The Rotation Of Crops





Doubtless you know what is meant by rotation, for your teacher has

explained to you already how the earth rotates, or turns, on its axis

and revolves around the sun. When we speak of crop-rotation we mean not

only that the same crop should not be planted on the same land for two

successive years but that crops should follow one another in a regular

order.



Many farmers do not follow a system of farming that involves a change of

crops. In some parts of the country the same fields are planted to corn

or wheat or cotton year after year. This is not a good practice and

sooner or later will wear out the soil completely, because the

soil-elements that furnish the food of that constant crop are soon

exhausted and good crop-production is no longer possible.



Why is crop-rotation so necessary? There are different kinds of plant

food in the soil. If any one of these is used up, the soil of course

loses its power to feed plants properly. Now each crop uses more of some

of the different kinds of foods than others do, just as you like some

kinds of food better than others. But the crop cannot, as you can, learn

to use the kinds of food it does not like; it must use the kind that

nature fitted it to use. Not only do different crops feed upon different

soil foods, but they use different quantities of these foods.



Now if a farmer plant the same crop in the same field each year, that

crop soon uses up all of the available plant food that it likes. Hence

the soil can no longer properly nourish the crop that has been year by

year robbing it. If that crop is to be successfully grown again on the

land, the exhausted element must be restored.






This can be done in two ways: first, by finding out what element has

here been exhausted, and then restoring this element by means either of

commercial fertilizers or manure; second, by planting on the land crops

that feed on different food and that will allow or assist kind Mother

Nature "to repair her waste places." An illustration may help you to

remember this fact. Nitrogen is, as already explained, one of the

commonest plant foods. It may almost be called plant bread. The wheat

crop uses up a good deal of nitrogen. Suppose a field were planted in

wheat year after year. Most of the available nitrogen would be taken out

of the soil after a while, and a new wheat crop, if planted on the

field, would not get enough of its proper food to yield a paying

harvest. This same land, however, that could not grow wheat could

produce other crops that do not require so much nitrogen. For example,

it could grow cowpeas. Cowpeas, aided by their root-tubercles, are able

to gather from the air a great part of the nitrogen needed for their

growth. Thus a good crop of peas can be obtained even if there is little

available nitrogen in the soil. On the other hand wheat and corn and

cotton cannot use the free nitrogen of the air, and they suffer if there

is an insufficient quantity present in the soil; hence the necessity of

growing legumes to supply what is lacking.






Let us now see how easily plant food may be saved by the rotation of

crops.



If you sow wheat in the autumn it is ready to be harvested in time for

planting cowpeas. Plow or disk the wheat stubble, and sow the same field

to cowpeas. If the wheat crop has exhausted the greater part of the

nitrogen of the soil, it makes no difference to the cowpea; for the

cowpea will get its nitrogen from the air and not only provide for its

own growth but will leave quantities of nitrogen in the queer nodules of

its roots for the crops coming after it in the rotation.






If corn be planted, there should be a rotation in just the same way. The

corn plant, a summer grower, of course uses a certain portion of the

plant food stored in the soil. In order that the crop following the corn

may feed on what the corn did not use, this crop should be one that

requires a somewhat different food. Moreover, it should be one that fits

in well with corn so as to make a winter crop. We find just such a

plant in clover or wheat. Like the cowpea, all the varieties of clover

have on their roots tubercles that add the important element, nitrogen,

to the soil.



From these facts is it not clear that if you wish to improve your land

quickly and keep it always fruitful you must practice crop-rotation?





AN ILLUSTRATION OF CROP-ROTATION



Here are two systems of crop-rotation as practiced at one or more

agricultural experiment stations. Each furnishes an ideal plan for

keeping up land.



---------------------++----------------------++----------------------

---------------------++----------------------++----------------------

FIRST YEAR SECOND YEAR THIRD YEAR

----------+----------++-----------+----------++-----------+----------

Summer Winter Summer Winter Summer Winter

----------+----------++-----------+----------++-----------+----------

Corn Crimson Cotton Wheat Cowpeas Rye for

clover pasture

----------+----------++-----------+----------++-----------+----------



or



----------+----------++-----------+----------++-----------+----------

Summer Winter Summer Winter Summer Winter

----------+----------++-----------+----------++-----------+----------

Corn Wheat Clover Clover Grass Grass for

and grass and grass pasture or

meadow

----------+----------++-----------+----------++-----------+----------

----------+----------++-----------+----------++-----------+----------



In these rotations the cowpeas and clovers are nitrogen-gathering crops.

They not only furnish hay but they enrich the soil. The wheat, corn, and

cotton are money crops, but in addition they are cultivated crops; hence

they improve the physical condition of the soil and give opportunity to

kill weeds. The grasses and clovers are of course used for pasturage and

hay. This is only a suggested rotation. Work out one that will meet your

home need.





=EXERCISE=



Let the pupils each present a system of rotation that includes the

crops raised at home. The system presented should as nearly as

possible meet the following requirements:



1. Legumes for gathering nitrogen.

2. Money crops for cash income.

3. Cultivated crops for tillage and weed-destruction.

4. Food crops for feeding live stock.





The Possibilities Of Irrigation The Sap Current facebooktwittergoogle_plusredditpinterestlinkedinmail

Feedback