FKKTII.I/KUS FOR FRUITS 813 



as to how much of the unavailable plant food in a soil may be 

 made available, I think it may be safely said from theoretical 

 deductions that the yearly plowing, the continuous tillage, the 

 well-regulated 'supply of moisture, and the addition of humus by 

 plowing under cover crops, have made available the plant food 

 which the apple trees in these two experiments needed. 



A once favorite theory which may still hold regarding fertilizers 

 is that the composition of the crop is a good guide to the fertilizer 

 requirements of that crop. Very 1111 fortunately, there have been 

 almost no well-conducted, long-continued experiments to ascertain 

 what the fertilizer requirements of fruits are. In America, there 

 have been less than a half dozen experiments, planned and carried 

 out for more than two years, which by any stretch of imagination 

 could be called fertilizer experiments. Therefore, having no 

 definite data for the apple as to fertilizer requirements, practically 

 all of our recommendations for fertilizing this fruit are based on 

 the differences in the chemical composition of this plant as com- 

 pared with the composition of grain and garden crops. But the 

 fertilizer requirements of fruits cannot be correctly apprehended 

 by comparing chemical composition of trees, bushes or vines with 

 those of grain and garden crops, because their habits of growth 

 are entirely different from those of the other crops: These differ- 

 ences in growth need to be kept in mind whenever the temptation 

 arises to draw comparisons between the fertilization of orchards 

 and of fields or gardens. Let us sum up the chief differences. 



Trees have a preparatory time of several seasons before fruit- 

 bearing begins; farm and truck crops make their growth, bear 

 a crop and pass away, for the most part, in a single season. Trees 

 begin to grow early in the spring and continue until late fall ; few 

 annual crops are in active growth more than half the time when 

 leaves and roots of trees are at work. The roots of trees go much 

 deeper and spread relatively farther than do those of succulent 

 crops. Such data as are at hand seem to show that fruit transpires 

 a greater amount of water in proportion to its leaf area than do 

 most succulent plants, which means that the nutritive soil solu- 

 tion may be less concentrated than for grains and vegetables and 

 yet feed the fruits equally well. Fruit crops are from 80 to 90 

 per cent water, and the leaves mostly remain on the ground; in 



