1848 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



crop is cut off and removed from the land, 

 the gain in nitrogen to the soil is slight 

 if any. It is generally estimated that for 

 most common forage crops, the dry matter 

 in the root system constitutes about one- 

 fifth, and the ahove-ground portion four- 

 fifths of the total growth. By comparing 

 this statement with that in the preceding 

 paragraph, it will be seen that, under or- 

 dinary conditions, the amount of nitrogen 

 returned to the soil by the decay of the 

 roots only of the crop would be just equal 

 to the proportion of the crop's total sup- 

 ply which originally came from the soil. 

 If, however, the tops, as pasturage, soiling 

 crop, or hay, are fed to live stock and the 

 manure therefrom returned to the land to 

 be plowed under, nearly ninety per cent of 

 the total nitrogen of the crop will be re- 

 stored to the soil. 



If the entire crop is plowed under, all 

 of the nitrogen which it contains is re- 



stored to the soil, and as the crop de- 

 cays, becomes available to succeeding 

 crops. 



Gain of Mtrogen per Acre and Market 

 Value 



The gain of nitrogen per acre to the 

 soil if any one of these crops be plowed 

 under as a green manure may be cal- 

 culated by multiplying the percentage of 

 nitrogen m the whole plant by the weight 

 of dry matter produced on an acre. This 

 weight of growth will, of course, vary ex- 

 tremely in different seasons, on different 

 soils, and with different cultivation. 

 Table V shows examples of possible gains 

 which may be made, computed from the 

 yields per acre as given. The present 

 market value of nitrogen in commercial 

 fertilizers as sold in this state is about 

 twenty cents per pound. The market 

 value of the gain in nitrogen per acre by 

 plowing under the average crop as shown 

 IS indicated in the last column. 



TABLE T 



Gains in Mtrogen by Plowing Crops Under 



CROP 



Nitrogen 



per ton, 



lbs 



Probable 

 yield per 

 acre, tons 



Nitrogen 

 gam per 

 acre, lbs. 



Market Value 

 of gam m 

 Nitrogen 



Red Clover 

 Alfalfa 

 Field Peas 

 Tangier Peas 

 Hairy Vetch 



43 

 30 

 52 

 70 

 56 



3 

 3 



4 

 3 

 4 



129 

 90 

 208 

 210 

 224 



$25 80 

 18 00 

 40 16 

 42 00 

 44 80 



It is probable that the yields assumed 

 in this table are higher than could be ob- 

 tained in actual field practice. Certainly 

 they are larger than would be obtained in 

 the dryer stetiOBS of the state They are 

 not larger, however, than may be secured 

 under irrigation, or in those parts of the 

 state where the annual rainfall is heavy 

 Not all of the nitrogen shown as gain, m 

 the above table, would be net gain in 

 every instance. On soils rich in nitrogen, 

 the crop takes only a part of its nitrogen 

 from the air, securing a considerable pro- 

 portion from the soil itself. Probably, 

 the poorer the soil is in nitrogen, the 

 greater the proportionate gain in nitro- 

 gen from the air. The net gain is, there- 



fore, likely to be greatest in those soils 

 which are in greatest need of nitrogen. 



R. W. Thatcher, 

 Baector Wash Bxpenment Station 



A BALAJfCEB CHEMICAL COMFOUiM) 

 m THE SOIL 



We know what it means to have a bal- 

 anced ration of human food. No matter 

 how good an article of food may be, if the 

 individual is compelled to eat that and 

 nothing else he not only tires of it, but it 

 is impossible for him to maintain on that 

 food alone a good degree of health. Per 

 haps the food that contains more of all 

 the nutritive substances than any other 

 is whole wheat or Irish potatoes, but 



