Transactions of the Chinese Society of Agricultural Engineering, the 1st in Agricultural Engineering, is supervised by China Association for Science and Technology, and sponsored by Chinese Society of Agricultural Engineering. It aims to introduce the latest scientific achievements and developing trends of Agricultural Engineering and provides the academic developments abroad and domestic of the discipline. The scope covers agricultural water-soil engineering, agricultural information and electrical technology, agricultural products processing engineering.
The journal is included in EI, JST, Pж(AJ), CA and CSCD.
Editor-in-Chief Zhu Ming
Deputy Editor-in-Chief Wei Xiuju Zhang Ruihong Xi Weimin Wang Liu Wang Yingkuan Li Pingping Ying Yibin Tong Jin Yun Wenju Zhao Chunjiang Kang Shaozhong
Soil moisture is a main limiting factor for crop growth and vegetation reconstruction in the arid and semi-arid areas of the world, and it is a key factor for agricultural sustainability and soil productivity. Changes in soil hydraulics and function are major aspects for assessing whether long-term fertilization is beneficial to soil sustainable development or not. The objectives of this study were to determine the soil water retention characteristics of different fertilization treatments based on the long-term located experiment of soil fertility at “the Chinese National Soil Fertility and Fertilizer Efficiency Monitoring Base of Loessial Soil” established in the autumn of 1990 in Yangling, Shaanxi, China, and to clarify the differences of soil physical properties affected by the fertilization. The experiment consisted of six treatments: abandonment (LH), fallow (tillage, without planting, XX), no fertilization (CK), single application of nitrogen (N), application of nitrogen, phosphorus and potassium (NPK), and application of organic manure + NPK (MNPK). LH and XX were not fertilized, and weeds were regularly removed at XX every year. The soil water retention curve, saturated hydraulic conductivity and soil strength were analyzed and determined by adopting the surface undisturbed soil. The results showed that: 1) Long-term fertilization treatment had significant effects on soil organic carbon, saturated hydraulic conductivity, and soil strength (
P < 0.05). Compared with CK, N and NPK, MNPK significantly (
P < 0.05) increased the soil organic carbon, saturated hydraulic conductivity, and porosity and reduced the soil bulk density and soil strength. 2) The soil water retention curve showed a significant difference between treatments, and the soil water holding capacity was XX < N ≈ NPK < CK < MNPK < LH. The soil water holding capacity of MNPK was increased by 2.57%, 3.33%, and 7.34% compared with those of CK, N, and NPK, respectively. The parameters of V-G model between different treatments showed that there were slightly significant differences in residual water content (
θ
r), saturated water content (
θ
s), and reciprocal of inlet air (
a).
θ
r was the largest in MNPK, and the smallest in XX;
θ
s was the largest in N, followed by MNPK, and the smallest at CK. Inlet air (1/
a) was the largest in XX and the smallest in LH. 3) The pores of different treatments mainly had the diameter > 9 μm, and the ratio of macropores in different treatments was higher than that of mesopores and micropores, ranging from 22.3% to 30.2%. Compared with mesopores, the ratio of micropores was more. LH had the largest ratio of micropores, followed by the MNPK, and XX had the lowest ratio. In summary, MNPK can improve the soil structure and soil water holding capacity, reduce the soil bulk density and soil strength, and enhance the soil stability, which is helpful for crop growth and yield, and is a suitable farming measurement in the semi-arid Guanzhong area.
To investigate the effects of spray precooling parameters on the cooling characteristics of litchi fruit, a spray precooling test platform was established. “Huaizhi” litchi fruit was chosen for this study. The effects of spray temperature and spray flow rate on the cooling coefficient, 7/8 cooling time, and cooling uniformity, as well as the characteristics of multilayer litchi spray cooling, were studied. For the spray precooling of single-layer litchis, the lower spray temperature was corresponding to larger cooling coefficient, shorter 7/8 cooling time, and worse temperature uniformity of the fruits. When the spraying temperature was less than (5 ± 0.5) °C, the 7/8 precooling time shortened, and the precooling unevenness increased significantly (
P < 0.05). The effect of spray temperature to achieve rapid precooling was limited. Therefore, a spray temperature of (5 ± 0.5) °C could be chosen in the actual precooling process, and it could maintain the precooling uniformity and accelerate the precooling rate of litchi. With the increase of spray flow rate, the cooling coefficient initially increased and then stabilized, the 7/8 precooling time initially shortened and then leveled gently, and the fruit temperature uniformity increased. The 7/8 precooling time had a quadratic function relationship with the spray flow rate. The 7/8 precooling time decreased slowly when the spray flow was higher than 5.9 L/(s·m
2). This was because the contact area between the litchi and cold water increased more slowly than the flow rate. Therefore, the flow rate of litchi spray precooling could be selected to be 5.9 L/(s·m
2), which could improve the precooling efficiency and reduce the energy consumption of the pump. When multilayer litchi fruits were stacked, the closer spray nozzle was corresponding to the larger cooling coefficient, shorter 7/8 precooling time, and better temperature uniformity. The relative precooling time had a quadratic function relationship with the number of layers, and the number of critical precooling layers was 4.1. When the number of litchi stacks was larger than or equal to 4, the relative precooling time varied little. To improve the precooling efficiency, the number of litchi stacks should be larger than or equal to 4. However, as the number of layers increased, the precooling uniformity gradually deteriorated. When the multilayer litchees were stacked, the cooling rate of each layer was inconsistent, the precooling time was longer, and the precooling final temperature was not coordinated. The whole process of precooling took 14.02 min. After precooling, the σ of the middle longitudinal section was 0.14, and the average temperature was 7.15 °C. In single-layer litchi spray precooling, the spray temperature could be selected as (5 ± 0.5) °C, and the spray flow could be selected as 5.9 L/(s·m
2). The parameters of the single-layer litchi spray precooling were used to precool the multilayer litchi, and the number of layers of the best stack of litchi was found to be 4. The research results provided a reference for the design of litchi spray precooling equipment as well as single-layer and multilayer litchi precooling applications.
In recent years, with the rapid development of the poultry industry in China, it has brought enormous challenges to the ecological environment. The reduction, recycling and innocuous treatment of these organic solid wastes can be achieved by aerobic composting. The vertical reactor has a simple structure, effectively shortens the compost reaction time and improves the composting reaction environment. Therefore, the aerobic compost reactor has good practical value. However, due to the gravity accumulation of the material, the reactor has some problems, such as compacted material, poor ventilation, high ventilation resistance, and difficulty in homogenizing the product. In order to solve these problems, a spiral-belt-spiral-impeller aerobic compost bioreactor was designed with real-time monitoring of insulation, temperature and oxygen content. This reactor has a volume of 100 L. The computational fluid dynamics method was used to analyze the flow field within the reactor. The 3D solid modeling of the internal flow field model in the reactor was completed by Soildworks modeling, and the MRF (multiple reference frame) method was used to deal with the interaction between the stationary reactor inner wall and the moving stirring blade. The analysis of the velocity field distribution and velocity vector on the y = 0 section demonstrated that the reactor had good axial flow through the internal velocity distribution. The performance of the reactor was studied in aerobic composting test. The raw materials for composting were cow manures, wheat straw and mushroom residues, and the total reaction time was 24 days. The reaction was evaluated by measuring the temperature, oxygen concentration, total carbon, total nitrogen, C/N, total phosphorus, total potassium, germination index, total heavy metals and sensory indicators in the upper, middle and lower layers of the reactor. During the composting reaction process, the performance of aerobic composting test showed that the upper, middle and lower temperatures above 50 °C were 7.3, 6.8, 5.5 days, respectively, and the temperature first increased and then decreased. The oxygen concentration during the reaction was higher than 8%. The lowest value appeared around the fourth day. In the aerobic composting process, the moisture content and total carbon content showed a downward trend, while the total nitrogen content, total phosphorus content and total potassium content showed an upward trend. The moisture content gradually decreased from 65.76% to 42.5%, 42.1% and 41.7%, the carbon content decreased from 39.3% to 33.8%, 33.6% and 33.5%, the total nitrogen content increased from 1.37% to 2.01%, 2.01% and 2.03%, the total phosphorus content increased from 0.88% to 1.04%, 1.03% and 1.04%, the total potassium content increased from 1.57% to 1.74%, 1.75% and 1.73%, which were related to the law of microbial activity in the reactor. After composting, it has no obvious foul smell compared with the initial heap. The C/N of each layer was between 15 and 20, and the germination index was greater than 88%. The heavy metals such as Cu, Zn, Cr, Pb and Cd met the national standards. Therefore, the reactor could achieve harmless and uniform compost.
Wheat is one of the main food crops, which has an important on the national life and social stability. At present, there are many problems in the traditional sowing of wheat, such as large amount of seeding, low utilization ratio of water and fertilizer, and high cost. In order to solve those problems, the wheat precision seeding technology has been proposed that ensures even and reasonable distribution of wheat seeds in the field. Aiming at the requirements of wheat precision seeding, a wheat precision seed meter, including metering box, seed separating and cleaning brush, type hole wheel, transmission axis, airflow entering mouth, seed leading board, and transmission sprocket, was designed with combination of pneumatic and type hole wheel, and it could achieve better single filling performance. And the type hole wheel was arranged with type hole, suction hole and seed-falling groove. Amount of seeds were poured into the metering box, and were arranged along the radial direction of the type hole wheel under the guidance of seed leading board. The seed was filled with the type hole by its own gravity and the friction force of type hole wheel, then the seed was adsorbed by the airflow through suction hole. When type hole wheel carrying seeds through seed-cleaning zone, more than one seed on the type hole fell back into metering box in the action of seed separating and cleaning brush, therefore one seed was kept in the type hole. After that, the wheat seed was transported stably by the adsorption force. In the seed-falling zone, the seed overcame the adsorption force and dropped from type hole under seed-falling plate barrier force and gravity, completed the seeding process. According to three dimensions size of wheat, the main structure parameters and motion parameters of wheat precision seed meter were determined that the diameter parameters of type hole wheel were 100 mm, type hole wheel surface with three rows, both type hole and suction hole were long slots. Three rows of type holes with spiral angles of 6° and 30 type holes were in each row. Each type hole had a length of 8.5 mm, a width of 5 mm, and a depth of 2.5 mm. By the fluid dynamics software, the influences of different diameter of suction hole on type hole wheel fluid field were simulated and analyzed, and the results showed that more ideal diameter parameters of suction hole were 1.4–1.8 mm. In order to get the optimal combination of parameters of the wheat precision seed meter, the three-factor and three-level orthogonal test was designed with airflow negative pressure, suction hole diameter and rotation speed of type hole wheel as test factors. The airflow negative pressure was set at 2 500, 3 000 and 3 500 Pa, the suction hole diameter was selected 1.4, 1.6 and 1.8 mm, and the rotation speed of type hole wheel was changed in 30, 40 and 50 r/min. A total of 9 groups of tests were performed that each group of tests was repeated 3 times, and the average of test results was recorded. According to the range analysis, the rotation speed of type hole wheel had the greatest influence on the multiple rate of wheat, followed by the diameter of the suction hole, and the influence of the airflow negative pressure was small. For the missing rate and seed-filling qualified rate, the order of affecting indicators was the airflow negative pressure, the rotation speed of the type hole wheel, and the diameter of the suction hole. Through analysis of variance, the airflow negative pressure had a significant effect on the multiple rate of wheat, and had a very significant effect on the missing rate and seed-filling qualified rate. The suction hole diameter had a very significant effect on the multiple rate, and had significant effects on the missing rate and seed-filling qualified rate. The rotation speed of type hole wheel had very significant effects on the multiple rate, the missing rate, and seed-filling qualified rate. The airflow negative pressure and the rotation speed of type hole wheel had significant effects on the multiple rate, and had very significant impacts on the missing rate and seed-filling qualified rate. The tests revealed that when the airflow negative pressure was 3 500 Pa, the suction hole diameter was 1.6 mm, and the rotation speed of type hole wheel was 40 r/min, which was a better combination of parameters. By experiment, the missing rate was 5.1%, multiple rate was 4.7%, and seed-filling qualified rate was 90.2%, which reached the requirements of wheat precision sowing. This seed meter improves the filling effect and obtains better parameters, which provides reference for the research and development of the wheat precision seed meter.
