1922.] 



Cultivation of the Hop Crop. 



1011 



the texture of all soils on the heavy side ; secondly, it keeps the soil " sweet" 

 by neutralising any acids present in the soil or added to the soil by chemical 

 manures ; thirdly, it is most beneficial to the growth of the numerous soil 

 organisms which are concerned with the decomposition of the humus in the 

 soil, so that its constituents may begome available for plant growth. Any 

 deficiency in lime should be made good from the outset by the application of 

 one of the forms of lime available — ground-lime, quicklime, or chalk — accord- 

 ing to the usual factors governing the use of lime {See Leaflet No. 170), and, 

 when necessary, this soil constituent should be periodically replenished, since 

 it is liable to rapid loss from the hop garden. 



The organic matter is perhaps for the hop-grower the most important 

 ingredient of the soil. Successful hop-growing depends upon keeping this at 

 a high level for many reasons : firstly, as with lime, the organic matter plays 

 a very important part in maintaining a good texture in the soil ; this is most, 

 important because in hop-growing it frequently happens that injury is done to 

 the texture by operations, such as washing, having perforce to be carried out 

 when the soil is too wet ; a soil containing a good supply of organic matter allows 

 a good state of texture to be recovered more quickly. Secondly, a good supply 

 of organic matter, both by helping the texture and by reason of its own 

 properties, enables the soil to hold and retain large supplies of moisture for the 

 hop roots. Lastly, all organic manure has been formed directly or indirectly from 

 plant life and therefore contains within itself all elements of plant food : these 

 are not necessarily present in the best proportion, nor are they immediately 

 available for the hop roots, but in the soil this organic matter is continually under- 

 going change by which the plant food it contains is gradually and continuously 

 made available for plant roots. The rate of these changes is not constant, 

 but varies according to a number of factors, of which moisture, temperature 

 and supply of air are the most important, and since the last factor, that of air 

 supply, is controlled by tillage, the hop grower is enabled to control to some 

 extent the rate at which the plant food stored in the organic material becomes 

 available. The amount of organic matter present in most soils, except 

 recently broken old pasture, requires to be considerably augmented before 

 it reaches the standard of fertility considered desirable for hop-growing. 



Nitrogen. — Practically all the nitrogen held in soils is combined within the 

 organic material; a soil which is well supplied with organic material will as a 

 general rule contain relatively large quantities of nitrogen. It has previously 

 been stated that this organic matter is constantly — though not always at the 

 same rate — undergoing change resulting in the production of plant food. 

 The most important resultants of these changes are the nitrates, which are 

 the forms in which plants absorb nitrogen as a food. Now it is important to 

 realise that nitrogenous plant food has a specific effect upon plant growth ; it 

 stimulates the growth of foliage— stem and leaf. If nitrogenous plant food 

 is deficient the bine is yellowish and stunt3tl in growth, the crop will be 

 small ; if nitrogen is abundant then growth of foliage will be luxuriant and 

 may result (provided other conditions are favourable) in a full crop. It is, 

 however, possible that the supply of nitrogenous plant food, especially in a 

 wet season, may be excessive. In this case foliage is too luxuriant and 

 abundant, the lateral branches become matted together so that the supply of 

 bght ami air are insufficient for the formation of " burr " and the growth 



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