-5- 



A question most frequently asked is, "When should water "be applied to orchards?" 

 Proper timing of Irrigation as to freauency can save orchardists many dollars. 



The electrical resistance method of measuring soil moisture has "been developed 

 to such an sjttent that direct reading moisture meters are available to growers at 

 cost of slightly over $100. It would "be of value to know at what percentage of 

 available soil moisture that irrigation water should he applied. 



With the previous statements in mind, it was felt that a research project on 

 apple orchard irrigation would he worth while with the following ohjectives in mind: • 



A - To determine how many years out of ten, apple trees on the experimental 

 site suffer for the lack of water. 



B - To study the effect of water shortage on the growth of apple trees, fruit 

 growth, color, qimlity and yield of fruit. 



C - To determine at what percentage of available soil moisture irrigation water 

 should "be applied. 



D - To find how the nutritional status of the fruit trees is affected hy 

 irrigation. 



Results of other Irrigation Pro.iecta 



Under California conditions some research workers have reported that various 

 fruit-crops growing in sandy soils do not suffer from gradual drying of the soil 

 but are able to obtain moisture readily iintil the permanent wilting percentage of 

 the soil is reached. ( Hot all moisture in the soil is available to plants. The 

 percentage of water in soil when plants wilt permanently is called the permanent 

 vjilting percentage of the soil.) This conclusion vuas based on yield, growth rate 

 of fruit and fruit size at harvest. On the other hand, the same workers and others 

 have reported the tree size is reduced before the permanent wilting percentage is' 

 reached. 



In work conducted in Maryland, it was found that growth of apples was not 

 slowed down until soil moisture was near the permanent wilting percentage. Dur- 

 ing 3 of the k years that the experiment was conducted, apple trees on rather 

 shallow shale soil showed reduced fruit growth rate due to moisture shortage at 

 sometime during the growing season. The fruit size was reduced in proportion to 

 the length and duration of the drought. In earlier work other research workers 

 had concluded that there was a slight slowing down of apple growth before the 

 soil reached permanent wilting percentage. 



In the Hudson Valley, It was found that fruit size on apple trees planted in a 

 shallow soil decreased when the soil moisture in the top two feet was decreased to 

 the permanent wilting percentage. 



In addition to the effect of soil moisture on fruit size and yield, its effect 

 on fruit quality, fruit storage life, flower bud formation, and tree growth has 

 also received considerable attention. It has been reported that differences in 

 soil moisture has no effect on susceptibility of apples to decay, but that irrigated 



