EXPERIMENT STATION BULLETINS. 



577 



orchards during the season of 1919. The problem, then, of developing 

 strong, vigorous fruit spurs most capable of setting fruit is a most im- 

 portant one to insure profitable crops. 



FACTOUS FAVOItlXG GROWTH. 



A fruit tree during its season of growth is constantly striving to 

 place itself in equilibrium with the forces of its environment. It is 

 therefore never stationary in its condition ; it is ever changing from day 

 to day, month to month, and season to season. The atmospheric condi- 

 tions of its environment are always changing, especially those of tem- 



FIG. I. WEAK FUUIT SPUKS CHARACTERISTIC OF NON-PRODUCTIVE TREES. 



perature, light and humidity, all of wliich influence growth and may be 

 limiting factors of production. The soil conditions affecting growth are 

 likewise ever changing in the supply of available plant food elements, 

 in temperature conditions and in moisture content. It is this ever- 

 changing condition of the soil content that more often largely deter- 

 mines v.hether the resulting changes in tree-growth are favorable or not 

 for fruit production. 



Soil moisture is a most important necessity for plant growth that is 

 often a limiting factor. All plant food in the soil must be taken 

 through tlie medium of soil moisture. It must be dissolved in the water 

 of the soil before it is available to the ])lant. Hence, a fruit tree in the 

 richest soil may starve at such times as wlien soil moisture is wanting. 

 JThis principle emjdiasizos tlie necessity of such cultural practices as 

 will insure an aniple and uniform supply of soil moisture during those 

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