402 



THE AGRICULTURAL NEWS. 



December 24, 1910. 



a high proportion of humus, and for this purpose the 

 trials were repeated, the difference being in this case 

 that plant remains were dug into the soil in the pots. 

 Confirmation of the former result was obtained, namely 

 that there was no action of the earthworms in causing 

 an increased rate of piovision of plant food. Further 

 confirmation was obtained by means of trials in which 

 a rich pasture soil was used. 



The work* that has been done at the same labora- 

 tory with partly sterilized soils led to the extension of 

 the investigation to include these, with the following 

 result: 'It was found that addition of dead worms caused 

 a small increase in the crop and a larger increase in the 

 percentages of nitrogen in the dry matter and in the 

 total nitrogen taken by the plant from the soil.' 



As it had been proved, by now, that the nitrogen 

 content of the soil is not increased through any direct 

 action of li\ing earthworms in it, attention was once 

 more directed to the effects which they prnduce through 

 their work as cultivators, and in this connexion trials 

 were made for the purpose of ascertaining the rate at 

 which nitr.ites accumulate in soil containing living 

 earthworms. As was to be expected, it was found that 

 where living earthworms had been present, the propor- 

 tion of nitrate nitrogen at the end of some months was 

 higher than in the soil which had not had the benefit 

 of being turned over by the worms. 



A further experiment was undei taken, with the 

 object of finding out the extent to which worms are 

 effective in mixing a grass mulch with soil. It 

 showed that the presence or absence of worms made 

 very little difference in the affair. Another matter 

 of interest in connexion with the subject was that the 

 soils used in the experiments were found to contain only 

 a trace of ammonia; this result is in contradiction to that 

 of other work, the conclusions from which were probably 

 vitiated because the soil, when annlysed, hud been 

 permitted to contain parts of the bodies of deail worms. 



Thr(jughout the investigation, there was no doubt 

 as to the efficacy of earthworms in opeiiing up the soil 

 and thus increasing its fertility indirectly. In relation 

 to this, an experiment is described in which one set of 

 pots is taken and filled with soil alone; while to 

 another, worms are added as well as the soil. In the 

 former case the surface ijuickly becomes covered with 

 algae and mosses; in the latter no such growths are 

 seen, on account of the continual distui'bance of the soil 

 by the worms. 



A summary of the conclusions that are reached at 

 the end of the invesligaiions shows that earthworms do 

 not appear to have any marked direct effect in hasten- 

 ing the formation of nitrates in the soil. They certainly 

 possess a direct manurial value, because of the 

 nitrogen that is given up by their bodies when they 

 decompose It is, however, their action in loosening 

 the soil, and thus assisting in its proper aeration, that 

 makes them useful aids to the agriculturist. 



See Agricnlti'ral Ne'c.-<, Vol. IX, p. 33. 



THE VALUE OF FIRST GENERATION 

 HYBRIDS IN CORN 



This is the title of Bulletin 191 of the Bureau of 

 Plant Industry of the United States of America, which 

 describes work showing the superioritv <if the first 

 generation hybrids of corn over the plants that are 

 produced from similar parents, and indicates the prac- 

 tical use that may be made of the existence of this. 

 Extracts from this bulletin are reproduced as follows: 



The ii.se of first generation hybrids offers one of the most 

 promising methods of increasing the yield of corn. The evid- 

 ence that crossing can in general be relied upon to give an 

 immediate increase of vigour and productiveness appears 

 conclusive, yet the practice seems never to have been ap[ilied 

 on a coranieicial scale. The plan of utilizing first generation 

 hybrids involves the making of the cross anew each year, and 

 this is readily feasible with corn. Many efforts have been 

 made to develoi) hybrid varieties, but the increased vigour 

 and productiveness that result from hybridization appear to 

 be confined largely to the first generation, and to disappear 

 gradually in later generations 



It was indicated more than three decades ago that seed 

 produce 1 by crossing two vaiieties of corn could be relied 

 upon to produce larger crops than the parents, and that this 

 increase was to a great extent lost in following generations. 



At about the time when it was discovered that an increase 

 in yield and vigour followed the crossing of two varieties, the 

 attention of investigators was attracted to the possibility of 

 the improvement of corn through what then appeared the 

 more scientific methods of selection The latter idea was in 

 accord with the most advanced ideas of evolution, while the 

 former ajipeared as an isolated fact discovered by accident. 



It was natural that investigators should follow out what 

 appeared to lie the more logical and scientific method. The 

 fact that yields could be materially increased by simply 

 crossing two varieties was lost sight of. Great strides have 

 been made in the knowledge and possiliilities of corn improve- 

 ment by selection, but until the past few years, the pos.-il)ility 

 of utilizing the vigour of first generation hybrids of corn has 

 remained almost e.vactly where it was left by the pioneer 

 e.x'perdnenters. 



Even after the increased vigour of first generation 

 hybrids became recognized as a general principle, it was not 

 appreciated that the i)eculiar haliits of the corn plant made 

 its commercial application to this crop entirely feasilile. Corn 

 is peculiar among the important crop plants in being wind- 

 pollinated, and in having the male and female flowers on 

 wi<lely separated parts of the plant. Tliis combination of 

 characters permits the production of crossed seed in large 

 quantities, by the simple expedient of planting two vaiieties 

 together and removing the tassels from the plants of one 



