System Engineering

LESSON 1. INTRODUCTION TO AGRICULTURAL SYSTEM

The phase and pattern of distribution of rainfall, temperature, occurrence of pest and disease problems are coupled with the change in farm activities. Some of these behaviors are cyclic.  If the past pattern and the exact impact of crop associated resources are known, one can foretell the likely occurrences of certain crop related attributes in advances, so that the farmer can plan early to tide over the controllable attributes, which may likely to have serious impact on crop growth and yield. Because of the uncertainty and risk involved in crop production it is better for the farm scientists to familiarize with the advanced crop production techniques and tools, which are mainly associated with the application of Crop simulation Models. The simulation models approach in crop research is very essential for accurate planning. Using the crop growth functions one can easily estimate crop growth rate, relative growth rate (RGR) at various stages of the crop. More the growth performance of different varieties of the same crop, different nutrient treatments and irrigation treatments can also be studied more effectively within the help of response functions, physical optimum, economic optimum and constrained optimum can also be obtained which save time, energy, money etc. Using the optimum concept, one can use the resources more efficiently and get maximum yield. The crop simulation models are very popular in recent crop research studies. The crop simulation models like, crop growth models, weed models, irrigation models, spacing models, response models and pest simulation models etc., are all require the knowledge of mathematics for proper estimation, interpretation and to assess the suitability of the model. Moreover simulation models very much essential for agricultural Economics such as price models, production functions econometric models etc. In the case of Agriculture the factors that influence crop yield may be divided as follows, factors that limit crop yields such as the availability of water and nutrients, factors that determine potential yields such as light, temperature etc and factors that reduce yields such as weeds, pests and diseases. Crop yields throughout India are often severely restricted by the lack of fertilizer.  In some cases, too much fertilizer or organic manure is applied and when this happens both yields and crop quality are severely depressed.  But at the same time, application of less fertilizer causes reduction in yield as demand for food production is ever increasing with rapid population explosion. Hence the optimal use of scarce resources without further degradation, intensification, sustainability, climate changes and productivity are the key issues.   It is therefore, required most efficient crop management techniques and tools to increase food production with optimum fertilizer use.

System approach in crop management:

The word system is derived from a Greek word system with meaning an assemblage of objects united in some form of regular interactions or interdependence.  All the components are united to form a system. System analysis is an intellectual tool used in the entire field to solve the complex problems. That is any phenomenon; either structural or functional having at least two separable components and some interactions between these components may be considered a system. e.g. farming system.  All the activities of farming will be included in the farming system. e.g. manuring, irrigation, weeding, etc. In agriculture the systems are mainly classified as Cropping systems, farming systems, pathosystems and agro ecosystems. Pathosystems may include hosts and parasite populations and their mutual integrations.  Similarly cropping system included the type of or sequence of crops during the particular period. Each component of the system can be regarded as a system.  For example, manuring in the farming system involves time of manuring, quantity of manuring, method of manuring etc.  Thus, any system can also be considered as collection of systems.  As time changes, the components of the system also change. A system is always identified by the function while performance.

Types of system:

Open system:

 If a system receives message from outside, it is called open system.  e.g. soil system, plant growth system, etc.  The plant growth system receives message from outside environment like temperature, rainfall, etc the effect of the environment on the system and their values must be closely monitored.

Closed system:

If a system does not receive anything from outside, it is called closed system. e.g. glass house experiment In the closed  system the effect of the driving variable on the environment on the systems at its boundaries are in control. Hence the interactions between the state variables can be effectively studied in the closed system.

Static system:

If a system does not vary with time, then it is called a static system.  e.g. soil texture in a short period, farming system for a short period. Generally any system is complex in nature and most of the systems are time varying configuration. To analyze and get a valid information from these systems and to avoid complications it can be treated as static system for a shorter period.

Dynamic system:

If a system varies with time, then it is called dynamic system.  e.g. soil system, agricultural technology, Farming systems and cropping systems. In cropping systems we repeat the crop experiments in different seasons to study the seasonal influence on the Crop sequence.

System Physical principles:

Any system will follow the following physical principles on systems.

1. Le Chatlier’s Principle

2. Newton’s Third Law

3. Lenz’s Law

1. Le Chatlier’s principle : Le Chatlier’s principle states that if a system in equilibrium is subjected to some external action, the system will adjust if possible to oppose the change or minimize the effect of the change.  For e.g. if there is an increase in fertilizer price, initially there is a resistance from all the people; afterwards we are trained to develop varieties that will give same yield at low level of fertilizer.

2. Newton’s third law : For every action, there will be an equal and opposite reaction”.

e.g. higher production results in lower price

3. Lenz’s law : Any system will receive message initially.  When it acquires sufficiently, then it opposes.

Life cycle of a system:

As soon as a system is introduced, it grows slowly till it attains maturity.  As soon as it attains maturity, it starts declining.  At the time of decaying, if we revamp the system, it will survive.  Otherwise the original system will die and a new system will come into existence.  For example consider a new technology.  As soon as it is introduced, it is popularized.  After some time, this technology becomes out-modeled.  If a revamping is done at this stage, it will survive, otherwise it will die and a new technology will be in use.

System ratio (K)

Let     O   be the output of the system and

                I   be the input of the system

Then K= O/I  is called as system ratio.  Any system will receive input and send output.

Suppose       K = 1,

then   O/I = 1

i.e.       O = I. 

In this case, the system give output exactly what it receives.

Suppose       K < 1,

then   O/I < 1

i.e.       O < I. 

In this case, the output is less than the input.  The system is called as a normal system.

Suppose       K > 1,

then   O/I > 1

i.e.       O > I. 

In this case, the output is more than the input.  The system is called as an abnormal system.