【作者】 王刚；

【导师】 贾洪雷；

【作者基本信息】 吉林大学 ， 农业机械化工程， 2016， 博士

【摘要】 玉米秸秆立茬覆盖地表是继玉米全秸秆粉碎还田保护性耕作之后的一种新型的秸秆处理方式；这种处理方式下玉米秸秆的上部被从田间移走,保留一定高度的站立玉米秸秆残茬,因此玉米秸秆的上部可以作为牲畜的越冬饲料和日常生活燃料等他用；除了站立的秸秆残茬之外,还有部分零散的碎叶散落在地表。为了评价这种耕作模式在控制土壤风蚀方面的表现,在吉林大学农业试验场进行了一个为期4年的试验(2011年至2014年)。试验中共采用了4种不同的处理模式,分别为全秸秆还田覆盖(玉米收获机收获过程中将玉米秸秆粉碎,然后铺撒在地表)和其余三种不同留茬高度的立茬覆盖；立茬的高度分别为30、40和50 cm。这个试验的设计为4种秸秆处理模式重复4年,即4次重复试验。试验中测量了所有处理模式下土壤颗粒的流失以及沉积。具有30,40和50 cm高度的站立残茬分别可以增加空气动力学粗糙度(相当于理论上土壤表面上方风速减小至0的高度)19.87,43.77和61.62 mm,并且分别增加风速阈值11%、25%和33%。对于全秸秆覆盖的地块,平均月土壤流失量为1.27Mg/ha,对于30、40和50 cm站立残茬覆盖地块,平均月土壤沉积量为0.725、1.088和1.967 Mg/ha。这些试验证实立茬覆盖可以作为一种有效的控制土壤风蚀的办法,同时节省一部分玉米秸秆作为牲畜的越冬饲料。除研究了玉米秸秆立茬覆盖在控制土壤风蚀方面的作用之外,我们也比较了立茬覆盖和全秸秆还田对土壤冰冻深度的影响。这个试验历经了3个冬季(2012年～2015年),其中每个冬季都测量土壤冰冻深度,从2013年～2015年的2个冬季也记录了相应的积雪厚度,最后一个冬季也测量了土壤热通量的变化。测量土壤冰冻深度的主要工具为CRREL-Gandahl冰冻管,测量土壤热通量的土壤热通量测量盘埋于地表之下8 cm处。相比较于全秸秆覆盖还田模式,玉米立茬覆盖可以在冬季捕获更多的积雪,较厚的积雪有效阻止了部分冷空气侵入土壤,因此显著地降低了最大土壤冻深(p<0.01)。这对于玉米的春季早播非常重要,早播有利于中晚熟玉米品种充分利用生长期,在下霜之前充分灌浆,籽粒将更加饱满,增加农民的经济收入。由于玉米立茬覆盖保护性耕作模式有效地控制了土壤风蚀、减小了土壤冻深、有利于中晚熟玉米品种的春季早播,所以需要研制与玉米秸秆立茬覆盖保护性耕作模式配合的、适合保留一定高度秸秆根茬(后文中此功能简记为“留高茬”,“一定高度秸秆根茬”简记为“留茬高度”)的秸秆切割器。本论文中设计的玉米秸秆切割器安装于两行卧辊式玉米收获机的割台之下,玉米收获机的果穗箱之下安装有秸秆粉碎装置。这样使该玉米收获机既可以完成“留高茬”作业,也可以完成全秸秆粉碎还田作业。该切割器采用旋转刀盘,刀盘的锯齿采用仿棉蝗[( Chondracris rosea rosea (De Geer)]口器外缘轮廓结构,该结构可以降低切削功耗与切割力；不仅如此,该切割器还可以调节刀盘离地高度(此后简记为“切割高度”),调节刀盘与地面之间夹角(此后简记为“切割角度”)。试验结果表明：随着切割高度的增加,秸秆的切断率上升,其切断率的平均值从82.61%增加到93.33%；在15°～0的范围内,随着切割角度的减小,秸秆切断率上升,其切断率的平均值从88.71%增加到89.08%；在切割角度一定的情况下,秸秆留茬高度平均值随切割高度的升高而升高,秸秆留茬高度平均值从314增加到504 mm,并且越来越接近切割高度值。在切割高度一定的情况下,秸秆留茬高度平均值随切割角度的减小而增大,其留茬高度的平均值从401增加到416 mm,并且越来越高于实际切割高度。本论文设计的适用于卧辊式玉米收获机的切割器能够满足玉米立茬覆盖保护性耕作模式的需要；实际解决了玉米立茬覆盖保护性耕作模式的推广问题。除了使传统的玉米收获机实现“留高茬”作业功能之外,提升玉米收获机的整机作业质量是农民和农业工作者的共同诉求。玉米秸秆堵塞“摘穗辊”是卧辊式玉米收获机工作中存在的一个不容小视的问题,分析产生该问题的原因,主要是因为沿摘穗辊的方向上,玉米秸秆已经到达末端,但是竖直方向上,玉米秸秆仍然存在于摘穗辊间隙中,又因为不断有玉米秸秆进入摘穗辊间隙,以致于造成堵塞。为了解决该问题,本论文对普通的摘穗辊进行了两方面的改进：第一,将摘穗辊表面等螺距的螺旋凸棱改成变螺距螺旋凸棱,人为使玉米秸秆沿摘穗辊方向的速度逐渐降低；第二,将固定间距的摘穗辊改变成可变间距的摘穗辊,让摘穗辊时刻紧紧夹持玉米秸秆。为了防止尺寸较小的玉米果穗被摘落后,夹在两摘穗辊缝隙上方,与摘穗辊摩擦产生的落粒和籽粒破损,本文将传统的两个摘穗辊之间相同的旋转速度改变为一快一慢的差速形式,目的是使这种夹在摘穗辊缝隙上方的小尺寸玉米果穗具有掉落到“升运器”上的趋势。本论文中应用CATIA软件和ADAMS软件分别完成了本摘穗辊的建模和仿真试验,仿真试验之后进行了田间试验,试验中未发生玉米秸秆堵塞摘穗辊的状况,而且落粒和籽粒破损率之和仅为0.11%,远低于国家标准的2%。如果玉米收获机能够保质保量地完成传统的摘穗、集箱等工作之外,还能够完成其他作业,将极大地提高工作效率、降低作业成本。例如获得田间的玉米植株数量对于优化不同玉米品种的种植密度有重要意义,玉米植株数量也是计算新玉米品种平均株产的重要参数。为了减轻人工获得玉米植株数量的劳动强度,提高数据的准确率,本论文利用基于机器视觉的图像处理技术来获得玉米植株数量。玉米秸秆立茬覆盖的地块,有一定高度的玉米秸秆长在地表,摄录这样的图像信息可以大大简化图像处理的难度,提高结果的精确度,所以将图像采集装置安装在玉米收获机之后来获得视频流。后处理过程中,将视频文件分解为图片文件,然后将真彩色的RGB图片文件转化成灰度图像进行图片的配准,再将灰度图像转化为二值图像进行图像分割与边界提取,最后找到玉米秸秆断面的几何中心并进行标记,统计标记结果即获得玉米植株数量。试验结果显示,人工播种与机械播种在图像识别的误差上没有显著差异(P>0.05)；机器视觉识别出来的玉米植株数量与实际数量也没有显著差异(P>0.05),其平均误差为6.7%；并且该误差不会随着图像中玉米植株数量的增加而产生积累。本论文充分利用玉米秸秆断面与其它物体的色差优势,降低了机器视觉在识别玉米植株数量过程中的难度,提高图像识别的准确率,更好地服务生产实际问题。本论文对于“玉米立茬覆盖”的有益效果进行了探究,发现此保护性耕作模式有利于控制土壤风蚀、减小冻土深度、有利于中晚熟玉米品种的春季早播。为了实现保留一定高度的玉米秸秆,研制了“留高茬”玉米收获机。并且对玉米收获机的摘穗辊进行了改进,一定程度上解决了玉米秸秆堵塞“摘穗辊”和玉米果穗的籽粒损失问题。除此之外,将基于机器视觉的玉米植株数量获取功能加入到该玉米收获机之中；整体上,实现了传统卧辊式玉米收获机作业功能的创新和作业质量的提升。更多还原

【Abstract】 Soil wind erosion is a serious concern in agricultural regions. Wind erosion is of particular concern in Northeast China where a north continental monsoon climate is prevalent and land is prepared for seeding using an ancient ridge culture technique. Cultural reluctance to adopting a cropping strategy that leaves residues is also based on local population use of corn stalks as animal fodder and fuel. In order to evaluate the conservation effects of standing residue on controlling soil wind erosion, a 4-year study (2011 to 2014) was conducted near Changchun city in Northeast China. Four experimental treatments were used:un-fixed corn residue coverage (shattering/cutting the corn stalks into small sections and spreading them on the soil surface) and three treatments with the standing corn residue of different height for each treatment; 30,40 and 50 cm. The corn stalk residue above that which remained in each treatment was removed from the field as much as practical. The standing residue treatments also resulted in some soil coverage by fugitive leaves and small stalk pieces. The experimental design was four treatments replicated four times, with years as replicates. Soil loss from the un-fixed corn residue coverage treatment and soil sediment from the standing residue coverage treatments was measured. Standing residue with the heights of 30,40 and 50 cm increased mean aerodynamic roughness length (equivalent to the height at which the wind speed theoretically becomes zero) by 19.87,43.77 and 61.62 mm respectively, and increased mean threshold wind speed by 11,25 and 33% respectively. Mean monthly soil loss mass balance for un-fixed corn residue was 1.27 Mg/ha, and the mean monthly values for soil sediment mass balance were 0.725,1.088 and 1.967 Mg/ha for 30,40 and 50 cm standing residue treatments respectively. These experiments indicate that standing residue conservation management can act as an effective way to control soil wind erosion, while providing a portion of corn stalks for the local population to continue using as animal fodder and fuel.Standing corn residue has been proven to reduce wind erosion in Northeast China but several questions remain regarding how standing corn residue affects soils during winter. Our objective was to compare soil frost depth associated with two zero-tillage methods [i.e., returning whole broken corn stalk into soil (hereafter referred to as’RWCS’) and standing corn residue (hereafter referred to as’SCR’)]. Frost tubes were used to determine soil frost depth during winter, and a soil heat flux plate was used to measure soil heat flux 8-cm beneath the soil surface. Compared with RWCS treatment, SCR significantly (p<0.01) reduced the maximum soil frost depth due to thicker snow cover which insulated the soil surface from cold winter air, which has implications for early planting. Early planting meant that corn could have longer growing time, which could help long-growing-time corn varieties become maturity before killing frost in cold areas, longer growing time could also result in fully filled grain, and increase economic profit for farmers at the same time.Conservation tillage with standing corn residue was testified that it has a strong control of soil wind erosion, and it can reduce maximum soil frost depth at the same time. In order to implement this mode of conservation tillage at a production scale, a cutter was developed in this paper. Subsequently, two experiments were conducted, one was to test the cutting ratio (defined as the totally cut off stalk population divided by total stalk population), and the other one was to test standing-residue height. The experiment results showed that the mean cutting ratio increased significantly (p<0.05) along with increasing height of cutter-head above the ground (cutting height); the cutting ratio’s mean value increased significantly (p<0.05) along with decreasing angle between the cutter-head and the ground (cutting angle). The average standing-residue height increased along with the elevation of cutting height from 300 mm to 500 mm. The average standing-residue height increased significantly (p<0.05) along with the decreasing of cutting angle from 15° to 0°. So the cutter can promote popularization of the conservation tillage with standing corn residue in Northeast China.One corn harvester can retain a certain height of corn stalk is not enough for modern farmers, improving the whole working quality is their common petition. The blocking between two snapping rollers will seriously constrict the harvesting efficiency for corn harvester. By analyzing the corn stalk’s movement along the snapping roller, one reason which could cause blocking is found:when the corn stalk arrives the end of cutting portion, if it still exists in the gap of snapping roller, and what makes worse is that the following corn stalks come into the gap of snapping roller continuously, the blocking will occur. In order to solve this problem, two alterations of snapping roller were done in my dissertation. Firstly, one variable screw pitch rib snapping roller was developed. Secondly, the fixed space between two snapping rollers was changed to variable space, so the snapping rollers can hold corn stalks all the time. The comparable experiments between fixed screw pitch rib snapping rollers and variable screw pitch rib snapping rollers, spacing-fixed snapping rollers and spacing-adaptive snapping rollers illustrated that variable screw pitch ribs and spacing-adaptive snapping rollers can avoid corn-stalk blocking effectively, and variable screw pitch ribs can improve working efficiency by 56.7%. The third modification was aiming to solve grain loss, two snapping rollers would rotate at differential speeds, so corn ears whose diameters are relative small could have a trend of falling into conveyer instead of rubbing with snapping rollers. The grain loss and damage rate is only 0.11% for differential-speed snapping roller, and the national standard is 2%. Another advantage of this newly designed snapping roller is it can prolong the working life of cutting table.It is no doubt that corn harvesters can improve working efficiency and reduce working cost if they can do additional job besides conventional job. For example, obtaining corn population has a significance meaning for optimizing planting density, corn population is also a key factor which is used for calculating average yield of each corn plant. In order to reduce labor intensity for counting corn population and increase accuracy, my dissertation also aimed to obtaining corn population based on machine vision technology. Taking pictures of standing corn stalk has its own unique advantage:it is easier for identifying images of standing corn stalk. There were 4 steps in this work. Firstly, the image acquisition equipment obtained vedio document which was fisrt hand document, then vedio document would be decompressed into RGB images. Secondly, the RGB images were converted into gray images for mosaicking. Thirdly, the gray images were converted into binary images for border extraction. Fourthly, the geometry center of corn stalk transection was found and marked. So the corn population can be obtained by counting marks. The results obtained by machine vision technology has no significance difference (p>0.05) compared with actual corn population, and the error is only 6.7%. My study took full advantage of color differences among corn-stalk transection, soil surface and other neighbor stuff, as a result of reducing the difficulty as well as improving the accuracy of image identification, which made a contribution to practical problem.My dissertation made a deep exploration of conservation tillage with standing corn residue. Conservation tillage with standing corn residue has a strong control of soil wind erosion, reducing maximum soil frost depth, helping long-growing-time corn varieties become maturity before killing frost in cold areas. In order to retain a certain height of corn stalk mechanically, one corn harvester with corn stalk cutter was developed, and corn ear snapping rollers were improved. All these modifications have good effects on avoiding corn stalk blocking, reducing corn ear grain loss. In addition, this corn harvester can acquire corn population by using machine vision technology. What were did in this dissertation is innovative, and enhanced the working efficiency and working quality of traditional horizontal roller corn harvester.更多还原