34 EXPERIMENT STATION BECOKD. [Vol. 37 



application of sulphur and 8,300 lbs. following a 100-lb. application of land 

 plaster. 



Air-slaked lime aud nitrate of soda were also tested, but failed to give 

 Increased yields. 



It is recommended that sulphur be applied not later than January or Febru- 

 ary, while land plaster should be applied early in March. 



Studies by means of both pot and solution culture of the phosphorus and 

 potassium requirements of the barley plant during its different periods of 

 growth, F. R. Pkmbku (Rhode Island ISta. Bui 169 (1917), pp. 50, pis. 2, figs. 

 3). — Investigations are reported to determine the actual requirements of the 

 barley plant for potassium and phosphorus during different periods of growth 

 and where most of the conditions e.s.sential to growth were under control. The 

 experiments include (1) those with plants grown in sand or soil and (2) those 

 with barley grown in .solutions. 



The first group of exiJcriiucnts included four tests of varying applications of 

 potassium and phosphorus applied at dilTerent periods in the growth of barley 

 grown in sand, a study of the relation of vigor of growth of the young plants to 

 the percentage of phosphorus contained in the seed, and a comparative study of 

 oats grown in sunken pots out of doors. 



Tests for the potassium requirement of the barley plant grown in sand were 

 not continued after the first experiment because of the large growth the 

 plants were capable of making when no potassium was added. Where little or 

 no potassium was added, the plants showed spots or flecks of brown on the 

 oldest leaves, the discoloration being greatest when no potassium was added. 

 Plants grown without the addition of phosphorus were darker green and 

 showed considerable purple in their stalks and leaves. 



In the .sand experiments the weight of dry straw, or straw and roots, was 

 practically the same whether all of the phosphorus was added at the beginning 

 in three equal applications, or one-third at the beginning and one-third at the 

 end of the second period, or two-thirds at the bogiiming and one-third at the 

 end of the second period. In the third experiiiunt the amount of seed pro- 

 duced was much greater where phosphorus had been received in three equal 

 applications, while in the fourth experiment plants having the full phosphorus 

 application at the beginning produced the most seed. 



Selected barley seed varied in the percentage of phosphorus contained, but 

 the weight of the entire dry plants grown from similar seeds bore no relation 

 to the amount contained. Plants grown for 19 days from planting with a full 

 pho.spliorus application at their disposal were not markedly larger than those 

 having only a one-third application of phosjihorus, but the amount of phos- 

 phorus recovered from the former was more than twice that recovered from 

 the latter. In the fourth experiment, the amount of phosphorus recovered from 

 the plants harvested at the end of the second period was much the same 

 whether the full phosphorus application was made at the beginning, or one- 

 third at the beginning of both the first and second periods. The best recovery 

 of phosphorus by the barley plants grown in sand was al)out S9 per cent of the 

 amount added. 



Oat plants grown in 1900 in soil receiving tlie full phosphorus application 

 before planting were larger and recovered more phosphorus than those which 

 had three equal applications, but the latter produced a larger amount of seed. 

 In the season of 1910 these differences were negligible. The best recovery of 

 phosphorus by the oat plant was one-fiftoenth of the ammmt added. 



The second group of experiments dealt with the actual requirements of the 

 barley plant for potassium and phosphorus during Its different periods of 

 growth In solutions. Studies were made of the phosphorus absorption during 



