Deep neural network algorithm for estimating maize biomass based on simulated Sentinel 2A vegetation indices and leaf area index

Accurate estimation of biomass is necessary for evaluating crop growth and predicting crop yield.Biomass is also a key trait in increasing grain yield by crop breeding.The aims of this study were(i)to identify the best vegetation indices for estimating maize biomass,(ii)to investigate the relationship between biomass and leaf area index(LAI)at several growth stages,and(iii)to evaluate a biomass model using measured vegetation indices or simulated vegetation indices of Sentinel 2A and LAI using a deep neural network(DNN)algorithm.The results showed that biomass was associated with all vegetation indices.The three-band water index(TBWI)was the best vegetation index for estimating biomass and the corresponding R2,RMSE,and RRMSE were 0.76,2.84 t ha−1,and 38.22%respectively.LAI was highly correlated with biomass(R2=0.89,RMSE=2.27 t ha−1,and RRMSE=30.55%).Estimated biomass based on 15 hyperspectral vegetation indices was in a high agreement with measured biomass using the DNN algorithm(R2=0.83,RMSE=1.96 t ha−1,and RRMSE=26.43%).Biomass estimation accuracy was further increased when LAI was combined with the 15 vegetation indices(R2=0.91,RMSE=1.49 t ha−1,and RRMSE=20.05%).Relationships between the hyperspectral vegetation indices and biomass differed from relationships between simulated Sentinel 2A vegetation indices and biomass.Biomass estimation from the hyperspectral vegetation indices was more accurate than that from the simulated Sentinel 2A vegetation indices(R2=0.87,RMSE=1.84 t ha−1,and RRMSE=24.76%).The DNN algorithm was effective in improving the estimation accuracy of biomass.It provides a guideline for estimating biomass of maize using remote sensing technology and the DNN algorithm in this region.

Using irrigation intervals to optimize water-use efficiency and maize yield in Xinjiang,northwest China

Worldwide, scarce water resources and substantial food demands require efficient water use and high yield.This study investigated whether irrigation frequency can be used to adjust soil moisture to increase grain yield and water use efficiency(WUE) of high-yield maize under conditions of mulching and drip irrigation.A field experiment was conducted using three irrigation intervals in 2016: 6, 9, and 12 days(labeled D6, D9, and D12) and five irrigation intervals in 2017: 3, 6, 9, 12, and 15 days(D3, D6, D9, D12, and D15).In Xinjiang, an optimal irrigation quota is 540 mm for high-yield maize.The D3, D6, D9, D12, and D15 irrigation intervals gave grain yields of 19.7, 19.1–21.0, 18.8–20.0, 18.2–19.2, and 17.2 Mg ha^-1 and a WUE of 2.48, 2.53–2.80, 2.47–2.63, 2.34–2.45, and 2.08 kg m-3, respectively.Treatment D6 led to the highest soil water storage, but evapotranspiration and soil-water evaporation were lower than other treatments.These results show that irrigation interval D6 can help maintain a favorable soil-moisture environment in the upper-60-cm soil layer, reduce soilwater evaporation and evapotranspiration, and produce the highest yield and WUE.In this arid region and in other regions with similar soil and climate conditions, a similar irrigation interval would thus be beneficial for adjusting soil moisture to increase maize yield and WUE under conditions of mulching and drip irrigation.

Influence of plastic film mulching and planting density on yield,leaf anatomy,and root characteristics of maize on the Loess Plateau

In rainfed areas of northwestern China,maize production is constrained mainly by low temperature during early growth and water limitation during the entire growth period.Plastic film mulching is commonly used to increase maize yield in this area,because it increases topsoil temperature and moisture content as well as water use efficiency.However,the physiological and anatomical bases of maize yield improvement with plastic film mulching are not well understood.The effects of plastic film mulching and planting density on maize yield,photosynthetic characteristics,respiration,leaf anatomy,and root growth were studied in a two-year field experiment conducted on the Loess Plateau of China in 2017 and 2018.The experiment used a split-split plot design with two mulching treatments(plastic film mulching and no mulching),two planting densities(7.5×104 and10.5×104 plants ha-1),and two maize cultivars,Zhengdan 958 and Xianyu 335.Compared with no mulching,plastic film mulching increased maize yields by 31.1%–46.4%in 2017 and3.6%–34.7%in 2018.Compared with low planting density,high planting density significantly increased and slightly reduced yields of both cultivars in the dry year 2017 and the rainy year 2018,respectively.Plastic film mulching increased photosynthesis and respiration as well as leaf stomatal density and aperture.Photosynthetic rate,dark respiration,and stomatal conductance and aperture were lower at high planting than at low planting density.Maize yield was positively correlated with photosynthesis,dark respiration,and stomatal aperture.Mulching increased root dry weight and length in the 0–20 cm soil layer and root activity at maturity.Overall,the changes in root growth and leaf anatomy resulted in increased photosynthesis and dark respiration,and the increased photosynthesis contributed to the increase in grain yield and biomass production under plastic film mulching conditions.Our results increase understanding of the physiological mechanisms by which plastic film mulching increases maize yield in water-and temperature-limited areas.

Research Advances in Monitoring Agro-meteorological Disasters Using Remote Sensing

Remote sensing is an important method for rapidly obtaining farmland information. Once meteorological disaster occurs,using the remote sensing technology to extract disaster area of crops and monitor disaster level has great significance for evaluating disasters and making a timely remedy. This paper elaborated the importance of monitoring agro-meteorological disasters using remote sensing in current special historical period,overviewed remote sensing methods both at home and abroad,analyzed existing problems,made clear major problems to be solved in monitoring agro-meteorological disasters using remote sensing,and discussed the development prospect of the remote sensing technology.

Comparison and analysis of maize grain commodity quality and mechanical harvest quality between China and the United States

Maize is a bulk commodity in international agricultural product trading,and unified and standardized quality inspection standards are the basis of purchase and sales and other trading behaviors.China and the United States are the largest maize producers and consumers in the world,jointly accounting for more than 60%of the world's total production.In this research,the used data were from annual maize harvest quality reports released by the U.S.Grains Council in 2011-2019 and 2987 groups of mechanical grain harvest sample data collected by the Crop Cultivation and Physiology Innovation Team of the Chinese Academy of Agricultural Sciences in 2012-2019,this study compares the quality standards of commercial maize grain in China and the United States,the mechanical harvest quality(which affects the quality of the maize grain commodity),and the status quo of harvesting and storage processes in the two countries.Additionally,this study analyzes the differences in the formulation of mechanical harvest quality standards between China and the United States,as well as the reasons behind these differences,and recommends requirements for the formulation of quality standards for maize production technology and commodities that are in line with the economic conditions and maize-production conditions in China and in line with international standards in order to provide support for the industrialization of modern maize production in China.

Evaluation of grain breakage sensitivity of maize varieties mechanically-harvested by combine harvester

A high grain breakage rate is the main problem that occurs during mechanical maize harvest in China.The breakage sensitivity of different varieties was significantly different,and the breakage resistance is heritable.Therefore,breakage resistant variety screening can help improve the field production efficiency and provide references for breeding work.In this study,42 varieties of maize were harvested with the same mechanical parameters and the same manipulator on a range of harvest dates at experimental stations in Xinxiang,Henan Province,in 2017 and Changji,Xinjiang Province,in 2018 to determine the sensitivity of grain moisture content on grain breakage rate during machine harvest for different varieties.The integral value of the grain breakage rate curve corresponding to the range of 15%to 30%grain moisture content was used as an index that expressed the sensitivity of maize grains to breakage depending on grain moisture content(BSW).Forty-two varieties were categorized as having weak,intermediate,or strong BSW.Among the same four varieties in the two stations,Lianchuang 825 and Lianchuang 808 were classified as sensitive and fragile varieties,Shandan 650 was classified as an intermediate variety,Zeyu 8911 was divided into weak sensitive and breakage-resistance varieties in Xinxiang and intermediate varieties in Changji.The BSW classification results at the two experimental sites were generally consistent,indicating that breakage sensitivity due to moisture content may be a relatively stable genetic characteristic.This study suggested that the integral method for determining BSW can be used to assess the resistance of different maize varieties to grain breakage during mechanical harvesting.The integral method was used to identify twelve breakage-resistant varieties in Xinxiang Station,and six breakage-resistant varieties in Changji Station.This study provides a method for screening maize varieties that are suited to mechanical grain harvesting and for studying the mechanisms of grain breakage resistance.

Review of combine harvester losses for maize and influencing factors

The high harvest losses associated with the mechanical harvesting of maize in China are currently a major barrier to the adoption of this technology.This paper summarizes works of literature regarding harvest losses from the combine harvesting of maize in China and abroad.The main findings are as follows:(1)In 2012-2019,2987 samples data obtained from the major maize production areas of China showed that the average harvest loss was 345.2 kg/hm2(3.5%of the average yield),with losses ranging from 0 to 9288.5 kg/hm2;(2)The harvest losses from combine harvesting are mainly caused by the dropping of ears.The ear losses include the pre-harvest loss caused by ear abscission,damage caused by maize borer,lodging,and the ear loss during combine harvesting,and the main pre-harvest loss is caused by lodging;(3)Harvest losses are affected by maize variety,planting mode,cultivation management,pests and diseases,weather conditions during harvesting,harvest date,combine harvester type,harvester adjustment,operator proficiency,and the terrain conditions of the maize field;(4)The harvest losses from combine harvesting are also related to the type of header,feeding and threshing methods,the adjustment of header stripping clearance,feeding amount,forward speed,cylinder or rotor speed,and the clearance between the cylinder and the concave of the harvester.However,the combine losses mainly come from header losses.In order to reduce the harvest losses,the following solutions were proposed:(1)Breed and select maize varieties which are resistant to lodging,especially during the field drying of mature grains,as well as those resistant to maize borer and stalk rot;(2)Select varieties suitable for grain harvest-which requires matching the accumulated-temperature demand of the maize hybrids,optimal plant density,row spacing,and irrigation and fertilizer management with the light and heat conditions of the production area while cultivating uniform populations and healthy plants-as well as preventing and controlling damage from maize borer,stalk rot,and ear rot,harvesting at the appropriate time;(3)Develop and select advanced maize combine harvesters,formulate standardized operating procedures for harvesting machinery,and standardize field operation;(4)select appropriate agricultural machinery and agronomic practices,and improve the training of maize producers and harvester operators.

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.

Device for determining critical wind speed of stalk breaking to evaluate maize lodging resistance

The accurate evaluation of the lodging resistance of maize plants can provide a basis for the breeding of lodging-resistant cultivars and the regulation of cultivation measures.However,the traditional methods for evaluating maize lodging resistance in terms of plant morphology and stalk mechanical strength have certain limitations.The objective of this research was to develop a device for determining the critical wind speed of maize stalk breaking.The device was equipped with a centrifugal fan to supply airflow and was powered by a frequency conversion motor.The frequency converter adjusted the motor speed and thus adjusted the wind speed.The wind speed decreased first and then increased with increasing height above the outlet of the device,and maximum wind speed can reach 40 m/s.This device was convenient for transportation in the field,has a low cost,and can quickly,accurately,and objectively determine the lodging resistance.Field tests showed that the device ran stably for a long time.The coefficient of variation of three repeated measurements was between 1.5%and 4.8%for four maize cultivars.The new device can measure the critical wind speed of maize lodging and identify the lodging resistance for different maize cultivars,cultivation practices,and plant health conditions,and can thus overcome barriers to measuring the maize lodging resistance under natural wind conditions.

Allocation of maize varieties according to temperature for use in mechanical kernel harvesting in Ningxia, China

The reasonable assessment of maize varieties in different ecological regions can allow temperature resources to be fully exploited and reach the goal of high yield and efficiency and is thus an important direction of modern maize development in China.In this study,a logistic power nonlinear growth model was used to simulate the accumulated temperature required for kernel dehydration to moisture contents of 25%,20%,and 16%for various maize cultivar,which were divided into six types based on the accumulated temperature required for kernel dehydration to a moisture content of 25%.The relationship between the yield of maize cultivars and the accumulated temperature required for kernel dehydration to a moisture content of 25%was found to follow a unary function model.Changing the planted maize variety was found to increase economic returns by more than 7000 RMB/hm2 in Ningxia,Northwest China.Under the conditions of mechanical grain harvesting,economic benefits can be further increased by means of selecting high yields and fast-dehydrating varieties,selling when the grain dehydration is below 16%.A better way to achieve grain dehydration to a moisture content below 16%is to postpone the harvest date as much as possible rather than drying after the harvest at physiological maturity.The areas of various types of maize varieties can be dehydrated to moisture contents of 25%,20%,and 16%were marked.Based on the distribution of heat resources in different regions of Ningxia from the normal sowing date to October 31 before winter irrigation,the appropriate cultivars for various regions in the province were determined based on production benefits.Therefore,in different areas of Ningxia,selecting suitable maize varieties according to temperature resources can reach a high yield and mechanical kernel harvesting,and ultimately obtain higher economic benefits.

Kernel position effects of grain morphological characteristics by X-ray micro-computed tomography (μCT)

Grain size and shape are important factors for yield and quality.The difference in grain phenotypic characteristics in the same maize hybrid is related to its position in the ear.This study aimed to clarify the distribution characteristics of grain morphological characteristics in the ear and to provide guidance for research of grain phenotype and kernel position effects.Three maize hybrids were used in the experiment,namely,Denghai 618(DH618),KX3564,and Xianyu 335(XY335),and the kernel number per row were 40,40,and 36,respectively.The X-rayμCT was applied to obtain five kernel morphological indicators,including grain length,width,thickness,volume,surface area.Grain sphericity,length-width ratio,specific surface area,and volume coefficient were further calculated.The results showed that there were three types of maize ear morphological indicators trends:grain length,width,volume,and surface area were parabolic;thickness and sphericity were inverted parabolic;length-to-width ratio and specific surface area were irregular.The volume coefficient of grain at different parts of the ear,namely the relation coefficient between grain volume and grain length,width,and thickness,was determined.The average value of the middle grains morphological indicators of the ear was taken to select kernels representing stable characteristics of the variety.Within the range of 5%deviation from the morphological mean value of the middle grains of the ear,the grains in the middle part accounted for 26.39%of the total ear,about 10 grains extending from the 14th grain at the base of the ear to the top.Within the range of 10%deviation,the middle accounted for 47.22%,about 18 grains extending from the 12th grain at the base of the ear to the top.This study found that grain morphological indicators were greatly different at different positions of the maize ear,and showed different change rules as extend from the base to the top of the ear.Therefore,there were different grain volume coefficients at different positions of maize ear.And the representative sampling range on maize ear was determined based on the comprehensive analysis of different morphological indexes variation of grain.

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.

Improving harvest efficiency of maize varieties via accumulated temperature in a certain planting area

The ripening and drying of maize(Zea mays L.)grain are closely related to temperature.In accordance with maize grain drying characteristics,regional accumulated temperature(AT0≥0℃)distribution is of great significance for a rational allocation of maize varieties,thus reducing grain moisture content(MC)to improve maize harvest efficiency.From 2016 to 2018,a multi-site trial was carried out in the spring maize production area of Northeastern China.In this study,under a guaranteed rate of 80%for AT0,this area was divided into 15 accumulated temperature zones(ATZs)with an interval of 100℃ based on climatic data of 78 local weather stations.Then the AT0 demand of different maize varieties during different growth stages was calculated by combining experimental records with the established prediction model of MC,and then,the spatial partition for different types of maize varieties under different MCs was analyzed.The results showed that all the tested varieties could not reach physiological maturity(PM)at ATZs 13-15,hence,where maize planting is risky.With the increasing accumulated temperature demand of different types of maize varieties from planting to PM,to the MC of 25%and to the MC of 20%,the unplantable areas were gradually expanded from south to north while the region where the maize varieties could be harvested under different MCs was also moved southwardly.Additionally,at 1-2 ATZs,it is entirely possible to achieve mechanical kernel harvesting under the MC of 20%,even though the AT0 requirements of the varieties are relatively high.Conclusively,on the grounds of AT0 demand law of maize varieties and heat resource distribution in Northeastern China,the layout optimization for achieving different harvesting scenarios is conducive to providing a basis not only for selecting suitable varieties but also for promoting mechanical kernel harvesting in the spring maize production area of this region.