To manufacture high bio-content degradable polyurethane-coated fertilizer, the co-liquefaction of corn straw and starch was carried out to convert more biomass into bio-polyol so as to substitute petroleum-based polyol. The effect of the corn straw to starch ratio on liquefaction behavior was mainly investigated by monitoring acid value, hydroxyl value, and liquefaction rate. Both chemical structures and properties of bio-polyols and their coatings were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), etc. The results indicated that adding a certain amount of starch to corn straw for co-liquefaction could contribute to a higher hydroxyl content of bio-polyol than that from sole biomass. Compared to molecular weight, the hydroxyl value was a more significant index to ensure coating quality. The incorporation of starch segments to bio-polyol led to good thermal stability, limited residual small molecules, and high crosslinking density of the coating. The controlled-release ability of coated urea prepared by co-liquefied bio-polyol was better than that of corn-straw-based bio-polyol, and the optimal ratio of corn straw to starch was 3:1. Overall, this study provides a new route to fabricate corn straw as a cost-effective and degradable coating with good controlled-release properties, which benefits solid biomass recycling.

Effects of cow manure ratios on methane production and microbial community evolution in anaerobic co-digestion with different crop wastes

In this study, a spatially stratified proportional fertilizer application device was designed, which was mainly composed of a fertilizer equalization and stirring structure, fertilizer guide plate, and fertilizer plate. This was aimed at solving challenges presented by current fertilizer devices that include a poor layering effect due to untimely return of soil, excess nutrients in the early stages of plant growth, and insufficient quantities in the later stages. The "seed fertilizer + chasing fertilizer" is time-consuming and laborious; seed and fertilizer (without layering) are applied to the soil at once, which tends to cause too much nutrients for plants in the early stage and not enough nutrients in the later stage; and the layered fertilizer machines currently on the market have a poor layering effect due to untimely soil return. Through theoretical analysis and calculation, the structural parameters of the device were determined, and the main influencing factors of the movement law of fertilizer in the device were analyzed. Through simulating soil tank tests, the main factors affecting the effect of fertilizer spatial stratification were designed by quadratic regression orthogonal rotation combination designs. The optimal parameters including the length of the first fertilizer plate was 100 mm, the installation angle of the fertilizer plate was 80°, the spacing of the fertilizer port was 30 mm, and the uniform stirring speed was 650 r/min. The results of the bench test showed that the fertilizer granules could be uniformly stirred at the optimized stirring speed, with average values of 74.56, 76.56, and 105.19 g, which met the agronomic fertilizer application requirements, and the coefficient of variation of fertilizer application amount in each layer was less than 1%. The field test results showed that the stratified proportional fertilizer application device could achieve the stratified proportional application of fertilizer in the soil in ranges of 80.2-95.4, 150.3-180.2, and 230.3-250.4 mm for the upper, middle, and lower layers, respectively, with an error within 10 mm from the designed theoretical application depth. Compared with the conventional fertilizer application method, this fertilizer application method had a more obvious promotion effect on the 100-grain weight and yield of corn.

Aiming at the problems of fast wear and short service life of rotary tillage blade in gneiss mountainous area, and the lack of accurate and reliable discrete element simulation parameters for exploring the interaction mechanism between soil and rotary tillage blade, taking the typical gneiss sandy loam in Taihang Mountain as the research objects, the relevant simulation parameters were calibrated and the wear characteristics of rotary tillage blade were analyzed. Firstly, the contact parameters between soil particles were calibrated. Taking the simulated accumulation angle of soil particles as the response value, the significance of the influencing factors was screened based on the Placket-Burman test in the Design-Expert software. Through the steepest climbing test and Box-Behnken test, the regression model of soil accumulation angle was determined. Through model optimization, the JKR surface energy, collision recovery coefficient, static friction coefficient and rolling friction coefficient are 4.85 J/m2,0.24,0.1 and 0.25, respectively. At this time, the simulated value of soil accumulation angle is 42.21°, and the relative error between the simulated value and the measured value is 3.8%. Secondly, the contact parameters between soil and 65 Mn steel were calibrated,and the static friction coefficient, rolling friction coefficient and collision recovery coefficient between soil and 65Mn steel were obtained through static friction, inclined plane and inclined plate collision tests. Taking the sliding friction angle of soil on 65Mn steel plate as the response value, the regression model of soil sliding friction angle was obtained based on Box Behnken method. By optimizing the model, the static friction coefficient, rolling friction coefficient and collision recovery coefficient between soil and 65 Mn steel are 0.49,0.13 and 0.32 respectively. At this time, the simulation value of static sliding friction angle is 19.90°, and the relative error with the measured value is 5.7%. Finally, the calibration parameters are verified to be accurate and reliable by soil disturbance test. Through the wear test and wear law analysis, it is concluded that the serious wear parts of the rotary tillage blade are mainly concentrated in the blade part and the tail of the tangential blade.,in which the tangent blade and side cutting blade wear more, and the wear at the transition between tangent blade and side cutting blade is relatively small.When the rotational speed of the rotary tillage blade is 160 ~ 200 r/min, the wear amount is not much different ; when the speed is greater than 200 r /min, the wear amount increases obviously. With the increase of rotational speed, the wear rate of rotary tillage blade increases. When the rotational speed is 160 ~ 200 r/min, the wear rate of rotary tillage blade is slower, while when the rotational speed is 220 ~ 240 r/min, the wear rate of rotary tillage blade is faster. When the rotational speed is 260 ~ 300 r/min, the wear rate of rotary tillage blade is the fastest. In addition, with the increase of tillage depth and forward speed, the wear amount and wear rate of rotary tillage blade also increase.

Aiming at the problems of low utilization rate of corn fertilizer, low precision of fertilization ratio, and time-consuming and laborious topdressing in the later stage, an U-shaped fertilization device with uniform fertilizer mechanism was designed. The device was mainly composed of uniform fertilizer mixing mechanism, fertilizer guide plate and fertilization plate. Compound fertilizer was applied on both sides and slow/controlled release fertilizer was applied at the bottom to form an U-shaped distribution of fertilizer around corn seeds. Through theoretical analysis and calculation, the structural parameters of the fertilization device were determined. Through the simulated soil tank test, the quadratic regression orthogonal rotation combination design was carried out on the main factors affecting the spatial stratification effect of fertilizer. The optimal parameters were obtained as follows: the stirring speed of the stirring structure was 300 r/min, the bending angle of the fertilization tube was 165°, and the operating speed of the fertilization device was 3 km/h. The results of bench verification test showed that under the optimized stirring speed and bending angle, the fertilizer particles were stirred evenly, and the average values of fertilizer flowing out of the fertilization tubes on both sides were 299.5 g and 297.4 g, respectively. The average fertilizer amounts of the three fertilizer outlets were 200.4 g, 203.2 g and 197.7 g, respectively, which met the agronomic requirements of 1:1:1 fertilization, and the variation coefficients of fertilizer amounts on both sides of the fertilizer pipe and each layer were less than 0.1% and 0.4%, respectively. The simulation results of the optimized U-shaped fertilization device can achieve the expected U-shaped fertilization effect around corn seeds. The results of field experiment showed that the U-shaped fertilization device could realize the U-shaped proportional application of fertilizer in soil. The distance between the upper end of fertilization on both sides and the distance between the base fertilizer and the surface were 87.3 ~ 95.2 mm and 197.8 ~ 206.0 mm, respectively. The transverse distance between the fertilizers on both sides was 84.3 ~ 99.4 mm, and the error with the designed theoretical fertilization was within 10 mm. Compared with the traditional side fertilization method, the number of corn roots increased by 5 ~ 6, the root length increased by 30 ~ 40 mm, and the yield increased by 9.9 ~ 14.8 %.

Aiming at the problems of low utilization rate of corn fertilizer, low precision of fertilization ratio, and time-consuming and laborious topdressing in the later stage, an U-shaped fertilization device with uniform fertilizer mechanism was designed. The device was mainly composed of uniform fertilizer mixing mechanism, fertilizer guide plate and fertilization plate. Compound fertilizer was applied on both sides and slow/controlled release fertilizer was applied at the bottom to form an U-shaped distribution of fertilizer around corn seeds. Through theoretical analysis and calculation, the structural parameters of the fertilization device were determined. Through the simulated soil tank test, the quadratic regression orthogonal rotation combination design was carried out on the main factors affecting the spatial stratification effect of fertilizer. The optimal parameters were obtained as follows: the stirring speed of the stirring structure was 300 r/min, the bending angle of the fertilization tube was 165°, and the operating speed of the fertilization device was 3 km/h. The results of bench verification test showed that under the optimized stirring speed and bending angle, the fertilizer particles were stirred evenly, and the average values of fertilizer flowing out of the fertilization tubes on both sides were 299.5 g and 297.4 g, respectively. The average fertilizer amounts of the three fertilizer outlets were 200.4 g, 203.2 g and 197.7 g, respectively, which met the agronomic requirements of 1:1:1 fertilization, and the variation coefficients of fertilizer amounts on both sides of the fertilizer pipe and each layer were less than 0.1% and 0.4%, respectively. The simulation results of the optimized U-shaped fertilization device can achieve the expected U-shaped fertilization effect around corn seeds. The results of field experiment showed that the U-shaped fertilization device could realize the U-shaped proportional application of fertilizer in soil. The distance between the upper end of fertilization on both sides and the distance between the base fertilizer and the surface were 87.3–95.2 mm and 197.8–206.0 mm, respectively. The transverse distance between the fertilizers on both sides was 84.3–99.4 mm, and the error with the designed theoretical fertilization was within 10 mm. Compared with the traditional side fertilization method, the number of corn roots increased by 5–6, the root length increased by 30–40 mm, and the yield increased by 9.9–14.8%.