But i mean surface irrigation

You may schedule irrigation by record keeping or measuring moisture level and rainfall in the field. In this method, you can have a water balance to the root zone of the crop. The inputs (irrigation, rainfall, an other inputs such as runoff etc.) can be added to the water level in the root zone and losses (such as deep percolation, runoff away from field, evapotranspiration, seepage etc.) can be deducted from the root zone water level. You can do this on daily basis and once you reach a predetermined water level in the root zone (management allowed deficit), you irrigate.

If you have moisture measuring devices (such as neutron probes etc.) installed in the field (root zone), you may irrigate it the soil moisture level reaches the predetermined moisture level.

You may also utilize CROPWAT to schedule irrigation in the field.

Everything Najim says is true. The irrigation management for a given farm will be farm specific. The use of limited irrigation water also depends on the relative value of the crops and the phases when the crops are most damaged by water shortages.

Hi.,

I think each method of irrigation which design and manage well the results will be satisfied. we should evaluate the field condition well.

The correct design of surface irrigation is very important, the knowlege of surface irrigation hydraulic is the fist step which means u should select the inflow discharge, irrigation time, water velocity, water advance to the end of the field,... according to the field condition.

You could manage the surface irrigation by correct selection of new method of surface irrigation: such as runoff recovery system:

because in surface irrigation, water is usually lost by runoff this method could reduce water losses effectively.

u could use surge irrigation or change the inflow hydrograph shape that i used and i think this way is more effective.

If u explain your field condition, i could help u better.

a question. irrigation interval is constant or on your request, in other words, I think you can not access to water any time?

There is no specific tool suitable for surface irrigation management. Some tools can be useful. Tool must link varying soil and climatic conditions, fluctuated water availability, management decisions and agricultural management practices as well as Irrigation principles discussed above by others

Surface irrigation management is a difficult task, especially under limited water availability. In the case of very arid conditions it is very important to keep in mind that there are physical limits to sustainable irrigation. Over-use of water resources and salinisation problems due to unsustainable irrigation are tremendous problems, as - most drastically - shown in the Aral Sea disaster.

Important for scheduling is - as mentioned above - the knowledge about the soil moisture at the start of irrigation. Best is measurement, however, climatic water balance modeling is often more applicable to large scale irrigation projects. The recommendable irrigation amount is the difference between the actual water content in the root zone and field capacity. Added to this, there is the leaching fraction if water with a high salt content is used.

The "Aquacrop" model, which is provided by FAO (http://www.fao.org/nr/water/aquacrop.html) can be used to calculate the water requirement based in a climatic water balance (Penman-Monteith) and schedule different irrigation events on plot scale. Depending on your available soil data the model can well predict water use by the plants and water storage in the soil. Plant response to drought stress can also be modeled. This model can be operated with a limited data set, but if good soil and climate data is available, it can be parametrized up to a high level of exactness.

(For very basic calculations you can use Cropwat (http://www.fao.org/nr/water/infores_databases_cropwat.html))

Starting from a water requirement calculation by Aquacrop you can build up your irrigation scheduling, considering that not only the amount of water applied to a certain irrigation district must be the sum of the calculated water requirement for the respective area (divided by the delivery and irrigation system efficiency), but also the flow in the main canal must be equivalent to the cumulative intake rate of all irrigated fields during the time of irrigation.

Apart from appropriate scheduling there are - of course - a lot of measures which help to increase water use efficiency. The re-use of blended drainage water was already mentioned. But also measures to reduce evaporation losses should be considered: Mulching, minimum tillage, shading (e.g. by trees), wind breaks, irrigation by night. And finally there is the option of deficit irrigation. Of course, there is unlimited literature about DI, but those articles may provide the best overview:

S. Geerts, D. Raes (2009) Deficit irrigation as an on-farm strategy to maximize crop water productivity in dry areas. Agricultural Water Management 96: 1275-1284

S. Geerts, D. Raes, M. Garcia (2010) Using AquaCrop to derive deficit irrigation schedules. Agricultural Water Management 98: 213-216

Surface irrigation is more complex. Tool which can ensure equitable sharing of available water resources for irrigation supply would be recommended.......... You may need to modify and adapt with your particular system.............ultimate goal is to efficient water use in crop production.Your system approach is very crucial for selecting/developing tool.

This is an interesting question. The answer depends on many aspects as stated in all the above comments. The main questions are: whether we are scheduling for a farmer in a remote village or for a farm with all the modern tools? I presume the later.

If you are part of a large irrigation system where the schedule is centrally decided, then the individuals have no choice than selecting their crop accordingly (eg. a drought tolerant crop with high return).

On the other hand, if you have a water source of your own, I would still suggest you to go by "irrigation interval" as it is the only "language" that the farmer understand. But, you may have to suggest a crop in consultation with the farmer (famer is also a researcher who can give us input and feedback).

Crop response to water shortage is the key to decision making on your part.

Dear colleagues, We have tried some approaches in irrigation systems of Central Asia, below publication describes how it designed and how it worked.

Article Handbook on implementing a time-based water distribution: fo...

Hi Noha

I would like to start with the question you asked but from my side: What tools/equipment you have?

Then: what is your weather like?

Then: What is the soil type?

Then: what is the crop you want to irrigate?

Then: How much water it needs?

Then: How much water you have?

Then: What is the evaporation in your area?

Then: you need the irrigation all year around or just for limited time?

Then: what is the weather characteristics in the area in subject?

Then: do you have skilled manpower for irrigation purpose?

Then: How do you irrigate this area currently?

Last: If you have money to invest or you want to use the current system, but to improve its performance?

After having answers to these questions we can think, all of us, how to help you. Otherwise any suggestion is like to fit shoes to a fatherless child, as if you analize the answers that you already have, you come nowhere as all of them are the right ones, but there is no relations between them so they can't be usefull.

Awaiting yourreply

In friendship

Amir

Hi Noha and everybody who participated in this discussion

I agree with everything said above.

But I am not sure what do you mean by Surface Rotational Irrigation! Do you mean a kind of flood irrigation or irrigation devices that rotates while irrigating?

I assume you meant a conventional flood irrigation.

If you are familiar with all irrigation scheduling calculations, then it is easy. You just need to pick the technique that is handy for you.

Crop water requirement, evaporation from free water surface, irrigation efficiency, water discharge and availability and soil physical properties information are needed to start irrigation scheduling.

For limited water, you better go with small basins or short furrow instead of long strips or furrow to reduce deep water percolation outside root zone.

As said above, you should be able to know the moisture content of the soil at the time of irrigation so you know precisely how much water to add to bring soil moisture to the field capacity or to the preset level.

Water balance techniques or evapotranspiration equations methods depend on assumptions and approximation which lead to errors that accumulate with time to become a big error unless you keep resetting your irrigation scheduling from time to time.

Some people use tensiometers for scheduling irrigation. Tensiometers are devices that used to measure water tension in the soil. In irrigation scheduling, Tensionmeters are used to determine soil water tension, which implementing crop water stress. It is easy to apply by farmers especially those who are not comfortable with calculations, but not precise enough which may not be suitable for an arid area where water is limited. In this method, tensiometers are installed in specific points in the filed at different depth in the root zone (usually two depths). Then get it ready to work and read tension. After irrigation, tensiometers should read close to ZERO since moisture content at field capacity or higher. As crop uses soil water, tension goes higher and that is read by tensiometers. Depends on the crop, once the tension reaches a specific value, the irrigation should start. For most crops, 25-30 cBar is the tension when field needs to be irrigated. Some drought tolerence crops can stand higher tension.

Personally, I used this method and did some calibration to tensiometers with the soil, so we were able to calculate needed water at any tension reading.

Also, I used sensors for irrigation scheduling. In this technique, soil moisture sensor are used to measure soil moisture content at the time of irrigation and then needed water is calculated using soil physical properties. There are several soil moisture sensors available in the market such as TDR, TDT, Theta probe, neotron probe, resistance sensors, gypsum blocks and many others. I found that TDT (Time Domain Transmittivity) devices are precise, rigid, easy to use and fast response as well as they measure volumetric soil moisture content directly.

Finally, I am a FAN of sensor based irrigation scheduling. This technique depends on the exact soil moisture content of the soil at the time of irrigation and then with the physical characteristics of soil, needed water depth that brings soil moisture to field capacity can be calculated. In this method, errors can not be accumulated.

Also, in this method of irrigation scheduling, farmer can determine irrigation time but irrigation amount can vary from time to time depends on soil moisture content.

http://physio-geo.revues.org/2632