4i- 



'a^GHARD IRRIGATICN 



Soms interesting points on this subject vrere brought out by Dr, J. R. Magness 

 at the WQk meeting in Azaherst, July ll;, He first pointed out the favorable situa« 

 tion^ in New England where the distribution of rainfall is about as uniform as in any 

 section of the country* In general, we get about the same amount of rainfall each 

 month during the growing season, and statistics show that serious droughts are less 

 frequent here than any\There else in the country* On our better soils we seem to re- 

 quire irrigation less than in any other fruit producing section. 



Fruit trees tend to root deeply and thus have access to moisture at levels not 

 penetrated by shallov/er rooted crops* A silt Icam holds about 20^ of its weip;ht of 

 vrater. Roughly half of this water is available for plant use. This iceans about 10 

 lbs« per cu. ft« of soil or the equivalent of about 1-3A aore»inGhes for each foot 

 of soil. Thus on a good soil, approximately 7 inches of vrater is stored in the soil 

 penetrated by the roots, and is available for plant use. In a sandy soil, not as 

 much T/ater is stored, A coarse sand yroULd held no more than $ or 6% of its weisht 

 of water, or about 1/2 inch per foot of depth, while a clay soil holds up to 2 inches 

 of water. Thus the texture of the soil and the depth of rooting are important fac- 

 tors to be considered in deciding whether or not irrigation will be a profitable in- 

 vestment. The depth to which the root system of a fruit tree develops is closely 

 correlated with its ability to withstand a drought. In some soils the major portion 

 of the root system is found vrithin tv;o feet of the surface. 



It is interesting to note that the rate of grovrth of apples, peaches, etc. is 

 affected by the water supply. Growth is retarded when insufficient v/ater is avail- 

 able. i;fhen the water supply is replenished, gro\7th is resumed at the previous rate 

 but the fruit never attains the size it would have reached if no shortage had occur- 

 ed. Hence the average size of fruits in an orchard affected by drought conditions 

 is lower than that in a normal orchard. 



Peaches grow most rapidly during the last 30 to kO days of the grovdng season. 

 If a shortage of vfater occurs during this period there is much reduction in size of 

 the individual fruits, I'Vith apples, a shortage of vrater for 10 days nay mean a lOjb 

 reduction in size, ,«'ith peaches, a similar stiortage during the latter part of the 

 season would have a greater effect. 



Mulching has au influence on the water supply in various vrays. It aids in the 

 penetration of rainfall and reduces tlie amount of evaporation. In the Shenandoah 

 area the apples in orchards on soils two feet deep -vdll be reduced by 10,S', on the 

 average, every other year, .ihere the soil is three feet or more in depth, this oc- 

 curs only one year in four. And where the soil is four or five feet deep an invest- 

 ment in irrigation facilities is not likely to prove profitable. 



lucre water is required for an effective job of irrigation than most folks 

 realize. One inch of water nay be enough for a complete spray program, v;hile six 

 inches may be needed for irrigating an apple orchard. For peaches, three or four 

 inches may be enough for irrigation during the critical season of 30 to i;0 days. 

 Setting up an irrigation system may cost about >100 per acre in addition to the 

 water supply, with an annual cost per acre of S20 to 62^, 



Irrigation does not promote annual bearing on biennial varieties, nor does it 

 tend to improve color except in a very dry season when apples mi.rht otherrdse have 

 a very dull color, The principal effect in a dry season is that of increasing the 

 size of individual fruits. Annual crops are more likely to respond to irrigation 



