TOOLS FOR AFTER-CULTIVATION
The main objects of after-cultivation are to destroy weeds and to form a soil mulch for the purpose of controlling soil moisture. These ends are secured by shallow surface work. It is not necessary to go more than two or three inches deep. Deeper work will injure the roots of the crop. Therefore the proper tools for after-cultivation in the garden are the hoe and rake and for field work narrow-toothed harrows and cultivators or horse-hoes which stir the whole surface thoroughly to a moderate depth. These field tools are supplemented in some cases by the hand hoe, but over wide areas of country the hoe never enters the field.
A light spike-toothed harrow can be used on corn, potatoes, and similar crops, and accomplish the work of cultivation rapidly until they get to be from four to six inches high; after that cultivators which work between the rows should be used.
A very useful cla.s.s of tools for destroying weeds in the earlier stages are the so-called "weeders." They somewhat resemble a horse hay rake and have a number of flexible wire teeth which destroy shallow rooted weeds but slip around the more firmly rooted plants of the crop. These weeders must be used frequently to be of much value, for after a weed is well rooted the weeder cannot destroy it.
There is a larger cla.s.s of hand wheel hoes which are very useful in working close planted garden and truck crops. They either straddle the row, working the soil on both sides at the same time, or, running between the rows, work the soil to a width of from six to eighteen inches.
For best results with the weeder and hand wheel hoes the soil should be thoroughly prepared before planting by burying all trash with the plow and breaking all clods with harrow and roller.
The objection made to the deep-working implements, like the plow, is that they injure the crop by cutting its feeding roots, and this has been found by careful experiment and observation to diminish the crop.
Some farmers object to using a light harrow for cultivation in the early stages of the crop because they say the harrow will destroy the crop as well as the weeds. This danger is not so great as it seems.
The seeds of the crop are deeper in the soil than the seeds of the weeds which germinate and appear so quickly. The soil has also been firmed about them. Hence they have a firmer hold on the soil and but few of them are destroyed if the work is carefully done.
In working crops not only should weeds be destroyed but also surplus plants of the crop, as these have the same effect as weeds; namely, they occupy the soil and take plant food and moisture which if left to fewer plants would produce a larger harvest.
HILLING AND RIDGING
Except in low, wet ground, the practice of hilling or ridging up crops is now considered by those who have given the matter thorough study, to be unnecessary, flat and shallow culture being cheaper. It saves more moisture, and for this reason, in the majority of cases, produces larger crops.
Sometimes during very long-continued periods of wet weather weeds and gra.s.s become firmly established among the plants of the crop. Under such circ.u.mstances it is necessary to use on the cultivator teeth having long, narrow sweeps that will cut the weeds just beneath the surface of the soil. Sometimes a broad-toothed tool is used that will throw sufficient soil over the large weeds near the rows to smother them.
The condition to be met and the effect of the operation should always be given serious thought.
We have considered after-cultivation as influencing soil fertility by checking a loss of water by evaporation and weed transpiration, and this is its main influence but other benefits follow.
Keeping the surface soil loose and open benefits fertility because it directly aids the absorption of rain, favors ventilation, and has a beneficial influence over soil temperature. Indirectly through these factors it aids the work of the beneficial soil bacteria and the chemical changes in the process of preparing plant food for crop use.
CHAPTER XIX
FARM MANURES
FUNCTIONS OF MANURES AND FERTILIZERS
In Chapter II we learned that the roots of plants for their growth and development need a soil that is firm yet mellow, moist, warm, ventilated and supplied with plant food. We also learned that of the plant foods there is often not enough available nitrogen, phosphoric acid, potash and lime for the needs of the growing plants.
Manures and fertilizers are applied to the soil for their beneficial effects on these necessary conditions for root growth and therefore to a.s.sist in maintaining soil fertility.
CLa.s.sIFICATION OF MANURES AND FERTILIZERS
Manures may be cla.s.sified as follows:
{ Barn or stable manures, Farm manures. { Green-crop manures, { Composts.
Commercial { Materials furnishing nitrogen, fertilizers { " " phosphoric acid, or artificial { " " potash, manures. { " " lime.
IMPORTANCE OF FARM MANURES
Of these two cla.s.ses of manures the farmer should rely chiefly on the farm manures letting the commercial fertilizers take a secondary place because:
Farm manures are complete manures; that is they contain all the necessary elements of plant food.
Farm manures add to the soil large amounts of organic matter or humus.
The decay of organic matter produces carbonic acid which hastens the decay of mineral matter in the soil and so increases the amount of available plant food.
The organic matter changes the texture of the soil.
It makes sandy soils more compact and therefore more powerful to hold water and plant food.
It makes heavy clay soils more open and porous, giving them greater power to absorb moisture and plant food. This admits also of better circulation of the air in the soil, and prevents baking in dry weather.
Farm manures influence all of the conditions necessary for root growth while the commercial fertilizers influence mainly the plant food conditions.
The farm manures are good for all soils and crops.
They are lasting in their effects on the soil.
BARN OR STABLE MANURE
Barn or stable manure consists of the solid and liquid excrement of any of the farm animals mixed with the straw or other materials used as bedding for the comfort of the animals and to absorb the liquid parts.
The liquid parts should be saved, as they contain more than half of the nitrogen and potash in the manure.
The value of barn manure for improving the soil conditions necessary for root growth depends in a measure upon the plant food in it, but chiefly upon the very large proportion of organic matter which it contains when it is applied to the soil.
These factors are influenced somewhat: by the kind of animal that produces the manure; by the kind of food the animal receives; by the kind and amount of litter or bedding used; but they depend particularly on the way the manure is cared for after it is produced.
LOSS OF VALUE
Improper care of the manure may cause it to diminish in value very much.
_Loss by leaching._
If the manure is piled against the side of the stable where water from the roof can drip on it, as is often the case, or if it is piled in an exposed place where heavy rain can beat on it, the rain water in leaching through the manure washes out of it nitrogen and potash, which pa.s.s off in the dark brown liquid that oozes from the base of the pile.