Soil compaction caused by the use of farm machinery is a widespread issue. Freeze-thaw cycles can improve the soil structure after compaction; however, the effect decreases as soil depth increases. Herein, we applied freeze-thaw cycle treatments to re-moulded compacted sandy loam soil (bulk density of 1.6 g/cm3) in two water content states (80 % and 30 % field capacities). Artificial perforation was performed to create long, straight pores in soil, which ensured that the soil mass was largely intact and unbroken, leaving the freeze-thaw cycles to complete the structural remediation and monitoring soil structure recovery. We measured the soil temperature, heat flux and thermal properties to explore the mechanisms of soil temperature regulation using artificial pores during freeze-thaw cycles. The pore and aggregate structure parameters before and after the freeze-thaw cycle treatment were measured. Under the freeze-thaw cycle treatment, the temperature in the bottom layer of compacted soil with artificial pores rapidly dropped below 0 degrees C during the third and second cycles under highand low-water-content conditions, respectively, whereas the temperature of soil without artificial pores decreased during the seventh and fourth cycles at the same water content states. Results indicated that the heat flux during the freezing phase was larger in the soil with artificial pores. However, no significant differences were observed in the thermal parameters, including thermal conductivity, volumetric heat capacity and thermal diffusivity, of soils with and without artificial pores at each water content state. The air-filled porosity, aggregate mean weight diameter and structure coefficient of the surface and bottom layers of the compacted soil columns were generally better in soil with artificial pores than in soil without artificial pores after repeated freeze-thaw cycles. This indicates that the artificial pores facilitated the restoration of compacted soil in the bottom layer during freeze-thaw cycles owing to the rapid drop in soil temperature. We deduced that the artificial long, straight pores in compacted soil created additional soil heat exchange areas in the heat transfer process to increase the rate of heat transfer, thus increasing soil heat exchange and causing the soil temperature of the bottom layer to drop rapidly during repeat freezing and thawing. However, further studies are required to investigate the remediation of artificial pores on compacted soils in fields and the optimal process for creating artificial pores in agricultural settings.

In order to measure wheat yield and wheat spike phenotypes, the grain number of wheat spikes is counted manually at present, but acquiring the grain number of wheat spikes is laborious and time-consuming. Counting the grain number of wheat spikes with an image processing method is promising, yet the application of this method is flawed due to its low accuracy. In this work, images of wheat spikes were collected and processed with technical procedures, including image cropping, image graying, histogram equalization, image binarization, eroding operation, removing small objects, filling image holes, revolving vertical spikes, cutting off stems, and removing stems. Wheat stems in binary images were eliminated by the sum pixels method, and the morphological characteristic parameters of the image areas of wheat spikes and lengths of wheat spike axes were calculated. Mathematical models relating the image areas of wheat spikes and lengths of the wheat spike axes to the grain number were established, and the mathematical models were verified. The results showed that the characteristic parameters of the image areas of wheat spikes and the lengths of the wheat spike axes for the spike images were linear relative to the grain number, and the maximum determination coefficients R2 were 0.9336 and 0.9012, respectively. The maximum determination coefficients R2 for the practical and predicted grain numbers were 0.9552 and 0.9369, respectively, and the minimum average absolute error was 2.3, while the average relative error for the mathematical models was 5.65%. The mathematical models relating the image areas of wheat spikes and the lengths of the wheat spike axes to the grain number were practical and accurate, and the mathematical model comparing the image area of wheat spikes and the grain number was superior to that comparing the length of the wheat spike axis and the grain number. The grain number of wheat spikes could be acquired accurately and quickly by the image processing method extracting the characteristic parameters of wheat spikes.

Field in situ infiltration experiments at different depths can be used to express the state of soil stratification, and the physical differentiation of soil layers, in order to quantify the changes in the water of the soil profile. This study aims to obtain the infiltration capacity and water retention of paddy soils. The field in situ soil infiltration experiments were also carried out at different depths to identify the soil stratification in the representative plot under long-term mechanized tillage of smallholder farmers in the rice-wheat rotation region of eastern China. Seven infiltration pits of different depths were excavated in the experimental plots. After that, the infiltration experiments were conducted at the bottom of the pits. Soil water content was then measured in the layers for 48 hours of infiltration. A systematic investigation was made to explore the soil infiltration capacity at the bottom of the pits and the soil water content of each layer. The results showed that an accurate description was achieved in the water infiltration and water holding capacity of the soil at different pits after the infiltration experiments at different depths. The location and thickness of the plow pan were also clearly identified during this time. The plow pan was started at a depth of about 15 cm, indicating the outstanding difference between the cultivated layer and the plow pan. The average soil penetration resistances of the cultivated layer and the plow pan were 1 005.79 kPa, and 1 910.73 kPa, respectively.The soil profile showed that the soil in the cultivated layer shared a loose morphology and dense root distribution, whereas, the soil in the plow pan presented a high bulk density, low porosity, and poor permeability, while the soil in the subsoil layer was in more iron-manganese spots and poor structure. Furthermore, the soil infiltration parameters decreased with the increasing pit depth. The average infiltration rate and cumulative infiltration in the 0-15 cm pit depth range were 17.04 and 18.06 times higher,respectively, than those in the ＞20-30 cm pit depth range. The three infiltration models were fitted using Horton, Kostiakov and Philip. Specifically, the Kostiakov model had the highest R~2（0.98-0.99） and the smallest RMSE（0.01-0.77 mm/min）, indicating the consistency of the fitted parameters. Infiltration parameters were extremely significant correlated with the soil bulk density,water content, total porosity, and field capacity（P＜0.01）, but not with the soil penetration resistance（P＞0.05）. Field in situ infiltration experiment at different depths was an important tool to identify the soil stratification and quantify the water function differentiation in the soil profiles, according to the soil profile, cone penetration and sampling. Long-term mechanized tillage under the smallholder production model in the rice-wheat rotation region of eastern China can be expected to result in the apparent stratification and vertical differentiation of soil water functions in paddy soils. In turn, there are also some significant differences in the infiltration capacity between the cultivated layer and soil layers below the cultivated layer. This study can provide a reference for mechanical cultivation and irrigation in rice-wheat rotation regions.

针对目前机具耕作试验多采用室内土槽和拖拉机挂接两种方式均存在一定不足、室内土槽对土壤进行了迁移重塑难以还原真实的田间土壤环境以及拖拉机挂接试验时参数较难精准控制、试验所需面积过大等问题,设计了一种控制方便、测试精准的田间耕作试验平台,包括导轨牵引系统、整机升降系统、移动台车系统、PLC运动控制系统和数据采集系统等.以铧式犁为研究对象,通过比对田间试验数据与EDEM仿真分析数据中铧式犁的耕阻效果,得出铧式犁最优工作方案,验证田间耕作试验台工作的稳定性与精确性.结果表明:在铧式犁自身结构不变的条件下,固定耕深25cm时,在3种耕速(0.2、0.3、0.4m/s)和3种推土角(38°、42°、45°)的9组双因素全面试验中,耕作速度为0.2m/s、推土角为45°时铧式犁耕阻最小最稳定,为最优工作方案.田间试验结果与仿真分析结果接近,存有误差符合田间真实试验环境.研究验证了搭载铧式犁耕作机具的田间耕作试验平台作业时的稳定性和精确性,可为进一步优化田间耕作试验提供参考.

【Objective】In order to quantify the influence of seed-to-seed distance on wheat root development in soil layers under single seed precision sowing,an integrated technique combining root architecture digitizer and MATLAB simulation was developed to quantify wheat root length density （RLD） and relative root length density （NRLD）,as well as related models in each soil layer in the field.【Method】Ningmai 13 was used as experiment marital and the seed was sown with single seed precision sowing method in no-till paddy soil.The experiment was carried out in 2020 and 2021,respectively.Five treatments （JT1.5,JT3,JT4.5,JT6.7,and JT9）with row spacing of 1.5,3.0,4.5,6.7 and 9.0 cm were introduced for field stand control.RLD was analyzed with combined technologies,i.e.root architecture digitizer and 3D root system architecture reconstruction with Pro-E,supplemented with MATLAB simulation,which facilitated fine segmentation and analysis of the rhizosphere dynamics under soil space voxel resolution of 3 mm~3,and this further results quantified RLD distribution dynamics and the development of NRLD models along soil layers.【Result】The post-paddy wheat RLD decreased gradually along the soil layers under different treatments.As much as 95%of the root system was confined within the top soil layer in 0-9 cm,below which,root length decreased rapidly.The wheat root expansion area of a single plant first increased along the soil layers and then decreased.Root expansion started from the seed site as its central point,and revealed an obvious directional and constraining effects induced by the soil environment.With the increase of seed-to-seed distance,wheat RLD experienced first an increasing and then a decreasing trend,and the maximum value of which was found at JT4.5.The expansion area of wheat RLD increased with the increased seed-to-seed distance,and the maximum value of which was 22 972 mm~2.Either the too high or the too low density stand was found adversely impacts the efficiency of root configuration.Only the most suitable sowing density led to the best 3D distribution of wheat root system,which has been considered as the primary mechanism for efficient utilization of soil spatial resources.The NRLD distribution within 0-20 cm soil layers satisfied both cubic polynomial and exponential models well （R~2＞0.99,RMSE＜0.1）,but when considered the field state root system architecture,it was found that the exponential model was more realistic and fit the field wheat RLD the best along the soil layers.【Conclusion】An integrated technique combining root architecture digitizer and MATLAB simulation was developed to quantify wheat RLD and NRLD in the field,which satisfactorily illustrated the influence of seed-to-seed distance on RLD and NRLD along the soil layers.The results showed that the proposed method could be applicable for studies of wheat precision cultivation,precise water and fertilizer management,root configuration regulation and so on in the future.

Soil compaction risk can be normally assessed, in terms of the relationship between the wheel contacting pressure and the soil pre-consolidation stress. It is still lacking in the evaluation of the damage degree of soil structure that is caused by quantitative mechanical compaction in production scenarios, such as wet tillage and rot under intensive rice farming. In this study, a prediction model of soil compacted bulk density was derived using soil rebound and compression index in paddy fields under intensive production conditions. The improved model was verified by the laboratory uniaxial compression test and in situ flat subsidence test of undamaged soil in paddy fields. An indoor uniaxial compression test was also carried out under the undisturbed soil with different moisture content（15%, 20%, 25%, 30%, and 35%）. Among them, there was no change in the bulk density of the undisturbed soil. The transfer functions were constructed for the soil initial bulk density（ρ）, initial moisture content（w）, elastic compression modulus（E s ）, plastic compression modulus（E c ）, and soil pre-consolidation stress(σ pc ) after the uniaxial compression test. The coefficient of determination was greater than 0.95 after fitting the test data with each transfer function. The results show that the improved model was operable and accurate using the transfer function. At the same time, the E s presented a significant negative correlation with the ρ, whereas, there was a significant positive correlation with the w. The E s reached the maximum when ρ=1.1 g/cm~3 and w=35%. The minimum was obtained, when ρ=1.8 g/cm~3 and w=15%. The Es value ranged from 0-0.25 cm/kPa. The Ec presented a significant negative correlation with the ρ, and there was a quadratic polynomial relationship with the w. The Ec reached the maximum when ρ=1.1 g/cm~3 and w=25%. The minimum Ec was obtained, when ρ=1.8 g/cm~3 and w=15%, where the value ranged from 0-0.8 cm/kPa. There was a significant positive correlation between the σ pc and ρ, whereas, a significant negative correlation was found between the σpc and w. The σpc reached the maximum when ρ=1.8 g/cm~3 and w=15%. The minimum was obtained, when ρ=1.1 g/cm~3 and w=35%. The value ranged from 20-160 kPa. The earth pressure was determined as 30, 60, 90, and 120 kPa in the in-situ flat subsidence test, according to the several types of harvesters. The soil bulk density in the uncompacted area was taken as the initial bulk density, while, the measured bulk density of the soil in the compacted area was as the measured bulk density. The ρ, w, elastic compression modulus, plastic compression modulus, and pre-consolidation pressure from the uncompacted region were then input into the prediction model of soil compacted bulk density to obtain the predicted bulk density. Finally, the measured bulk density was compared with the predicted. In-situ plate sinkage test showed that there was less than 5% error between the measured and the predicted using the transfer function-derived soil elastic compression and plastic compression modulus. At the same time, it was found that the wheel contacting pressure was greater than the soil pre-consolidation stress under the large w and the small ρ. There was a risk of soil compaction, even with the small contacting pressure of the wheel in the harvester. Therefore, a reasonable time and machine type can greatly contribute to the implementation of field tillage. Consequently, the prediction model of soil compaction can be expected to accurately quantify the soil bulk density under mechanical compaction. The finding can provide a strong reference for a better prediction model in regional agricultural usage.

分析秸秆-土壤-机具之间的交互关系,明确秸秆运动规律及分布效果,对秸秆管理及耕作机械优化设计具有重要的作用.为探究秸秆-土壤-旋耕机交互下的关键作业参数对秸秆位移和埋覆效果的影响,利用Design-Expert软件,根据Box-Behnken试验原理进行了室内土槽试验.以旋耕埋草作业中的秸秆长度、耕作深度、刀轴转速为影响因素,以秸秆位移和埋覆率为指标进行三因素三水平的二次回归正交试验.通过建立响应面数学模型,分析了各因素对旋耕埋草效果的影响.试验结果表明:影响秸秆埋覆率和位移的主次顺序为耕作深度、秸秆长度、刀轴转速;秸秆长度与耕作深度交互作用对秸秆埋覆率和位移影响显著,其余参数交互作用不显著.多目标优化结果表明:当秸秆长度为5 cm、耕作深度为14.99 cm、刀轴转速为320 r/min时,埋草效果最优,其对应指标秸秆埋覆率与位移分别为95.5％和27.6 cm.利用优化后的参数进行试验验证,秸秆埋覆率与位移分别为93.3％和28.1 cm.研究结果可为旋耕埋草作业参数调整提供参考,为秸秆-土壤-机具交互机理研究提供理论支撑.

针对目前小麦种子尺寸小、形状不规则导致传统排种器存在漏充率高、充种合格率低等问题,设计了一种限制充种姿态-正负压式小麦精密排种器.排种器基于限制种子充种姿态的原理,增设弧形辅助充种板和搅种盘,使种子长轴与型孔长轴近似位于同一平面,在正负压良好充种的基础上获得更佳的单粒充种性能.通过对充种过程及种子田间分布情况的分析,计算确定排种器关键结构参数:型孔列数3列,每列型孔个数30个,型孔长度8 mm、宽度5 mm、深度3 mm;并采用EDEM软件进行仿真试验,确定了弧形辅助充种板的最优角度为5°.在此基础上,利用Design-Expert软件,以型孔轮转速、真空度、搅种盘转速为试验因素,以充种合格率、漏充率、重充率为评价指标,进行三因素三水平二次回归正交试验.通过构建回归方程及响应面数学模型,分析了各试验因素对排种器充种性能的影响,且对试验参数进行综合优化,确定最佳参数组合:型孔轮转速66.27 r/min、真空度3.52 kPa、搅种盘转速52.00 r/min,并进行试验验证,得到排种器充种合格率为92.70％,漏充率为3.47％,重充率为3.83％.该排种器满足小麦精密播种对排种器的性能要求.

[目的]提高收获作业效率能够节约农业生产成本,减少粮食损失.纯作业效率和实际作业效率是衡量收获效率的重要指标,研究两者在不同作业路线下随地块条件变化的规律,可为作业路线与地块条件的匹配、土地整理提供优化方案.[方法]在调查研究的基础上,基于收割机作业时间构成的综合分析,建立不同作业路线下的收割机纯作业效率和实际作业效率的计算模型.为验证计算模型的准确性,利用沃得锐龙尊享版112收割机在2种作业路线下收获20块地的试验值与模拟值进行误差和相关性分析.最后基于建立的计算模型利用MATLAB模拟不同作业路线、收割机型号纯作业效率和实际作业效率随地块条件变化的规律.[结果]2种作业路线效率计算模型的纯作业效率误差均小于7％,实际作业效率误差均小于8.7％,试验值与模拟值的相关性系数均在0.90以上,模型模拟效果良好.通过模拟分析表明收割机纯作业效率和实际作业效率随地块面积和地块长宽比的增大而增大;收割机收获路线中,Ⅱ型作业路线与Ⅰ型作业路线的纯作业效率和实际作业效率相差最高,分别为18.2％、3.7％;通过2种作业路线的纯作业效率和实际作业效率比较,表明:随着地块面积增大Ⅰ型作业路线实际作业效率将大于Ⅱ型作业路线.[结论]农田整理时,适当增加地块面积和长宽比可以提高收获效率.不同作业路线匹配相应的地块条件可以有效提高作业效率,南方小地块条件下Ⅱ型作业路线优于Ⅰ型作业路线,大地块Ⅰ型作业路线优于Ⅱ型作业路线.

为了探明长江中下游稻麦轮作区单体精播技术的适配性及其农艺效应,揭示基于区域土壤力学特征的精密播种机设计原则,以2BMYFQ型免耕播种机单体为例开展田间台架播种试验,提出符合农机-农艺融合原则的4个精播主控目标和技术要素,探讨2种耕作处理方式(免耕、旋耕)、3个预定播深(2.5、4.0、6.0cm)和3个下压力(0.6、1.0、1.2kN)因子组合下的种子播深、土壤物理变化及小麦出苗效果.结果表明,播种单体与土壤力学性质交互影响并导致播深变化差异显著,土壤力学变异造成高达37.61％的播深变异,基于线性弹力张紧特征的下压力控制技术与不合理耕作方式组合下的精确播深控制目标无法实现.现有试验单体既存在土壤对双圆盘开沟器支撑力过大导致的限深轮虚支撑,也存在土壤支撑力不够且限深轮过度下陷导致农学意义上过深的种子位.单体造成种子位土壤压实状况也受耕作方式及下压力影响,并最终反映为出苗率的变化.综合比较发现,稻田原茬免耕、预定播深4 cm、下压力1.2 kN工况下,实际播深与预定播深差异较小,播深稳定性高,出苗率高,但种沟侧壁压实程度大;在旋耕条件时最优播深为预定播深4 cm和下压力1.0 kN组合;旋耕处理的单体播深控制整体效果优于免耕.因此智能精密播种技术应首先探明土壤力学条件和农艺播深目标的合理下压力控制策略,实现基于"播种单体-土壤力学关系"的单体创新设计和智能化土壤力学在线检测系统是区域精播技术的关键.

为揭示耕作方式对小麦根系构型及生长趋势影响的作用机理.基于根系构型数字化平台研究全幅旋耕(FT)和2种带状耕作(ST1、ST2)方式对小麦根系3D构型及生长趋势的影响,提出了土体空间覆盖率差异系数(P)、角度拓展趋势差异系数(Pa)、长度拓展趋势差异系数(PL)3种量化指标.结果表明,带状耕作条件下,小麦根系沿种沟方向生长趋势明显,ST1处理下在距离苗期14、28 d时沿种沟方向土体P、Pa、PL分别比FT处理高出1455％、4520％、3583％和2610％、241％、740％.ST1、ST2处理相比较发现,涂抹后的种沟壁对根系生长的限制更为明显,在距离苗期14、28 d时,ST1处理下小麦根系沿种沟方向P、Pa、PL分别比ST2处理高出78％、88％、31％和20％、81％、37％.耕作方式直接影响小麦根系的空间拓展趋势,本研究提出的研究方法和评价指标能够简明耕作方式对小麦根系生长趋势影响的作用机理,为耕作机具的优化设计提供更加全面的理论支持.

不断拓展的秸秆资源应用途径丰富了亚地块尺度下秸秆信息丰度的研究,但界定和表达亚地块尺度下秸秆信息丰度尚缺乏科学规范.本文以机收小麦原茬地的秸秆信息丰度为研究对象,设计系列指标(立茬与碎秸的质量分布、碎秸堆叠层数、立茬侧影覆盖度),分别探讨原位网格取样称草、平板匀铺图像处理、背景板图像处理、碎秸筛分、人工观察计数等手段与方法,进行原茬秸秆信息的指标化.将获取的多维秸秆信息进行归一化处理,并运用图像相似度分析法研究信息指标间的相关性.结果表明,本文提出的秸秆信息参数及测试方法增加了亚地块尺度下的秸秆信息丰度,秸秆信息图像间的相关分析也能反映出各指标间的内在联系.所得信息反映了收获机的留茬状态与碎草性能,碎秸质量集中分布在割幅中间区域.立茬质量分布受作物行间距影响,碎秸堆叠层数表达了机排草口的排草状况,立茬侧影覆盖度分布可反映收获机的留茬碾压破坏情况.秸秆信息指标间的相关分析表明,地表秸秆总质量与碎秸质量的相似度为0.89、与立茬质量相似度为0.43,碎秸质量与碎秸堆叠层数相似度为0.64,立茬质量与立茬侧影覆盖度相似度为0.48.本文界定的亚地块尺度下秸秆信息丰度及其参数化研究结果可为系统开展亚地块尺度下秸秆信息技术研发提供参考.

应绿色可持续农业的发展要求,带状免耕播种技术在我国南方稻麦种植区得到推广与应用.为简明耕作部件对带状旋耕耕作质量的影响,在280、380和510 r/min刀轴转速下对凿型旋耕刀、直刃旋耕刀和IT225型旋耕刀进行田间耕作试验.试验结果表明,影响耕作质量的主要因素是耕作部件形状和刀轴转速.在刀轴转速为510 r/min时,IT225型旋耕刀创造的土壤回填率只有7％,土壤回填效果明显低于具有较小正切刃的直刃旋耕刀和凿型旋耕刀.凿型旋耕刀能够创造出较好的回填和土壤破碎的效果,但由于其没有侧切刃无法创造出整齐的种床截面.在刀轴转速为180 r/min时,凿型旋耕刀造成的种床截面扰动率高达20％.直刃旋耕刀能够形成齐整的种床截面和高于50％的土壤回填率,但产生的土壤破碎体粒径过大,不能满足播种的需求.本研究为带状旋耕耕作部件优化指明方向,即兼顾直刃旋耕刀和凿型旋耕刀的特点,将两种或几种刀具进行有机结合,以满足不同土壤条件下带状旋耕播种的需求.

秸秆在土壤中的空间分布质量会对秸秆腐解速率、土壤养分分布等产生显著影响.为了探究不同旋耕作业参数对秸秆空间分布质量的影响,本文基于离散元法构建旋耕仿真模型,模拟秸秆旋耕还田作业过程,并结合田间试验对不同前进速度和刀辊转速下的秸秆空间分布质量进行对比验证.对仿真及田间试验区域进行垂直分层和水平划分的空间分割处理,计算各区域内秸秆数量并以秸秆占比变异系数为指标评价不同旋耕作业参数下的秸秆空间分布质量.结果表明,在垂直分层处理中,刀辊转速的增加会使得各层秸秆占比变异系数呈递增的趋势,其中240 r/min时最小,仿真值与试验值分别为60.09％和80.65％,而随着前进速度的增加,变异系数呈先减少后增加的规律,其中0.50 m/s时变异系数最小,仿真值与试验值分别为61.00％和79.90％;在水平划分处理中,刀辊转速的增加对各层秸秆占比变异系数无明显规律性影响,但前进速度的增加可以减小纵向划分区域内的变异系数,最小值为0.75 m/s时的11.36％和20.12％,仿真值与试验值变化趋势基本一致.垂直分布和水平分布秸秆占比变异系数仿真值与试验值间差值平均最大分别为22.13％和12.23％,误差在可接受范围内.离散元仿真能够模拟不同旋耕作业参数下的秸秆空间分布状态,可以为旋耕秸秆还田作业质量的快速预测评价研究提供支持,也可为旋耕机械的作业参数选择提供理论依据.

Abs tr a c t. Maximum head rice yield is related to the optimal harvest time or moisture content during rice maturity. The physi-cal properties of rice grains, such as the breaking forces, changed with the increasing degree of rice maturity. Harvest moisture con -tent, breaking forces for the dorsal and ventral sides of the brown rice kernel in a three-point bending test and the milling quality properties of rice at different maturity stages were investigated. The relationships between head rice yield and harvest moisture content and also between head rice yield and the breaking forces for the dorsal side and ventral side were analysed. The breaking forces for the dorsal side and ventral side increased at 30/37 and at 44/51 days after heading and decreased at 58/65 days after head-ing, the increasing and decreasing extent of the breaking force for the ventral side was larger than that for the dorsal side. The break-ing force for the ventral side was larger than that for the dorsal side during the maturity period. Head rice yield increased at 30/37 and at 44/51 days after heading, but head rice yield decreased at 58/65 days after heading. The breaking force for the ventral side increased by 9.52, 10.13, 8.59, and 7.33 N, head rice yield increased correspondingly 38.7, 30.7, 34.7 and 15.3% during maturity for different varieties. The moisture content at optimal harvest time with the maximum head rice yield and maximum breaking force for ventral side or dorsal side was 25-30%.

为明确带状旋耕式免耕播种机耕作过程中耕作机具与土壤间的相互作用机理,利用离散元仿真软件从微观层面对典型的且已广泛应用的IT225型旋耕刀、直刃旋耕刀和凿型旋耕刀进行仿真,研究发现旋耕刀具的抛土特性是影响土壤回填效果的关键因素.田间试验表明,土壤破碎体的回填率随刀轴转速的增加而下降.IT225型旋耕刀在高刀轴转速(＞280 r/min)下侧向抛土现象最为明显,在超高刀轴转速(510 r/min)时创造的土壤侧抛率最高,达到了92％,因此产生回填效果最差,回填率仅为8％,无法满足播种时种—土接触的需要.凿型旋耕刀耕作过程中可以勾带起部分土壤破碎体向机具前进方向抛洒,在刀轴转速为510 r/min时土壤侧抛率为85％,能够产生接近36％的土壤回填效果.直刃旋耕刀的侧向抛土集中在刀轴两侧10 cm范围内,在刀轴转速为510 r/min时侧抛率只有70％,回填率高达60％显著高于其他两种刀具.鉴于土壤回填效果对种—土接触的重要性,直刃旋耕刀耕作过程中具有土壤扰动范围小、土壤破碎体侧抛率低、回填效果好等优点,本文推荐直刃旋耕刀作为带状旋耕播种机的耕作部件.

【目的】高通量表型技术不仅是现代育种领域的重要手段,也是解析田间作物生理生态行为的工具,但不同类别高通量表型技术的基础架构特征仍不清楚,因此需要针对机器视觉高通量表型技术进行专门探讨。【方法】本文用机器视觉技术检测计算稻茬麦茎穗一体的表型指标。使用宁麦13、鲁原502和郑麦9023 3个小麦品种,进行小区化对比试验,使用等孔距栅条精播板进行单粒精播,准确控制条播小麦的群体条件。于稻茬麦成熟期进行茎穗一体图像获取,对图像进行灰度增强、直方图均值化、S分量提取、Otsu阈值分割、茎穗分离和茎穗形态参数提取等操作。提取的稻茬麦地上部单茎穗各器官的形态参数包括茎秆长、茎秆平均宽度、茎秆投影面积、茎秆周长、麦穗长、麦穗平均宽度、麦穗投影面积和麦穗周长。同时,使用传统方法获取小麦单叶片质量、单茎秆质量、单穗质量和单穗籽粒产量等农艺性状指标。分别构建线性模型、二次模型、指数模型及拓展模型进行多维指标拟合,包括小麦单茎穗生物量与单穗籽粒产量关系、单茎穗的麦穗形态参数与单穗籽粒产量关系等拟合分析。在单茎穗层面对小麦茎穗的表型指标与单穗籽粒产量之间的关系进行相关分析和回归分析,进而基于机器视觉在小麦茎穗一体方面的个例应用,讨论大田高通量表型分析的机器视觉技术研发的要点。【结果】宁麦13、鲁原502和郑麦9023 3个小麦品种的单叶片质量与单穗籽粒产量的相关系数依次下降,小麦单茎穗形态参数与单穗籽粒产量的相关性显著低于生物量指标,但单穗投影面积、单穗长与单穗籽粒产量依然存在显著正相关。3个小麦品种在单茎穗的各生物量指标与单穗籽粒产量的最优回归模型各不相同,麦穗图像的形态参数不能准确反映单穗籽粒产量,但单茎穗的茎秆和麦穗形态参数的组合应用表现出最佳的拓展模型拟合结果。利用茎穗一体的数字图像处理所得的复合型形态参数可以准确预测单穗籽粒产量,从而表明利用机器视觉技术观测小麦的生长过程并实时预测产量的可行性。【结论】机器视觉技术能提供远高于常规农艺性状的高通量指标集,为解析各类农艺性状之间的联系及产量的通径分析提供更多的途径,但也造成高维指标集和有价值信息提取的技术困难。应用于田间小麦群体的机器视觉技术应具备多尺度智能化自适应的技术架构,同时应具备基于场景、群体、个体和器官的多空间尺度和苗期、分蘖期、拔节期等多生理时间尺度的统计性数字表型发现和计算能力,同时,机器视觉各技术研发环节和各技术模块都需要农艺学深度参与和校准,而配备标准表型数据库更是保障高通量技术实用性和可靠性的基础。

针对目前基于有限尺度环刀的土壤应力传递系数(Stress transmission coefficient,STC)取值方法无法满足不同深度土壤条件下集中系数随加载环境变化研究的问题,将土壤剖面分割为有限尺度的土层,基于分析模型推导ΠSTC公式,以多层土壤应力传递系数连乘方式计算田间指定深度土壤应力传递系数.基于传感器技术进行田间原位土壤平板下陷试验,通过控制压板直径和土层厚度实测9种加载状态下土壤的应力传递系数;同时,通过有限尺度(Φ50×50 mm环刀)取样于室内,结合土压力传感器进行非扰动土单轴压缩试验,测量各土层(0～50 mm、50～100 mm、100～150 mm、150～200 mm)应力传递系数.运用HSTC公式计算3种深度(100、150、200 mm)土壤的应力传递系数分别为0.30、0.17、0.07,综合实测数据通过双因素方差分析研究应力传递系数随加载环境的变化规律,由此反算不同加载条件的集中系数.结果 显示,随着压板尺度的改变,实测与计算所得相同深度土壤的应力传递系数间并无显著差异,表明土壤应力传递系数与压板-土壤接触面当量半径无关,利用HSTC公式计算田间土壤应力传递系数方法可行;随土层厚度的增加,应力传递系数显著减小,说明应力传递性能随土层厚度的增加而逐渐减弱;集中系数随压板直径和土层厚度的增加而逐渐减小.利用分析模型较为准确地预测了田间指定加载环境和土壤环境中因连续加载而变化的土壤应力,优化了土壤压实应力传递的研究方法.

土壤压实模型是预测压实破坏的常用方法,但土壤压实模型的应用常因输入参数(土壤压缩特性及其与不同土壤物理性质之间的关系)的缺乏而受到限制.为定量地评价土壤水力学性质和土壤结构对土壤压缩特性的影响,该文利用土壤固结仪对25种不同含水率和容重的重塑土样进行单轴压缩试验,并采用Gompertz函数对试验数据进行拟合以获取土样的回弹指数、压缩指数和先期固结压力.试验结果表明,Gompertz函数对水稻土试验数据的拟合效果较优,决定系数为0.991～0.999.水稻土回弹指数为0.003～0.138,与容重呈负相关,与含水率呈正相关.水稻土压缩指数为0.115～0.839,与容重呈负相关,与含水率呈二次多项式关系.水稻土先期固结压力为33～127 kPa,与容重呈正相关,与含水率呈负相关.该研究建立的土壤压缩特性与含水率和容重之间的传递函数,可用于大尺度范围内水稻土压缩特性的预测;同时这些传递函数可作为土壤压实模型的输入参数,用于农业机械作业引起的压实破坏的量化和土壤压实风险的评估.

为研究不同机械脱粒方式收获粳稻霉菌量和种用品质的差异性,以手工脱粒收获粳稻为对照组,对切流式、轴流式脱粒收获粳稻进行霉菌菌落计数试验和发芽试验,测定不同机械脱粒方式收获粳稻的裂颖率、发芽性能指标、粳稻霉菌量、糙米霉菌量、全部裂颖籽粒霉菌量、正常籽粒霉菌量.结果 表明:切流式与轴流式脱粒收获粳稻霉菌量差异显著(P＜0.05),切流式脱粒收获粳稻霉菌量超出105 CFU·g-1,轴流式脱粒收获粳稻霉菌量接近105 CFU·g-1,手工脱粒收获粳稻霉菌量略高于104 CFU·g-1;粳稻霉菌量、糙米霉菌量与裂颖率呈极显著一元线性关系(P ＜0.001),决定系数R2分别为0.9082、0.8719;粳稻霉菌量与发芽性能指标相关性显著(α＜0.01),粳稻霉菌量与发芽势、发芽率的负相关系数分别是0.917、0.905,粳稻霉菌量与畸变数、幼苗根部发霉数的正相关系数分别是0.896、0.959.从粳稻储藏安全性和种用品质考虑,粳稻优先考虑选择轴流式脱粒收获.