| China is a large agricultural country,and rice is one of China’s important food crops.Rice production is of great significance for ensuring the safety of our country.However,with the over-application of chemical fertilizers year by year,it not only caused a decrease in crops’ ability to absorb chemical fertilizers,but also caused huge damage to the ecological environment.Therefore,it is of great significance to study the relevant fertilization technology and fertilization equipment for the rational and scientific use of fertilizers,the improvement of rice yield and quality,and the protection of ecology.At present,rice fertilization is mainly based on artificial sprinkling or mechanical quantitative uniform application.The above-mentioned methods will cause a large amount of fertilizer loss,and there are problems such as uneven fertilization and improper fertilizer ratio.At the same time,in view of relevant research at home and abroad,there is still a lack of precision fertilization machinery and devices based on rice nitrogen levels.In order to achieve precise spraying of liquid fertilizer on rice,the study designed a vehicle-mounted variable spraying liquid fertilizer system based on the nitrogen level of the rice canopy;and carried out experiments on the effects of variable fertilization in the field.The main research contents and results of this article are as follows:(1)Rice nitrogen content sensing model based on Crop Spec sensor: The key parameters of Crop Spec sensor are measured,and the perception range of Crop Spec is calculated through the relevant parameters of Crop Spec sensor.Taking three typical rice as research objects,the relationship model of S1 value(nitrogen adequacy index)and rice nitrogen content and nitrogen application rate was established.The test results show that the amount of nitrogen application has a very significant effect on the S1 value,and the linear,quadratic,and exponential regression models all have a high degree of fit.The measured value of S1 has a good consistency with the predicted value of the model,in which the maximum relative error is 6.25% and the minimum relative error is 0.39%.The S1 value of rice perceived by cropspec can effectively reflect the nitrogen content of rice.(2)PWM solenoid valve nozzle variable spraying model and test: a PWM solenoid valve variable nozzle test platform was built.Regression analysis method was used to establish the mathematical model between the spray volume,pressure and duty ratio of the two solenoid valve nozzles of Tee Jet XR 11001 vs and Tee Jet XR 11003 vs.The test results show that there is a significant regression relationship between flow and pressure and duty cycle.When the duty ratio is greater than 20%,the solenoid valve nozzle starts to work.Comparing the flow rates of the two nozzles,in the common pressure and duty cycle statistical interval(duty ratio 20%-100%,pressure 0.2MPa-0.4MPa),the flow rate of the11003 vs nozzle varies from 6.345g/s-11.3038g/s Between,the flow rate of the 11001 vs nozzle varies between 2.94g/s-4.73g/s.It can be seen that under the same duty cycle and pressure,the flow rate of the 11003 vs nozzle is larger and the flow rate variation range is larger.The flow model verification test results show that the relative errors between the flow rate and the measured flow rate of the Tee Jet XR 11001 vs and Tee Jet XR11003 vs nozzle models are respectively 0.494% to 8.67%,0.092% to 6.428%.The flow rate of the nozzle regression model is in good agreement with the measured flow rate.(3)Design of variable spraying system based on Crop Spec sensor: The hardware system of variable spraying system was built on the basis of the PWM solenoid valve variable spraying head test platform,and Crop Spec was re-developed.The sensor CAN bus communication protocol based on STM32 microprocessor is designed.According to the mathematical model of sensor S1 value and PWM duty cycle,the software algorithm of variable spraying system is constructed.(4)Field test of liquid fertilizer variable spraying based on on-board spectrum sensor:In order to verify the actual production and application effect of variable spraying system based on Crop Spec,field verification test was carried out.At the heading stage of the fertilization node,the Crop Spec sensor was used to collect real-time nitrogen content data of the rice,and variable spraying was performed.Compared with the traditional fertilization method,the rice growth was compared.The results showed that the variable spraying system can make the rice grow evenly and reach the rice variable.The expected effect of spraying. |
