IMPORTANCE OF RAINFALL AT THE RIGHT TIME 



Water Requirements of Some Crops 



91 



* Average of four weeds purslane, pigweed, lamb's quarter and ragweed. 



Soil Gives up More Water Than That Transpired. The figures 

 in the table indicate only the amount of water that passes through 

 the plant. In addition to this there is about one-fifth this amount 

 of water lost by evaporation from the soil under conditions of 

 good soil management. 1 



Factors Influencing Water Requirement of Plants. The 

 factors which influence the water requirement of crops are: 



(a) The weather. If the air is hot and dry much more water 

 is required than when the air is cool and moist. Wind and much 

 sunshine also increase the amount of water transpired (last 

 column in table). 



(b) The water supply in the soil. When the soil contains a 

 large supply of available water, plants are more lavish with it 

 than when there is a low supply or when the soil gives up its 

 moisture more slowly, as in a clay loam or silt loam. 



(c) Richness of the soil. When other conditions are the same, 

 a plant requires about one-half the amount of water when grown 

 on a rich soil than when grown on a poor one. 



(d) Manure and fertilizer treatments. The use of manure or 

 commercial fertilizers on poor soils not only increases the yield 

 but may decrease the water requirement of plants from thirty to 

 fifty per cent. 



Importance of Rainfall at the Right Time. If the rainfall came 

 at the right time and were evenly distributed in sufficient amounts, 

 wonderful results would be obtained. The size of the hay crop 

 .is largely determined by the character and amount of the rainfall 



1 King's Soil Management. 



