Irrig a t io n Sch e d u lin g a n d Mo n it o rin g Te ch n o lo g ie s

M O D U L E 4

The purpose of this module is to describe t h e e le m e n t s o f irrig a t io n sc h e d u lin g ,a n sw e rin g w h e n a n d h o w m u c h to irrig a t e .

Th e se q u e st io n s a re a n sw e re d in t h e c o n te xt o f m o n ito rin g d e vic e s a n d t e c h n o lo g ic a l syst e m s w h ic h c a n b e le ve ra g e d to g ive g re a t e r in sig h t in to t h e sig n ific a n t fa c to rs w h ic h in flu e n c e th e n e e dto irrig a t e ye t u t ilize w a te r e ffic ie n t ly.

Go a l

Describe irrigation scheduling and its benefits.Le a rn in g Ob je c t ive s

List a n d d e sc rib e t h e fa c to rs w h ic h a ffe c t irrig a t ion sch e d u lin g .

Un d e rst a n d d iffe re n t m e th o d s o f d e t e rm in in g th e m o istu re st a tu s o f so ils a n d h o w th e y h e lp a n sw e r t h e q u e st io n s o f w h e n a n d h o w to irrig a t e .

Id e n t ify m o n ito rin g d e vic e s a n d syst e m s fo r d e c isio n su p p o rt .

List th e st e p s in d e sig n in g a n irrig a t ion sch e d u le .

• Irrigation scheduling is the process of determining the frequency and constancy of applying controlled amounts of water to crops.

• It considers the crop and the amount of water the crop uses via the process of evapotranspiration.

Irrig a t io n Sch e d u lin g

Be n e fit s o f ir r ig a t io n s c h e d u lin g in c lu d e :

• It optimizes crop yields.

• Ensures best management of water resources.

• Significantly decreases soil and nutrient loss due to excessive runoff or leaching.

• Helps maintain soil health (aeration, structure, flora and fauna).

Irrig a t io nSch e d u lin g

So il Typ e : Texture and Structure affects w ate r h old in g cap acity an d in te rn a l flow

Cro p Typ e : Crop p h ysio log ica l an dm orp h olog ica l ch a rac te rist ics a ssocia te d w ith WUE

Clim a t ic Fa c t o rs : ETc

La n d Ma n a g e m e n t : Cu lt iva t ion p rac t ice s su ch a s t illag e

Fa c t o rs Affe c t in g Irrig a t io n Sch e d u lin g

Effective scheduling can be achieved by m on itorin g h ow m u ch w a te r th e crop h a s u se d , th e so il m oistu re sta tu s, an d b y crop g row th an d d e ve lop m e n t . Th e fo llow in g th re e m e th od s a re fu rth e r d e scrib e d b e low :

• Clim a te -b ase d Sch e d u lin g (Evap otran sp ira t ion (ET) sch e d u lin g )

• Soil Moistu re Con te n t

• Plan t-b a se d Irrig a t ion Sch e d u lin g

Effe c t ive Sch e d u lin g

The water balance equation is used to account for all the incoming and outgoingw ate r from th e so il root zon e . Th e “id e a l irrig a t ion d e p th ” can b e d e te rm in e du sin g th is m e th od , Eq u a t ion 1:

Dc – Dp = ETc – P– I + R + DP ………………………………………………….…………………………….................. Eq u a t ion 1

Wh e re

• Dc = so il w a te r d e fic it• Dp = so il w a te r d e fic it (p re viou s d ay)• ETc = crop e vap otran sp ira t ion• P = p re c ip ita t ion• DP = d e e p p e rcola t ion• R = ru n off• I = irrig a t ion

Clim a t e -Ba se d Sch e d u lin g

• Irrigation scheduling software allows them to leverage data and computing power to improve WUE.

• Such software mainly contains pre -programmed settings for crops which only requires farmers to plug in data, such as the crop they are irrigating and location amongst other things.

• CROPWAT is a decision support tool developed by the Land and Water Development Division of FAO. CROPWAT 8.0 for Windows is a computer program for the calculation of crop water requirements and irrigation requirements based on soil, climate and crop data.

http://www.fao.org/land -water/databases -and -software/cropwat/en/.

Irrig a t io n Sch e d u lin g So ft w a re

• Soil-based methods of irrigation, use sensors to analyze soil moisture content and/ or potential to determine when and how much to irrigate.

• The amount as well as the availability of the water can be determined both spatially and temporally, enabling real time management of irrigation and significantly reducing water wastage, leading to improved efficiency.

• “Barrel” vs “Maintenance” approaches.

So il-Ba se d Sch e d u lin g

Tensiometers offers a more responsivesolu t ion to c rop w a te r d e m an d an d re la t ion sh ip to yie ld , a s th e y m e asu re so ilw a te r p ote n t ia l (ava ilab ility to p lan t roots).

Te n siom e te rs a re fie ld d e vice s n ow w ithcon n e ct ivity p ote n t ia l an d d a ta log g in g cap ab ility th a t can b e u se d to con tro lau tom a te d irrig a t ion syste m s su ch a s in g re e n h ou se s.

Te n siom e te rs a re lim ite d in th em e asu re m e n t ran g e on ly b e in g ab le to m e asu re b e tw e e n 0 to 80 ce n t ib a rs n orm a llyan d 60 ce n t ib a rs ove r e le va t ion s of 30 0 0 ft .

Te n s io m e t e rs

• Gypsum and granular matrix blocks are electrical resistance -based sensors made of gypsum and other material.

• A modified ohmmeter is used to read the resistance in the block on a numerical scale, which generally reads from 0 to 100.

• A calibration is required specific to each soil, for interpreting water content from resistance readings.

Re s is t a n ce De vice s -Gyp su m a n d Gra n u la r Ma t rix Blo cks (GMB)

• The most common electromagnetic sensors which can measure dielectric constant are capacitance sensors/frequency domain reflectometry (FDR) sensor and time domain reflectometry (TDR) sensors.

• The sensors indirectly measure volumetric water content based on the dielectric and electric properties of the soil medium (soil bulk permittivity or soil dielectric constant).

• The units can be used as mobile or permanently installed systems and offer rapid results to improve the decision -making aspect of irrigators.

TDR Se n so rs a n d Pro b e s

• Le a f w a t e r p o t e n t ia l (LW P ): is the negative pressure or tension found in the plant leaves. To measure this pressure or tension, a pressure chamber is employed.

• Canopy temperature: this can be measured using infrared thermometer sensors that measure the temperature of the plant canopy.

Pla n t -Ba se d Sch e d u lin g

Source: https://ictinternational.com/

Irrigation scheduling significantly improves WUE.Le sso n s Le a rn t

Irrig a t io n sc h e d u lin g is in flu e n c e d b y so il t yp e , c ro p typ e , c lim a t ic fa c to rs a n d la n d m a n a g e m e n t .

Th e “id e a l irrig a t io n d e p th ” c a n b e c a lc u la t e d u sin g : Dc – Dp = ETc – P – I + R + DP

Irrig a t io n sc h e d u lin g c a n b e b a se d o n so il, c lim a te o r p la n t -b a se d a p p ro a c h e s. Ho w e ve r, t h e se a p p ro a c h e s a re e it h e r re fle c t ive o f w a te r c o n te n t o r p o t e n t ia l.

Mo d e rn se n so rs a n d re a l t im e w a te r re la t io n s m o n ito rin g h a s p o sit ive ly im p a c te d irrig a t io n sc h e d u lin g , im p ro vin g WUE.