The damage risk evaluation of Aphis gossypii on wheat by host shift and fitness comparison in wheat and cotton

Aphids are considered as one of the key pests for wheat production worldwide. Major aphid species that infest wheat in China include Sitobion avenae, Rhopalosiphum padi, Schizaphis graminum and Metopolophium dirhodum. However, during our wheat field survey in Wenshang County of Shangdong＇Province, China, we observed that Aphis gossypii can feed on wheat. The damage risk of A. gossypii on wheat was assessed using host shift method. A population of A. gossypii collected from a wheat field in 2015 and another population reared on cotton under laboratory conditions for a decade without exposure to insecticides were used in the study. The results of host shift demonstrated that the A. gossypfi colony from wheat has not yet developed wheat specialization. Moreover, the assessment of A. gossypii fitness on wheat and cotton showed that fecundity and net reproductive rate of A. gossypii population fed on wheat was significantly higher comparing to the population fed on cotton, whether the initial host of A. gossypii population was wheat or cotton. This study raises a warning that the cotton aphid has potential to establish well on wheat and it may cause significant effects under specific circumstances. Therefore, future studies are required to evaluate the effects of A. gossypfi on wheat production.

Fiber damage of machine-harvested cotton before ginning and after lint cleaning

Machine harvesting increases the foreign matter content of seed cotton. Excessive cleaning causes fiber damage and economic loss. Most trading companies in the Xinjiang Uygur Autonomous Region, China have indicated reluctance to use machine-harvested cotton. The first objective was to determine how the fiber quality was affected by the ginning and lint cleaning and how the fiber damage during levels of lint cleaning changed. The second objective was to determine the optimum number of lint cleaners for machine-harvested cotton based on fiber damage. Cotton samples were collected from 13 fields and processed in seven ginneries between 2013 and 2015. The results indicated that ginning and lint cleaning didn＇t have significant effect on fiber strength and significantly affected both fiber length and short fiber index. Fiber length was reduced by more than 1.00 mm from six of 13 fields after lint cleaning, then the damage rate on short fiber index from 11 of 13 fields was more than 20%. The third lint cleaning caused great fiber damage, reducing fiber length by 0.35 mm and increasing short fiber index by 0.65%. So, the lint should be cleaned by one lint cleaner in the Xinjiang, however, the stage of lint cleaning was sometimes omitted when the foreign matter content of lint was little.

Effect of Cotton Straw Extract on Wheat Root Growth

Objective] The aim was to study the effects of cotton straw extract on wheat root growth and define the al elopathic effect of cotton straw on wheat root. [Method] A sand culture experiment was conducted under different cotton straw ex-tract levels （0%, 1.0%, 2.0%, 4.0%, 8.0% and 10.0%）, and the morphology and physiological activity of wheat （Yangmai 13） root were studied. [Result] The cotton straw extract inhibited the elongation of wheat roots, but increased the root diame-ter, resulting in the decreased root surface area and volume; The extract treatments induced the increase of root reactive oxygen species （ROS） level, which led to an increased root membrane lipid peroxidation, thereby reducing the root vigor and in-hibiting the root water uptake and formation of biomass; With the increase of con-centration of cotton straw extract, the total phenolic acid content in the extract in-creased continuously, and the total phenolic acid content was closely related to the morphogenesis and physiological activity of wheat root. [Conclusion] The cotton straw extract inhibited the morphogenesis and physiological activity of wheat root through affecting the root ROS level, and the total phenolic content was one of the main limiting factors.

Effects of planting patterns on yield, quality, and defoliation in machine-harvested cotton

The aim of this study was to elucidate the effects of different machine-harvested cotton-planting patterns on defoliation,yield,and fiber quality in cotton and to provide support for improving the quality of machine-harvested cotton.In the 2015 and 2016 growing seasons,the Xinluzao 45(XLZ45)and Xinluzao 62(XLZ62)cultivars,which are primarily cultivated in northern Xinjiang,were used as study materials.Conventional wide-narrow row(WNR),wide and ultra-narrow row(UNR),wide-row spacing with high density(HWR),and wide-row spacing with low density(LWR)planting patterns were used to assess the effects of planting patterns on defoliation,yield,and fiber quality.Compared with WNR,the seed cotton yields were significantly decreased by 2.06–5.48%for UNR and by 2.50–6.99%for LWR,respectively.The main cause of reduced yield was a reduction in bolls per unit area.The variation in HWR yield was–1.07–1.07%with reduced bolls per unit area and increased boll weight,thus demonstrating stable production.In terms of fiber quality indicators,the planting patterns only showed significant effects on the micronaire value,with wide-row spacing patterns showing an increase in the micronaire values.The defoliation and boll-opening results showed that the number of leaves and dried leaves in HWR was the lowest among the four planting patterns.Prior to the application of defoliating agent and before machine-harvesting,the numbers of leaves per individual plant in HWR were decreased by 14.45 and 25.00%on average,respectively,compared with WNR,while the number of leaves per unit area was decreased by 27.44 and 36.21%on average,respectively.The rates of boll-opening and defoliation in HWR were the highest.Specifically,the boll-opening rate before defoliation and machine-harvesting in HWR was 44.54 and 5.94%higher on average than in WNR,while the defoliation rate prior to machine-harvesting was 3.45%higher on average than in WNR.The numbers of ineffective defoliated leaves and leaf trash in HWR were the lowest,decreased by 33.40 and 32.43%,respectively,compared with WNR.In conclusion,the HWR planting pattern is associated with a high and stable yield,does not affect fiber quality,promotes early maturation,and can effectively decrease the amount of leaf trash in machine-picked seed cotton,and thus its use is able to improve the quality of machine-harvested cotton.

Effects of plant density and mepiquat chloride application on cotton boll setting in wheat–cotton double cropping system

Sowing cotton directly after harvesting wheat in the Yangtze River Valley of China requires early mature of cotton without yield reduction.Boll-setting period synchronisation and more yield bolls distributed at the upper and middle canopy layers are also required for harvesting.The objective of this study is to quantify the individual and interaction effects of plant density and plant growth regulator mepiquat chloride(MC)on temporal and spatial distributions of yield bolls,as well as yield and yield components.During the 2013–2016 cotton growing seasons,the experiments were conducted on a shortseason cotton cultivar CRRI50 at Yangzhou University,China.Various combinations of plant density(12.0,13.5 and 15.0 plants m^(–2))and MC dose(180,270 and 360 g ha^(–1))were applied on cotton plants.The combination of 13.5 plants m^(–2)and 270 g ha^(–1)MC resulted in the greatest boll number per unit area,the highest daily boll setting number and more than 90%of bolls positioned within 45–80 cm above the ground.In conclusion,appropriate MC dose in combination of high plant density could synchronize boll-setting period and retain more bolls at the upper and middle canopy layers without yield reduction in the system of direct-seeded cotton after wheat harvest,and thus overcome the labor-intensive problem in current transplanting cropping system.

A Study of Mechanization of Cotton Harvesting in India and Its Implications

Cotton is one of the most important crops throughout the history of India and it also plays an important role in social and economic aspects of the Indian society in the present age. Recent technological advances and trade liberalization have made India a major player in international cotton markets. In the year 2011-2012, India was the world＇s second largest producer, consumer and exporter of cotton. The increasing role of the Indian cotton sector in international markets is a direct challenge to other major players like the US. Within this context, a better understanding of the Indian cotton sector and the impact of mechanization on cotton cultivation are needed. The overall objective of this paper is to assess the competitiveness of Indian cotton producers and potential implications for India as a competitor in the world cotton market if it mechanizes harvesting of cotton. The results demonstrate that the net income of the Indian cotton farmers will increase considerably with the mechanization of cotton harvesting. But the adoption of the practice of harvesting cotton by mechanical means is possible only if efforts from many private and public agencies come together. In that scenario, the cotton production in India can increase considerably which can impact the international markets.

Wheat yield scenarios for rainwater harvesting at Northern Sinjar Mountain, Iraq

Iraq is part of West Asia and North Africa (WANA) region. The area is known as dry land, famous with gap of crop yield as a result of the water shortage problem. Six basins with total catchment area of 614.19 km2 at rain-fed of Northern Sinjar District (Iraq) had been chosen to investigate both of the potential of rainwater harvesting (RWH) and three supplemental irrigation (SI) scenarios S1, S2, and S3 (100%, 75%, and 50% of full irrigation requirement) to support the wheat yield (bread and durum) under various rainfall conditions for the study period 1990-2009. The results indicated that, the total volume of harvested runoff can be considered for irrigation practices, that reached up to 42.4, 25.1, 0.6, 10.9 (× 106 m3) during 1995-1996, 1996-1997, 1998-1999, and 2001-2002, respectively. The total irrigated area ranged between 10.9 - 5163.7 and 8.8 - 3595.7 (ha) for bread and durum wheat crop for the four selected seasons respectively. The yield scenarios for supplemental irrigation condition Y1, Y2, and Y3 give 68 - 9712, 94 - 12,999, and 105 - 22,806 Ton for bread wheat, and for durum wheat give 56 - 8035, 87 - 10,906, and 103 - 17,396 Ton.

Several Cotton Rotation and Intercropping Systems in Cotton Planting Area of Eastern Henan Province

In recent years,the area dedicated to cotton cultivation in eastern Henan Province has experienced a continuous decline.Developing efficient multi-cropping systems for cotton and increasing the multiple cropping index represent effective strategies to stabilize the cotton planting area and enhance the income of cotton farmers.This paper presents an overview of intercropping systems and the benefits associated with cotton rotation and intercropping practices.Specifically,it discusses the"early maturing cotton-wheat"rotation system,the"cotton-watermelon"intercropping system,the"cotton-Dutch bean"intercropping system,and the"early maturing cotton-peanut-garlic"intercropping system.

Effects of Ridge-Mulching with Plastic Sheets for Rainwater-Harvesting Cultivation on WUE and Yield of Winter Wheat

A field experiment was conducted in a manural loesial soil in middle of Shaanxi Province ofChina, a sub-humid area prone to drought, to study the effects of rainwater-harvestingcultivation on water use efficiency (WUE) and yield of winter wheat. Ridge-furrow tillage wasused, the ridge being mulched by plastic sheets for rainwater harvesting while seeding in thefurrows. Results showed that from sowing to reviving stage of winter wheat, water stored in 0-100 cm layer was significantly decreased whereas that in 100-200 cm layer did not change.Compared to the non-mulching, plastic mulch retained 6.5 mm more water as an average of the twoN rate treatments, having a certain effect on conservation of soil moisture. In contrast, atharvest, water was remarkably reduced in both the 0-100 cm and the 100-200 cm layers, andmulched plots consumed 34.8 mm more water as an average of the two treatments: low N rate (75kg N ha-1) with low plant density (2 300 000 plants ha-1) and high N rate (225 kg N ha-1)with highplant density (2 800 000 plants ha-1), in 0-200 cm layer than those without mulching, the formerbeing beneficial to plants in utilization of deep layer water. Mulching was significant inharvesting water and in increase of yield. Mulched with plastic sheets, biological and grainyields were 22.5 and 22.6% higher for the average of the high N rate than for the low N rate,and the high N rate with low plant density was 29.8 and 29.1% higher in both biological andgrain yields than that of the low N rate with low plant density. With high N rate and high plantdensity, the mulched biological and grain yields were 39.5 and 28.9% higher than the correspondingtreatments without mulching. Of the treatments, that with high N rate and low plant density wasthe highest in both biological and grain yields, and the water use efficiency reached 43.7 kgmm-1 ha-1 for biological yield and 22 kg mm-1 ha-1 for grain yield, being the highest WUE reportedin the world up to now.

Isolation and Functional Characterization of a B3 Transcription Factor Gene <i>FUSCA3</i>Involved in Pre-Harvest Sprouting Resistance in Wheat

Pre-harvest sprouting (PHS) reduces yields and grain quality, resulting in seriously economic losses in wheat. It has been showed that PHS is significantly correlated to seed dormancy levels. FUSCA3 (FUS3) gene is considered to be the key regulator of seed dormancy. However, little information is available about the function of FUS3 gene (TaFUS3) in wheat. In this study, three homologous genes were identified in wheat grain, and their functions were investigated by gene silencing. Three full-length DNA (3477, 3534 and 3501 bp) and cDNA (1015, 1012 and 1015 bp) sequences encoding a B3 transcription factor, designated TaFUS3-3A, TaFUS3-3B and TaFUS3-3D, were first isolated from common wheat. The transcription of three TaFUS3 genes in seed development and germination process was detected. TaFUS3-3B and TaFUS3-3D had similar expression profiles, and high levels of gene transcripts were detected in seeds at 25 DAP (days after pollination) and after 24 h of imbibition. However, the transcription of TaFUS3-3A was not detected. Silencing of TaFUS3 in common wheat spikes resulted in increased seed germination and PHS. Compared with wild-type, the TaFUS3-silenced plants showed increased expression of genes related to GA biosynthesis and ABA metabolism, and decreased expression of genes associated with ABA biosynthesis. Moreover, silencing of TaFUS3 in wheat plants led to a decrease in embryo sensitivity to ABA and changed the expression of genes involved in ABA signal transduction. The results of gene silencing indicated that TaFUS3 plays a positive role in wheat seed dormancy and PHS-resistance, which might be associated with ABA, GA level and signal transduction.

Harvest Splitting as a Good Agricultural Practice to Ensure the Quality of Cotton Fiber (Gossypium hirsutum L.) in Côte d’Ivoire

Context: The major challenges of cotton cultivation in Côte d’Ivoire are the improvement of field yields and fiber quality. One of the methods proposed to ensure the quality of cotton fiber is split cotton harvesting. In order to study the influence of this practice on the technological characteristics of cotton fiber, a study was undertaken in three production zones in Côte d’Ivoire. In the present study, seed cotton was harvested at 50%, 75% and 100% boll opening. After ginning, the fibers were analyzed on an HVI chain and their main technological characteristics were evaluated. Results: The results obtained show that regardless of the area, the crop splitting influences the parameters studied, such as the length, short fiber rate, tenacity, brightness and yellowness index of the fiber. Thus, harvesting at 50% capsule opening improves the fiber length by 1.5 mm, tenacity by 1.04 g/tex and brightness by 1.23, while reducing the short fiber rate by 0.84% and the yellowness index by 0.47. As for harvesting at 75% capsule opening, it increases the length by 0.72 mm, tenacity by 0.79 g/tex and brightness by 1.13, while decreasing the short fiber rate by 0.69% and the yellowness index by 0.45. Conclusion: Splitting the cotton harvest improves the quality of the fiber. It is therefore a practice to be recommended to producers in order to preserve the quality of the fiber, especially that carried out at 50% opening of the cotton bolls.

QTL mapping revealed TaVp-1A conferred pre-harvest sprouting resistance in wheat population Yanda 1817×Beinong 6

Pre-harvest sprouting （PHS） occurs frequently in most of the wheat cultivation area worldwide, which severely reduces yield and end-use quality, resulting in substantial economic loss. In this study, quantitative trait loci （QTL） for PHS resistance were mapped using an available high-density single nucleotide polymorphism （SNP） and simple sequence repeat （SSR） genetic linkage map developed from a 269 recombinant inbred lines （RILs） population of Yanda 1817xBeinong 6. Using phenotypic data on two locations （Beijing and Shijiazhuang, China） in two years （2012 and 2013 harvesting seasons）, five QTLs, designated as QPhs.cau-3A. 1, QPhs.cau-3A.2, QPhs.cau-5B, QPhs.cau-4A, and QPhs.cau-6A, for PHS （GP） were detected by inclusive composite interval mapping （ICIM） （LOD≥2.5）. Two major QTLs, QPhs.cau-3A.2 and QPhs.cau-5B, were mapped on 3AL and 5BS chromosome arms, explaining 6.29-21.65% and 4.36-5.94% of the phenotypic variance, respectively. Precise mapping and comparative genomic analysis revealed that the TaVp-1A flanking region on 3AL is responsible for QPhs.cau-3A.2. SNP markers flanking QPhs.cau-3A.2 genomic region were developed and could be used for introgression of PHS tolerance into high yielding wheat varieties through marker-assisted selection （MAS）.

Effects of Different Drip Irrigation Modes on Growth and Yield of Cotton

This study aimed to explore the optimum drip irrigation belt arrangement mode for mechanically-harvested cotton in Xinjiang. The Xinluzao 61 was selected as the experiment material, and the effects of two different drip irrigation modes（6 cotton rows with 2 drip irrigation pipes under plastic film, 6 cotton rows with 3 drip irrigation pipes under plastic film） on the growth and yield of Xinluzao 61 were investigated under mechanical harvest. The results showed that under the mode of 6 cotton rows with 2 drip irrigation pipes, the growth rate of edge-row cotton was lower in the early growth period, and its emergence rate and agronomic traits were all lower than those of the interior-row cotton; under the mode of 6 cotton rows and 3 drip irrigation pipes, the difference in cotton growth between edge and interior rows was smaller. The yield and benefit under the mode of 6 cotton rows with 3 drip irrigation pipes were higher than those under the mode of 6 cotton rows and 2 drip irrigation pipes by 255 kg/hm^2 and 1 500 yuan/hm^2, respectively. Therefore, the cultivation mode of 6 cotton rows with 3 drip irrigation pipes under plastic film should be promoted in the production.

Long-Term Impacts of Cover Crops, Chicken Litter, and Crop Rotations on Soil Health in No-Till Systems

Identification of management practices that can improve soil health is critical to improving the sustainability of soybean [Glycine max (L.) Merr.] production. The objective of this study was to examine the long-term effects of continuous soybean, corn-soybean, and soybean-cotton rotations with chicken litter and cover crops (hairy vetch, wheat, fallow) on soil health parameters, including nutrient accumulation and soil organic matter dynamics under a split plot design. The depth intervals of soil sampling were 0 - 15, 15 - 30, 30 - 60, and 60 - 90 cm. Chicken litter resulted in 62.1% and 32.8% higher water extractable organic soil N content than fallow and wheat, respectively, in the surface 0 - 15 cm of soil only. However, there was no significant difference in 1-day Solvita respiration, water extractable organic C, C/N ratio, health score, moisture, earthworm, organic matter, pH, or CEC of soil among fallow, hairy vetch, chicken litter, and wheat regardless of soil depth. Unexpectedly, annual application of chicken litter at 4.4 Mg ha−1 as an N source or growing a winter-season cover crop such as hairy vetch or wheat for continuous 16 years did not significantly increase soil organic matter or water extractable organic soil C. Annual application of chicken litter at 4.4 metric tons (Mg) ha–1 for 16 years increased soil nitrate-nitrogen (NO3−-N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn) contents by 92%, 400%, 134%, 20%, 43%, 206%, and 430% in 0 - 15 cm depth compared with their initial soil values, respectively, extracted with Haney H3A-2 (2 g L–1 lithium citrate + 0.6 g L–1 citric acid + 0.4 g L–1 malic acid + 0.4 g L–1 oxalic acid) solution. The increases enhanced soil supply of these nutrients to following crops, but also increased the risks of losing them to the environment. Hairy vetch caused higher H3A extracted soil manganese (Mn) content than fallow and chicken litter in 0 - 60 cm. There was no significant difference in 1-day Solvita respiration, water extractable organic C and N, health score, moisture, organic matter, pH, CEC, or population of earthworm of soil among continuous soybean, corn-soybean, and soybean-cotton in any soil depth. Another major finding of this study was that continuous soybean exerted no adverse effect on soil health relative to the commonly used corn (Zea mays L.)-soybean and soybean-cotton (Gossypium hirsutum L.) rotations under no-tillage after 16 years. To mitigate the risks of nutrient runoff and leaching from long-term chicken litter application, we recommend reducing litter application rates and integrating cover crops into crop rotations to enhance nutrient cycling and reduce environmental impacts.

Impact of extreme weather and climate events on crop yields in the Tarim River Basin,China

The Tarim River Basin(TRB)is a vast area with plenty of light and heat and is an important base for grain and cotton production in Northwest China.In the context of climate change,however,the increased frequency of extreme weather and climate events is having numerous negative impacts on the region's agricultural production.To better understand how unfavorable climatic conditions affect crop production,we explored the relationship of extreme weather and climate events with crop yields and phenology.In this research,ten indicators of extreme weather and climate events(consecutive dry days(CDD),min Tmax(TXn),max Tmin(TNx),tropical nights(TR),warm days(Tx90p),warm nights(Tn90p),summer days(SU),frost days(FD),very wet days(R95p),and windy days(WD))were selected to analyze the impact of spatial and temporal variations on the yields of major crops(wheat,maize,and cotton)in the TRB from 1990 to 2020.The three key findings of this research were as follows:extreme temperatures in southwestern TRB showed an increasing trend,with higher extreme temperatures at night,while the occurrence of extreme weather and climate events in northeastern TRB was relatively low.The number of FD was on the rise,while WD also increased in recent years.Crop yields were higher in the northeast compared with the southwest,and wheat,maize,and cotton yields generally showed an increasing trend despite an earlier decline.The correlation of extreme weather and climate events on crop yields can be categorized as extreme nighttime temperature indices(TNx,Tn90p,TR,and FD),extreme daytime temperature indices(TXn,Tx90p,and SU),extreme precipitation indices(CDD and R95p),and extreme wind(WD).By using Random Forest(RF)approach to determine the effects of different extreme weather and climate events on the yields of different crops,we found that the importance of extreme precipitation indices(CDD and R95p)to crop yield decreased significantly over time.As well,we found that the importance of the extreme nighttime temperature(TR and TNx)for the yields of the three crops increased during 2005-2020 compared with 1990-2005.The impact of extreme temperature events on wheat,maize,and cotton yields in the TRB is becoming increasingly significant,and this finding can inform policy decisions and agronomic innovations to better cope with current and future climate warming.

棉-粮-油菜宽带轮作提升作物产量和光能利用率

棉-粮-油菜宽带轮作种植模式,能够充分利用农田资源,但种植体系内不同作物光能资源利用特性尚不明确。本研究在田间设置棉花单作(对照)、小麦-玉米一年两熟(对照)和棉花-小麦-玉米-油菜宽带轮作(以下简称“宽带轮作”) 3种种植模式,测定棉花、玉米和小麦的产量、地上部干物质重以及叶面积指数、消光系数、光能截获量等指标。结果表明,与棉花单作比较,棉花宽带轮作单位面积产量和地上部干物重分别显著增加15.20%和10.35%。与小麦-玉米一年两熟比较,玉米和小麦宽带轮作的单位面积产量分别显著增加21.61%和11.53%,玉米地上部干物质重显著增加6.17%。7月16日(盛花期)至9月13日(吐絮期),棉花宽带轮作叶面积指数比棉花单作显著增加7.21%~12.76%, 7月24日(盛花期)和8月4日(盛铃期),棉花宽带轮作光能截获率比棉花单作分别显著降低3.59%和3.24%。玉米和小麦宽带轮作的叶面积指数、消光系数和光能截获率未发生显著变化。与棉花单作、小麦-玉米一年两熟比较,棉花宽带轮作和玉米宽带轮作的全生育期光能截获量分别显著降低3.14%和显著增加0.76%,小麦宽带轮作的全生育期光能截获量未发生显著变化,棉花、玉米和小麦的光能利用率分别显著增加18.81%、6.76%和14.10%。本试验条件下,边行优势和轮作效应同时发挥作用增加了棉花、玉米和小麦的单位面积产量以及棉花和玉米的地上部干物质重,改善作物干物质的积累和分配,进而提升棉花、玉米和小麦的光能利用率。该研究明确了棉-粮-油菜宽带轮作对作物产量和冠层光能利用率的影响,可为该模式的推广应用提供理论基础。

全株小麦青贮适宜收获期及青贮添加剂配比技术的研究

为了确定全株小麦作为青贮饲料的适宜收获期及最佳的青贮添加剂配比组合,首先分析了全株小麦开花期、乳熟期、蜡熟期的干物质产量及营养成分含量,综合各生育期全株小麦的各项饲用指标(可消化干物质产量、非结构性碳水化合物含量等),表明蜡熟期是最适宜作为青贮的时期。其次通过添加不同浓度的乳酸菌与糖蜜来研究添加剂配比组合对全株小麦青贮料发酵效果及养分损耗,结果表明同时添加两种添加剂的全株小麦青贮料的饲用品质和发酵品质显著优于只添加其中一种添加剂。两种添加剂配比中,添加乳酸菌浓度较低时(≤0.02‰),糖蜜添加浓度为2%较添加浓度为1%的全株小麦青贮料的饲用品质和发酵品质好;添加乳酸菌浓度较高时(≥0.04‰),糖蜜添加浓度的变化对全株小麦青贮料的饲用品质和发酵品质影响不显著。研究结果可为全株小麦青贮适宜收获期以及乳酸菌与糖蜜配比组合在青贮饲料中应用提供参考。

连阴雨胁迫下成熟期麦穗发芽霉变估测

为精确监测和评估小麦在成熟期受连阴雨胁迫后穗霉变发芽情况。该研究以2023年5月底黄淮西部一次大范围连阴雨天气过程为例,从气象致灾危险性和遥感变量表征小麦承灾能力两方面,综合应用气象和多源卫星遥感资料,构建模型因子。分别用Spearman和Pearson相关性分析,以及ReliefF特征选择方法进行关键因子筛选,形成3组因子,分别应用Logistic回归等5种分类器和多元线性回归等5种回归方法构建模型,实现了对灾变的精准识别、程度分级和指数回归预测。通过对不同模型性能评估和各因子影响的对比分析,结果表明:所选分类器在气象与遥感因子协同及各独自建模情形下,均能识别穗发芽霉变并准确预测其等级,识别的准确率(accuracy,AC)在0.649~0.811,等级预测的AC在0.432~0.622之间;在穗发芽霉变指数(ear germination and moldiness index,EGMI)预测方面,构建的PCFXGBR模型表现最佳,R^(2)为0.25,均方根误差(root mean square error,RMSE)为15.68,平均绝对误差(mean absolute error,MAE)为11.93。研究发现,遥感模型在灾变识别上更具优势,而气象模型在灾变程度分级上更优,结合两者的气象-遥感协同模型性能最佳。该研究成果为小麦连阴雨减损与灾后评估提供了有力的技术支持。

小麦育种单穗电动脱粒机设计与试验

【目的】针对小麦育种单穗收获、采样工作量大、田间实时采样不便等问题,设计了一款便携式的小麦育种单穗电动脱粒机。【方法】单穗脱粒机采用了脱粒板和清选风机同轴、U型清选风道、清选风量调节可调的结构设计。确定了脱粒板结构、脱粒板转速,清选风机直径、叶片数及风机风速等参数。通过计算流体力学(compu-tational fluid dynamics,CFD)对最小进口风速5 m·s^(-1)、最大进口风速10 m·s^(-1)分别进行清选性能试验。由仿真可知清选区风速均小于小麦籽粒的悬浮速度,大于杂余的悬浮速度,都能够达到小麦清选的要求。利用离散元法(distinct element method,DEM),采用多尺度颗粒聚合的方法建立可脱粒小麦植株模型;通过仿真试验,分析小麦籽粒在脱粒机内的速度和位移随时间的变化规律,对滞种问题进行分析。【结果】为研究脱粒滚筒转速、喂入量、凹板筛间隙对脱粒机滞种的影响,设计3因素3水平正交试验,极差分析法结果表明,各因素于滞种率主次顺序依次为脱粒滚筒转速>喂入量>凹板筛间隙,其中滞种率最小的工作参数组合是滚筒转速为1000 r·min^(-1),喂入量为3穗·次^(-1),凹板筛间隙为6 mm。在小麦育种单穗电动脱粒机样基础上进行了试验验证。结果表明,脱粒机没有滞种现象,脱出籽粒含杂率为0.83%。【结论】小麦育种单穗电动脱粒机有良好的脱粒性能且无滞种问题,满足小麦育种单穗脱粒的要求。