10 N. H. Agri. Experiment Station [Bulletin 284 



of 1934 had pH values of 5.70 and 6.05 respectively. It is interesting to 

 note that, while plowing has usually resulted in decidedly decreased pH 

 values for soils, in this case, without the addition of lime, the pH values were 

 increased. It is thought that the plowing resulted in the thorough mixing 

 of the residues of the six year old applications of limestone with the soil, 

 resulting in its renewed activity in neutralizing acids. 



The highest pH value ohtained by the application of ground limestone 

 at the rate of eight tons per acre was 6.5. Mixed samples taken to the depth 

 of seven inches gave this result. The ground limestone was applied in the 

 spring of 1931 and harrowed in well. After two years the neutralizing effect 

 of the heavy application of limestone is hardly evident below the six-inch 

 level, and with four tons or less no appreciable effect is noticed below the 

 four-inch level. 



An attempt to reconcile the need for lime on the part of legumes in the 

 rotation with scab-free potato production compared applications of alumi- 

 num sulphate and sulphur at the rate of 900 pounds and 300 pounds each 

 per acre. In these attempts to acidulate soil prior to potato planting, the 

 heavier application of aluminum sulphate proved the most effective of the 

 treatments, and the percentage of scab was considerably reduced over the 

 no-treatment plots. In no case, how^ever, were the potatoes free from scab. 

 The limed plots in the rotation show increased yields of about 70 bushels 

 per acre over the no-lime plots. This is doubtless due to the fact that the 

 soy beans on these plots grew much better yields following the lime applica- 

 tions, and the beans were used as green manure. 



Magnesium limestone has been giving such a significant increase over 

 other plots in the soy bean experiments at Greenland that it seems evident 

 that this element is a limiting factor for the crop on this soil. 



Dairy Farm Rotation at Pittsfield. The omission of phosphorus and 

 doubling the phosphorus content caused little difference in yield. This was 

 in direct contrast to similar experiments in northern Coos County. Changes 

 in the nitrogen application also did not prove significant. The omission of 

 potash, however, caused a serious decrease in yield, a difference almost as 

 great as omitting the fertilizer altogether. Magnesium does not appear to be 

 a limiting factor on this soil. In the oats plots, the only treatments which 

 caused a wide variation was the omission of phosphorus and the omission 

 of fertilizer altogether. In both these series of plots the yields were de- 

 pressed. 



Potato Rotation. In the potato rotation at Colebrook, extra phosphorus 

 as well as extra potash has given consistent increases during the past six 

 years. Last year, therefore, high phosphorus and high potash were com- 

 bined. This gave a significant increase over check plots. In the potato plots, 

 an application of sulphur at planting time served to bring a scab count on 

 the four-ton lime series considerably lower than in the two-ton series. 

 Smaller lime applications are being tried on other plots to see how much 

 lime can be used without scab difffculties and still encourage the growth of 

 clover. The oats plots have apparently suffered considerably when an ele- 

 ment is omitted in the fertilizer, or when a sliortage of plant food has been 

 applied, but they respond to the lime which had previously been applied in 

 the rotation. 



Pasture Experiments. In the pasture top-dressing experiments at Clare- 

 mont, of the nitrogen carriers tried, Cal-Nitro seems to have given the best 



