10 MASS. EXPERIMENT STATION BULLETIN 444 



In some years soil nitrates and pH values were determined one or more times 

 during the seasons. 



The results obtained in 1928 are shown in Table 6 and Figure 2. There is little 

 evidence that any of the treatments of the limed soils increased tree growth ex- 

 cept where K was added to the soil from the N + L plot. This plot was known 

 to be very low in K and the increase here may have been caused by the added 

 potassium. The addition of lime to the soil from the unlimed plots always in- 

 creased growth and it is suggested that the optimum rate is about two tons per 

 acre (34 grams per pot). In one case the weight of the check plants was only 

 5.7 grams, but if this is abnormally low it may still be inferred that lime increased 

 the growth of the plants. 



In 1929 the tests were planned to see whether additional nitrogen and potash 

 with and without lime would favor increased growth of the plants. As in the 

 previous year, lime seemed to favor growth, but the addition of nitrogen resulted 

 in only slight or insignificant gains in growth while muriate of potash rather 

 distinctly injured growth. In two cases tankage seems to have caused slightly 

 better growth. (Table 7.) 



The striking and consistent result of the 1929 pot trials is that lime is the only 

 material that clearly promoted the growth of the peach seedlings growing in 

 soils from the field plots chosen. The lime used in the soil from the unfertilized 

 plot was a magnesium-free calcium carbonate. That used in the soil from the 

 P, K, and PK plots was a dolomitic lime. In all the four cases where 34 grams of 

 lime was added, growth was just about doubled. In other words, the pure CaCOa 

 was as effective as the lime containing magnesium. 



A deficiency of magnesium in the soil of a neighboring plot had been discovered 

 before 1930. The pot tests in that year were planned to indicate whether a 

 magnesium deficiency might exist in the orchard plots. Soil from plot 4 (un- 

 fertilized) was treated with pure calcium carbonate, 34 grams per pot, with and 

 without N, P, and K. The weight of the trees from the untreated pots was low, 

 but it seems clear that the calcium carbonate favored growth and that the N, P, 

 K fertilization may have done so. (Table 8.) 



Soil from plot 8, also an unfertilized plot, was treated with potash and calcium 

 carbonate, with and without magnesium sulfate, also with potash and basic 

 magnesium carbonate. The magnesium carbonate ruined the growth of the trees 

 and the magnesium sulfate added to calcium carbonate seemed of doubtful value. 



Soil from the unlimed PK plot treated with calcium carbonate gave the usual 

 response to lime and here again the addition of magnesium sulfate gave no in- 

 crease. (Figure 3.) The addition of potash did not materially increase growth. 

 Soil from this same plot was not benefited by increasing amounts of nitrate of 

 soda. (Figure 4.) 



Soil from the unlimed NP plot was treated with 25 grams of powdered charcoal. 

 The trees grew no better; when potash was added, growth seemed to have been 

 injured, but calcium carbonate increased growth. 



With soil from a limed no-fertilizer plot the addition of a complete fertilizer 

 made a slight increase of growth but K and NK injured growth. 



The pot tests of 1930 gave further indications that lime was the first need of 

 this soil, either to correct acidity or to supply calcium, and that the addition of 

 magnesium was of no benefit. 



The tests in 1931 were directed mainly toward learning the effects of organic 

 forms of nitrogen and of acidifying the soil with sulfur and with aluminum sulfate. 

 Again the addition of magnesium limestone improved growth, but acidifying soil 

 from the limed plots with sulfur was disastrous especially with the larger amounts. 



