Conservation Tillage With Standing Corn Residue And Its Corresponding Corn Harvester

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.