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.

The Effect of Maize Grain Size on the Physicochemical Properties of Isolated Starch, Crude Maize Flour and Nixtamalized Maize Flours

Usually, the maize cob is formed by grains of medium size. However, the extremes have larger or smaller size grains. The objective of this study was to investigate the influence of grain size from the same hybrid on the physicochemical properties of isolated starch, crude maize flours and nixtamalized maize flours. Two hybrids, one from CIMMyT-Mexico called IMIC-254 and one commercial sample from Monsanto (Puma) were studied. The isolated starch granules from small, medium, and large grains exhibit the same size and distribution. The grain size has influence in the determination of cooking and steeping times;small grains reach these parameters faster than medium and large ones. The hardness of the grain size for both hybrids does not showed statistical differences between them. The starch from small, medium and large grains is mainly composed of amylopectin;this result is confirmed by X-ray diffraction and Megazine analysis. The apparent viscosity of the isolated starches of small grains showed statistically significant higher peak values. According to these results, it is possible to use small, medium, and large grains to obtain products with the same physicochemical properties, by adjusting the cooking and steeping times and Ca2+ content.

Maize （Zea mays L.） Growth and Grain Yield under Conventional and Site-Specific Nitrogen Management in a Dryland Farming System

Large amount of pre-plant nitrogen （N） fertilizer results in low N use efficiency due to poor synchrony between soil N supply and maize N demand, especially during N sensitive growth stages. The objectives of the study were to compare growth and yield of maize （Zea rnays L.） under conventional and site-specific N management in a dryland farming system. The study, which was designed as randomized complete block design was conducted over three site-years under continuous maize cropping system in the semi-arid regions of the Limpopo Province in South Africa. Treatments of the study consisted of three N management strategies on a maize field planted to drought resistant SNK 2147 hybrid maize cultivar. Treatments were： （i） no N application （NO）, （ii） site-specific N at variable rates ranging between 18 kg N/ha and 33 kg N/ha based on soil analysis results （N l） and （iii） conventional and uniform N application broadcasted during planting at 58 kg N/ha （N2）. Sufficiency index as indication of N deficiency was determined using CCM-200 on maize leaves based on leaf numbers during maize vegetative growth stages V6, V10 and Vl4, and thereafter N was applied only when needed. The highest maize grain yield of 5.2 Mg/ha for N 1 was significantly higher （P 〈 0.05） than 3.2 Mg/ha and 4.0 Mg/ha of N0 and N2 in site-year I, respectively. Maize grain yield of 2.2 Mg/ha （Nl） at site-year ll was significantly higher （P _〈 0.05） than 1.7 Mg/ha of the NO. The maize growth and yield under N2 and N1 was compared, N1 required between 43% and 69% lesser N fertilizer as compared to N2 over site-years, and resulted in higher maize height, number of leaves per plant, leaf length, and leaf area than that of conventional N management strategy. Therefore, site-specific N management strategy sustains and improves growth and yield of maize using minimal N fertilizer as compared to conventional approach in low fertility soils of semi-arid regions in dryland farming systems. In examining the results of this study, there was a consistent benefit of site-specific N management strategy on improving growth and yield of maize while saving fertilizer use in small-scale dryland maize farming system.

Association between Aspergillus flavus Colonization and Aflatoxins Production in Immature Grains of Maize Genotypes

Aspergillus flavus maize colonization leads to crop contamination by toxic secondary metabolites and carcinogens called aflatoxins （AF）; it has negative effects in public health and has caused economic losses in agricultural activities. Eleven genotypes of immature maize grain frequently used in Mexico were inoculated in vitro with two indigenous toxigenic strains ofA. flavus. The size of inoculum, temperature, humidity and presence of other phytopathogens were assessed. Genotypes Popcorn, C-526, Garst 8366, As910 and 30G40 showed resistance to rating of fungal colonization （FC） and AF accumulation, while 3002W, 30R39, Creole, C-922, HV313 and P3028W genotypes were less resistant. AFB~ had the highest concentrations （26.1 mg/kg ± 14.7 mg/kg）, while AFB2, AFG1 and AFG2 showed only residual concentrations 1.6, 2.0 and 4.0 ~tg/kg, respectively. Concerning FC and AF, there were significant differences （P 〈 0.01） between strains and genotype. Both strains showed significant association （P 〈 0.01） between FC and the concentrations of AFB1 and AFB2 （R2： 99.5% and 93.2%; 87.2% and 73.2%, respectively）. Results suggest that the level of resistance to fungus infection and AF accumulation is related to maize genotype. It emphasizes the relevance of developing A. flavus resistant maize genotypes as an alternative to control contamination in foodstuff intended for human and animal consumption.

Effect of steam-flaking on chemical compositions,starch gelatinization,in vitro fermentability,and energetic values of maize,wheat and rice

Intact and steam-flaked grains of maize,wheat and rice（with whole hulls） were analyzed for chemical composition,starch gelatinization degree（SGD） and in vitro fermentation characteristics to investigate the influence of cereal type and steam-flaking（SF） processing on their nutritive values.The treatments were arranged in a 3×2 factorial design.Obvious differences（P〈0.001） in chemical composition and energetic values were observed among the different cereal types.SGD and gas production（GP） rate was significantly increased（P〈0.001） by SF processing.SF processing also increased（P〈0.01） the proportion of propionic acid and decreased the acetic：propionic acid ratio in vitro.Steam-flaking also increased organic matter digestibility and the energetic value of the cereal grains,especially rice.Based on these results,rice probably is more amendable to SF processing than maize and wheat.In conclusion,it is feasible to partially substitute maize grain with wheat or rice in ruminant diets,and steam-flaking can significantly improve the nutritional value of wheat and rice grains.

Non-destructive method of small sample sets for the maize moisture content measurement during filling based on NIRS

In maize breeding,limitations on sampling quantity and associated costs for measuring maize grain moisture during filling are imposed by factors like the planting area of new varieties,maize plant density,effective experimental spikes,and other conditions.However,the conventional method of detecting moisture content in maize grains is slow,damages seeds,and necessitates many sample sets,particularly for high moisture content determination.Thus,a strong demand exists for a non-destructive quantitative analysis model of maize moisture content using a small sample set during grain filling.The Bayes-Merged-Bootstrap(BMB)sample optimization method,which built upon the Bayes-Bootstrap sampling method and the concept of merging,was proposed.A critical concern in dealing with small samples is the relationship between data distribution,minimum sample value,and sample size,which has been thoroughly analyzed.Compared to the Bayes-Bootstrap sample selection method,the BMB method offers distinct advantages in the optimized selection of small samples for non-destructive detection.The quantitative analysis model for maize grain moisture content was established based on the support vector machine regression.Results demonstrate that when the optimal resampling size is 1000 times or more than the original sample size using the BMB method,the model exhibits strong predictive capabilities,with a determination coefficient(R2)>0.989 and a relative prediction determination(RPD)>2.47.The results of the 3 varieties experiment demonstrate the generality of the model.Therefore,it can be applied effectively in practical maize breeding and determining grain moisture content during maize machine harvesting.

Analysis of factors affecting the impurity rate of mechanically-harvested maize grain in China

The grain impurity rate is an important index for assessing the quality of mechanical maize harvesting.Therefore,it is of great significance to clarify the current situation of maize impurity rate and study the factors that affect the impurity rate in order to promote the development of mechanical maize harvesting technology.From 2012 to 2019,a total of 2504 maize impurity rate measurements were obtained.The results showed that the average impurity rate at maize harvest was 1.18%in China,in which the Huang-Huai-Hai summer maize area was 1.68%,which was significantly higher than the 0.65%in the Northwest spring maize area and 0.77%in the North China spring maize area.There was a significant positive correlation between the impurity rate and the moisture content of the maize harvest.The average moisture content of maize at harvest in Huang-Huai-Hai summer maize area was the highest at 27.55%,which was the main reason for the high impurity rate in this area.When harvesting different varieties with the same moisture content,there were significant differences in the impurity rate between different varieties.The cob hardness of the variety may also affect the impurity rate of maize.Different harvesters and weather conditions during harvesting are also important factors affecting the impurity rate.Therefore,by breeding fast dehydrated varieties and harvesting maize in time,the impurity rate of maize during mechanical harvesting can be effectively reduced.

Bionic design and performance test of maize grain cleaning screen through earthworm motion characteristics

The maize mixture feeding with a large mass cannot be migrated backward rapidly along the planar reciprocating vibrating screen,and it is easy to accumulate in the front of the screen,which leads to the decrease of screening efficiency.Based on the reverse engineering technology,using the wavy geometry formed during the earthworm(Pheretima guillelmi)moving as a bionic prototype,a bionic screen was designed to make the maize mixture migrate backward rapidly in the front of the screen.The contour curve of earthworm’s head in an axial contracted state was extracted and fitted to obtain its equation.Based on the difference of concave position of the lower surface’s wavy geometry during the earthworm moving,the motion of the bionic screen was divided into four postures,and the conversion between different postures of the bionic screen was realized by the cam drive mechanism.The kinematics simulation of the bionic screen was carried out through ADAMS,and the displacement and velocity of the bionic screen were analyzed.When the feeding mass of the maize mixture was set at 5 kg/s,6 kg/s and 7 kg/s,the test results showed that the time of the maize mixture migrated(TOMMM)in the front of the bionic screen was shortened by 0.18 s,0.71 s,and 1.36 s,respectively,compared with that of planar reciprocating vibrating screen.The total screening time(TST)of the bionic screen was shortened by 1.28 s,1.33 s,and 1.53 s,respectively.The ability of the maize mixture to be migrated backward was improved.This study can provide a reference for the innovative design of the cleaning screen.

Influences of moisture content and compressive loading speed on the mechanical properties of maize grain orientations

Determination of the mechanical properties(rupture force,deformation,hardness,and toughness)of maize grain could be a significant concern for designing the harvester,thresher,and handling,processing,and storage equipment.Thus,the present research was conducted to assess the vertical and lateral rupture force,deformation,hardness,and toughness of maize grain(Beijing Denong,Lianchuang,Suyu 20,Liyu 88 and Suyu 29)influenced by different moisture contents(11.2%,17.5%,and 21.3%)and compressive loading speeds(5,10,15,20,and 25 mm/min,respectively).Besides,the mean length,width,thickness,geometric mean diameter,equivalent diameter,arithmetic diameter,sphericity,grain volume,surface area,and aspect ratio of the selected varieties were measured.The results showed that the highest length,width,thickness and sphericity,grain volume,surface area,and aspect ratio were obtained at moisture of 21.3%,whereas the lowest was at 11.2%.Moreover,it was observed that as increasing the loading speed from 5 to 25 mm/min,the vertical and lateral rupture forces decreased.However,as increasing moisture contents from 11.2%to 21.3%,the vertical and lateral rupture forces,hardness,and toughness decreased noticeably.Furthermore,the maximum correlation(R2=0.9957)between rupture force and loading speed was found for Liyu 88 at moisture of 17.5%and minimum correlation(R2=0.7002)was found for Suyu 29 at moisture of 11.2%.Moreover,the highest lateral and vertical rupture force was noticed(p<0.05)at a loading speed of 5 mm/min.Based on the experimentally obtained results,it was concluded that the properties of maize grain evaluated were relevant to the design of planter,harvesters,thrashers,and processing machine.

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).

In-field harvest loss of mechanically-harvested maize grain and affecting factors in China

Field harvest loss is a common problem of maize grain mechanical harvesting in China and abroad.From 2012 to 2019,2987 groups of samples for the quality of mechanical grain harvesting in field were obtained in 21 major maize-producing provinces,cities,and regions of China.The analysis performed in this study showed that the average harvest loss of fallen ears was equivalent to 76.5%of the total harvest loss,indicating that the harvest loss in the mechanical harvesting of maize grain mainly came from the loss of fallen ears.Meanwhile,statistical analysis of the harvest loss in different ranges of grain moisture contents showed that,when the grain moisture content fell below 20%,the harvest loss rate of fallen ears and the total harvest loss rate both increased sharply,and the harvest loss of fallen ears increased faster than the harvest loss of fallen grain with a decreasing grain moisture content.Moreover,the results of multi-point experiments and harvest experiments in different periods showed that,during harvesting time,the harvest loss of fallen ears caused by lodging was the main reason for in-field harvest losses in the mechanical harvesting of maize grain.Apart from the above mentioned,the test results of 35 groups of harvesters for the in-field mechanical harvesting of maize grain showed that the harvester types and their operating parameters were important factors affecting the harvest loss in the mechanical harvesting of maize grain.Therefore,the principal paths to reduce harvest loss in the mechanical harvesting of maize grain are to breed lodging-resistant maize varieties,adopt reasonable planting densities,cultivate healthy plants,develop harvesters with low harvesting loss,intensify the training of operators,and harvest at an appropriate time.

Experimental study on specific grinding energy and particle size distribution of maize grain,stover and cob

Reducing the particle size of biomass is of great significance for rational and efficient utilization of biomass.In this study,maize grain,stover,and cob were comminuted at different speeds(2000-2800 r/min)by hammer mill with a mesh size of 2.8 mm.The mechanical energy for smashing three selected samples was obtained directly through the sensor and data testing system.Experimental results demonstrated that the maize cob had the highest total specific energy while the maize grain had the lowest(135.83-181.10 kW·h/t and 27.08-36.23 kW·h/t,respectively).In addition,for the same material,higher hammer mill speed generated more specific energy consumption.And the effective specific energy of maize stover had a similar trend to the total specific one.However,the effective specific grinding energy of maize cob and grain increased initially and then decreased with the increase of rotating speed.The fitting curves of the specific energy to mill speeds were determined,and the range of determination coefficients of the regression equation was 0.933-0.996.Particle size distribution curves were drawn by sieving the pulverized particles of the three samples based on a series of standard sieves.Fourteen relevant parameters characterizing the particle size distribution were calculated according to the screening data.Calculation results demonstrated that larger rotational speed leads to smaller particle sizes.Combining the size parameters,distribution parameters,and shape parameters,it was found that the distributions of the three samples all exhibit a distribution of“well-graded fine-skewed mesokurtic”.The Rosin-Rammler function was considered to be suitable for characterizing the particle size distribution of maize grain,stover,and cob particles with a coefficient of determination between 0.930 and 0.992.

Improvement of Soil Fertility and Crop Yield through Biochar Amendment from Salt Affected Soil of Central China

Soil salinity has been considered a brutal environmental factor for decreasing crop yield due to the accumulation of excessive sodium salts in soil under arid and semi-arid region of the world. This study tries to address the potential use of biochar. An organic matter rich material, used to reclaim salt-stressed soil in order to enhance crop production in dry croplands as well as to increase soil organic carbon （SOC） and to improve soil fertility. In this regard, a field experiment for two years was conducted in a moderately salt-stressed soil of Central China with wheat-maize cropping system. The soil was amended with biochar composted with poultry manure （BPC） at 12 t/ha with diluted pyroligneous solution （PS） at 0.15 t/ha a week before sowing of crop. Results showed significant improvement in soil physical properties, soil nutrient content with reduction of sodium salts and soil pH by amendment of BPC-PS1 and BPC-PS2 over the experimental control salt-stressed cropland. Furthermore, wheat and maize grain yield, nitrogen, phosphorous potassium and K/Na ratio increased while sodium decreased with the application of BPC-PS amendment in wheat and maize grain. This study concluded that the biochar amendment in conjunction with PS greatly improved SOC storage, crop nutrient uptake and soil fertility. Thus, waste treatment of crop straw and poultry manure compost as biochar could be combined to alleviate salt stress and improve crop production in the vast area of arid and semi-arid regions of the world.

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.

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.

Effects of Integrated Soil-Crop System Management on Soil Organic Carbon Characteristics in a Primosol in Northeast China

A synchronous increase in crop productivity, nutrient use efficiency, and soil carbon(C) sequestration is important from the point of view of food security and environmental protection. In recent years, integrated soil-crop system management(ISSM), which uses crop models and advanced nutrient management to redesign cropping systems, has been successfully demonstrated to achieve both high crop productivity and high nutrient use efficiency in China, but the effects of ISSM on soil organic C(SOC) characteristics remain unknown. In this study, the effects of current farmers' practice(FP), high-yielding practice(HY), which maximizes yields without considering costs, and ISSM on the content and chemical composition of SOC were studied in a 4-year(2009–2013) field plot experiment with maize(Zea mays L.) monoculture in an Alluvic Primosol in Northeast China. The ISSM resulted in higher soil total organic C(TOC), water-soluble organic C, easily-oxidizable organic C, particulate organic C, and humic acid C compared with HY and FP in the region. The SOC contents in aggregate size fractions generally followed a similar pattern to TOC. Compared with FP,HY decreased the mean weight diameter, geometric mean diameter, percentage of > 0.25-mm water-stable aggregates, and the stability ratio of water-stable aggregates, and increased the structure-deterioration rate and index of unstable aggregates. The opposite trend was observed between ISSM and HY. Solid-state ^(13)C nuclear magnetic resonance spectra of bulk soil showed that ISSM had higher O-alkyl C and aliphatic C/aromatic C ratio, but lower aromatic C, carbonyl C, and alkyl C/O-alkyl C and hydrophobic C/hydrophilic C ratios than HY and FP. Our results suggest that ISSM improves the quantity and quality of SOC and has a positive effect on soil aggregation and aggregate stability.

Comparing kernel damage of different threshing components using high-speed cameras

Grain damage research has been a focus of many experts in the agriculture machinery industry.A threshing test-bed was developed to investigate the movement and influence of different threshing and separating units on maize grains.The damage to maize grains was analyzed with a high-speed camera to observe the movement and damage received by the maize grains.The results showed that the threshing and separating effects of the perforated concave plate were obviously lower than that of the round steel concave plate,the threshing effects of the rigid rasp bar and polyurethane rasp bar were similar,and the damage ratio of the polyurethane rasp bar was relatively low.It also indicated that moisture content has a significant effect on the damage ratio and damage type of maize grains.The different threshing component types used in this study had an obvious effect on the degree of damage to high moisture content maize grains and the damage to high-moisture kernels during threshing could be further identified.The results can provide a reference for the design of threshing and separating devices in the maize combine harvesting machinery.