Ontario Teachers' Manuals: Nature Study

by Ontario. Department of Education

SOIL STUDIES

The classes of soil should be reviewed. Pupils should gather examples from many places. The samples may be kept in bottles of uniform size and should include not only the four types but varieties of each, also various kinds of loam.

EXERCISES AND EXPERIMENTS

SOIL CONSTITUENTS

1. With a sharp spade, cut a piece about twelve inches deep from (1) the forest floor, (2) an old pasture field. Note character and order of the layers of soil in (1) leaves, humus, loam, sand, or clay; in (2) grass, dead grass, humus, loam, sand, or clay. Observe soils shown in railway cuttings, freshly dug wells, post holes.

2. Note the effect produced on the soil of a field by (1) leaving it a few years in pasture, (2) ploughing in heavy crops, (3) applying barn-yard manure. In all these cases vegetable matter is mixed with the soil.

3. Dry some good leaf-mould. Throw a handful on the surface of some water. The mineral matter sinks, while the vegetable portion remains suspended for some time. Try this experiment with gravel, sand, and clay. Note that the gravel sinks rapidly, the sand less rapidly, and that the clay takes a long time to settle. If the water be kept in rapid motion, the finer soils will all remain suspended till motion becomes slower. Apply this in geography. The bed of a stream will consist of stones if it be swift, of sand if less swift, and of clay if very slow. How are alluvial plains formed?

4. Place half an ounce of dry humus on an iron plate or fire-shovel and heat strongly in a stove. Note that it begins to smoke and a large part smoulders away to ashes; the mineral portion remains. Weigh the part left and find what fraction of the humus consisted of vegetable material.

Try to find the proportion of vegetable matter in each of the following: loams from various sources, sand, clay, gravel. The last three will show scarcely any change. This experiment will give rise to some good arithmetical problems in fractions.

WATER IN SOILS

5. Compare a handful of fresh garden soil with the same soil dried. Note the glistening of the fresh soil, also its weight and darker colour. The fresh soil admits of packing though no water can be squeezed from it. In its best condition, the water of the soil adheres as a film of moisture about every particle. Free water is to be avoided since it excludes the air from the soil.

6. Equal weights of soils of different kinds and degrees of fineness are placed in funnels or in inverted bottles with bottoms removed. Water is then slowly added to each until it begins to drop from the lower end. From this is seen (1) the great value of humus as a water holder, (2) the advantage of fine soil over coarse. For retention of water by absorption, consult Nature Study and Life, Hodge, page 382.

7. Take two wooden boxes (chalk boxes will do), fill one box with moist sand and the other with moist leaf-mould. Weigh the boxes separately and leave them for three or four days in a warm room. Weigh again and note decrease from evaporation. The sand dries out much faster than the humus. Test with clay, gravel, and loam, also with mixtures of these and leaf-mould.

8. Take three paint cans; punch holes in the bottoms. Fill each with good soil well shaken down. Stand the cans in water till the tops are moist, then place them in a warm, dry place. Loosen the soil on the top of No. 1 to a depth of one inch; on No. 2 to a depth of two inches; leave No. 3 untouched. Find out after a few days which is drying out fastest. How may soil be treated so as to lessen evaporation of water?

DRAINAGE

9. Gravel and sand allow water to run away rapidly, but where the soil is fine or closely packed as in clay soils, under-drains are necessary (1) to carry off the surplus water, (2) to allow air to enter the soil, (3) to warm the soil (wet soil is colder than dry).

Take two equal-sized tin cans, make several holes in the bottom of one, place therein a layer of broken pottery or stones, and fill with good soil. Fill the other with similar soil but make no holes for drainage. Plant in each can a healthy plant of the same size and kind. Water both till the soil is saturated and continue watering every two or three days for six weeks. Note (1) the progress of the plants, (2) the temperature of the soils, (3) which plant has the largest and deepest roots. (See Bulletin 174, Ontario Department of Agriculture.)

10. Take five equal-sized boxes, provide for drainage, and fill No. 1 with wood, earth, or humus, No. 2 with clay, No. 3 with sand, No. 4 with a mixture of clay and humus, No. 5 with a mixture of sand and humus. Plant corn in each box, set in a warm room, and keep watered for two or three weeks. Note in which case growth is most rapid. Set boxes in a dry place and cease watering. Which suffers most from the drought? Which bakes hardest in the sun? Test the temperature of each after watering and standing in the sun for an hour. Sand is warmer than clay, also the presence of humus raises the temperature. This item is important, since most seeds decay instead of sprouting if the temperature is below 45° Fahrenheit.

11. Enumerate the services rendered to the soil by humus.

12. In Experiment 10, let the corn grow for some time and determine whether the very rich humus is the best in the end. Sand and clay are almost altogether mineral; leaf-mould almost entirely organic; neither alone is good, but a mixture gives the best results.