after successful completion of this lesson, you have learned to answer: 1.what characteristics of...

After successful completion of this Lesson, you have learned to answer:

1. What characteristics of sorghum contribute to its adaptation to dry conditions?

2. What is the amount of water required for good crop of sorghum?

3. List the important growth stages when soil moisture stress affects sorghum crop?

4. What practices help in conserving soil moisture in sorghum cultivation?

5. What will be the problemwith continuous rains during grain filling stage?

Virtual Academy for the Semi Arid Tropics

Lesson 1: Soil Moisture Relationships

Module X: Soil Moisture Relationships and Irrigation

Course on Sorghum ProductionPractices





The evolution of sorghum under the pressures of drought and high temperatures lead to the crop’s adjustment to drier climates.

Sorghum is grown in areas with average annual rainfall of 40 to 100 cm.

Sorghum is adapted to a wide range of environmental conditions but is particularly adapted to drought.





It has a number of morphological and physiological characteristics that contribute to its adaptation to dry conditions, like:

• extensive root system,

• waxy bloom on the leaves that reduces water loss, and

• the ability to stop growth in periods of drought and resume it again when conditions become favorable.





Sorghum roots are normally concentrated in the top 90 cm of soil but may extend to twice that depth, and to 1.5 m in lateral spread.

The stem is solid, usually erect. Its center can be dry or juicy, insipid or sweet to taste. The center of the stem can become pithy with spaces.

Leaves vary in number from 7–24, depending on the cultivar.





Sorghum is called water sipping crop as it uses water very efficiently.

Crop kg of water used for kg of dry matter

Sorghum 322

Maize 368

Wheat 514





Sorghum is a natural replacement for less water efficient crops; an example being when 500 mm or less of water is available during the growing season sorghum will be favored over maize for better production.

Sorghum is also tolerant to water logging and can be grown in high rainfall areas.





Water (soil moisture) is the most common limiting factor for better yields in sorghum production.

Sorghum crop need 450 to 650 mm of water over the season for a high-yielding crop.

This can come from either rain, irrigation or stored soil moisture.





However it is not the total amount of moisture that the crop receives that is most important.

Timing of rainfall or irrigation can have a dramatic effect on both crop yield and quality.





The critical growth stages of sorghum in relation to water requirement are:

• Initiation of grand growth stage 20-25 DAS

• Flag-leaf stage or boot stage 50-55 DAS

• Flowering stage 70-75 DAS

• Grain-filling stage 90-100 DAS

(DAS: Days after sowing)





The water absorbed by sorghum during the first month after sowing is relatively small.

Hence the very early growth phase after seedling emergence is not highly sensitive to moisture stress.

The period of 40 to 85 days after sowing when flowering and grain formation stages are very sensitive to moisture stress.





Source: http://sanangelo.tamu.edu/agronomy/sorghum/gsprod.htm#seed

http://sanangelo.tamu.edu/agronomy/sorghum/gsprod.htm#seed





Very often rainfed sorghum crop experiences soil moisture stress when rains fail during the monsoon season.

Practices like contour cultivation in a sloping field, soil mulching, intercultivation, and good weed control help in soil moisture conservation to face failure of rains during the crop growth.

Spraying 2% urea at the times of soil moisture stress experienced by crop also helps to overcome moisture stress.





Continuous rains with cloudy weather leading to high humidity during grain filling and hardening stages can result in sprouted, moldy, low-quality grain (Fig.) as well as excessive losses due to stalk lodging, grain shattering, and bird feeding.

Grain mold and sprouting on

sorghum





In areas with such weather conditions, the grain quality deterioration can be overcome by growing mold resistant varieties like PVK 801.

Grain mold resistant variety

With this, the Lesson 1 on soil moisture relationships in sorghum cultivation concludes.

The next Lesson in this Module, is about irrigation practices in sorghum cultivation.

Select Lesson 2 from Module X contents

Virtual Academy for the Semi Arid TropicsModule X: Soil Moisture Relationships and Irrigation


after successful completion of this lesson, you have learned to answer: 1.what characteristics of...

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