UTILIZING OUR SOIL RESOURCES — SALTER 325 



with tlio hay removed, about offset the losses from a crop of corn. Al- 

 falfa and sweet clover are even more effective in contributing organic 

 matter and nitrogen to the soil. They will almost offset losses from 

 a crop of both corn and small grain. 



Deep-rooted crops are the major factor in maintaining structural 

 stability and permeability, aeration, and drainage in the deeper soil 

 layers. In addition to the physical effects, deep-rooted crops feed not 

 only in the topsoil, but also in the subsoil. An active root system is 

 about the best defense against nutrient-leaching losses. Decomposition 

 of root and crop residues of such plants releases into the surface soil 

 nutrients that come from deeper layers. 



On sloping soil subject to erosion, legume and grass mixtures are 

 better than either legumes or grasses alone. Legumes furnish needed 

 nitrogen while grass holds the soil from eroding between the crowns 

 of legume plants. 



Grown alone or in combination with grasses, deep-rooted legumes 

 leave large residues of organic matter and nitrogen within the soil 

 even when the tops are removed as hay or pasture. They improve soil 

 tilth and drainage and effectively protect the soil from the erosive 

 impact of rain. Plowing down a good two-year stand of alfalfa, for 

 example, will leave in the soil more than 3,000 pounds of dry weight 

 of roots and 80 pounds of nitrogen per acre. 



Critics of this system maintain that it takes too long. They say 

 that by following this route for building soil productivity we shall 

 need to sacrifice some immediate production, and that farmer income 

 will be impaired. Recent research findings suggest otherwise, pro- 

 vided the cropping system for a farm is planned for an extended 

 period, such as 5 to 10 years, \\liile the cost of shifting often requires 

 a temporary economic sacrifice, the new system soon becomes more 

 profitable than the old. 



For example, in a four-year rotation of corn, wheat, alfalfa, alfalfa, 

 in Ohio, with the use of only moderate levels of mineral fertilizer over 

 a 13-year period, corn produced an average yield of 68 bushels per acre, 

 wheat 41.8 bushels, and alfalfa averaged three tons of hay each year. 

 At current farm prices this would permit realizing a gross return of 

 more than $100 per acre during each year of the rotation. With 

 liberal applications of fertilizer, yields were substantially higher. A 

 farmer following such a system certainly is not sacrificing farm 

 income. And he is maintaining soil productivity while producing 

 at a high level. 



In straight corn-small-gi-ain rotations, substantial gains can be 

 realized from the use of legumes as a catch crop with small grain, to 

 be plowed under the following spring before planting to corn. In- 

 creases in corn yields as much as 35 bushels per acre are possible under 



