September, 1913. 



THE CANADIAN HORTICULTURIST 



223 



Rotation of Vegetable Garden Crops 



H. F. East, North 



THIS is a subject worthy of the at- 

 tention of those who aim to attain 

 the largest possible results and the 

 highest jx)ssible quality with every kind 

 of vegetable crop, for it concerns the 

 natural relations of the plant and the soil 

 as to their several chemical constituents. 

 The principle may be illustrated by con- 

 sidering the demands upon the soil of 

 two of the most common vegetable gar- 

 den crops. 



We submit a cabbage to the destruc- 

 tive agency of fire and analyse the ashes 

 that remain. We shall find in them, in 

 round numbers, eight per cent, of sul- 

 phuric acid, sixteen per cent, of phos- 

 phoric acid, four per cent, of soda, forty- 

 eight per cent, of potash, and fifteen f)er 

 cent, of lime. It is evident that we can- 

 not expect to grow a cabbage on ;i soil 

 that is destitute of these ingredients, to 

 say nothing of others. If we submit a 

 potato tuber to a similar process the 

 ashes will be found to contain fifly-nine 

 per cent, of potash, two per cent, soda, 

 six per cent. lime. 



Now the lesson for the cultivator is 

 that to prepare a soil for cabbage, it is of 

 the utmost importance to employ a 

 manure containing sulphates, phosphates 

 and potash salts in considerable quanti- 

 ty. As for lime, that can be supplied 

 -separately, but the cabbage must have 

 it. On the other hand to prepare a soil 

 for potatoes we must strongly charge it 

 with salts of potash and phosphates. 

 But it need not be highly charged with 

 soda and lime for we find but a small 



Toronto, Onf 



proportion of these elements in the po- 

 tato. 



There are soils so naturally rich in fer- 

 tilizing constituents that they may be 

 tilled for years without the aid of man- 

 ures, and still yield an abundant return. 

 But these soils are exceptional. Those 

 that constantly need manuring are the 

 rule. In almost every soil, whether 

 strong clay, loam, poor sand or chalk, 

 there are to be found ail the minerals re- 

 quired by plants. Indeed, if there were 

 not, we should see no herbage on out 

 of the way places ; for instance at the 

 top of limestone rocks. Usually, how- 

 ever, a considerable portion of those 

 mineral constituents on which plants feed 

 are in an insoluble form, and are slowly 

 made available as the rain, the dew, and 

 sunshine operate upon them. 



As the rock slowly yields up its phos- 

 phates, alkalies and solutions of silica 

 to the wild vegetation that clings to it, 

 so the cultivated field (which is but rock 

 in a state of decay) yields more readily 

 its constituents for the service of plants. 

 Because it is the practice of the cultiva- 

 tor to stir the soil and continually ex- 

 pose fresh surfaces to the transforming 

 power of the atmosphere, it has been said 

 that the air we breathe is a powerful 

 manure. So it is, but not in the sense 

 that is applicable to stable manure or 

 guano. The air may, and does, afford 

 lo plants much of their food. Every fresh 

 exposure of the soil to the air, and es- 

 pecially to frost and snow, is as the 

 opening of a new mine of fertilizers for 



the service of those plants upon which 

 man depends for his subsistence. 



SCIEJSTTiriC PEINCIPLES APPLIED 



The practical application of these con- 

 siderations is an extremely simple matter 

 in the first instance, but it may become 

 complicated if followed far enough. Here 

 we can only touch the surface of the 

 subject. Suppose that we grow cabbage 

 or cauliflower on the same plot of 

 ground, one crop following the other 

 for a long series of years, and never re- 

 fresh the soil with a scrap of manure. It 

 must be evident that we shall some day 

 experience a crop failure because of the 

 exhaustion of the soil. 



But if this soil were allowed to lie fal- 

 low for some time it would again pro- 

 duce a crop of cabbage, owing to the lib- 

 eration from the unavailable state of 

 mineral matters which when the crops 

 were failing were not liberated fast 

 enough. But as this method necessi- 

 tates keeping the ground idle for some 

 time, it is obviously an unprofitable 

 mode of procedure and tends to still fur- 

 ther exhaust the soil. Whether a soil 

 can be brought to a stage of utter ex- 

 haustion is at present unknown. In- 

 stead, however, of following an exhaus- 

 tive practice, we enrich the soil witTi 

 manure, and change the crops on the 

 same plot so that when one crop has 

 largely taxed it for one class of minerals 

 a different crop will tax it for another 

 class. 



Let us consider the arrangement of a 

 rotation. Beets contain very little sul- 

 phur, but both turnips and beets are 

 strongly charged with potash and soda 

 (common salt.) If we take a piece of 

 ground on which is cabbage (which is 

 low in soda content) and wish to avoFd 

 the failure that may follow the continual 

 growing of this crop, we may expect to 

 do well by giving the ground a dressing 

 of common salt and alkalies and then 

 crop it with beets. 



DEEP vs. SHALLOW FEEDERS 



Crops differ in their mode of seeking 

 nourishment. For instance if we grow 

 cabbage and other surface-rooting crops 

 until the soil begins to fail, a good crop 

 of parsnips or carrots might be obtained 

 from it for the simple reason that these 

 send their roots down to a stratum that 

 the cabbage never reached. Parsnips 

 can thus thrive on land that has been 

 badly tilled for years because the root 

 pushes down to a mine that has been 

 but little worked. 



It is quite proper to say that good 

 land, well tilled and abundantly manured 

 cannot be soon exhausted. But even in 

 this case a rotation of crops is advis- 

 able. A good rotation will include both 

 chemical and mechanical differences. We 

 grow deep feeders after shallow feeders, 

 and potash-loving plants, say, after those 

 that draw more heavily on other fertiliz- 

 ing ingredients. 



