12 University of Xkw ilA.Mi'siiiKK | Sta. Bull. 324 



lime applications were applied but once in the six year period, while the 

 two and four t(m applications (Jackson farm) were applied once in twelve 

 years. Serious scab resulted from the heavy api)lications. but no appre- 

 ciable efifect upon scab was noted from the smaller applications in either 

 case. 



With particular reference to the Jackson farm, it seems that, although 

 the average pH value of the soils of the check series is about 4.8. this acid- 

 ity is not sufiiciently strong to reduce potato growth, but it does limit 

 clov-er and hay yields tremendously as will later be shown. 



This seems to support the work of Smith (22) who states that there 

 were no significant differences in ])otato yields on plots between pH range 

 of 4.8 and 7.1. He also states that yields declined below pH 4.8. and this 

 fact is corroborated by our work on certain plots on Jackson farm on which 

 Ammo Phos was used in large amounts, causing the soil to become some- 

 what more acid. 



These plots received a fertilizer made up of e(jual (piantities of Ammo 

 I'hos "A" and Nitrate of Potash, in amounts ap])roximatelv equalling one 

 ton, and one and one-half tons of 4-8-7 fertilizer. N'ields for these plots, 

 over the second si.x-year period, comparrd with tlir check plot series were 

 as follows : 



TABLE VIII. 6-year average yields of Jackson farm potatoes 

 with acidifying fertilizer. 



I rralinciU Yield per acre i'. K. DitT. froiu check I'. IC. 



1 Tun 4-8-7 Check 

 D. S. E(|uiv. 



1' , 'r.iii I), s. i-:(iniv 



While the differences repfjrted are not statistically significant, vine 

 growth has always been inferior to that of the check ])lots, the foliage hav- 

 ing a slightly darker color, along with a bronzing indicative of magnes- 

 iinn hunger. The bronzing was es])ecially marked on the lyj T. D.S. ]ilots. 

 This would lead us to place some confidence in tlie decreasing yields under 

 this fertilizer formula even though as imieh, or more actual ])lant tuod was 

 applied. 



Clover was i)ractically a failine when these plots were seeded to hay. 

 and the growth of grasses was inhibited as well. Sctrrel came into the 

 plots in great abundance during the year they were in hay. indicating that 

 for some reason the soil had become unsuited to hay production. Acidity 

 studies were conducted annually on all the jilots and while the ]iM values 

 of the soils of the 1)..S. plots are not consistently lower than those of the 

 check treatment, they tend toward a lower ])11. the D.S. series in 1939 

 having a |)M (>\ 4.48. and the 1 I^S T. D.S. a pll of 4.23. while the compar- 

 able check plots averaged pll 4.66. It ai)pear>. therefore, that the etTect 

 of the Ammo Phos on increasing soil acidity along with the greater re- 

 moval of basic elements, including magnesium, may account for lower 

 pf)tato yields and poor hay growth. 



The conclusion .seems justified, then, that the Jackson farm soil is at 

 the moment suited to maximum ])ot;ito growth, but that any material which 

 increases acidity is likely to interfere with full ])ot,-ito yit-lds. .Since the soil 



