6 MASS. EXPERIMENT STATION BULLETIN 318 



The Effect of Lime 



Owing to the importance of the question of the value of lime in Connecticut 

 Valley onion culture at the time these experiments were started, particular 

 attention was given it in the planning of the experiments. In all experiments with 

 fertilizers and cover crops, two contiguous plots were treated as one plot in respect 

 to the fertilizer treatment, but the south half received lime in addition, while 

 the north half received fertilizer only. This difference in liming continued for 

 three years (1925-1927), after which it was eliminated or reduced by liming the 

 north half of each plot. 



With the exception of the 6-8-4 treatment in 1926, where there was a slight 

 but insignificant decrease in yield from the addition of lime, the favorable effect 

 of lime was marked. The greatest increases occurred in 1927, following the second 

 application of lime in the fall of 1926, when increases varied from 70 per cent to a 

 little over 100 per cent. For the 3-year period (1925-1927) the mean percentage 

 increase varied from 20.8 to 44.8 with a weighted mean increase of 34.8 per cent. 

 In this series a large number of plots was involved, there being 19 check (4-8-4) 

 plots and 20 others. This large number of repetitions reduces the probable error 

 of the mean to a low figure. Mean differences of 10.0 per cent or more may be 

 considered significant in this experiment. 



For the purpose of determining the optimum dosage of lime for onions, an 

 experiment was conducted with different quantities of lime varying from to 7 

 tons per acre. The results showed a very definite and significant response of 



NOTE ON STATISTICAL INTERPRETATION OF DATA FROM EXPERIMENTS 

 WITH FERTILIZER AND COVER CROPS 



In these experiments there were 19 check plots which were used throughout the experiment. 

 In order to get a basis for judging the reliability of the numerical result*; of the experiments the 

 data from the check plots, which were well distributed over the experimental field, were studied 

 by conventional statistical methods. 



In a stud\ of this kind, the first thing to do is to see how nearly the data fit a normal distribution 

 curve. The mean yields of onions grown from seed during the period 1927-1929 were first studied, 

 and a bimodal curve was obtained with small or large classes. The mean yields of onions grown 

 from sets in the period of 1930-32 pave a curve of normal shape but "skewed". These curves in- 

 dicate that the data are not capable of strict statistical interpretation, and that results with onions 

 grown from seed are less reliable than with those grown from sets. 



However, in order to get some numerical basis for judging the reliability of the means obtained, 

 certain constants were worked out by means of methods described in a previous bulletin* of this 

 Station. The constants are as follows: 



Seed Onions Set Onions 



Mean Probable error of the mean Mean Probable error of the mean 



100's lno\ Percent 100's 100's Percent 



All checks \r,:i.:i 4:5 2.8 229.2 II 19 



4 random enccks (a) Ml 8 7 7 S t 219 2 8.3 3.8 



Ditto (b) 149 1 10.6 7.1 L'L'll 7 19 2 2 



Ditto (c) 181.5 19 2.7 200 8 :5 2 1.6 



I ' tto id) 129. 1 8 I 6.5 213.7 10 1 4.8 



ipproximating those obtained for random lots of 4 checks above were obtained for 

 other lot • f I receiving different fertilizers. Conventional treatment of these constants showa 

 that in case of fertilizer treatments, differences of about 25 per cent between mean yields of checks 

 and treated plots are necessary to be significant in the case of seed onions, and about 10 per cent 

 in the case of set onions. Since the data are not capable of strict statistical interpretation, these 

 figures were used as an aid but n it a final criterion in evaluating the results. 



♦Beaumont, \. I'... Snell, M. I... and Holland. !•'.. 15. The Effect of Certain Cropping Systems 

 on the Yield and Quality of Havana Tobacco. Mass. Alt. Exp. Station Bulletin 297 (193:5). 



