Study On Water And Fertilizer Regulation Method And Application Based On Nutrition Information Of Facility Vegetables

The facilities area of China has occupied the world's first place,and the output of facility vegetables is approximately 300 million tons,of which the greenhouse vegetable area accounts for the vast majority,however,the total area still relies on manual management and regulation,therefore the degree of automation is very low.The use of large amount of water and fertilizers phenomenon is widespread.The decision of fertilization mainly depends on subjective experience judgment,which cannot be achieved by the purpose of saving water and fertilizer.Moreover,the flooded irrigation and fertilizer also causes serious non-point source pollution.In order to improve the greenhouse water and fertilizer management level of solar greenhouse and steel frame greenhouse,it can be found by the research and exploration of greenhouse water and fertilizer utilization rate.This paper provides information about non-destructive testing methods to detect crop nutrition information,combines water and fertilizer integration technology to study water and fertilizer regulation methods based on crop nutrition information.By using the terahertz time-domain spectroscopy system to scan the vegetables with different nutrient contents,the absorption intensity of the crop under different nutrients can be obtained.Therefore,the different nutritional status of the crops will be reversed,also the best crop nutrient status and fertilization decision-making methods will be found in combination with the fresh weight and fertilization concentration of the crops.Furthermore,the existing integrated water and fertilizer application device will be designed to improve the water and fertilizer use efficiency of the solar greenhouse,to improve the degree of automation.This article takes the facility lettuce as the research object,the main research contents are as follows:(1)The seedling cultivation of nitrogen,phosphorus,potassium and water levels of different nutritious lettuces and different gradient nutrient solution preparation and pouring work were carried out by using soilless culture techniques.The contents of nitrogen,phosphorus,potassium and water in the canopy of lettuce leaves were measured by physical and chemical methods.After that the terahertz system was used to scan the absorption spectra of different nutrient leaves,and the terahertz time domain spectral information was also collected.(2)Processing and analyzing the terahertz absorption spectrum data and the nutrient physicochemical value of lettuce,using SG smoothing,derivative and normalization algorithm to preprocess the data,and using SPXY algorithm,KS algorithm and RS algorithm to complete the sample verification set and the division of the prediction set.In order to obtain the best characteristic spectrum of optimal nutrient water,iteratively retains informative variables(IRIV),stable competitive adaptive reweighted sampling(SCARS),interval combination optimization algorithm(Interval Combination Optimization,ICO)and(successive projections algorithm,SPA)were used to extract NPK nutrients and water characteristics.Finally,a multivariate regression detection model for nutrition testing was established by using the PLSR(partial least squares regression).The regression coefficient R~2 and the root mean square error(RMSEC)were used as the indicators.Finally,the moisture detection model was obtained as D-RS-IRIV-SPA-PLSR.The best prediction accuracy of N,P and K detection model is G-RS-IRIV-SPA-PLSR,G-SPXY-ICO-SPA-PLSR and G-RS-ICO-SPA-PLSR,respectively.(3)Through the growth curve logistic function,the relationship between leaf water content and fresh weight was calculated for lettuce.The dry substrate moisture content of lettuce leaves was found as 2500%-3500%,however,the amount of water was estimated for the need of growing vegetables.The relationship between the nitrogen,phosphorus and potassium content of leaves and the fresh weight of lettuce was estimated by a quadratic function.The optimal range of nitrogen,phosphorus and potassium was calculated in the leaves of lettuce which were 3.5%-4.0%in nitrogen,0.62%-0.85%phosphorus and 7.3%-8.0%in Potassium.Furthermore,when the concentrations of nitrogen,phosphorus and potassium exceeded from 254.532mmol/L,20.061mmol/L and 185.015mmol/L respectively,then it affects the yield of lettuce,however,it needed to be supplement with nutrition.(4)To design and optimize the water and fertilizer integrated irrigation system in the solar greenhouse,first complete the design of the machine,hardware selection and processing,in order to overcome the problems of labor intensity and particle blockage of artificial fertilizer.,The fertilizer machine adds double impeller stirring.In order to increase the distal pressure,the water pump and the filter device was used at a constant pressure of water and fertilizer supply system.Moreover,the system control software completed the program design based on Siemens S7-200PLC system,however,it realizes the free switching of manual and automatic control.The automatic control system mainly adjusts the frequency of the inverter by feedback of the pressure sensor signal to PLC,it realizes PID algorithm control and guarantees the pipeline,whereas,the pressure was stable.The turbidity sensor controls the start and stop of the agitation,and the EC and PH sensors monitor the water and fertilizer mixing effect with respect to the real time.Throughout the experiments,the fertilizer application machine basically achieves the desired effects.