EXPERIMENT STATION BULLETINS. 357 



is backward because of a severe winter or a late spring the use of ligbt 

 top dressings of nitrates on some soils is a profitable and desirable 

 practice. Where weather conditions are such that very late fall seed- 

 ing is obligatory or late seeding is practiced on account of the Hessian 

 Fly, the use of readily available fertilizers is urgent in as much as they 

 cause a rapid growth and winter injury is less serious. Moreover where 

 an early marketable crop is desired the use of commercial fertilizers 

 is advisable. In addition the use of readily available fertilizers is sound 

 in regions where the growing period is short since they tend to hasten 

 growth and maturity. Still another point to consider is that fertilizers 

 may increase the root development of plants and consequently their 

 feeding range, thereby assisting them to obtain additional elements of 

 plant-food from the soil. This probably accounts for the benefit derived 

 from small applications. Naturally such practices do not comprise 

 permanent systems of fertility. 



The vegetable matter or humus content of soils may be increased by 

 the use of commercial fertilizers. It has been shown that the roots and 

 above ground portions of crops may be increased by this means if proper 

 rotations of crops are followed. There is more material left in soils and 

 larger quantities of residues or manure, straw, etc., to return to the 

 land. If on the other hand the soil is improperly managed or the resi- 

 dues are carelessly handled, burned or not returned to the land, small 

 amounts of available commercial fertilizers will result in more rapid 

 depletion of humus than if they are not used. 



Some soils are actually deficient in one or more elements of plant 

 food and fertilizers are added to meet this need. As has been pointed 

 out this is the case with many of Michigan's lieavy soils with respect 

 to phosphoric acid, and sandy soils are not only low in phosphoric acid 

 but are also generally deficient in humus and nitrogen. Although potash 

 is usually present in abundance in the mineral soils, we have found that 

 its use on some sandy lands is desirable for the production of the legumes 

 and many growers report also that it is desirable — when prices are 

 normal — for the production of potatoes and root crops. Some muck 

 and peat soils respond to lime, some to phosphoric acid, some to i^otash, 

 and some to both phosphoric acid and potash. 



We have in progress many field tests that are being conducted co- 

 operatively by farmers, county agents and representatives of the Soils 

 Section. It is proposed to continue these at least one round of a rota- 

 tion and longer if practicable. Although it is recognized that the value 

 of such tests increases with the length of time they are continued, it 

 seems advisable to report the results we have obtained at this time. A 

 summary is given in table 9 followed by a detailed report. 



In calculating the returns from the application of the materials ap- 

 plied to the soils the following prices per bushel were used: Wheat, 

 12.00; corn, $1.25; oats, $0.G0; rye, |1.50; soy beans, $5.00. The follow- 

 ing in terms of tons: Clover hay, |22.00; straw, |8.00; lime, |1.50; acid 

 phosphate, |32.00; sodium nitrate, $90.00; potash, -|17G.00, rock phos- 

 phate, 120.00; sulphate of ammonia, flOO.OO. If the price of farm prod- 

 ucts were only one-half the amounts used and the cost of the fertilizers 

 were the same, naturally the returns derived from their use would be 

 less. 



