ارزیابی کارگاهی سامانه کنترلی مدیریت موضعی کوددهی محصولات ردیفی (مطالعه موردی: چغندرقند)

Extended Abstract
Introduction
Chemical fertilizers, with more than 40 thousand tons of annual consumption in the country's sugar beet fields (117000 hectares), have the largest share of energy consumption in the production of this product.. Since the characteristics of soil and plants (such as soil fertility, soil texture and production potential) are not the same throughout the field and there is spatial variability, therefore, the variability in the fertility of fields has made it possible to increase productivity by local management of crops. One of the main methods to accelerate the adoption of variable rate technologies, especially in developing countries, is to install control system on conventional machines (uniform rate) and convert them into variable rate type. Hence, in this study, the hydro-electric fertilizing control system was developed and installed on a traditional fertilizer applicator (uniform rate). Then, fertilizing error and the system delay time were evaluated in the workshop.
Materials and Methods
A control system was built and installed on a traditional fertilizer applicator. The components of this system include electronic control unit, positioning system, sensor of fertilizer distributor gate position, traveling speed sensor, double acting hydraulic cylinder, hydraulic flow control valve, hydraulic oil direction control valve, hydraulic oil hoses, oil pressure control valve, and the gates movement mechanism. It is necessary to evaluate the accuracy of the control system before investigating its overall accuracy in the field. Fertilizing error and delay time are two main components in determining the accuracy of the control system. In order to evaluate the system in workshop under similar conditions to the field, a 220V single-phase gear box and electric motor unit (with the ability to continuously change the output speed) was replaced by the ground wheel of the machine. The equation of the fertilizing rate and the factors affecting it (traveling speed and gate opening) for the distance between the rows of the sugar beet fields (60 cm) was defined in the electronic control unit of the system.
In order to evaluate the accuracy of the system, effect of traveling speed (3.5, 5.75 and 8 km.h-1) and fertilizing rate (80, 100, 150, 200, 250 and 350 kg.ha-1) on the fertilizing error of the system was evaluated using spss software.
The total delay time was calculated from the sum of the mechanical delay time and fertilizer particles fall delay time.
The effect of the fertilizing rate (at intervals of 100, 150, 200 and 250 kg ha-1) and the machine traveling speed (at three levels of 3.5, 5.75 and 8 km h-1) in two cases of decreasing and increasing the fertilization rate changes was evaluated on total system delay time.
Results and Discussion
Results of variance analysis showed that the effect of fertilizing rate on fertilizing error was significant (p < 0.01), however the effect of traveling speed was not significant, which indicates the proper performance of the control system in eliminating the effect of traveling speed on fertilizing accuracy.
The effect of the amount and direction (increasing or decreasing) of fertilizing rate change and their mutual effect on the total delay time of the machine was significant (p < 0.01), while the effect of the traveling speed was not significant. The regression functions of the total delay time in the states of increasing and decreasing the fertilizing rate were determined according to the equations (1) and (2).
in which t is the machine total delay time (seconds) and ΔX is the fertilizing rate (kg ha-1).
Since the movement speeds of the double acting hydraulic cylinder (the gate actuator) in the opening and closing states were not equal, it caused two separate equations being calculated to determine the machine total delay time in fertilizing rate change modes (decreasing and increasing).
The machine total delay time was better (less) compared with the results of some other studies This indicates the appropriate delay (reaction) time of the system.
Conclusion
The results of the experiments showed that the effect of fertilizing rate on the system error was significant (p<0.01) and the error increased at low fertilization rates. This was due to the construction and operation of the fluted wheel type fertilizer distributor device. The overall fertilizing error of the innovated control system was 8.01%. Reduction of the delay time of the system due to the hydraulic actuators application indicated the appropriate accuracy in the sugar beet and other row crops fields. In general, according to the results of the study, the following items are suggested:
1-            In order to check the overall accuracy (such as the positioning system and fertilizer controlling system accuracies) of the variable rate fertilizer applicator and to adapt it to the field conditions, additional experiments are recommended.
2-            In order to increase the accuracy of the system at low fertilizing rates, it is recommended to make improvements in the structure of the fluted wheel type of fertilizer distributor.
3-            It is suggested to evaluate the effect of different positioning systems on the accuracy of variable rate fertilizing in row crops cultivation fields
Keywords
Agricultural mechanization, Precision agriculture, site specific crops management, sugar beet fertilizing.
References
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