SOIL LABORATORY WORK

255

experiments while others are testing the capillarity of different soils of their farms. Some may be working on lime while others are working with the effects of humus on soils. In the recitations which follow the laboratory exercises students must show that they are gaining by lessons from the laboratory work. Even though some of the students are not required to perform all of the exercises in the course, they will have gained much from the exercises performed by other students and by the recitation following them.

Certain students may be required to prepare composts for garden work. This may precede or accompany their projects in the growing of garden crops. Some students who are pursuing

FIG. 124. Teach students that soil with a baked crust cannot retain moisture, while a dust mulch will conserve it. Teach also the effect of foot pressure on loose soil. (Right, from Dunham Co., Berea, O.)

field crop projects may make special tests in metal cylinders to demonstrate the value of special fertilizers in the growth of those crops. If students have projects in the growth of legumes, they may demonstrate the need or lack of need for inoculation of soils by growing young plants of these crops in pots or cylinders. If it is desirable, these trials may be made more efficient by having the tests in plots outdoors. The mixing of fertilizers for special crops to be grown by students in their project work will be of value. Such exercises may be performed in the winter before it is time to start the field work.

In testing soils for acidity (Fig. 122), and in the study of the physical composition of soils, let each student use samples from his own home place if possible. He will then know more about his own soils and can act directly on the results of his laboratory trials.

Laboratory Exercises in Soils.-The following list of exercises is given for aid of teachers in formulating a suitable course in laboratory work. These are taken from five laboratory manuals to which reference is given. The manuals are:

(1) "Soils Laboratory Manual and Notebook" by Eastman and Davis (Lippincott); (2) "Soil Physics Laboratory Guide" by Stevenson and Schaub (Orange Judd); (3) "Soil Physics Laboratory Manual" by Mosier and Gustafson (Ginn); (4) "A Manual of Soil Physics" by Barker and Young (Ginn); (5) "Physical Properties of Soils" by Arthur G. McCall (Orange Judd).

These are referred to after each exercise by the number just given. The instructor should read over the list of exercises somewhat carefully and refer to them in the manuals before deciding which ones he wishes to include in the course in his own school.

Effects and Determination of Organic Matter.

Effect of Lime and Other Chemicals on a Clay Soil.

Moisture Determination...

Capillary Rise of Water in Soils.

Effect of too Much Organic Matter on Rise of Water.

Percolation of Water Through Soils...

Clod Formation and Crusting..

Effect of Soil Surface and Cultivation on Percolation and Tem

Capacity of Loose and Compact Soil to Hold Water.

1, 2, 3.

1, 4.
1.

1, 4.

1, 2, 3.
1, 2, 3, 4.

1.

1, 2, 3, 4.

1, 2, 3, 4, 5.

1, 2, 3, 4, 5. 1, 2, 3, 4, 5. 1, 2, 3, 4, 5. 1, 2, 3.

1, 2.

1, 2, 3, 4.

1, 2, 3.

perature....

Effect of Evaporation on Soil Temperature..

Value of Mulches in the Retention of Moisture.

1, 2, 4.

1, 2, 3, 4, 5.

Optimum and Critical Moisture.

1.

Drainage and Soil Temperature.

Effect of Color on Soil Temperature.

1, 2, 3,

4.

Soil Ventilation.

1, 5.

The Effect of Alternate Wetting and Drying upon Granulation. 2, 4.

The Effect of Alternate Freezing and Thawing upon Granulation 2, 4.
The Effect of Organic Matter on Granulation.

STUDYING SOILS IN THE FIELD

257

Studying Soils in the Field.-Classes may be taken to the fields of their homes or neighboring places. There they should learn such lessons as how to know whether or not soils need inoculation for special crops. They should study the needs of the fields with reference to drainage, terracing (Figs. 125 and 128), irrigation, prevention of erosion, addition of humus, prevention of heaving, etc.

They should learn also the value of special crops for soil improvement, winter covers, green manure, and prevention of wash

FIG. 125.-Gullies have been stopped and graded over as home project work.
(E. H. Thompson.)

ing. They can contrast good and bad ways of handling manure; the effects of special fertilizers; the influence of certain crops on percolation; the effect of certain treatment on alkali soils; suitability of certain crops to sandy soils, or marsh soils.

On such field trips students should consult with owners and study methods and management in detail. Learn how they could apply the lessons on their own places. They should always take notes of the lessons learned. They should discuss the lessons later in class meetings. They should be able to use the results of such field studies in the various assignments of class-room work and recitations.

FIG. 127. Students of vocational agriculture running terraces with machine. (E. H.

FIG. 128.-Have students practice filling ditches with terrace machines. (E. H. Thompson, Okla.)

Judging Soil Conditions. Not only the novice but often the experienced farmer has much difficulty in judging the condition

JUDGING SOIL CONDITIONS

259

of the soil, as to whether it is fit to plow or not, fit to plant or not; whether the moisture is too much or too little, and whether certain treatments of the soil would be best.

Frequent exercises in judging soil conditions should be conducted by the instructor with his students. Some of the following questions will be suitable to use on different occasions or under different circumstances before the ground is plowed:

1. Is the soil warm enough for spring plowing?
2. Is the soil too dry for fall plowing?

3. What tests would be required to answer the two preceding questions? 4. To what depth can the soil be plowed without injuring the texture? 5. Would plowing under present conditions be best or should it have been plowed earlier or be plowed later? Why?

If ground is already plowed when the judging exercise is being conducted, the following questions should be answered:

6. How deep was the ground plowed?

7. Was the plowing too shallow or too deep?

8. Has ground been harrowed since plowing?

9. If not, should it have been harrowed? When?

10. Why should spring plowing always be harrowed immediately after plowing?

11. What effect would a plank drag have on the field if used at the time of your visit?

12. Would other conditions be better for this operation than now?

13. Effect of disking now or later?

14. Effect of use of spike-toothed harrow now or later?

15. What operations are best to put the field in good seed condition for small seed, as grass or clover?

16. For corn or cotton?

17. For potatoes?

If the judging exercise is being held while the crop is growing, the following questions should be answered:

18. What kind of tillage is now needed?

19. Has deep or shallow tillage been conducted preceding your visit?

20. In early spring would a roller or harrow on the grain field be most useful? Why?

21. Is the soil rather too sandy for hay crops?

22. Is the soil rather too heavy for potatoes or sweet potatoes?

23. What signs of good fertility do you find?

24. What signs of impoverished soil do you find?

25. What signs for need of liming do you find?

26. What signs of bad handling when too wet or too dry do you find?

27. What remedies would you suggest?

28. Do you think subsoiling would suit this field? Why?

29. What indications are there of lack of humus or abundance of humus? 30. Does the soil need draining?

31. Would irrigation be practical?

Students should ask themselves these questions frequently when in the field. Too much skill in the judging of soil conditions cannot be attained by even the very best farmers. Formulate