The Apple in Oregon: Part II. Vol 



(6.) It pumps the surplus water out of the soil early in spring so that 

 the ground warms up and may l)e plowed earlier than if no cover crop were 

 used. 



(7.) When plowed under these crops add enormous amounts of vegetable 

 matter or humus to the soil. The humus improves the mechanical condition 

 of the ground by loosening up tlie soil particles ; it increases the water-holding 

 power of the soil, provides a favorable home for soil bacteria, furnishes ele- 

 ments of plant food in available form, and assists in breaking up chemical com- 

 pounds of plant food which would otherwise remain unavailable. 



{8.) Exjjerience has shown tliat the continued use of cover crojjs will, 

 to a certain extent, make heavy land lighter and light land heavier. This is 

 an immense advantage in practical orchard operations." 



Cover crops may be grouped into two — possibly three — classes ; the legumi- 

 hous, as peas, beans, alfalfa, clovers, vetches, cow peas, and tlie like; the 

 potasli gatherers, as turnips, and rape and probably kale, and the non-leguminous 

 as rye, whea!t, 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 important materials 

 used in plant growth is nitrogen. This material bought as a commercial fer- 

 tilizer or applied witli 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 tlie air, which is inexhaustible, is made available as plant food 

 through the agency of leguminous plants, while other pl;in(s must get the nitro- 

 gen required for their growth from the supply in the soil 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. 



P>y recent analyses* it is made evident that certain jjlants. cowliorn tur- 

 nips and rape, are rich in potash. It tlius appears that such crops used for 

 cover purposes miglit put the potasli supplies of the soil witliin easier reach 

 of the tree. If the soil of an orchard is rich 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 or- 

 charding. But, as before stated, only practical tests upon the site will deter- 

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

 will depend upon the local conditions and the successful orchardist will be 

 the intelligent experimenter in these matters. 



A rotation of cover crops is as important as a rot;ition of general farm 

 crops. The constant use of a leguminous crop would tend to make the soil very 

 rich in available nitrogenous materials. This v/ould induce excessive wood 

 and foliage growth at tlie expense of flowers and fruit. To offset this 

 crops, 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 tlimigh a cover crop may 

 not, of itself, use the free nitrogen of the air, it wiU -avaW itself of such nilro- 



*I>elaware station. 



