102 CONSERVATION AND IMPROVEMENT OF SOIL 



and the amount of moisture present. It may also depend somewhat 

 upon the character of the stems and growth and the maturity of 

 the crop. If a large quantity of green manure be plowed under 

 at any one time the decay may be very slow indeed. The best 

 plan is to plow under a moderate growth each time, rather than a 

 heavy growth. If the soil be well packed after the crop is plowed 

 in, decay will take place more quickly. 



Under favorable conditions green manure plowed under in 

 the spring will liberate an abundance of plant food for the grow- 

 ing crop the same season (Fig. 75). 



3. If all or a part of the plants forming the green manure crop 

 belong to the legume family a supply of nitrogen will be gathered 

 from the soil and be changed to the form of nitrates for the use 

 of money crops. This is usually the cheapest way to supply 

 nitrogen to any soil. Commercial forms of nitrogen are becoming 

 much more expensive year by year. The gardener or farm mana- 

 ger will find much profit in growing leguminous crops to supply 

 nitrogen to the soil for the production of market crops. Not only 

 is there a saving of money, which would be expended for com- 

 mercial nitrogen, but the results are more satisfactory. Larger 

 crops are produced when the equal amounts of nitrogen are 

 compared. 



4. Many chemical changes take place in the soil during the 

 growth and decay of the green manure crop. Comparatively 

 inert particles are acted upon. The soil as a whole is in better 

 condition for the future crop. 



5. The soil is a better medium for the growth and multipli- 

 cation of beneficial bacteria of many kinds. Indeed the soil is 

 made into an active, live mass instead of an inert, soggy, dead 

 clay or sand. 



The above five benefits arising from the use of well- planted 

 systems of green manure 'are not in any sense theoretical. They 

 have all been proved to exist in a very practical way, with the 

 result that the best farm managers have formulated some regular 

 system of green manuring as a part of the annual maintenance of 

 the farm. 



Planning Ahead. Any one intending to have crops ready to 

 be plowed under for the frequent or yearly improvement of soils 

 will find it necessary to make definite plans for the succession or 

 rotation of crops on each field. In many southern states, for 

 example, corn or cotton is grown annually on the same field as 



