Water Requirement of crops

Topics

1)      Introduction

2)      Important definitions

3)      Duty, Delta & base period relationship

4)      Crop seasons and  Indian Agriculture

5)      Irrigation Efficiencies

Introduction

• Every crop requires a certain quantity of water after a certain fixed interval thought its period of growth. हर फसल को निश्चित अवधि के बाद पानी की एक निश्चित मात्रा की आवश्यकता होती है।
• In a tropical country like India, the natural rainfall is either insufficient, or the water does not fall regularly. भारत जैसे उष्णकटिबंधीय देश में, प्राकृतिक वर्षा या तो अपर्याप्त है, या पानी नियमित रूप से नहीं गिरता है।
• The area where irrigation is must for agriculture is called Arid region. जिस क्षेत्र में कृषि के लिए सिंचाई होनी चाहिए वह शुष्क क्षेत्र कहलाता है।
• The area in which inferior crops can be grown without irrigation is called semi-arid region.
  जिस क्षेत्र में सिंचाई के बिना निम्न स्तरीय फसलों को उगाया जा सकता है उसे अर्ध-शुष्क क्षेत्र कहा जाता है।
• The term ‘water requirements of a crop’ means the total quantity and way in which a crop requires water, from the time it is shown to the time it is harvested.
  'फसल की पानी की आवश्यकता' शब्द का अर्थ कुल मात्रा और जिस तरह से एक फसल को पानी की आवश्यकता होती है, फसल की बुवाई से लेकर फसल कटाई तक.
• Water requirement, will vary with the crop as well as with place.
  पानी की आवश्यकता, फसल के साथ-साथ जगह के साथ अलग-अलग होगी।

Certain Important Definitions

(1)    Crop Period - The time period that elapses from the instant of its sowing to the instant of its harvesting is called crop period. फसल बुवाई के तुरंत बाद से फसल कटाई के समय तक समय अवधि को फसल अवधि कहा जाता है।

(2) BASE Period –The time between first watering of a crop at the time of its sowing to its last watering before harvesting is called Base period of the crop.
फसल की पहली बुवाई के समय इसकी कटाई से पहले इसकी आखिरी पानी की कटाई के बीच के समय को फसल का आधार काल कहा जाता है।

NOTE-  Crop period is slightly more than base period, but for practical purposes, they are taken same , generally expressed in days and represented by B. 

फसल अवधि आधार अवधि की तुलना में थोड़ा अधिक है, लेकिन व्यावहारिक उद्देश्यों के लिए, उन्हें समान लिया जाता है, आमतौर पर दिनों में व्यक्त किया जाता है और B द्वारा दर्शाया जाता है।

(3) Frequency of irrigation/Rotation period – The time interval between two consecutive watering. सिंचाई की आवृत्ति दो लगातार पानी के बीच का समय अंतराल
कहा जाता है।

• Rotation period is inversely proportional to climatic temperature.

(4) Kor-Watering - The first watering which is given to a crop, when the crop is a few centimeters high is called kor-watering. पहला पानी  जो एक फसल को दिया जाता है, जब फसल कुछ सेंटीमीटर ऊँची होती है उसे कोर-वाटरिंग कहा जाता है।

• Depth of water applied is max.
• Ex. Rice – 19 cm , Wheat – 13.5 cm, Sugarcane – 16.5 cm.

(5) Paleo Irrigation- In the initial stages before the crop is sown, the soil is moistened with water, so as to help in sowing of crops is known as Paleo irrigation.
फसल बोने से पहले शुरुआती चरणों में, मिट्टी को पानी से सिक्त किया जाता है, इसलिए फसलों की बुवाई में मदद करने के लिए पैलियो सिंचाई के रूप में जाना जाता है।

(6)    Crop Ratio – The ratio of proposed areas, to be irrigated in Kharif season to that of Rabi season is called crop ratio/ Kharif – Rabi ratio. खरीफ मौसम तथा रबी मौसम के अनुसार सिंचित होने वाले क्षेत्रों के अनुपात को फसल अनुपात / खरीफ - रबी अनुपात कहा जाता है।

Note- This ratio is generally 1:2 i.e. Kharif area is one-half that of Rabi area.

(7) Delta (∆) – It is the total depth of water required  during its base period for full growth of crop.

(8) Duty (D)– Duty of water is defined as the number of hectares of land irrigated for full growth of a given crop by supply of 1 m³/sec of  water continuously during the entire base period (B) of that crop.
पानी की ड्यूटी को उस फसल की संपूर्ण आधार अवधि (B) के दौरान लगातार 1 m3 /sec पानी की आपूर्ति द्वारा दी गई फसल की पूर्ण वृद्धि के लिए सिंचित भूमि की हेक्टेयर की संख्या के रूप में परिभाषित किया गया है।

Unit of Duty – hectare/ cumec

Relation between Duty, Delta & Base period

                Let there be a crop of base period B days . Let 1 cumec of water be applied to this crop on the field for B days.

                So, volume of water applied during B days

                                                V = discharge x time = (1 x B x 60 x 60 x 24) m³

                                                V = 86,400 B  (m³)

                By the definition of duty (D), one cubic meter supplied for B days matures D hectare of land.

                B total depth of water applied on this land = Volume / Area

                                                                         D = A/ Q                      [ Q = 1 cumec]

                                                                         A = D hectare

                                                                       ∆ = 86,400 x B/ 10⁴ D

                                                                       ∆ = 8.64 B/D (meters)

                                                                                                       ∆ = 864 B/D   ( cm.)

                Where B in days and D is in hectare/ cumec

Different types of Duty

1)      Flow duty    -  at the head of flowing channel 

2)       Storage Duty  - at the head of storage channel

3)       Lift Duty – At the head of lifting channel

Flow Duty

• Duty at the head of flowing channel is known as flow duty.
•  Types of flow duty

• Duty at head of field is called Net Quantity (N.Q) – at sec.4
• Duty at head of water- course is called Outlet Factor (O.F) – at sec 3
• Duty at the head of distributaries/ laterals is called Lateral Quantity (L.Q) – at sec 2
• Duty at head of main canal is called as Gross Quantity (G.Q) – at sec 1

Duty at various places –

• In irrigation system , the water from its source, first of all flows into the main canal ; from main canal it flows into branch canal; from branch canal it flows into distributary ; from the distributary it flows into minor; and then into field channel and finally into the field. सिंचाई प्रणाली में, अपने स्रोत से पानी, सबसे पहले मुख्य नहर में बहता है; मुख्य नहर से यह शाखा नहर में बहती है; शाखा नहर से यह वितरण में बहती है; वितरण से यह छोटे चैनल में बह जाता है; और फिर फील्ड चैनल में और अंत में फील्ड में।
• During passage of water from these irrigation channels, water is lost which are called conveyance losses.
• Duty of water increases as one moves downstream from the head of main canal towards the head of branches  or water courses. पानी की ड्यूटी बढ़ जाती है जब पानी मुख्य नहर से नीचे की ओर बढ़ता है।’
• Note - Duty N.Q>O.F>L.Q>G.Q

Crop Seasons & Indian Agriculture

•  More Than 70% of Indian Population is directly or indirectly connected with agriculture.
• Avg. rainfall in India is about 125 cm.
• From the agriculture point of view, the year is divided into three principal cropping seasons.

(1)    Rabi season –

• This season starts from 1^st October and ends on 31^st March.
• Crops of this season is known as ‘winter crops’.
• Ex. – wheat, barley, gram , linseed, mustered, potato, etc./ गेहूं, जौ, चना, अलसी, सरसों, आलू, आदि।

(2)  Kharif season –

• This season starts from 1^st April and ends on 30^th September.
• Crops of this season is known as ‘summer crops’.
• Ex. – rice, bajra, jowar, maize, cotton, tobacco, groundnut etc./ चावल, बाजरा, ज्वार, मक्का, कपास, तंबाकू, मूंगफली आदि।

(3)  Zaid season –

• Short season between kharif and Rabi crops in month of March to July is known as Zaid.
• Ex. – Seasonal vegetables and fruits etc.

Special type of crop

• Perennial Crops – The crops which require more than one season for their growth
• Ex – Sugarcane, strawberry etc.

               

Important terms-

1)      Gross command area/ सकल कमांड क्षेत्र ( GCA) –

• The total area of land irrigated by a canal if there is unlimited supply of water is available. यदि पानी की असीमित आपूर्ति हो तो नहर द्वारा सिंचित भूमि का कुल क्षेत्र उपलब्ध है।
• It is total Cultivable and non- cultivable area covered by a canal. यह कुल कृषि योग्य और गैर कृषि योग्य क्षेत्र है जो नहर द्वारा कवर किया जाता है ।

2)      Cultivable command area / खेती योग्य कमांड क्षेत्र (CCA) –

• It is the part of GCA on which cultivation is possible.
  यह सकल कमांड क्षेत्र का वह हिस्सा है जिस पर खेती संभव है।
• CCA = GCA – uncultivable areas

3)      Intensity of irrigation ( IOI) –

• It is that part of CCA on which irrigation is done in given period of time. यह खेती योग्य कमांड क्षेत्र का वह हिस्सा है जिस पर सालाना सिंचाई की जाती है।

4)      Total Intensity of irrigation –

• It the intensity of irrigation for whole year
• IOI of rabi season + IOI of kharif season

5)  Optimum water depth –

•  It is the maximum quantity of water for any crop at which crop yield is maximum.
  यह किसी भी फसल के लिए पानी की अधिकतम मात्रा है जिस पर फसल की पैदावार अधिकतम होती है।
• Crop yield increases with water, reaches a certain maximum value and then falls down.

6)  Warabandi System/ वारबंदी सिस्टम -

• It is a rotational water allocation system in which can fulfill the requirement of equality. यह एक घूर्णी जल आवंटन प्रणाली है जिसमें समानता की आवश्यकता को पूरा किया जा सकता है।

7)  Capacity Factor -

• It  is the ratio of actual  discharge  in canal to design discharge of canal. यह नहर के डिस्चार्ज को डिजाइन करने के लिए नहर में वास्तविक निर्वहन का अनुपात है।

Irrigation Efficiencies

• Efficiency is the ratio of the water output to the water input, is usually expressed as percentage.
• Efficiency is inversely proportional to the losses.
• Different Irrigation efficiencies are -

1. Water Conveyance Efficiency
2. Water Application Efficiency
3. Efficiency of water use
4. Water Storage Efficiency
5. Water Distribution Efficiency

I) Water Conveyance Efficiencies / जल संवहन क्षमता (η_c )

• It is the ratio of  the water delivered  into the fields to the water entering into the channel at its starting point. यह अपने आरंभिक बिंदु पर चैनल में प्रवेश करने वाले पानी में खेतों में वितरित पानी का अनुपात है
• It takes conveyance losses into consideration.                                                                                       

II) Water Application  Efficiencies/ जल अनुप्रयोग दक्षता (η_a )

• It is the ratio of the water stored into the root zone of crops to the water delivered into the field. यह फसलों के जड़ क्षेत्र में जमा पानी का अनुपात है जो पानी को खेत में पहुंचाता है।
• Also called farm efficiency,
•  It takes into consideration the water lost in the farm. 

III Efficiency of water use / पानी के उपयोग की क्षमता (η_u )

• It is the ratio of the water beneficially used by plant to the water delivered into the field. यह पौधे द्वारा पानी के लिए इस्तेमाल किए गए पानी का अनुपात है जो खेत में पहुँचाया जाता है।

IV) Water Storage Efficiency/ जल संग्रहण क्षमता(η_s)

• It is the ratio of the water stored in the root zone during irrigation to the water needed in to the root zone prior to irrigation. यह सिंचाई से पहले रूट ज़ोन के लिए आवश्यक पानी को सिंचाई के दौरान रूट ज़ोन में संग्रहीत पानी का अनुपात है।

IV) Water Distribution Efficiency/ जल वितरण क्षमता(η_d)

• This efficiency represents the extent to which the water has penetrated to a uniform depth, thought the field. यह क्षेत्र में क्षेत्र के माध्यम से जड़ क्षेत्र में समान रूप से पानी के प्रवेश की डिग्री का मूल्यांकन करता है।

    Important questions       

                                                

Q01  The base period of paddy is 120 days. If the duty for this crop is 900 hectare per cumec, the delta of paddy is.

a)      1.15 cm                                 

b)      11.5 cm

c)       115 cm

d)      None

Q02 If delta of wheat is 36 cm and its base period is 140 days then the outlet factor at the head of field is?

a)      3.360 ha/cumec

b)      33.6 ha/cumec

c)       336 ha/cumec

d)      3360 ha/cumec

Q03 Transplantation of rice requires 10 days and total depth of water required during transplantation is 48 cm. During transplantation there is an effective rainfall of 8 cm. The duty of irrigation water in hectare/cumecs is?

a)      612

b)      216

c)       300

d)      108

 Q04 A canal was designed to supply the irrigation needs of 1200 hectares of land growing rice of 140     days base period having a delta of 134 cm. If this canal water is used to irrigate wheat of base period 120 days having a delta of 52 cm, the area in hectares that can be irrigated is?

a)      543

b)      850

c)       2650

d)      3608

Q05 The culturable command area for a distributary is 400 hectares out of which 40% is culturable, if intensity of  winter crop is 60% , then area under crop is?

a)      240 hectares

b)      160 hectares

c)       136 hectares

d)      96 hectares

Q06 The culturable command area for a distributary is 20,000 hectares. Wheat is grown in the entire area and the intensity of irrigation is 50%. The kor period for wheat is 30 days and kor depth is 120 mm. The outlet discharge for distributary should be in cumecs?

a)      2.85

b)      3.21

c)       4.63

d)      5.23

Q07 In an irrigation project, in a certain year , 70% and 46% of the culturable command area in kharif and Rabi, respectively, remained without water and rest of the area got irrigation water. The intensity of irrigation in that year for project was?

a)      30%

b)      54%

c)       84%

d)      116%

Q08 The gross command area for a distributary is 5000 hectares, 80% of which is culturable. The intensity of irrigation for Rabi is 50% and for Kharif is 30%. The average duty at the head of the distributary for Rabi season is 2000 hectares/cumec and that of Kharif season is 900 hectare/cumec. The discharge ( in cumec )required at the head of distributary is?

a)      1

b)      1.33

c)       2.33

d)      3.33

Q09 One cumec of water is pupmed into a farm distributio system. 0.8 cumec is delivered to from outlet 1 km from well. Conveyance efficiency of irrigation is?

a)      70%

b)      80%

c)       85%

d)      90%

Q10 A field measures 40 hectares. When 8 cumecs of water was supplied for 6 hours, 30 cm of depth was stored in the root zone. The field app;ication efficiency is nearly?

a)      70%

b)      80%

c)       85%

d)      90%

Q11 One cumec of water is pupmed into a farm distributio system. 0.8 cumec is delivered to from outlet 1 km from well. The depth of water penetration varied linearly from 1.7 m at the head end of field and 1.1 m at the tail end. The water distribution efficiency of irrigation is?

a)      58%

b)      68%

c)       78%

d)      88%