44 



SCIENTIFIC AGRICULTURE 



October 



sired type and form," we would cautiou 

 against swinging from severe pruning to 

 absolutely no pruning for a considerable 

 period, tlie sequal of which would ultim- 

 ately be a rather too severe heading back 

 and cutting cut to correct past neglect 

 with a possible 'consequent upset in the 

 balance between nitrogen and carbohydra- 

 tes. In shoit, more or less severe heading 

 back and thinning out during the first 

 four years after planting may be neces- 

 sary to mould the form of the tree and 

 may be practised without economic loss of 

 vigor. After that, however, severe an- 

 nual pruning should be discontinued and 

 trees which are bearing annually should 

 receive light annual pruning, sufficient 

 only to maintain symmetry, to prevent too 

 long or rangy growth and to prevent the 

 establishment of long limbs with growth 

 only at the tips. 



The principles which lie behind these 

 pruning recommendations will be discus- 

 sed later in this paper. In the meantime 

 let us consider the status of orchard fer- 

 tilization. 



Unfortunately Ave aie only beginning to 

 see the light in, this direction, but even now 

 there is much food for thought, and a note 

 of caution should be sounded here against 

 the too liberal use of potash and phospha- 

 tes througliout our orchards. In so far as 

 the individual is concerned this problem 

 will need to be investigated locally on or- 

 chards situated on as many different types 

 of soils as are common in the orcharding 

 sections. 



Tn the meantime, however, science lias 

 given us some general principles wliich 

 sliould materially assist many in reducing 

 their fertilizer bills. 



Kraus and Krayl)ill liave shown us (1) 

 that there must be a correct balance be- 

 tween nitrogen, cai-lxiliydi-ates and moistui'e 

 before we can get fertilization and vegeta- 

 tion combined, (2) that an abundance f)f 

 moisture and nitrogen without an available 

 supply of carbohydrates results in weak 

 and unfruitful plants, (3) that an alp.in- 

 dant supply of nitrogen and available car- 

 bohydrates gives increased vegetation and 

 non-fruitfuluess, and (4) that lack of ni- 

 trates with available carbohydrates is sim- 

 ilar in results to an abundant nitrogen 

 supply and a low amount of carbohydrates. 



that is weakened and unfruitful plants re- 

 sults. 



There must exist, therefore, an available 

 supply of carbohydrates, available moisture 

 and sufficient, but not an over abundant 

 supply of nitrates if fruitfulness and vigor 

 are to be obtained. In short it is not so 

 much the absolute amount of each present 

 that counts but their propoition to one 

 another. 



Unless artifically supplied to the soil, 

 the plant is dependent for its nitrogen upon 

 processes known as nitrification wherein 

 unavailable supplies of nitrogen are 

 changed into nitrates and thus made avail- 

 able for plant consumption. Nitrifica- 

 tion requires a comparatively warm and 

 well aerated soil. As trees start into 

 growth early in spring before the soil 

 temperature is relatively high, it is con- 

 ceivable that nitrification processes are at 

 that time not very rapid, and except on 

 soils rich in nitrogen, the actual supply 

 available for the plants at that time of 

 year is probably insufficient for the plant's 

 needs. 



Carbohydrates are manufactured by the 

 leaves and it should be here added that 

 any quantity of carboliydrates in excess 

 of what is required for the immediate con- 

 sumption of the tree is stored in the form 

 of starches in that portion of the tree close 

 to the leaves which manufactured it. 



This is the condition of healthy trees 

 during winter, viz.. stored reserve supply 

 of carboliydrates within the plant tissues. 

 Although there is some storage of nitro- 

 gen, practical experiments indicate that 

 the tree in early spring calls upon tlie soil 

 for a further su])ply of tiiis element. 



Soil nitrification being slow in the 

 spring and slower still in a cold wet spring, 

 early applications of nitrate of soda often 

 result in increased productiveness. With- 

 out available nitrogen at this time of year 

 the carbohydrates are in too large a pro- 

 portion to the nitrates with resulting sup- 

 l)ression of both vegetation and fruitful- 

 ness. 



Although an early aiiplication of nitro- 

 geii will give desired residts it is not to V>e 

 ])resumed that applications made in mid- 

 summer or late spring will do likewise. At 

 these seasons soil nitrification is at its 

 height and further applications of nitra- 



