June IS, 1920 Effect of Manure-Sulphur Composts on Greensand 251 



The diagrams of figure i give a graphic representation of the relation 

 of the water-soluble acidity to the water-soluble potassium at different 

 time periods for the greensand-sulphur-manure composts and for the 

 greensand-sulphur-soil-manure composts to which were added 10 gm. 

 of calcium carbonate. 



A comparison of compost 3 with compost 7 and compost 10 with 

 compost 14 brings out the fact that the replacement of one-half of the 

 manure by soil has reduced the acidity and at the same time decreased 

 the amount of potassium in the water extract. No. 7 and 14 show also 

 the stimulation in acidity during the early weeks due to the addition of 

 calcium carbonate. 



The degree of acidity and the amount of sulphates and of potassium in 

 the water extracts at the beginning of the period and at the end of 23 

 weeks for all the composts are shown in Table VI, which is a summary of 

 Tables III, IV, and V. 



Table VI. — Water-soluble acidity, sulphate, and potassium in water extract from lo gm. 

 of moisture-free compost at beginning and after 2j weeks of composting 



Attention is called to the fact that the potassium liberated from the 

 New Jersey greensand is much greater than that recovered from the 

 Maryland greensand. This is to be expected, since the former had an 

 initial potassium content of 5.88 per cent, while the latter contained 

 only 1.42 per cent of potassium, as shown in Table I. It will be seen 

 that the largest amount of potassium was extracted from compost 3, 

 containing the New Jersey greensand, and the second largest amount 

 from compost 10, which is the corresponding mixture made with Mary- 

 land greensand. The fact that both of these composts have twice the 

 amount of manure contained in No. 4, 7, 11, and 14 would indicate that 



