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The increasingly lack of water resources
affects and restricts the potential development of modern society and will
become the main problem of the global water resources and environment in this
century 1.

The world population has doubled in the
past 60 years, a total of over six billion inhabitants with an increasing
demand for food and other consumer goods. This made the men should explore new
areas and to get a constant increase of productivity, food quality, reduction
of production costs and using in particular the irrigated agriculture
rationally.

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China is not only a country with shortage
water resources but also a big agricultural country with a large population. It
is also a big country for agricultural water uses 2, 3. At present the total
agricultural water utilization in china estimated about 60% of the total water
utilization in the whole country 4, 5. Water-saving agriculture is a high
degree of agricultural rational use of water. Water-saving agriculture should
be developed on the basis of water-saving technology 6, 7. Water-saving
agriculture technology is the basic work of developing Water-saving agriculture
8, 9. As an important part of Water-saving agricultural technology,
Water-saving irrigation technology was a variety of irrigation measures, such
as sprinkler irrigation, drip irrigation etc. To effectively utilize
precipitation and irrigation water according to the water demand law of crops
and the local water resources conditions 10

As a rule, pressurized irrigation
systems are composed of water lifting devices, piped networks, water delivery
devices, and pressure and water control devices. At times, because of the
topography, no water lifting devices are required and water gravitates into the
system. Irrespective of whether pumps are used or not, the water in the
irrigation system is always under pressure. The magnitude of pressure depends
on the requirements of a particular technology. Generally, localized irrigation
systems operate at lower pressure than sprinkler irrigation systems. It is
therefore necessary that during the preparation of the designs and bills of
quantity (Module 8 and 9) the pressure requirements of the system are clearly
stated and the equipment to meet these requirements is identified.

Drip irrigation is a type of micro-irrigation that
has the potential to save water and nutrients by allowing water to drip slowly
to the roots of
plants, either from above the soil surface or buried below the surface. The goal is to
place water directly into the root zone and
minimize evaporation. Drip irrigation systems distribute
water through a network of valves, pipes, tubing, and emitters.
Depending on how well designed, installed, maintained, and operated it is, a
drip irrigation system can be more efficient than other types of irrigation
systems, such as surface irrigation or sprinkler irrigation((Drip-Irrigation Systems)Overview of Drip Irrigation(reference)).

As an advanced
water-saving irrigation technology at present, drip irrigation technology has
attracted widespread attention both at home and abroad and has greatly promoted
16-21. Cause of It is not only has high water saving efficiency but also easy
to control the amount of irrigation and can realize irrigation precision. In
agricultural production the basic guarantee for maintaining normal growth of
crops is water and the key to achieving high yield is fertilizer. Therefore in
order to make crop yield high it is especially important to supplement the
nutrient and fertility of farmland soil.

One of the major advantages of pressurized irrigation
systems is the potential for the application of chemicals mostly water-soluble
fertilizers through the irrigation water. Numerous equipment has been developed
for this purpose including the fertilizer tank, the bladder tank, water-driven
injector pump and Venturi injector.

Venturi injectors fertilizer is one of the most
important parts of micro- irrigation system and are usually placed in the first
irrigation system for fertilization operations fertilization 1-2. Using
venturi injectors could not only achieve saving water fertilizer, time and
labor, but also can obtain high crop yield and good quality with the least
pollution. This method is very suitable for crop production with high and
easiness of accuracy control 3-4.

At present, the most commonly used
fertilizer plants in the world are self pressure fertilizer device, pressure
difference fertilizer applicator, proportional fertilization pump and venturi
fertilizer device. In the small-scale drip irrigation system, venturi
fertilizer applicator is one of the most common fertilization devices at home
and abroad in recent years due to the obvious advantages such as
simple structure design, cheap and robust system without mobile pieces,
convenient to operation, Low cost, stable performance and without an external
power 9-11.

However, there are still many deficiencies in
the practical application of Venturi fertilizer injector, such as greater
pressure loss, strict fertilizer absorption and poor concentration of
fertilizer absorption, which also bring inconvenience to many users.Research
Motivation

According
to the California Institute of Technology Irrigation Training Research Center
of the research and analysis, the use of drip fertilization under normal
circumstances can save 25% of fertilizer, saving labor and mechanical energy
consumption 5.

The
development of agriculture water-saving can’t be separate from advanced
equipments. In order to develop the benefit Water-saving irrigation technology,
United States, Australia and Israel are more developed countries and paying
attention to new products research and developments and constantly improve the
properties to introduce a new products and paying attention to the advancement
and matching of the Irrigation system at the same time.

Compare
china with other developed countries, still there was a big gap in the level of
modern irrigation technology. And one of the main problems is the backward
development of irrigation preparation research and the backward of production
technology. At present, China have main companies of drip irrigation equipment such
as Shaanxi Yangling Qinchuan water saving irrigation equipment company,
Xinjiang Tianye company, Gansu Da Yu Xinjiang Karez water-saving irrigation
equipment company, Hebei Longda water-saving irrigation equipment company,
Shandong Laiwu company, Beijing Luyuan company and a other few compan, the
specifications of irrigation products the produce in china are relatively less
than foreign countries products, matching level was low, besides quality of
products had not stability of foreigner products. And the, comprehensive
analysis showed that the qualified rate of water-saving irrigation products in
China was only about 60% 27.

There
were 4 main reasons of this situation

1)     
Companies with small production capacity, outdated
equipments and modest level of production technology.

2)     
Equipment key technologies were protected or secret by
patent of each country research and development capability of irrigation
componies was not seriously deficient and weak technical capacity.

3)     
The development of new products and new technologies
was not enough.

4)     
Quality inspection system and standard system was not
perfect (8, 9)2.

As
more and more technologically advanced foreign irrigation companies such as
(Israel, NATEFIM and MAZZEl INJETOR Companies and the United States
RAINBIRD and NELSON Companies etc.) China establishment of offices and
factories had a strong impacted on the domestic irrigation market. Therefore,
domestic manufacturers of irrigation equipment should follow the foreigner
technologies of the modern world and actively introduce, digest, absorb and
industrialize the water-saving irrigation equipment. The development of a new
generation of irrigation products and equipment suitable for China national
conditions was of great significance for narrowing the gap between China
irrigation technology and foreign countries and promoting the development of
water-saving irrigation in China. 28.

In this research, the concentration of Venturi fertilizer will
test to find out the good result and suitable control method by adjusting the
valves in three parts of Venturi injector (import, export and fertilizer
suction) under low pressure irrigation system.

Low pressure drip irrigation system doesn’t mean that the pressure
is absolutely low, but need to consider the ground topography and the
scientific value of working pressure when designing the system.

Using low-pressure drip irrigation technology can be used in gravity
irrigation or drip irrigation according to topography of the landform and especially suitable for mountain landform using
applicators without power supply. (????? ?????)

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