RENOVATING GRASS LANDS. 257 



but both show a decline in the second ten years as compared with the first. Experiment 2 

 received 14 tons of ordinary yard manure annually for the first eight years of the period, in 

 all 112 tons per acre; but since the first eight years it has received no manure. During the 

 eight years of the application of the dung, the increase of hay obtained on Plot 2 over the 

 unmanured land was 2,139 pounds of hay per acre, and for the next six years after the 

 application of the dung had ceased, the increase was much the same, being 2,147 pounds per 

 acre; since then the produce has gradually declined, but even at the present time seventeen 

 years after the last application of dung the produce is still several hundred pounds more than 

 that of the unmanured land ; and compared with the constituents contained in the dung, 

 there is still a very large amount to be accounted for which has not been taken off by the 

 increased produce. 



In the two experiments 5 and 15 we have equal quantities of nitrogen supplied to the 

 grass every year; in one, the nitrogen is in the form of ammonia combined with sulphuric 

 and hydrochloric acid; in the other, it is in the form of nitric acid combined with soda. 

 The ammonia experiment commenced two years earlier than the other, but in 1858 when 

 the first application of the nitrate took place the hay produced in the two experiments was 

 nearly equal; since then the produce under the ammonia salts has rapidly declined, until it 

 is now very little above that of the unmanured produce, while upon the experiment receiving 

 the nitrate, the produce of the last ten years, as compared with the first eight years, has been 

 the same. 



This great superiority of the hay-producing properties of the nitrate over the ammonia 

 equal to about 1,000 pounds of hay per acre annually over the whole period is due partly 

 to the superior power of the nitrate to liberate and render available the stores of the soil, and 

 partly to the supply of soda which it yields to the plant. 



The property possessed by growing vegetation of using soda where there is a deficiency 

 of potash in the soil, is very clearly established in several of these experiments. 



The superiority of nitrate over ammonia is equally apparent when all the necessary 

 minerals are employed in conjunction with these two substances, as is the case in Experi 

 ments 9 and 14. During the first period, which includes ten years with ammonia and only 

 eight years with nitrate, the average produce is almost exactly even in the two experiments, 

 being 6,000 pounds of hay per acre annually. In the same period of ten years, the produce 

 of the ammonia plot had fallen from 6,000 pounds to 5,421 pounds; while the nitrate 

 had risen to 6,777 pounds, thus again showing the superiority of the nitrate over the 

 ammonia. 



In Experiments 11 and 12, where much larger quantities of ammonia are used with the 

 minerals, we have the largest growth of hay produced on any of the plots the average in 

 one case is close upon 7,000 pounds of hay per acre; and even this does not show the full 

 effect of the manure, for since 1874 we have been taking two crops of hay annually, and 

 the produce has amounted on the average to 10,000 pounds; and in 1877 it reached the 

 amount of 12,344 pounds of hay per acre. Of this great weight of produce the soil has 

 contributed about 8 or 9 per cent., and the remainder comes from the atmosphere. 



In Plot 7 we have an experiment in which, from the commencement, no manure con 

 taining nitrogen has been placed upon the land; a very liberal supply of potash, soda, mag 

 nesia and phosphate of lime has been applied every year, and the average produce of the 

 twenty years has been close upon 4,000 Ibs. of hay per acre. It may be noticed also that the 

 produce of the last ten years is rather the highest. Compared with the unmanured land, the 

 produce upon Plot 7 is a little over 1,500 Ibs., but it is nearly 1,800 Ibs. below the increase 

 given by the minerals combined with ammonia, and 2,448 Ibs. below the minerals combined 

 with the nitrate, annually. 



In experiment 18, which has only been carried on eleven years, up to 1875, wo supply 



