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Fertilizer is essential to safeguard food security, and rationalizing fertilization and improving fertilizer use efficiency can reduce its detrimental impact on environment and sustain agriculture production. Current corn fertilization in China is largely growth stage-based with a base fertilization coupled with a number of topdressings. This is inefficient in fertilizer use and labor-intensive, difficult to meet the requirements for sustainable agriculture. Delivering the fertilizer to the location in soil where the crop mostly demands for is a technology to effectively improve fertilizer use efficiency and increase crop yield. In this paper we present a pneumatic centralized device to stratifying fertilizer in soil based on the demand of crop roots. The structure and working parameters of the key components in the device were calculated theoretically; the diameter of the conveying pipe in the device was 76 mm, the inlet airflow velocity should be higher than 25 m/s, and the distribution ratio of the fertilizer can be adjusted arbitrarily from 1:1 to 1:2. The performance of the device was analyzed using the discrete element method coupled with the computational fluid dynamics by taking the rotational speed of the rotary cone (A), the inlet airflow velocity (B) and the fertilization velocity (C) as determinants, and the coefficient of variation (CV) of the fertilizer amount at each fertilizer outlet as an performance index. A quadratic-regression rotation orthogonal simulation test was used to link the performance index to the determinants. The results showed that both rotational speed of the rotating cone and the inlet airflow velocity had a significant effect on the CV. When rotational speed of the rotary cone was 735-1 196 r/min, the inlet airflow velocity was 36-41 m/s, the fertilization velocity was 0.14-0.42 kg/s and the distribution ratio was 1:2, the associated CV at different fertilizer outlets varied from 3.7% to 4.9%. The influence of all determinants on the CV was ranked in the order of A>B>C. Bench test of the device was conducted in the Conservation Tillage Research Center of the Ministry of Agriculture and Rural Areas, with rotational speed of the rotary cone being 735 r/min, the inlet airflow velocity being 36 m/s, the fertilization rate being 0.42 kg/s and the distribution ratio being 1:2. The results showed that the CV was less than 5.18% and the deviation of the distribution ratio was less than 2.68%, consistent with the results obtained from simulation and meeting the requirements for fertilization operation. This work provides a new technology with theoretical support to optimize pneumatic centralized device for stratifying fertilizers into soil. [ABSTRACT FROM AUTHOR]

Pollination is a key process in the hybrid rice seed production. At present, the traditional artificial assisted pollination is still the main method of hybrid rice seed production in China. Traditional artificial assisted pollination methods have some disadvantages, and they are not conductive to the realization of full mechanization of hybrid rice seed-making. In order to find a more efficient and more reliable auxiliary pollination method to facilitate the full mechanization of hybrid rice seed production, a ducted-fan pollination machine based on high-clearance chassis for hybrid rice was designed in this paper. The flow field characteristics of ducted-fan-pollinator were simulated and analyzed by using computational fluid dynamics technology (CFD). The simulation and measurement airflow field results showed that, when the motor velocity of ducted-fan pollinator was 9 000 rad/min, the uniformity of air velocity distribution was better and the average wind velocity was 4 m/s at 6.0 m from the air outlet. It satisfied the minimum requirements for pollen lifting and suspension transportation during hybrid rice pollination. In addition, the ducts played a certain role in enclosing the airflow formed by the rotor rotation, and avoided the airflow formed by the rotor rotation to diffuse around in a certain area. A prototype had been trial-produced accordingly. Field validation tests were carried out by optimizing the parameters of the device. The ducted-fan pollination machine was composed of high ground clearance power chassis, micro gasoline generator, DC power supply, truss, truss automatic leveling device, ducted-fan start-up controller, truss lifting mechanism and several ducted-fan-pollinators. The chassis clearance was 1.7 m, the wheelbase was 2.4 m. The tread was 2.5 m, which could span one compartment of male parent. And the truss width was 11.0 m. The coverage width of single pollination operation could reach 31.5 m. Under the walking velocity 1.5 m/s, the operation efficiency could reach 7 hm2/time (30 minutes for each pollination). The results showed that under the conditions of 1.5 m/s walking velocity and 9 000 rad/min motor revolving velocity of the pollination machine, the average number of pollen grains was 8.39 grains in the pollen collection point of the female parent compartment in the unit visual field, which satisfied the minimum requirement of hybrid rice seed production and pollination (at least 3 grains of pollen were required in the agronomy of hybrid rice seed production). A comparative experiment was conducted on the actual production of hybrid rice pollination by ducted-fan pollination machine based on high-clearance chassis and agricultural UAV. The results showed that the seed-setting rates of the 2 pollination methods were 44.2% and 42.7% respectively. The results of the 2 operations were similar, which showed that the designed ducted-fan pollination machine based on high-clearance chassis for hybrid rice could meet the actual production requirements of hybrid rice seed-making. This study provides a reference for the mechanization of hybrid rice seed production. [ABSTRACT FROM AUTHOR]

Belt dryers are the most popular equipment for betel nut drying. One of the drawbacks of this dryer is the non-uniformity in the desired moisture content of end product. In order to improve the structure of flow field and the moisture uniformity for the belt dryer, on the theoretical basis of computational fluid dynamics, the effects of the accumulative thickness, air velocity, air temperature and moisture content of hot air on the moisture uniformity of betel nut dried were simulated and discussed by using FLUENT software package. The orthogonal table about 4 factors and 3 levels was designed. In this paper, the betel nut was considered to be a wet porous medium, and the air flow through the areca layer was seen as the flow inside the porous medium, as well as the flow in the layer. By adding momentum equation source term to the momentum equation, the porous medium model was formed. The momentum equation was divided into 2 parts which included viscous item loss and inertia item loss. Experimental verification was carried out. Experimental test was finished in a multilayer belt dryer designed by Hunan Chain Co. Ltd.. The dryer was a five-layer mesh belt with cross flow drying system. Observation hole was set in the 1st path (top layer) and the 5th path (bottom layer), and the hole position was X=0.8, 2.4, 4.0, 5.6, 7.2 m, respectively. After washing, soaking, air-curing, separating, removing the film, rinsing and draining, betel nut was dried in dryer. The QDF-2B hot ball type electric wind speed meter was set to test the wind speed of the dryer, and the measured data had a good agreement with the calculation results. Based on the Shannon-Wiener index, the water content uniformity index was put forward, which was compared to the conventional index and the calculation result. Two deflectors with different shape (traditional deflector and wing-shape deflector) were put forward and analyzed. Simulation results showed that in the length direction of top path, the wind speed at the positions of X=4 m and X=6 m was relatively larger, which was 0.8 and 0.7 m/s respectively. The wind speed when X was equal to 4-6 m was gradually reduced, while that when X was equal to 4.5-5.5 m was the lowest (0.4 m/s). The wind speed curve had the “camel peak” shape. In the length direction of bottom path, the hot air was divided into 2 parts, most of which flowed along the length direction, and the remaining moved upward through the material layer. The speed was gradually reduced in bottom channel, and the speed through the material layer was maintained above 1.05 m/s. Results showed that the moisture content of the betel nut layer with a thickness of 80 mm was more uniform than 40 or 60 mm. Therefore, the thickness of betel nut had most effect on the uniformity of moisture content than the other 2 factors. The general trends of water content uniformity index, conventional index and “camel peak” curves were similar, but that of the water content uniformity index was more close to the calculation result. It indicated that layer thickness of 80 mm, inlet temperature of 70 ℃, flow rate of 1.5 m/s, moisture content of 0.24 were more conducive to moisture uniformity. The deflector could obviously improve the uniformity of moisture. Installing simple deflector mildly expanded the contact area of air inlet and slightly reduced the moisture of betel nut, yet there still had partial areas without drying. These areas were mainly distributed in the middle and sides of the dryer. After equipping with wing deflector at the entrance of dryer, hot air was evenly distributed to the entire first path, while moisture content of the betel nut layer decreased from 0.285 to 0.215, and moisture uniformity was improved. In the case of shortening the drying time by 5 min, the water content uniformity index was 0.926, and the drying efficiency was promoted. [ABSTRACT FROM AUTHOR]