EXTEISrSION COUESE IN SOILS. 45 



it is often well to make an application at a time when the crop is in 

 especial need of help or stimulation in its growth. 



Need of decaying vegetable matter in the soil. — Doubtless one of the 

 greatest needs of the soUs of the United States is more nitrogen 

 through the growth of leguminous crops. This is especially true in 

 the South, where long summers and much sandy soil cause the vege- 

 table matter quickly to become depleted. Growing legumes for green 

 manure, or, preferably, feeding the legumes and returning the manure 

 to the soil, are the cheapest and most effective ways of supplying 

 nitrogen for staple crops. Other advantages which green manure or 

 barnyard manure have over commercial nitrogenous substances in 

 the soil are: (1) They do much to maintain the moisture content; (2) 

 they unprove the texture; (3) they increase the temperature; and (4) 

 they promote bacterial action. These advantages should never be 

 overlooked in farm practice. Some of these benefits to the soil from 

 decaying vegetable matter have been mentioned in previous lessons, 

 but they will bear repetition. 



EXERCISES, LESSON VI. 



Materials required. — Four boxes; some poor, sandy soil; a few peas, oats, or grains 

 of corn; sodium nitrate, ammonium sulphate, and pulverized Umestone. 



Leguminous plants. — If conditions permit, carefully dig up different species of 

 leguminous plants and examine the roots for nodules. If plants are carelessly removed 

 from the ground the nodules will be pulled off and remain in the soil. If plants are 

 taken up vvith a spade or shovel so that considerable earth remains on the roots, and 

 then if the soil be very caref ally washed away, an examination of the fine roots will 

 show the nodules. These will vary on different legumes from the size of a pinhead 

 to that of a small pea, or even' larger. If plants can not be dug out of doors, peas or 

 beans planted in a box and kept growing well will show the nodules after a few weeks. 



Inoculation. — -It will be found interesting as a field test to sow two strips side by 

 side of some leguminous plant not commonly grown in the community, inoculating 

 the seed used for sowing one strip and sowing the other strip from uninoculated seed. 

 Cultures for inoculation may be secured by applying to your State experiment station 

 or to the United States Department of Agiiculture, Washington, D. C. After growing 

 some six weeks the roots of plants from the two plats should be carefully examined 

 for nodules. After two or three months of growth note whether there is a difference 

 in the growth of plants on the two plats. 



Salts containing nitrogen.— ¥\\\ four boxes with poor sand. Plant either peas, oats, 

 or corn in all four boxes. Keep warm and moist until the seeds are up. Mix into the 

 soil of one box a good sprinkling of sodium nitrate ; mix a like quantity of ammonium 

 sulphate into the soil of the second box, and ammomium sulphate and powdered 

 limestone into the soil of the third; leave the fourth box undisturbed. Keep all the 

 plants in good condition for growth and watch for a few weeks. Note results. 



PROBLEMS. 



1. A 30-bushel wheat crop removes from 1 acre about 48 pounds of nitrogen; a 50- 

 bushel oat crop removes about 50 pounds; and a 65-bushel corn crop removes about 

 85 pounds of nitrogen per acre. How many pounds of nitrogen are removed from 

 the soil on a grain farm where 30 acres of wheat are raised averaging 20 bushels per 



