The Apple in Oregon. 145 



like; the potash gatherers, as turnips, rape, and probably kale, and the 

 non-leguminous, as rye, wheat, oats, barley, mustard, buckwheat, rape, 

 millet, corn, and others. 



The first class are the so-called nitrogen gatherers, and may be 

 considered as fertilizers as well as cover crops. One of the most impor- 

 tant materials used in plant growth is nitrogen. This material bought 

 as a commercial fertilizer or applied with barnyard compost is quite 

 expensive. It abounds in the air as one of the principal gases and, 

 so far as we know at present, this gas can be used directly only by 

 leguminous plants. Or, in other words, this free nitrogen of the air, 

 which is inexhaustible, is made available as plant food through the 

 agency of leguminous plants, while other plants must get the nitrogen 

 required for their growth from the supply in the soll or that set free by 

 decomposing plants or animals. Then, since nitrogen is one of the most 

 valuable of plant foods, it is evident that any plant which is able to 

 get its supply of this element from the inexhaustible stock of the air 

 must be doubly valuable as a cover crop. 



By recent analyses* it is made evident that certain plants, cowhorn 

 turnips and rape, are rieh in potash. It thus appears that such crops 

 used for cover purposes might put the potash supplies of the soll 

 within easier reach of the tree. If the soil of an orchard is rieh in 

 humus and nitrogen, a cover crop of potash-gathering plants, if from 

 such knowledge as we have of them, we may call them such, would be 

 the logical one to use. In this connection it may be well to note the 

 fact that Scotch kale, a plant closely related to the turnip, has been 

 giving some remarkable yields in Western Oregon, as a forage plant 

 for dairy purposes. It seems probable that this plant would do efficient 

 Service as a cover crop on soils in good tilth and well supplied with 

 humus. And since potash tends to hasten the maturity of a crop, 

 increase the sugar content, and heighten the color, indirectly, at least 

 as a consequence of earlier maturity, its importance to the fruit grower 

 in the moisture sections of our State becomes evident, and any secondary 

 or catch crop that will render the potash of the soil more readily 

 available for the trees is to be held as a useful factor in örcharding. 

 But, as before stated, only practical tests upon the site will determine 

 the course to be followed in each instance. The crops, rotation or 

 tillage, will depend upon the local conditions and the successful orchard- 

 ist will be the intelligent experimenter in these matters. 



A rotation of cover crops is as important as a rotation of general 

 farm crops. The constant use of a leguminous crop would tend to 

 make the soil very rieh in available nitrogenous materials. This would 

 induce excessive wood and foliage growth at the expense of flowers 

 and fruit. To offset this, cover crop as often as the trees appear to 

 be growing too vigorously at the expense of fruit production. 



Then we must not lose sight of the fact that though a cover crop 

 may not of itself use the free nitrogen of the air, it will avail itself 

 of such niti'Ogen material as is obtainable in the soil during its period 

 of growth, and, as this is at a time when the dormant tree could 

 make no use of such nitrogen material, which, if not used, soon escapes 

 as' a waste by leaching from the soil, it is seen that the cover crop 

 thus becomes a saver of nitrogen as well as other substances and thus 

 performs a work as important as that of a nitrogen gatherer under 

 the circumstances. 



In Western Oregon orchards in particular, not a foot of soil should 

 remain uncovered or bare of plant growth from the time the crop is 

 fully grown to the time when the fruit begins to form the following 



♦Delaware Station. 



