon emissions and yield simultaneously.

The influence of potassium to mineral fertilizers on the maize health

Field experiments （2009-2011） were conducted at the Department of Agronomy at Poznar~ University of Life Sciences on the fields of the Research Institute in Swadzim. We evaluated the health of maize plants of two types, depending on the variations in mineral fertilization. The conducted research recorded the occurrence of pests such as oscinella frit （Oscinella frit L.） and the European corn borer （Pyrausta nubilalis Hbn.）. Diseases recorded during the research included two patho- genes： Fusarium （Fusarium ssp.） and corn smut （Ustilago maydis Corda）. It was shown that the meteorological conditions during the maize vegetation had a significant influence on the occurrence of pests. Adding potassium to mineral fertilizers increased the maize resistance to Fusarium. Cultivation of ＂stay-green＂ cultivar shall be considered as an element of in- tegrated maize protection. The occurrence of oscineUa flit was correlated with the occurrence of Fusarium as well as the occurrence of the European corn borer for both examined cultivars.

Nitrogen, phosphorus and potassium recycling in an agroforestry ecosystem of Huanghuaihai Plain: with Paulownia elongata intercropped wheat and maize as an example

The studies show that in the whole community, P is deficient, and N and K are basically balanced. N, P and K are accumulated in plant tissues and litters, but depleted in soil. N and P contents in surface soil(0—20 cm) are the main factors affecting crop growth, and P contents in 20 80 cm soil layer is the major affecting Paulownia elongata growth. The absorption coefficients of N, P and K in the communities are 0 078, 0 014 and 0 052 respectively, their utilization coefficients are 0 95, 0 90 and 0 94, and the recycling coefficients are 0 042, 0 05 and 0 063 respectively.

Potassium nutrition of maize:Uptake,transport,utilization,and role in stress tolerance

Potassium(K) is an essential macronutrient for plant growth and development and influences yield and quality of agricultural crops.Maize(Zea mays) is one of the most widely distributed crops worldwide.In China,although maize consumes a large amount of K fertilizer,the K uptake/utilization efficiency(KUE)of maize cultivars is relatively low.Elucidation of KUE mechanisms and development of maize cultivars with higher KUE are needed.Maize KUE is determined by K+uptake,transport,and remobilization,which depend on a variety of K+channels and transporters.We review basic information about K+channels and transporters in maize,their functions and regulation,and the roles of K+in nitrogen transport,sugar transport,and salt tolerance.We discuss challenges and prospects for maize KUE improvement.

Effects of Different Potassium Stress on Leaf Photosynthesis and Chlorophyll Fluorescence in Maize (Zea Mays L.) at Seedling Stage

Leaf early senescence caused by nutrition deficiency is one of the major limitation reasons in the world crop production. Potassium (K) is one of important nutrient elements in crop growth, which modifies dozens of enzyme activations and controls stomatal movement of photosynthesis. The yield and quality of maize (Zea Mays L.) have been limited due to K deficiency in plough layer soil. However, the mechanism of K deficiency tolerance is not fully understood in maize. In this study, two inbred lines, 099 (tolerance to potassium deficiency) and 835 (sensitive to potassium deficiency) were carried out to investigate the variations of chlorophyll content, photosynthetic and chlorophyll fluorescence parameters related with senescence under different K+ concentrations in maize at seedling stage. The results showed that the Chlorophyll a, b and (a + b) of 835 were significantly decreased under different K deficiency treatments, whereas those of 099 were remained normal. In addition, 099 showed a lower stomatal restriction and higher electronic transition capacity under different K deficiency treatments. The variations of F0, Fv/Fm, ΦPSⅡ, qP and NPQ in 835 were largely higher than those in 099. These results indicated that the inbred line 099 tolerance to K deficiency could keep chlorophyll content to maintain photosynthesis and to alleviate the injury of PSII under K deficiency condition. This study should contribute to explaining the physiological mechanism tolerance nutrition deficiency and improving breeding program in maize.

Combining field data and modeling to better understand maize growth response to phosphorus(P) fertilizer application and soil P dynamics in calcareous soils

We used field experimental data to evaluate the ability of the agricultural production system model (APSIM) to simulate soil P availability,maize biomass and grain yield in response to P fertilizer applications on a fluvo-aquic soil in the North China Plain.Crop and soil data from a 2-year experiment with three P fertilizer application rates(0,75 and 300 kg P_(2)O_(5) ha^(–1)) were used to calibrate the model.Sensitivity analysis was carried out to investigate the influence of APSIM SoilP parameters on the simulated P availability in soil and maize growth.Crop and soil P parameters were then derived by matching or relating the simulation results to observed crop biomass,yield,P uptake and Olsen-P in soil.The re-parameterized model was further validated against 2 years of independent data at the same sites.The re-parameterized model enabled good simulation of the maize leaf area index (LAI),biomass,grain yield,P uptake,and grain P content in response to different levels of P additions against both the calibration and validation datasets.Our results showed that APSIM needs to be re-parameterized for simulation of maize LAI dynamics through modification of leaf size curve and a reduction in the rate of leaf senescence for modern staygreen maize cultivars in China.The P concentration limits (maximum and minimum P concentrations in organs)at different stages also need to be adjusted.Our results further showed a curvilinear relationship between the measured Olsen-P concentration and simulated labile P content,which could facilitate the initialization of APSIM P pools in the NCP with Olsen-P measurements in future studies.It remains difficult to parameterize the APSIM SoilP module due to the conceptual nature of the pools and simplified conceptualization of key P transformation processes.A fundamental understanding still needs to be developed for modelling and predicting the fate of applied P fertilizers in soils with contrasting physical and chemical characteristics.