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Drought relation to agriculture/K-12

How does this relate to agriculture? 

Severe Drought Stress in Corn

Figure C: Severe Drought Stress in Corn
www.ent.iastate.edu/images/plantpath/corn/spidermite/corn_drought_stress.jpg

This example primarily focuses upon agricultural drought.  Drought stress affects the individual plant, as well as the whole crop canopy.  Drought stress on a plant can have irreversible damage upon a plant, even before symptoms can be seen (i.e. wilt).  Although drought tolerance varies among crop plants, most need adequate water throughout their lifecycle (from germination to harvest) in order to be high yielding.  There are many plant breeding programs now that are looking to develop crop plants that do not require as much water.  Other breeding programs are looking at developing plants that are salt tolerant in order to use reclaimed water (such as on golf courses).

Drought signs in a plant include decreased leaf area, leaf drop, root growth, stomatal close, yellowing leaves, wilt, and finally complete death.  It is interesting to note that plants undergo damage from water stress, even before the wilt signs are seen. 

Drought Stress in Tobacco

Figure D: Drought Stress in Tobacco
http://news.clas.virginia.edu/biology/images/tobacco_drought_stress.jpg

When a water deficit occurs, the plant’s first response is to limit leaf expansion (less water is lost through transpiration).  The size of each leaf might decrease, but also the number of leaves on each plant is decreased.  As the stress continues, the plant will respond by dropping its leaves.  In some arid places, a plant might go through this cycle three or four times in a season.  Below the soil, the plant is also growing longer and more dissected roots in order to seek out pockets of water, or deeper sources of water.  Continued water stress also forces the plant to close stomata on the leaves to decrease respiration, which in turn decreases the amount of photosynthesis that occurs in the plant (yellow leaves will appear).  As the plant continues to be stressed, leaves may wilt and droop (in broadleaves) or curl inward (in grasses such as corn).  This action minimizes the amount of leaf surfaces in contact with air and the sun.  If the plant continues to be water-stressed, it will finally turn brown and simply die.

Indeterminate Peanut Plant

Figure E: Indeterminate Peanut Plant
Kokalis-Burelle, N. et al. (eds) 1997 Compendium of Peanut Diseases. St. Paul, Minnesota: APS Pres

 

Some plants have more ability to develop drought tolerance than others. Plants also have the ability to take advantage of erratic water cycles if they are indeterminate in their fruiting pattern (i.e. peanuts and cotton).  This means that they can grow vegetatively, as well as reproductively at the same time.  Determinate crops such as corn have a very small window of opportunity to set corn ears, and if water is limited at that time, corn yield is severely reduced.

 

Some plants, like cacti are much better adapted to dry weather (arid conditions).  These plants are usually very efficient at using water, but may also have thick fleshy leaves that store water. This stored water allows the plant to survive in times of dry weather.  In fact, many who live in the Southwest areas of the US practice xeriscaping which uses drought tolerant plants as well as construction practices that capture any available rainfall.

 

North Carolina, along with many other Southern states, experienced one of the worst droughts in history during 2007 and 2008.  Many farmers had lower than average yields, and people saw the landscaping industry change in response to the lack of water.  It was not uncommon for farmers to completely deplete their water reservoirs that are used for irrigation.  Many landscaping companies resorted to using reclaimed water to irrigate residential and commercial landscapes.  Many homeowners were mandated to adhere to a restricted watering schedule, with severe fines from the city if not followed.  Some even resorted to drilling their own wells if they resided in the city to use for irrigation water.  A common sight in the landscape is now the rain barrel.  These are used to capture rainwater from roofs and gutters, and then used when needed to water the landscape or garden.

Last modified date: Friday, November 5, 2010 - 1:38pm