1917] FIELD CEOPS. 35 



fortnightly periods ; the effect of different cultural methods, of boron and 

 manganese, and of varying the relation of the potassium, nitrogen, and phos- 

 phorus ; applications of potassium and phosphorus made according to certain 

 curves ; the stage of growth at which the minimum phosphorus is best utilized ; 

 the ability of barley plants to utilize phosphorus if it is mainly withheld until 

 the last four weeks of growth ; and the necessary amount of phosphorus for 

 the optimum growth of the barley plant. The results of these investigations 

 are briefly summarized as follows : 



Ten plants receiving an average of 13 mg. of PzOs per week for the first 

 10 weeks absorbed nearly all of it, while plants receiving the maximum 

 amount of phosphorus absorbed about 30 mg. PaOe per week from the third 

 to the sixth week, inclusive. The small application of phosphorus was sufficient 

 for the needs of the plants but the percentage of phosphorus recovered was 

 much increased by the largest application. Plants receiving minimum amounts 

 of phosphorus the first eight weeks of growth were noticeably handicapped in 

 size and in color of stems and leaves, while those receiving liberal amounts of 

 phosphonjs during the next four weeks made a liberal growth and appeared 

 perfectly normal at harvest. The minimum phosphorus requirement for 10 

 plants producing the optimum amount of seed was about 75 mg. of P206. 



Plants grown in cultures and receiving 80 mg. of K2O5 did not mature seed, 

 were limp, and showed a marked spotting of stems and leaves. The amount 

 of potassium recovered from the seed showed little variation regardless of the 

 amount of potassium applied, while the amount recovered from the seed-free 

 plants was markedly influenced by the amount added. 



The amount of potassium, nitrogen, or phosphorus absorbed by the plants 

 was greatly influenced by the relation of the other nutrients. Changes in 

 cultural methods, that is, aerating the solutions daily, keeping a piece of fresh 

 charcoal in the solutions, or lowering the temperature of the solutions in sum- 

 mer weather, had no noticeable influence on plant growth. Titrations of cer- 

 tain composite samples of the residual solutions showed slight variations from 

 the neutral point. In the quantity used in these tests, the addition of boron 

 or manganese to the culture medium had no apparent effect upon the growth 

 of the plants. 



Results of tests made for potassium and phosphorus in distilled water, in 

 which plants were allowed to remain for one to two weeks after they attained 

 their growth, did not substantiate the belief that either element was freely 

 given off by way of the roots at maturity. 



Report on com and cotton varieties, 1916, C. K. McClelland {Georgia 

 Sla. Circ. 75 (1917), pp. 8). — This reports the results of variety tests with corn 

 and cotton for 1916 and is a continuation of work previously noted (E. S. R., 

 35. p. 830). 



Fifteen varieties of corn were tested. Scott Marlboro and Steinheimer Marl- 

 boro gave the highest yields of 22 and 21 bu., respectively, while Rockdale 

 gave the lowest yield of 12.6 bu. per acre. Nearly all of the varieties were 

 the prolific two-eared type. 



Of 28 cotton varieties tested, Wanamaker Big Boll, with a yield of 1,575 

 lbs., and Smith Piedmont Big Boll, with a yield of 1,550 lbs. of seed cotton 

 per acre, were the leading varieties. Forty-nine per cent of the bolls of the 

 former and 60 per cent of those of the latter were open by the second picking, 

 October 6. Blackshear Wilt-Resistant Lee, with a yield of 960 lbs., was the 

 lowest yielding variety. The Cleveland types of cotton, which have led in 

 variety tests 8 out of the last 11 years, are considered the best all-around 

 varieties for the middle Piedmont region. These varieties yielded from 1,310 

 to 1,420 lbs. of seed cotton per acre this past year. 



