The Springdale news., 1916-04-07
SOILS AND SOIL FERTILITY
No. 5. Organic Matter.

- 1o II Ial4 < Si4oIu, Assistant Az
 ronomist, University of Arkansas.
 The organic matter Of the soil Is that part which has been derived from the decay of plants. When the leaves. blades of grass, stems and roots Q. plants die they are at once attaot
 by molds and bacteria. The deal Yegation gradually deeomposes or
 lntegrates until the original app
 ance and structure is lost and the material becomes dark eolored shapeless mass, called humus.
 Effect of Organic Matter on the Soil.
 Organic matter is beneficial to both sandy and clay soils, but in different ways. clay soil without organic matter is too sticky and compact. The organic matter loosens it, permitting the surplus water 10 drain away and allows air to penetrate to the roots Of the crop. On the other hand, sandy soils are too loose and open Water drains away too rapidly and too much air is permitted to enter.
 Effect of Organic Matter on Moisture.
 Sandy soils that are well supplied with organic matters are more reten. tive of moisture than if lacking in that substance. The large spaces between the sand permit the water 10 draw away so rapidly that it is soon lost. and the soil dries out If these spaces are filled with organic matter the Watar meets more opposition in it's downward movement, consequently it remains for a longer time In the zone occupied by the plant roots The fact that organic matter is exceedingly porous adds 10 ifs water holding power. This is shown clearly by ex- pertments showing that 100 pounds Of straw will take up 200 pounds of wa ter whereas the same amount of sand will hold only twenty-five pounds. and 100 pounds of peat soil, which con- sists entirely of humus, will take up from 500 to 1000 pounds of water
 Clay soils do not need to have their water holding capacity increased be- cause they are naturally very renten- tive of moisture. such soils are so compact. however, that the roots have difficulty in penetrating deeply into the subsoil. Consequently the crops are likely to be shallow rooted. The surface soil dries out quickly and the crop suffers. This accounts for the fact that crops often suffer from drought on clay lands sooner than on more sandy soils If organic matter is supplied to clay soils the crop will root deeper as a result of the more open structure and therefore will be able to utilize the moisture stored in the sutsoil and can resist drought
 Organic Matter and Plant Food.
 Organic matter not only improves the physical condition of soils and aids moisture control but it also con- tains large amount of nitrogen and other plant feeds in an available form When the organic matter decays this plant food can be used by the sue ceeding crops.
 Soils That Need Organic Matter.
 The soils of the South are. as rule, deficient in organic matter be, cause the high temperature of the summer seasons causes decomposition to take place very rapidly. This ten i dency is enumerated to certain ex- tent on the creek and river bottom soils by the fact that the large amount of vegetation produced has caused a large supply of organic mat ter to be stored up. Continuous crop i ping to corn and cotton however, soon exhausts this original supply go ! that even the rich bottom soils be. come depleted after twenty-five or thirty years The presence of an abundance of organic matter is shown by black or dark brown color extending several inches below the surface lack of organic matter is shown by light gray or red color
 Methods of Increasing Organic Mat
 ter Content of the Soil.
 The amount of organic matter in the soil can be increased by applying barnyard manure, by turning under all the corn and cotton stubbs, stubble from grain, sod Of meadows and by turning under green crops. The sub i 1ect or maHureS Will De treated III another lesson. The practice of turn ing under green crops is called green manuring" Where few live stock are kept this is an excellent means or adding organic matter to the sou The crops used for this purpose include cowpeas. soy beans, clover, rye, oats and wheat. The first three mentioned i. e. peas beans and clover, are legumes and are capable of taking nitrogen from the air and putting il into the soil They do this with the help of bacteria living ou